The UV responses of bacterioneuston and bacterioplankton isolates depend on the physiological condition and involve a metabolic shift (original) (raw)
Related papers
Letters in applied microbiology, 2011
Aims: To assess the variability in UV-B (280–320 nm) sensitivity of selected bacterial isolates from the surface microlayer and underlying water of the Ria de Aveiro (Portugal) estuary and their ability to recover from previous UV-induced stress.Methods and Results: Bacterial suspensions were exposed to UV-B radiation (3·3 W m−2). Effects on culturability and activity were assessed from colony counts and 3H-leucine incorporation rates, respectively. Among the tested isolates, wide variability in UV-B-induced inhibition of culturability (37·4–99·3%) and activity (36·0–98·0%) was observed. Incubation of UV-B-irradiated suspensions under reactivating regimes (UV-A, 3·65 W m−2; photosynthetic active radiation, 40 W m−2; dark) also revealed diversity in the extent of recovery from UV-B stress. Trends of enhanced resistance of culturability (up to 15·0%) and enhanced recovery in activity (up to 52·0%) were observed in bacterioneuston isolates.Conclusions: Bacterioneuston isolates were less sensitive and recovered more rapidly from UV-B stress than bacterioplankton isolates, showing enhanced reduction in their metabolism during the irradiation period and decreased culturability during the recovery process compared to bacterioplankton.Significance and Impact of the Study: UV exposure can affect the diversity and activity of microbial communities by selecting UV-resistant strains and alter their metabolic activity towards protective strategies.
Ambient Solar Radiation-Induced Photodamage in Marine Bacterioplankton
Photochemistry and Photobiology, 1996
There has been much recent concern about the effects of increased UV radiation at certain locations on the earth's surface. There have been extensive studies of ultraviolet radiation effects on phytoplankton and primary production, yet the effects of UVB upon bacterioplankton have been largely overlooked. Bacteria play a central role in the cycling of nutrients and energy flow to higher trophic levels, serving as both mineralizers and secondary producers that are consumed by higher organisms. We have begun to investigate the induction of DNA photodamage by UVB in marine planktonic communities using a highly specific radioimmunoassay to measure cyclobutane pyrimidine dimers in samples collected from the northern Gulf of Mexico. DNA damage in the bacterioplankton size-fraction (C0.8 pm) was greater than in the larger eukaryotic size fraction (>0.8 pm <120 pm) in 9 of 10 samples. Die1 patterns of dimer accumulation and repair were observed in surface waters over a 48 h period in the bacterioplankton size fraction and in the larger eukaryotic plankton size fraction. Depth profiles of DNA damage in the bacterioplankton size fraction appear to be dependent on surface water mixing. Damage was greatest in surface waters, decreased with depth and could be detected to 10 m in calm seas. No net accumulation of damage was observed in moderate seas, even at the surface. Solar radiation was found to inhibit significantly both jH-thymidine and 14C-leucine incorporation. Ultraviolet B was responsible for approximately half of the total inhibition of JH-thymidine incorporation, UVA contributing the other half of the inhibition. The vast majority of 14C-leucine incorporation inhibition was due to UVB, suggesting that protein synthesis is less affected by UVA. The results demonstrate that direct measures of DNA damage can be made of indigenous planktonic communities and that bacterioplankton are highly susceptible to UVB damage and may serve as a more sensitive indicator of UVR stress than other microorganisms.
Aquatic Sciences, 2011
The effects of ultraviolet-B (0.4 W m -2 ) radiation on the abundance, diversity and heterotrophic metabolism of bacterioneuston and bacterioplankton communities from Ria de Aveiro (Portugal) were assessed and compared to those of freshwater communities from Lake Vela (Portugal) in microcosm experiments. Exposure to 9 h of artificial ultraviolet radiation (UVR) led to 24-33% reduction in bacterial abundance and up to a 70% decrease in bacterial diversity. Maximum extracellular enzyme activity and monomer incorporation rates were reduced by 16-90% and 80-100%, respectively. Recovery of bacterial activity during post-UV dark incubations ranged from 10 to 100% for extracellular enzyme activity and 40% for monomer incorporation rates. In general, the heterotrophic activity of bacterioneuston was more inhibited by UVR than that of bacterioplankton. However, DGGE profiles revealed greater UVR-induced reductions in the diversity of bacterioplankton compared to bacterioneuston. The similarity between bacterioneuston and bacterioplankton communities in samples collected at early morning was lower than at noon (pre-exposed communities) and increased upon experimental irradiation, possibly indicating selection for UV-resistant bacteria. The observation that UV exposure resulted in enhanced reduction of bacterioneuston activity, but a lower reduction in bacterial diversity accompanied by enhanced dark recovery potential compared to bacterioplankton, indicates re-directioning of bacterioneuston metabolism towards stress defence/recovery strategies rather than the sustained heterotrophic metabolism. Our results indicate that UVR can significantly decrease the abundance, diversity and activity of bacteria inhabiting the surface and sub-surface layers of freshwater and estuarine systems with potentially important impacts on the biogeochemical cycles in these environments.
