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Papers by Carmen Rizzo

Journal of Marine Science and Engineering

Background: The cold-adapted Idiomarina sp. 185 from Antarctic shoreline sediment and the mesophi... more Background: The cold-adapted Idiomarina sp. 185 from Antarctic shoreline sediment and the mesophilic Idiomarina sp. A19 from the brackish Lake Faro (Italy) were screened for their efficiency in biosurfactant production by a temperature-mediated approach, when grown in rich culture medium and mineral medium supplemented with biphenyl. Methods: oxidation of polychlorobiphenyls and standard screening tests were performed, i.e., E24 index detection, surface tension measurement, blood agar plate and C-TAB agar plate. Results: During incubation in rich medium, the strain Idiomarina sp. A19 produced an excellent stable emulsion, recording an E24 of 73.5%. During growth in mineral medium, isolates showed good efficiency in at least one performed condition by showing species-specific differences related to optimum temperature. In the presence of biphenyl, both Idiomarina isolates created stable emulsions (E24 ≈ 47.5 and 35%, respectively), as well as surface tension reductions of 30.05 and 3...

Journal of Marine Science and Engineering

Luminescent bacteria are a fascinating component of marine microbial communities, often related t... more Luminescent bacteria are a fascinating component of marine microbial communities, often related to the light emissions in deep sea marine organisms. They are mainly affiliated with specific phylogenetic groups, such as Photobacterium, Vibrio, and Photorhabdus, and are sometimes involved in symbiotic relationships. However, the luminescence of some marine organisms remains a poorly understood process, and it is not always certain whether their luminescence is attributable to associated luminescent bacteria. In this study, for the first time, luminescent bacteria were isolated from two deep sea organisms, namely, the cephalopod Neorossia caroli and the teleost Chlorophthalmus agassizi. The isolation was carried out on glycerol-supplemented medium, and the search for the luxAB gene was performed on all isolates as a complementary tool to the culture-dependent techniques to detect bioluminescence by molecular approach. The optimum of salinity, temperature, and pH was evaluated by physio...

Polar Biology

Marine Porifera (sponges) are known to produce several bioactive metabolites having a biotechnolo... more Marine Porifera (sponges) are known to produce several bioactive metabolites having a biotechnological potential, mostly derived from their bacterial symbionts; however, current knowledge on the production of metabolites such as enzymes and antibacterial molecules in sponges living in Antarctic environments is not fully exhaustive and needs further deepened investigation. The interest in discovering the broad spectrum of natural products potentially derived from species adapted to colonize extreme environments stimulates the research toward Antarctic sponge bioprospection. In this study, whole homogenates of Antarctic Demospongiae, belonging to five different species [Haliclona (Rhizoniera) sp., Haliclona (Rhizoniera) dancoi, Microxina sarai, Dendrilla antarctica, and Mycale acerata] were collected from Terra Nova Bay (Ross Sea) and examined for presence and activity of enzymes, including lysozyme, and antibacterial substances. Enzyme activities (leucine aminopeptidase, beta-glucosi...

Minerals, 2022

Marine hydrothermal systems are a special kind of extreme environments associated with submarine ... more Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the living organisms, which have to develop adaptation strategies to survive. Hydrothermal systems have attracted the interest of researchers due to their enormous ecological and biotechnological relevance. From ecological perspective, these acidified habitats are useful natural laboratories to predict the effects of global environmental changes, such as ocean acidification at ecosystem level, through the observation of the marine organism responses to environmental extremes. In addition, hydrothermal vents are known as optimal sources for isolation of thermophilic and hyperthermophilic microbes, with biotechnological potential. This double aspect is the focus of this review, which aims at providing a picture ...

Water, 2022

Antarctic freshwater ecosystems are especially vulnerable to human impacts. Polychlorobiphenyls (... more Antarctic freshwater ecosystems are especially vulnerable to human impacts. Polychlorobiphenyls (PCBs) are persistent organic pollutants that have a long lifetime in the environment. Despite their use having either been phased out or restricted, they are still found in nature, also in remote areas. Once in the environment, the fate of PCBs is strictly linked to bacteria which represent the first step in the transfer of toxic compounds to higher trophic levels. Data on PCB-oxidizing bacteria from polar areas are still scarce and fragmented. In this study, the occurrence of PCB-oxidizing cold-adapted bacteria was evaluated in water and sediment of four coastal lakes at Edmonson Point (Northern Victoria Land, Antarctica). After enrichment with biphenyl, 192 isolates were obtained with 57 of them that were able to grow in the presence of the PCB mixture Aroclor 1242, as the sole carbon source. The catabolic gene bphA, as a proxy for PCB degradation potential, was harbored by 37 isolates...

