Sri Ramkumar Vijayan | Agricultural Research Organization of Israel (original) (raw)

Papers by Sri Ramkumar Vijayan

Journal of Polymers and the Environment

ACS Sustainable Chemistry & Engineering

In the present study, evaluation of antimicrobial, antioxidant, phytochemical constituents and to... more In the present study, evaluation of antimicrobial, antioxidant, phytochemical constituents and toxicological properties of six coastal medicinal plants (CMP's) such as Ipomea biloba, Cantharanthus roseus, Cymbopogon citratus, Vitex negundo, Thespesia populnea and Pandanus tectorius was done. The maximum antimicrobial activity was recorded by methanolic extracts of V. negundo and T. populnea against bacterial and fungal pathogens. Similarly, methanolic extracts of V. negundo and T. populnea evidenced highest antioxidant properties. The extract of T. populnea showed the maximum cytotoxicity against Artemia salina with the LC 50 value of 478.11 mg/ml. The hemolytic property of CMP's extracts was V. negundo (8.91%), T. populnea (21%) and C. citratus (64%) also the hemolytic index did not show any hemolysis of human erythrocytes. Furthermore, the TLC separation of V. negundo and T. populnea extracts exhibited the presence of Flavonoids (Rf-0.74) and Terpenoids (Rf-0.64). The present findings propose the promising clinical applications of selected CMP's.

A simple eco-friendly approach for the hasty synthesis of stable, potent and benign silver nanopa... more A simple eco-friendly approach for the hasty synthesis of stable, potent and benign silver nanoparticles (AgNPs) using seagrass, Syringodium isoetifolium was proposed and described here. The UV-Vis, DLS, XRD, AFM, FESEM, EDX and HRTEM analysis highly characterized and confirmed the presence of polydispersed (2-50 nm) spherical and stable AgNPs. FT-IR and phytochemical analysis suggested that the proteins act as reducing and also as capping agent. A hypothetical approach using bioinformatics tools revealed that the Phytochrome B protein of S. isoetifolium might be responsible for the biosynthesis of NPs. Furthermore, biosynthesized AgNPs showed magnificent antibacterial activity against thirteen clinical bacterial pathogens with maximum zone of inhibition of 14.3 AE 0.12 mm due to their smaller size and longer stability even at minimal nanomolar (nM) concentration. In addition, the MIC and MBC values also suggested the same. Moreover, the percentage of haemolysis (8.49 AE 3.10 to 73.34 AE 1.79%) and haemolytic index revealed the satisfactory biocompatibility of AgNPs that showed less/no haemolysis up to 3 nM concentration. Further, the toxicity effect of biosynthesized AgNPs against the brine shrimp, Artemia salina exhibited significantly increasing mortality (13 AE 4.7 to 100%) with LC 50 value at 4 nM concentration. Thus, the optical property, crystal structure, size, shape, stability, bactericidal activity, cytotoxicity, and biocompatibility apparently proved that the biologically synthesized AgNPs have typical properties of nanomaterials.

Marine bionanotechnology is one of the most promising areas of research in modern science and tec... more Marine bionanotechnology is one of the most promising areas of research in modern science and technology. Although there are multitude methods for the synthesis of nanoparticles (NPs), there is an increasing attention in developing high-yield, low-cost, non-toxic and eco-friendly procedures. The vital advantages of greener synthesis are cost-effective, reduced usage of toxic chemicals and abundant availability of resources. During the last ten years, there have been many biological entities used to elevate novel, greener and affordable methods for the metal NPs synthesis. Rate of synthesis and stability are higher for plant material mediated NPs. However, in comparison with terrestrial resources, marine resources have not been fully explored for synthesis of noble metal NPs. Our present review is designed to speculate the importance of usage of vast marine resources and its mediated NPs synthesis, in particular seaweed-mediated NPs synthesis to overcome the limitations involved in physical and chemical methods. Finally, recent advancements in greener synthesis of metal NPs, their size, distribution, morphology and applications such as antimicrobial, antifouling and anticancer potentials are briefly described along with portraying the prospective scope of research in this field without any negative impact on the environment.