Marine Bacterial Isolates Display Diverse Responses to UV-B Radiation
Applied and Environmental Microbiology, 1999
The molecular and biological consequences of UV-B radiation were investigated by studying five species of marine bacteria and one enteric bacterium. Laboratory cultures were exposed to an artificial UV-B source and subjected to various post-UV irradiation treatments. Significant differences in survival subsequent to UV-B radiation were observed among the isolates, as measured by culturable counts. UV-B-induced DNA photodamage was investigated by using a highly specific radioimmunoassay to measure cyclobutane pyrimidine dimers (CPDs). The CPDs determined following UV-B exposure were comparable for all of the organisms except Sphingomonas sp. strain RB2256, a facultatively oligotrophic ultramicrobacterium. This organism exhibited little DNA damage and a high level of UV-B resistance. Physiological conditioning by growth phase and starvation did not change the UV-B sensitivity of marine bacteria. The rates of photoreactivation following exposure to UV-B were investigated by using diffe...
Applied and environmental microbiology, 2012
The effects of UV radiation (UVR) on estuarine bacterioneuston and bacterioplankton were assessed in microcosm experiments. Bacterial abundance and DNA synthesis were more affected in bacterioplankton. Protein synthesis was more inhibited in bacterioneuston. Community analysis indicated that UVR has the potential to select resistant bacteria (e.g., Gammaproteobacteria), particularly abundant in bacterioneuston. FIG 1 UV-B dose-dependent variation of abundance of culturable bacteria (A) and total prokaryote abundance (B). Results are expressed as percentages of those for the dark controls. Mean values of triplicate determinations in three subsamples from three independent experiments (n ϭ 27) were plotted. Error bars represent standard deviations. The absence of error bars indicates that standard deviations are too small to see on the scale used.
Contrasting effects of ultraviolet radiation on the growth efficiency of freshwater bacteria
Aquatic Ecology, 2011
In this study, we tested the hypothesis that the growth efficiency of freshwater bacteria is differentially affected by ultraviolet radiation (UVR, 280–400 nm) as mediated through changes in their production and respiration rates. Five bacterial strains affiliated to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria were isolated from different freshwater habitats and exposed in the laboratory to photosynthetically active radiation (PAR) and PAR + UVR, or kept in the dark for 4 h. Afterward, bacterial carbon production and respiration were assessed by measuring leucine incorporation and oxygen consumption rates, respectively. Ultraviolet radiation decreased significantly the bacterial production of Acidovorax sp., Pseudomonas sp. and Actinobacterium MHWTa3, and the respiration rate of Acidovorax sp. and Acinetobacter lwoffii. Measurements of respiration of a natural bacterial community collected from the same lake where A. lwoffii was isolated resulted in significantly higher rates after exposure to PAR + UVR than in the dark. In the presence of UVR, bacterial growth efficiency significantly decreased in Acidovorax sp., Pseudomonas sp., and Actinobacterium MHWTa3, but it increased in A. lwoffii or it remained unchanged in Sphingomonas sp. Our results indicate that although the outcome was strain-specific, UVR has the potential to alter the efficiency by which dissolved organic matter is transformed into bacterial biomass and thus to affect the biogeochemical carbon cycle.