Native bilge water bacteria as biosurfactant producers and implications in hydrocarbon-enriched wastewater treatment

Journal of Water Process Engineering, 2021

Abstract Seawater and bilge water samples were used to isolate hydrocarbon-degrading bacteria to ... more Abstract Seawater and bilge water samples were used to isolate hydrocarbon-degrading bacteria to be screened for biosurfactant production in the presence of different carbon sources, namely tetradecane, d -glucose and sunflower oil. The panel of tested isolates, affiliated to Alcanivorax, Acinetobacter, Pseudomonas, Halomonas and Marinobacter genera, showed promising results both in terms of emulsifying activity and surface tension reduction. The selected strains Marinobacter sp. BIC3M3, Alcanivorax sp. BIC1A5 and Halomonas sp. BIC1H44 achieved total raw biosurfactant amount of 3.148, 2.922 and 2.596 g/L, respectively. The sunflower oil, here proposed as low-cost carbon source, was successfully used by all strains as substrate for biosurfactant production, with the only exception of Halomonas sp. BIC1H44, while different efficiency levels were detected during incubation in the presence of glucose and tetradecane. Among all strains, Marinobacter spp. strains from bilge waters were proven to be very competitive, although this genus has been poorly reported for biosurfactant production. The high efficiency exhibited by some strains (especially Alcanivorax sp. BIC1A5, Acinetobacter sp. BIC1AC, and Marinobacter sp. BIC3M3) during growth with tetradecane and sunflower oil suggested a promising potential for application in bioremediation purposes and hydrocarbon-enriched wastewater treatment.

Metabolomics - New Insights into Biology and Medicine, 2018

The marine biosphere represents a yet underexploited natural source of bioactive compounds, mainl... more The marine biosphere represents a yet underexploited natural source of bioactive compounds, mainly of microbial origin. Among them, biosurfactants (BSs) are functional molecules, which are attracting a great interest due to their biocompatibility, versatility, and applications in several biotechnological fields. BSs are surface active amphipathic compounds, containing both a hydrophilic and a hydrophobic moiety, which are grouped in low (glycolipids and lipopeptides) or high molecular weight (polymeric complexes) compounds. A number of environmental factors such as pH, salinity, temperature, and nutrient availability can affect microbial BS production. Marine microorganisms with different phylogenetic affiliations and isolated from several marine habitats (e.g., seawater, sediments, and higher organisms) worldwide (spanning from the Mediterranean Sea to Antarctica) have been reported as surfactant producers. However, most of the marine microbial world remains still unexplored. The present chapter aims at giving a general overview on the recent advances about BSs of marine origin, in order to enhance the knowledge inherent their production, chemical characterization and identification, interesting biological properties, and potential biotechnological applications.

The Science of the total environment, Jan 14, 2017

Open fjords are subject to contrasting environmental conditions, owing to meltwater glacial input... more Open fjords are subject to contrasting environmental conditions, owing to meltwater glacial inputs, terrestrial runoff, and marine water mass exchanges, which are exacerbated by anthropogenic and climate perturbations. Following a slope-dependent water circulation, the subtidal sandy sediment belt regulates the convergent transport of nutrients downward the fjord depths, and the effective entrapment of suspended particles and microorganisms. In this study, we aimed at testing how glacial and seawater inputs may influence the bacterial community structure of subtidal sand deposits in the Kongsfjorden. Through total and viable cell counting and an amplicon sequencing approach, we found relevant differences in bacterial community structure along the glacio-marine sampling transect. Viable and high nucleic acid content (HNA) cells represented an important fraction of the total community, generally decreasing toward the glacier front. Besides the predominance of Alpha- and Gammaproteobac...

Applied and environmental microbiology, Jan 27, 2017

Four sponge-associated Antarctic bacteria (i.e. Winogradskyella spp. CAL384 and CAL396, Colwellia... more Four sponge-associated Antarctic bacteria (i.e. Winogradskyella spp. CAL384 and CAL396, Colwellia sp. GW185 and Shewanella sp. CAL606) were selected for the highly mucous appearance of their colonies on agar plates. The production of extracellular polymeric substances (EPSs) was enhanced by a step-by step approach varying the carbon source, substrate and NaCl concentrations, temperature and pH. The EPSs produced under optimal conditions were chemically characterized, resulting in a moderate carbohydrate content (range 15-28%), and the presence of proteins (range 3-24%) and uronic acids (range 3.2-11.9%). The chemical hydrolysis of the carbohydratic portion revealed galactose, glucose, galactosammine and mannose as principal constituents. The potential biotechnological applications of the EPSs were also investigated. The high protein content in the EPSs from Winogradskyella sp. CAL384 was probably responsible for the excellent emulsifying activity towards tested hydrocarbons, with st...

Journal of Environmental Sciences, 2017

Joostella strains are emerging candidates for biosurfactant production. Here such ability was 22 ... more Joostella strains are emerging candidates for biosurfactant production. Here such ability was 22 analyzed for Joostella strain A8 in comparison with Alcanivorax strain A53 and Pseudomonas 23 strain A6, all previously isolated from hydrocarbon enrichment cultures made of polychaete 24 homogenates. In pure cultures Joostella sp. A8 showed the highest stable emulsion percentage 25 (78.33%), hydrophobicity rate (62.67%), and an optimal surface tension reduction during 26 growth in mineral medium supplemented with diesel oil (reduction of about 12 mN/m), thus 27 proving to be highly competitive with Alcanivorax and Pseudomonas strains. During growth in 28 pure culture different level of biodegradation were detected for Alcanivorax strain A53 (52.7%), 29 Pseudomonas strain A6 (38.2%) and Joostella strain A8 (26.8%). When growing in consortia, 30 isolates achieved similar abundance values, with the best efficiency that was observed for the 31 Joostella-Pseudomonas co-culture. Gas-chromatographic analysis revealed an increase in the 32 biodegradation efficiency in co-cultures (about 90%), suggesting that the contemporary action 33 of different bacterial species could improve the process. Results were useful to compare 34 the efficiencies of well-known biosurfactant producers (i.e. Pseudomonas and Alcanivorax 35 representatives) with a still unknown biosurfactant producer, i.e. Joostella, and to confirm them 36 as optimal biosurfactant-producing candidates.