A novel green route has approached for the synthesis of silver doped fluor-hydroxyapatite/␤-cyclo... more A novel green route has approached for the synthesis of silver doped fluor-hydroxyapatite/␤-cyclodextrin composite by the assistance of fluorine-based ionic liquid. The selected [BMIM]BF 4 ionic liquid for this work plays a dual role as fluoride source and templating agent. It helps to improve the crystalline structures and the shape of the composites. The crystallinity, surface morphology, topographical studies of the synthesized composite were validated. The XRD results of the composite show typical Ag reflection peaks at 38.1 • , 44.2 • and 63.4 • . The ionic liquid assisted composite displayed the hexagonal shaped HA particles, which are surrounded by spherical nano-Ag particles and these particles are uniformly dispersed in the ␤-cyclodextrin matrix in both horizontal and cross sections from surface morphology observations. The Ionic liquid assisted silver doped fluor-hydroxyapatite/␤-cyclodextrin composite exhibited very good antibacterial activities against Escherichia coli, Salmonella typhi, Klebsiella pneumonia and Serratia liquefaciens pathogens. The antibacterial proficiencies were established using Confocal Laser Scanning Microscopic developed biofilms images and bacterial growth curve analysis. The cytotoxicity results of the ionic liquid assisted composite analyzed by cell proliferation in vitro studies using human osteosarcoma cell line (MG-63) and this study has shown excellent biocompatibility. (S. M.). phate primarily nano-hydroxyapatite (69%), it could be natural or synthetic has given an excellent biocompatibility with bones, teeth, skin and muscles .

A novel biomimetic f-HAp/PVP/Ag nanocomposite was synthesized under the ionic liquid medium, whic... more A novel biomimetic f-HAp/PVP/Ag nanocomposite was synthesized under the ionic liquid medium, which was composed of inorganic and organic nanofillers like fluor-hydroxyapatite, silver nanoparticles and polyvinyl pyrrolidone. In composite synthesis, the first time we were used fluorine based ionic liquid for the fluorine contents on the fluor-hydroxyapatite nanoparticles which were resulting in very good crosslinking and interfacial bonding with the PVP and Ag nanoparticles. Ionic liquid has assisted good morphological structure of both inorganic materials. The chemical interaction and crystallinity changes of the nanocomposite were evaluated by FTIR and XRD studies. The surface morphology and composition of the samples were observed by FE-SEM, HR-TEM and EDS analyses. This report reveals that the greener approach for synthesis of fluor-hydroxyapatite nanocomposite and sustained delivery of silver and fluorine ions from the fluor-hydroxyapatite surface to the bacterial surface have been reducing the bacterial growth rate which was evaluated by different pathogenic bacterial strains via different methods and it also favourable cytotoxicity effect with human osteosarcoma (MG-63) cells.

Silver and gold nanoparticles were synthesized using an aqueous extract of the seaweed Turbinaria... more Silver and gold nanoparticles were synthesized using an aqueous extract of the seaweed Turbinaria conoides and their antibiofilm activity against marine biofilm forming bacteria is reported here. The UV-Vis spectra showed the characteristics SPR absorption band for Ag NPs at 421 and for Au NPs at 538 nm. Further, the synthesized nanoparticles were characterized using FT-IR, XRD, FESEM, EDX, and HRTEM analysis. Spherical and triangular nanostructures of the Ag and Au nanoparticles were observed between the size ranges of 2–17 nm and 2–19 nm, respectively. The synthesized Ag NPs are efficient in controlling the bacterial biofilm formation; however, Au NPs did not show any remarkable antibiofilm activity. The maximum zone of inhibition was recorded against E. coli (17.6 ± 0.42 mm), followed by Salmonella sp., S. liquefaciens, and A. hydrophila. The macrotube dilution method inferred the MIC (20–40 í µí¼‡L mL −1) and MBC (40–60 í µí¼‡L mL −1) of Ag NPs. The CLSM images clearly showed the weak adherence and disintegrating biofilm formation of marine biofilm bacterial strains treated with Ag NPs. The Artemia cytotoxicity assay recorded the LC 50 value of 88.914 ± 5.04 í µí¼‡L mL −1. Thus the present study proved the efficiency of Ag NPs as a potent antimicrofouling agent and became the future perspective for the possible usage in the biofouling related issues in the aquaculture installations and other marine systems.

Environmental Monitoring and Assessment, 2015

The present study was undertaken to investigate the diversity of mangrove-associated bacterial ge... more The present study was undertaken to investigate the diversity of mangrove-associated bacterial genera at Manakudy estuary, Southwest coast of India. The root and rhizosphere sediments of both mangrove and their associated plants were collected from chosen area. Results inferred that the maximum nutrients, THB density, and diversity indices were recorded in rhizosphere and root sample of Avicennia officinalis. Altogether, 258 bacterial strains were isolated from the chosen mangrove samples and screened for nitrogen fixing and phosphate solubilizing ability. Screened result inferred that, 36.43 % isolates had nitrogen fixing and 29.45 % isolates had phosphate solubilizing ability. Here, the genus Bacillus spp. (21.71 %) was the most dominant genera. The bacterial diversity indices, i.e., univariate analysis showed remarkable variation between the chosen samples; however, maximum diversity indices was registered by rhizosphere and root sample of A. officinalis. The 95 % confidence interval and ellipse showed that samples were well mendacious within AvTD and VarTD. Likewise, the multivariate analysis like similarity percentage was good discriminator from 16.64 to 100 % by Bray-Curtis dissimilarity. The prinicipal component analysis (PCA) showed marked variation between the tested bacterial communities. Cluster analysis and non-metric multi-dimensional scaling (MDS) were grouped by Bray-Curtis similarity index which strongly evidence that the rhizosphere and root samples of A. officinalis were highly diversified in the study area.