Growth conditions influence UVB sensitivity and oxidative damage in an estuarine bacterial isolate
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2013
The present work aimed to identify the reactive oxygen species (ROS) produced during UV-B exposure and their biochemical targets, in a set of isolates displaying different UV susceptibilities. For that, specific exogenous ROS scavengers (catalase/CAT, superoxide dismutase/SOD, sodium azide and mannitol) were used. Biological effects were assessed from colony counts and heterotrophic activity (glucose uptake). DNA strand breakage, ROS generation, oxidative damage to proteins and lipids were used as markers of oxidative stress. Sodium azide conferred a statistically significant protection in terms of lipid oxidation and cell survival, suggesting that singlet oxygen might play an important role in UV-B induced cell inactivation. Mannitol exerted a significant protection against DNA strand breakage and protein carbonylation, assigning hydroxyl radicals to DNA and protein damage. The addition of exogenous CAT and SOD as well as mannitol significantly protected the capacity for glucose uptake, suggesting that superoxide, H2O2 and the hydroxyl radical are involved in the impairment of activity during UV-B exposure. The observation that amendment with ROS scavengers can sometimes also exert a pro-oxidant effect suggests that the intracellular oxidant status of the cell ultimately determines the efficiency of antioxidant defenses. Suggested Reviewers: Isabel Barcina Phone +351 234 370 784 Fax + 351 234 426 408 The manuscript entitled "Contribution of reactive oxygen species to UV-B-induced damage in bacteria" reports on the study of the identity of the reactive oxygen species (ROS) involved in biological and biochemical damage induced by UV-B radiation on a set of phylogenetically distinct bacterial isolates displaying distinct UV sensitivities using specific exogenous ROS scavengers (catalase/CAT, superoxide dismutase/SOD, sodium azide and mannitol). The results obtained indicate the involvement of singlet oxygen in UV-induced cell inactivation, mediated by its role in lipid peroxidation. The hydroxyl radical was found to contribute for DNA damage and protein oxidation, while superoxide and hydrogen peroxide played important roles in impairment of membrane transport processes during UV-B exposure. To our knowledge this is the first study directly addressing the identity of ROS involved in UV-B-induced damage in bacteria, and considering the relevance and novelty of the reported work we hope that our manuscript is up to the high standards of scientific excellence of Journal of Photochemistry and Photobiology B: Biology. Best regards, Angela Cunha Cover Letter Highlights (for review) Abstract 9 *Manuscript Click here to view linked References
Role of ultraviolet-B radiation on bacterioplankton and the availability of dissolved organic matter
Plant Ecology, 1997
Attenuation of ultraviolet (UV)-radiation into the water column is highly correlated with the concentration of the dissolved organic matter (DOM). Thus UV penetrates deeper into marine waters than into freshwater systems. DOM is efficiently cleaved by solar surface radiation levels consuming more oxygen than bacterial metabolism. This photolytically cleaved DOM exhibits higher absorbance ratios (250/365 nm) than untreated DOM. Natural bacterioplankton reach higher abundance if inoculated in previously solar-exposed DOM than in untreated DOM; during bacterial growth the absorbance ratio declines steadily indicating the utilization of the photolytically cleaved DOM. On the other hand, bacterioplankton are greatly reduced in their activity if exposed to surface solar radiation levels. Photoenzymatic repair of DNA induced by UV-A radiation, however, leads to an efficient recovery of bacterial activity once the UV-B stress is released. Turbulent mixing of the upper layers of the water column leads to a continuous alteration of the UV exposure regime. Close to the surface, bacteria and DOM are exposed to high levels of UV-B leading to a reduction in bacterial activity and to photolysis of DOM. Once mixed into deeper layers where UV-B is attenuated, but sufficient UV-A is remaining to allow photoenzymatic repair, the photolytically cleaved DOM is efficiently taken up by bacterioplankton leading to even higher bacterial activity than prior to the exposure. Thus, the overall effect of UV on bacterioplankton is actually an enhancement of bacterial activity despite their lack of protective pigments.
Sensitivity of selected bacterial species to UV radiation
Current Microbiology, 1995
The effect of exposure of bacterial suspensions to UV radiation by means of the dose-response curves was assessed. The D37 and D10 values were used for subsequent statistical analysis of the results. The aim of this article is to evaluate the sensitivity to UV radiation of several microorganisms of different habitats (Rhizobium melitoti, Rhodobacter sphaeroides, Escherichia coli, and Deinococcus radiodurans), two mutants with nonfunctional SOS DNA repair system (R. meliloti recAand E. coli recA-), and a mutant in the synthesis of carotenoids (R. sphaeroides crtD). The results reveal that D. radiodurans was an extremely resistant bacterium, R. meliloti was more resistant than R. sphaeroides, and E. coil was the most sensitive bacterium tested. The high sensitivity ofrecAmutants was also verify. Moreover, it seems that the possession of pigments had no important effect in the sensitivity ofR. sphaeroides to UV radiation.