Marine pollution bulletin, Jan 30, 2017

Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), have been detecte... more Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), have been detected in abiotic Arctic matrices: surface sediments and seawater from coastal areas in the Kongsfjorden were collected and analyzed. Levels of PCBs varied depending on the sampling site. Total PCB concentrations were between 11.63 (site C2W) and 27.69pgl(-1) (site AW). These levels were comparable to those reported previously in lake sediments from the northern Svalbard. The occurrence and biodegradation potential of cold-adapted PCB-oxidizing bacteria in seawater and sediment along the fjord was also evaluated. After enrichment with biphenyl, 246 isolates were obtained with 45 of them that were able to grow in the presence of the PCB mixture Aroclor 1242, as the sole carbon source. The catabolic gene bphA was harbored by 17 isolates with affiliates to the genera Algoriphagus, Devosia and Salinibacterium that have been never reported as able to utilize PCBs, thus deserving further investigat...

Journal of basic microbiology, Jan 27, 2016

Among filter-feeders, pennatulids are the most complex and polymorphic members of the cnidarian c... more Among filter-feeders, pennatulids are the most complex and polymorphic members of the cnidarian class Anthozoa. They display a wide distribution throughout all the oceans, constituting a significant component of the sessile megafauna from intertidal to abyssal depths. In this study, a total of 118 bacterial isolates from enrichment cultures, carried out with homogenates of the sea pen Pteroeides spinosum (Ellis, 1764), were screened for hydrocarbon utilization by using the 2,6-dichlorophenol indophenol assay. Among them, 83 hydrocarbon-oxidizing isolates were analyzed for biosurfactant production by standard screening tests (i.e., emulsifying activity, E24 detection, surface tension measurement, microplate assay). The 16S rRNA gene sequencing revealed the affiliation of the most promising isolates to the genera Brevibacterium and Vibrio. Biosurfactant production resulted strongly affected by salinity and temperature conditions, and occurred in the presence of diesel oil and/or crude...

Ecotoxicology, 2015

The effect of heavy metals on the activity of biosurfactants produced by Joostella strain A8 from... more The effect of heavy metals on the activity of biosurfactants produced by Joostella strain A8 from the polychaete Megalomma claparedei was investigated. Biosurfactant activity was first improved by evaluating the influence of abiotic parameters. Higher E 24 indices were achieved at 25°C in mineral salt medium supplemented with 2 % glucose, 3 % sodium chloride (w/v) and 0.1 % ammonium chloride (w/v). Considerable surface tension reduction was never recorded. Heavy metal tolerance was preliminarily assayed by plate diffusion method resulting in the order of toxicity Cd [ Cu [ Zn. The activity of biosurfactants was then evaluated in the presence of heavy metals at different concentrations in liquid cultures that were incubated under optimal conditions for biosurfactant activity. The production of stable emulsions resulted generally higher in the presence of metals. These findings suggest that biosurfactant production could represent a bacterial adaptive strategy to defend cells from a stress condition derived from heavy metals in the bulk environment.

Polar Biology, 2015

The risk of hydrocarbon contamination in marine polar areas is constantly increasing. Autochthono... more The risk of hydrocarbon contamination in marine polar areas is constantly increasing. Autochthonous bacteria, due to their ability to cope and survive under extreme environmental conditions, can play a fundamental role in the hydrocarbon degradation. The degradation process is often enhanced by the production of biosurfactant molecules. The present study reports for the first time on the isolation of biosurfactant-producing bacteria from Arctic and Antarctic shoreline sediments. A total of 199 psychrotolerant bacterial isolates were obtained from hydrocarbonamended (with crude or diesel oil) microcosms. A total of 18 isolates were selected for their ability to grow in the presence of crude oil and produce biosurfactants, as it was revealed by the production of good E 24 values (C50 %) and/or reduction in the surface tension (under 30 mN/m). The positive response of the isolates to both tests suggests a possible production of biosurfactants with emulsifying and interfacial activities. Biosurfactant-producing isolates were mainly affiliated to the genera Rhodococcus (14 isolates), followed by Pseudomonas (two isolates), Pseudoalteromonas (one isolate) and Idiomarina (one isolate). Thin-layer chromatography of biosurfactant crude extracts revealed that the majority of the selected isolates were able to produce glycolipidic surfactants. Our results enlarge the knowledge, which is still poor and fragmentary, on biosurfactant producers from polar areas and indicate marine polar sediments as a source of bacteria with potential applications in the remediation of hydrocarbon-contaminated cold environments.

Bacteria associated with sabellids (Polychaeta: Annelida) as a novel source of surface active compounds

Marine Pollution Bulletin, 2013

A total of 69 bacteria were isolated from crude oil enrichments of the polychaetes Megalomma clap... more A total of 69 bacteria were isolated from crude oil enrichments of the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum, and screened for biosurfactant (BS) production by conventional methods. Potential BS-producers (30 isolates) were primarily selected due to the production of both interesting spots on thin layer chromatography (TLC) plates and highly stable emulsions (E₂₄ ≥ 50%). Only few strains grew on cetyltrimethylammonium bromide and blood agar plates, indicating the probable production of anionic surfactants. The 16S rRNA gene sequencing revealed that selected isolates mainly belonged to the CFB group of Bacteroidetes, followed by Gammaproteobacteria and Alphaproteobacteria. A number of BS-producers belonged to genera (i.e., Cellulophaga, Cobetia, Cohaesibacter, Idiomarina, Pseudovibrio and Thalassospira) that have been never reported as able to produce BSs, even if they have been previously detected in hydrocarbon-enriched samples. Our results suggest that filter-feeding Polychaetes could represent a novel and yet unexplored source of biosurfactant-producing bacteria.

Influence of salinity and temperature on the activity of biosurfactants by polychaete-associated isolates

Environmental Science and Pollution Research, 2013

Influence of different parameters on biosurfactant (BS) activity was carried out on strains that ... more Influence of different parameters on biosurfactant (BS) activity was carried out on strains that were isolated from the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum and additional 30 strains that were previously identified as potential BS producers from crude oil enrichments of the same polychaete specimens. The selection of BS-producing strains from polychaete natural samples was carried out by using standard screening tests. The BS activity by each isolate was evaluated for the effect of salinity and temperature on emulsion production and surface tension reduction, during incubation in mineral medium supplemented with tetradecane or diesel oil. All isolates showed a similar time course of BS activity, and the latter was more influenced by salinity rather than temperature. Some of the BS producers belonged to genera that have not (i.e. Citricoccus, Cellulophaga, Tenacibaculum and Maribacter) or have poorly been (Psychrobacter, Vibrio, and Pseudoalteromonas) reported as able to produce BSs. This is remarkable as some of them have previously been detected in hydrocarbon-enriched samples. Results confirm that filter-feeding polychaetes are an efficient source for the isolation of BS producers.

Microorganisms, 2022

Environmental contamination by heavy metals (HMs) poses several indirect risks to human health, i... more Environmental contamination by heavy metals (HMs) poses several indirect risks to human health, including the co-spreading of genetic traits conferring resistance to both HMs and antibiotics among micro-organisms. Microbial antibiotic resistance (AR) acquisition is enhanced at sites anthropogenically polluted by HMs, as well as in remote systems naturally enriched in HMs, such as hydrothermal vents in the deep sea. However, to date, the possible role of hydrothermal vents at shallower water depths as hot spots of microbial AR gain and spreading has not been tested, despite the higher potential risks associated with the closer vicinity of such ecosystems to coasts and human activities. In this work, we collected waters and sediments at the Panarea shallow-water hydrothermal vents, testing the presence of culturable marine bacteria and their sensitivity to antibiotics and HMs. All of the bacterial isolates showed resistance to at least one antibiotic and one HM and, most notably, 80% ...

Water, 2021

The effects of climate change-induced ice melting on the microbial communities in different glaci... more The effects of climate change-induced ice melting on the microbial communities in different glacial-fed aquatic systems have been reported, but seasonal dynamics remain poorly investigated. In this study, the structural and functional traits of the aquatic microbial community were assessed along with the hydrological and biogeochemical variation patterns of the Arctic Pasvik River under riverine and brackish conditions at the beginning (May = Ice-melt (−)) and during the ice-melting season (July = Ice-melt (+)). The microbial abundance and morphometric analysis showed a spatial diversification between the riverine and brackish stations. Results highlighted different levels of microbial respiration and activities with different carbon and phosphorous utilization pathways, thus suggesting an active biogeochemical cycling along the river especially at the beginning of the ice-melting period. At Ice-melt (−), Gammaproteobacteria and Alphaproteobacteria were dominant in riverine and brackish stations, respectively. Conversely, at Ice-melt (+), the microbial community composition was more homogeneously distributed along the river (Gammaproteobacteria > Alphaproteobacteria > Bacteroidetes). Our findings provide evidence on how riverine microbial communities adapt and respond to seasonal ice melting in glacial-fed aquatic ecosystems.

New Trends in Antarctic Bioprospecting: The Case of Cold-Adapted Bacteria

Extreme Environments

Isolation and Identification of Bacteria with Surface and Antibacterial Activity from the Gut of Mediterranean Grey Mullets

Microorganisms

Fish gut represents a peculiar ecological niche where bacteria can transit and reside to play vit... more Fish gut represents a peculiar ecological niche where bacteria can transit and reside to play vital roles by producing bio-compounds with nutritional, immunomodulatory and other functions. This complex microbial ecosystem reflects several factors (environment, feeding regimen, fish species, etc.). The objective of the present study was the identification of intestinal microbial strains able to produce molecules called biosurfactants (BSs), which were tested for surface and antibacterial activity in order to select a group of probiotic bacteria for aquaculture use. Forty-two bacterial isolates from the digestive tracts of twenty Mediterranean grey mullets were screened for testing emulsifying (E-24), surface and antibiotic activities. Fifty percent of bacteria, ascribed to Pseudomonas aeruginosa, Pseudomonas sp., P. putida and P. anguilliseptica, P. stutzeri, P. protegens and Enterobacter ludwigii were found to be surfactant producers. Of the tested strains, 26.6% exhibited an antiba...

Journal of Marine Science and Engineering

Background: The cold-adapted Idiomarina sp. 185 from Antarctic shoreline sediment and the mesophi... more Background: The cold-adapted Idiomarina sp. 185 from Antarctic shoreline sediment and the mesophilic Idiomarina sp. A19 from the brackish Lake Faro (Italy) were screened for their efficiency in biosurfactant production by a temperature-mediated approach, when grown in rich culture medium and mineral medium supplemented with biphenyl. Methods: oxidation of polychlorobiphenyls and standard screening tests were performed, i.e., E24 index detection, surface tension measurement, blood agar plate and C-TAB agar plate. Results: During incubation in rich medium, the strain Idiomarina sp. A19 produced an excellent stable emulsion, recording an E24 of 73.5%. During growth in mineral medium, isolates showed good efficiency in at least one performed condition by showing species-specific differences related to optimum temperature. In the presence of biphenyl, both Idiomarina isolates created stable emulsions (E24 ≈ 47.5 and 35%, respectively), as well as surface tension reductions of 30.05 and 3...

Journal of Marine Science and Engineering

Luminescent bacteria are a fascinating component of marine microbial communities, often related t... more Luminescent bacteria are a fascinating component of marine microbial communities, often related to the light emissions in deep sea marine organisms. They are mainly affiliated with specific phylogenetic groups, such as Photobacterium, Vibrio, and Photorhabdus, and are sometimes involved in symbiotic relationships. However, the luminescence of some marine organisms remains a poorly understood process, and it is not always certain whether their luminescence is attributable to associated luminescent bacteria. In this study, for the first time, luminescent bacteria were isolated from two deep sea organisms, namely, the cephalopod Neorossia caroli and the teleost Chlorophthalmus agassizi. The isolation was carried out on glycerol-supplemented medium, and the search for the luxAB gene was performed on all isolates as a complementary tool to the culture-dependent techniques to detect bioluminescence by molecular approach. The optimum of salinity, temperature, and pH was evaluated by physio...

Polar Biology

Marine Porifera (sponges) are known to produce several bioactive metabolites having a biotechnolo... more Marine Porifera (sponges) are known to produce several bioactive metabolites having a biotechnological potential, mostly derived from their bacterial symbionts; however, current knowledge on the production of metabolites such as enzymes and antibacterial molecules in sponges living in Antarctic environments is not fully exhaustive and needs further deepened investigation. The interest in discovering the broad spectrum of natural products potentially derived from species adapted to colonize extreme environments stimulates the research toward Antarctic sponge bioprospection. In this study, whole homogenates of Antarctic Demospongiae, belonging to five different species [Haliclona (Rhizoniera) sp., Haliclona (Rhizoniera) dancoi, Microxina sarai, Dendrilla antarctica, and Mycale acerata] were collected from Terra Nova Bay (Ross Sea) and examined for presence and activity of enzymes, including lysozyme, and antibacterial substances. Enzyme activities (leucine aminopeptidase, beta-glucosi...

Minerals, 2022

Marine hydrothermal systems are a special kind of extreme environments associated with submarine ... more Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the living organisms, which have to develop adaptation strategies to survive. Hydrothermal systems have attracted the interest of researchers due to their enormous ecological and biotechnological relevance. From ecological perspective, these acidified habitats are useful natural laboratories to predict the effects of global environmental changes, such as ocean acidification at ecosystem level, through the observation of the marine organism responses to environmental extremes. In addition, hydrothermal vents are known as optimal sources for isolation of thermophilic and hyperthermophilic microbes, with biotechnological potential. This double aspect is the focus of this review, which aims at providing a picture ...

Water, 2022

Antarctic freshwater ecosystems are especially vulnerable to human impacts. Polychlorobiphenyls (... more Antarctic freshwater ecosystems are especially vulnerable to human impacts. Polychlorobiphenyls (PCBs) are persistent organic pollutants that have a long lifetime in the environment. Despite their use having either been phased out or restricted, they are still found in nature, also in remote areas. Once in the environment, the fate of PCBs is strictly linked to bacteria which represent the first step in the transfer of toxic compounds to higher trophic levels. Data on PCB-oxidizing bacteria from polar areas are still scarce and fragmented. In this study, the occurrence of PCB-oxidizing cold-adapted bacteria was evaluated in water and sediment of four coastal lakes at Edmonson Point (Northern Victoria Land, Antarctica). After enrichment with biphenyl, 192 isolates were obtained with 57 of them that were able to grow in the presence of the PCB mixture Aroclor 1242, as the sole carbon source. The catabolic gene bphA, as a proxy for PCB degradation potential, was harbored by 37 isolates...

Native bilge water bacteria as biosurfactant producers and implications in hydrocarbon-enriched wastewater treatment

Journal of Water Process Engineering, 2021

Abstract Seawater and bilge water samples were used to isolate hydrocarbon-degrading bacteria to ... more Abstract Seawater and bilge water samples were used to isolate hydrocarbon-degrading bacteria to be screened for biosurfactant production in the presence of different carbon sources, namely tetradecane, d -glucose and sunflower oil. The panel of tested isolates, affiliated to Alcanivorax, Acinetobacter, Pseudomonas, Halomonas and Marinobacter genera, showed promising results both in terms of emulsifying activity and surface tension reduction. The selected strains Marinobacter sp. BIC3M3, Alcanivorax sp. BIC1A5 and Halomonas sp. BIC1H44 achieved total raw biosurfactant amount of 3.148, 2.922 and 2.596 g/L, respectively. The sunflower oil, here proposed as low-cost carbon source, was successfully used by all strains as substrate for biosurfactant production, with the only exception of Halomonas sp. BIC1H44, while different efficiency levels were detected during incubation in the presence of glucose and tetradecane. Among all strains, Marinobacter spp. strains from bilge waters were proven to be very competitive, although this genus has been poorly reported for biosurfactant production. The high efficiency exhibited by some strains (especially Alcanivorax sp. BIC1A5, Acinetobacter sp. BIC1AC, and Marinobacter sp. BIC3M3) during growth with tetradecane and sunflower oil suggested a promising potential for application in bioremediation purposes and hydrocarbon-enriched wastewater treatment.

Metabolomics - New Insights into Biology and Medicine, 2018

The marine biosphere represents a yet underexploited natural source of bioactive compounds, mainl... more The marine biosphere represents a yet underexploited natural source of bioactive compounds, mainly of microbial origin. Among them, biosurfactants (BSs) are functional molecules, which are attracting a great interest due to their biocompatibility, versatility, and applications in several biotechnological fields. BSs are surface active amphipathic compounds, containing both a hydrophilic and a hydrophobic moiety, which are grouped in low (glycolipids and lipopeptides) or high molecular weight (polymeric complexes) compounds. A number of environmental factors such as pH, salinity, temperature, and nutrient availability can affect microbial BS production. Marine microorganisms with different phylogenetic affiliations and isolated from several marine habitats (e.g., seawater, sediments, and higher organisms) worldwide (spanning from the Mediterranean Sea to Antarctica) have been reported as surfactant producers. However, most of the marine microbial world remains still unexplored. The present chapter aims at giving a general overview on the recent advances about BSs of marine origin, in order to enhance the knowledge inherent their production, chemical characterization and identification, interesting biological properties, and potential biotechnological applications.

The Science of the total environment, Jan 14, 2017

Open fjords are subject to contrasting environmental conditions, owing to meltwater glacial input... more Open fjords are subject to contrasting environmental conditions, owing to meltwater glacial inputs, terrestrial runoff, and marine water mass exchanges, which are exacerbated by anthropogenic and climate perturbations. Following a slope-dependent water circulation, the subtidal sandy sediment belt regulates the convergent transport of nutrients downward the fjord depths, and the effective entrapment of suspended particles and microorganisms. In this study, we aimed at testing how glacial and seawater inputs may influence the bacterial community structure of subtidal sand deposits in the Kongsfjorden. Through total and viable cell counting and an amplicon sequencing approach, we found relevant differences in bacterial community structure along the glacio-marine sampling transect. Viable and high nucleic acid content (HNA) cells represented an important fraction of the total community, generally decreasing toward the glacier front. Besides the predominance of Alpha- and Gammaproteobac...

Applied and environmental microbiology, Jan 27, 2017

Four sponge-associated Antarctic bacteria (i.e. Winogradskyella spp. CAL384 and CAL396, Colwellia... more Four sponge-associated Antarctic bacteria (i.e. Winogradskyella spp. CAL384 and CAL396, Colwellia sp. GW185 and Shewanella sp. CAL606) were selected for the highly mucous appearance of their colonies on agar plates. The production of extracellular polymeric substances (EPSs) was enhanced by a step-by step approach varying the carbon source, substrate and NaCl concentrations, temperature and pH. The EPSs produced under optimal conditions were chemically characterized, resulting in a moderate carbohydrate content (range 15-28%), and the presence of proteins (range 3-24%) and uronic acids (range 3.2-11.9%). The chemical hydrolysis of the carbohydratic portion revealed galactose, glucose, galactosammine and mannose as principal constituents. The potential biotechnological applications of the EPSs were also investigated. The high protein content in the EPSs from Winogradskyella sp. CAL384 was probably responsible for the excellent emulsifying activity towards tested hydrocarbons, with st...

Journal of Environmental Sciences, 2017

Joostella strains are emerging candidates for biosurfactant production. Here such ability was 22 ... more Joostella strains are emerging candidates for biosurfactant production. Here such ability was 22 analyzed for Joostella strain A8 in comparison with Alcanivorax strain A53 and Pseudomonas 23 strain A6, all previously isolated from hydrocarbon enrichment cultures made of polychaete 24 homogenates. In pure cultures Joostella sp. A8 showed the highest stable emulsion percentage 25 (78.33%), hydrophobicity rate (62.67%), and an optimal surface tension reduction during 26 growth in mineral medium supplemented with diesel oil (reduction of about 12 mN/m), thus 27 proving to be highly competitive with Alcanivorax and Pseudomonas strains. During growth in 28 pure culture different level of biodegradation were detected for Alcanivorax strain A53 (52.7%), 29 Pseudomonas strain A6 (38.2%) and Joostella strain A8 (26.8%). When growing in consortia, 30 isolates achieved similar abundance values, with the best efficiency that was observed for the 31 Joostella-Pseudomonas co-culture. Gas-chromatographic analysis revealed an increase in the 32 biodegradation efficiency in co-cultures (about 90%), suggesting that the contemporary action 33 of different bacterial species could improve the process. Results were useful to compare 34 the efficiencies of well-known biosurfactant producers (i.e. Pseudomonas and Alcanivorax 35 representatives) with a still unknown biosurfactant producer, i.e. Joostella, and to confirm them 36 as optimal biosurfactant-producing candidates.

Marine pollution bulletin, Jan 30, 2017

Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), have been detecte... more Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), have been detected in abiotic Arctic matrices: surface sediments and seawater from coastal areas in the Kongsfjorden were collected and analyzed. Levels of PCBs varied depending on the sampling site. Total PCB concentrations were between 11.63 (site C2W) and 27.69pgl(-1) (site AW). These levels were comparable to those reported previously in lake sediments from the northern Svalbard. The occurrence and biodegradation potential of cold-adapted PCB-oxidizing bacteria in seawater and sediment along the fjord was also evaluated. After enrichment with biphenyl, 246 isolates were obtained with 45 of them that were able to grow in the presence of the PCB mixture Aroclor 1242, as the sole carbon source. The catabolic gene bphA was harbored by 17 isolates with affiliates to the genera Algoriphagus, Devosia and Salinibacterium that have been never reported as able to utilize PCBs, thus deserving further investigat...

Journal of basic microbiology, Jan 27, 2016

Among filter-feeders, pennatulids are the most complex and polymorphic members of the cnidarian c... more Among filter-feeders, pennatulids are the most complex and polymorphic members of the cnidarian class Anthozoa. They display a wide distribution throughout all the oceans, constituting a significant component of the sessile megafauna from intertidal to abyssal depths. In this study, a total of 118 bacterial isolates from enrichment cultures, carried out with homogenates of the sea pen Pteroeides spinosum (Ellis, 1764), were screened for hydrocarbon utilization by using the 2,6-dichlorophenol indophenol assay. Among them, 83 hydrocarbon-oxidizing isolates were analyzed for biosurfactant production by standard screening tests (i.e., emulsifying activity, E24 detection, surface tension measurement, microplate assay). The 16S rRNA gene sequencing revealed the affiliation of the most promising isolates to the genera Brevibacterium and Vibrio. Biosurfactant production resulted strongly affected by salinity and temperature conditions, and occurred in the presence of diesel oil and/or crude...

Ecotoxicology, 2015

The effect of heavy metals on the activity of biosurfactants produced by Joostella strain A8 from... more The effect of heavy metals on the activity of biosurfactants produced by Joostella strain A8 from the polychaete Megalomma claparedei was investigated. Biosurfactant activity was first improved by evaluating the influence of abiotic parameters. Higher E 24 indices were achieved at 25°C in mineral salt medium supplemented with 2 % glucose, 3 % sodium chloride (w/v) and 0.1 % ammonium chloride (w/v). Considerable surface tension reduction was never recorded. Heavy metal tolerance was preliminarily assayed by plate diffusion method resulting in the order of toxicity Cd [ Cu [ Zn. The activity of biosurfactants was then evaluated in the presence of heavy metals at different concentrations in liquid cultures that were incubated under optimal conditions for biosurfactant activity. The production of stable emulsions resulted generally higher in the presence of metals. These findings suggest that biosurfactant production could represent a bacterial adaptive strategy to defend cells from a stress condition derived from heavy metals in the bulk environment.

Polar Biology, 2015

The risk of hydrocarbon contamination in marine polar areas is constantly increasing. Autochthono... more The risk of hydrocarbon contamination in marine polar areas is constantly increasing. Autochthonous bacteria, due to their ability to cope and survive under extreme environmental conditions, can play a fundamental role in the hydrocarbon degradation. The degradation process is often enhanced by the production of biosurfactant molecules. The present study reports for the first time on the isolation of biosurfactant-producing bacteria from Arctic and Antarctic shoreline sediments. A total of 199 psychrotolerant bacterial isolates were obtained from hydrocarbonamended (with crude or diesel oil) microcosms. A total of 18 isolates were selected for their ability to grow in the presence of crude oil and produce biosurfactants, as it was revealed by the production of good E 24 values (C50 %) and/or reduction in the surface tension (under 30 mN/m). The positive response of the isolates to both tests suggests a possible production of biosurfactants with emulsifying and interfacial activities. Biosurfactant-producing isolates were mainly affiliated to the genera Rhodococcus (14 isolates), followed by Pseudomonas (two isolates), Pseudoalteromonas (one isolate) and Idiomarina (one isolate). Thin-layer chromatography of biosurfactant crude extracts revealed that the majority of the selected isolates were able to produce glycolipidic surfactants. Our results enlarge the knowledge, which is still poor and fragmentary, on biosurfactant producers from polar areas and indicate marine polar sediments as a source of bacteria with potential applications in the remediation of hydrocarbon-contaminated cold environments.

Bacteria associated with sabellids (Polychaeta: Annelida) as a novel source of surface active compounds

Marine Pollution Bulletin, 2013

A total of 69 bacteria were isolated from crude oil enrichments of the polychaetes Megalomma clap... more A total of 69 bacteria were isolated from crude oil enrichments of the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum, and screened for biosurfactant (BS) production by conventional methods. Potential BS-producers (30 isolates) were primarily selected due to the production of both interesting spots on thin layer chromatography (TLC) plates and highly stable emulsions (E₂₄ ≥ 50%). Only few strains grew on cetyltrimethylammonium bromide and blood agar plates, indicating the probable production of anionic surfactants. The 16S rRNA gene sequencing revealed that selected isolates mainly belonged to the CFB group of Bacteroidetes, followed by Gammaproteobacteria and Alphaproteobacteria. A number of BS-producers belonged to genera (i.e., Cellulophaga, Cobetia, Cohaesibacter, Idiomarina, Pseudovibrio and Thalassospira) that have been never reported as able to produce BSs, even if they have been previously detected in hydrocarbon-enriched samples. Our results suggest that filter-feeding Polychaetes could represent a novel and yet unexplored source of biosurfactant-producing bacteria.

Influence of salinity and temperature on the activity of biosurfactants by polychaete-associated isolates

Environmental Science and Pollution Research, 2013

Influence of different parameters on biosurfactant (BS) activity was carried out on strains that ... more Influence of different parameters on biosurfactant (BS) activity was carried out on strains that were isolated from the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum and additional 30 strains that were previously identified as potential BS producers from crude oil enrichments of the same polychaete specimens. The selection of BS-producing strains from polychaete natural samples was carried out by using standard screening tests. The BS activity by each isolate was evaluated for the effect of salinity and temperature on emulsion production and surface tension reduction, during incubation in mineral medium supplemented with tetradecane or diesel oil. All isolates showed a similar time course of BS activity, and the latter was more influenced by salinity rather than temperature. Some of the BS producers belonged to genera that have not (i.e. Citricoccus, Cellulophaga, Tenacibaculum and Maribacter) or have poorly been (Psychrobacter, Vibrio, and Pseudoalteromonas) reported as able to produce BSs. This is remarkable as some of them have previously been detected in hydrocarbon-enriched samples. Results confirm that filter-feeding polychaetes are an efficient source for the isolation of BS producers.

Microorganisms, 2022

Environmental contamination by heavy metals (HMs) poses several indirect risks to human health, i... more Environmental contamination by heavy metals (HMs) poses several indirect risks to human health, including the co-spreading of genetic traits conferring resistance to both HMs and antibiotics among micro-organisms. Microbial antibiotic resistance (AR) acquisition is enhanced at sites anthropogenically polluted by HMs, as well as in remote systems naturally enriched in HMs, such as hydrothermal vents in the deep sea. However, to date, the possible role of hydrothermal vents at shallower water depths as hot spots of microbial AR gain and spreading has not been tested, despite the higher potential risks associated with the closer vicinity of such ecosystems to coasts and human activities. In this work, we collected waters and sediments at the Panarea shallow-water hydrothermal vents, testing the presence of culturable marine bacteria and their sensitivity to antibiotics and HMs. All of the bacterial isolates showed resistance to at least one antibiotic and one HM and, most notably, 80% ...

Water, 2021

The effects of climate change-induced ice melting on the microbial communities in different glaci... more The effects of climate change-induced ice melting on the microbial communities in different glacial-fed aquatic systems have been reported, but seasonal dynamics remain poorly investigated. In this study, the structural and functional traits of the aquatic microbial community were assessed along with the hydrological and biogeochemical variation patterns of the Arctic Pasvik River under riverine and brackish conditions at the beginning (May = Ice-melt (−)) and during the ice-melting season (July = Ice-melt (+)). The microbial abundance and morphometric analysis showed a spatial diversification between the riverine and brackish stations. Results highlighted different levels of microbial respiration and activities with different carbon and phosphorous utilization pathways, thus suggesting an active biogeochemical cycling along the river especially at the beginning of the ice-melting period. At Ice-melt (−), Gammaproteobacteria and Alphaproteobacteria were dominant in riverine and brackish stations, respectively. Conversely, at Ice-melt (+), the microbial community composition was more homogeneously distributed along the river (Gammaproteobacteria > Alphaproteobacteria > Bacteroidetes). Our findings provide evidence on how riverine microbial communities adapt and respond to seasonal ice melting in glacial-fed aquatic ecosystems.

New Trends in Antarctic Bioprospecting: The Case of Cold-Adapted Bacteria

Extreme Environments

Isolation and Identification of Bacteria with Surface and Antibacterial Activity from the Gut of Mediterranean Grey Mullets

Microorganisms

Fish gut represents a peculiar ecological niche where bacteria can transit and reside to play vit... more Fish gut represents a peculiar ecological niche where bacteria can transit and reside to play vital roles by producing bio-compounds with nutritional, immunomodulatory and other functions. This complex microbial ecosystem reflects several factors (environment, feeding regimen, fish species, etc.). The objective of the present study was the identification of intestinal microbial strains able to produce molecules called biosurfactants (BSs), which were tested for surface and antibacterial activity in order to select a group of probiotic bacteria for aquaculture use. Forty-two bacterial isolates from the digestive tracts of twenty Mediterranean grey mullets were screened for testing emulsifying (E-24), surface and antibiotic activities. Fifty percent of bacteria, ascribed to Pseudomonas aeruginosa, Pseudomonas sp., P. putida and P. anguilliseptica, P. stutzeri, P. protegens and Enterobacter ludwigii were found to be surfactant producers. Of the tested strains, 26.6% exhibited an antiba...