In shallow coastal regions, bacteria are believed to play an important role in the recycling of m... more In shallow coastal regions, bacteria are believed to play an important role in the recycling of matter. A study concerning total heterotrophic bacteria and phosphate solubilizing bacterial populations in the water and sediment samples of the Karangadu and Devipattinam, Palk Strait, Southeast coast of India were carried out from July 2008-May 2009. THB and PSB were high in November month. THB was ranged between 5.23-9.75x10 5 cells ml -1 and 2.36-11.21x10 5 cells g -1 and PSB was fluctuated between 0.98-5.6x10 3 cells ml -1 and 1.12-6.84x10 3 cells g -1 from water and sediment samples respectively. Among all the PSB isolates, twenty proficient PSB strains were selected for phosphatase activity and P solubilization efficiency under in vitro condition.

A total of 17 bacterial isolates including Azotobacter chroococcum (N=5), Azotobacter beijerincki... more A total of 17 bacterial isolates including Azotobacter chroococcum (N=5), Azotobacter beijerinckii (N=4), Pseudomonas aeruginosa (N=4), and Bacillus sp (N=4) were isolated and tested for siderophore, HCN, ammonia and indole acetic acid production in vitro. The bacterial cultures were positive for siderophore, HCN and ammonia. Among the isolates, The amount of IAA produced by Azotobacter chroococcum and Azotobacter beijerinckii were 23.6 and 17.6 µg ml -1 respectiviely, whereas the phosphate solubilizers Pseudomonas aeruginosa and Bacillus sp showed maximum IAA production of 26.5 and 19.8 µg ml -1 of IAA in Luria Bertani broth. The single inoculation effects of N 2 -fixing and PS bacteria on the growth, chlorophyll content, P and N content of black gram plants in green house experiments varied considerably between the treatments. The N contents in roots and shoots differed considerably among the treatments.

Journal of environmental biology / Academy of Environmental Biology, India, 2014

In this study, methanogenic consortia were isolated and characterized from eight different sedime... more In this study, methanogenic consortia were isolated and characterized from eight different sediment samples of mangrove ecosystem located in Ennore, Chennai. Out of eight samples, two consortia (SpR6 and SSS8) were consistent and good at methane production. The maximum methane (6.95%) was produced by the sample collected from the swampy sediments (SSS8) of mangrove environment on 5th day of incubation. The pure colonies of methanogenic consortia (SSS8) isolated in the roll tube produced maximum methane (5%) on 70th day. Further, all the isolated consortia produced methane when it was grown with and without gaseous (H2 and CO2) substrate and the maximum production of 15.1% (SSS8) on 12th day of incubation in the presence of gaseous substrate. Also, the methanogenic consortium isolated from the mangrove environment produced significant amount of methane in tyndallized cow dung (4.7%) than in raw cow dung. The fluorescence of isolated colony and individual cells of methanogenic consort...

Archives of Applied …, 2011

Samples of water and sediment were collected from July to December 2009 in Kottaipattinam coast (... more Samples of water and sediment were collected from July to December 2009 in Kottaipattinam coast (Palk Strait, Southeast coast of India). Kottaipattinam coast is one of the major fish landing centre in Palk Strait and receives a considerable amount of sewage and man made waste. Qualitative and quantitative analysis of the composition of the microbial flora were conducted on samples from three stations. The highest bacterial densities, in water and in sediment samples, were found in December and the lowest, in August. Among Gram-negative bacteria, the predominant genus was Pseudomonas; Aeromonas, Vibrio and Flavobacterium were also recorded. Gram-positive bacilli were abundant at all sampling points. Along with physico-chemical parameters were also monitored at every month of sampling.

Archives of Applied …, 2011

Water samples from the Karangadu coast, Palk Strait, Southeast coast of India were sampled bimont... more Water samples from the Karangadu coast, Palk Strait, Southeast coast of India were sampled bimonthly for enumeration of total heterotrophic bacteria as well as phosphate solubilizing bacteria between January and December 2008.THB was high in November month and PSB was also high in September and November months, population density of THB ranged from 4.25-8.25x10 6 cells ml -1 and phosphate solubilizing bacterial population from 2.02-2.6x10 3 cells ml -1 . A wide variation in the capacity to solubilize phosphorous by the isolates of PSB were observed. Further, all the isolates were able to secrete phytohormones like Indole acetic acid (IAA) and Gibberellic acid (GA 3 ) and also studied phosphatse activity by efficient PSB isolates under in vitro condition.

Biocatalysis and Agriculture Biotechnology, Nov 1, 2014

Biofouling is a panic issue in the marine environment where the major perpetrator is the biofilm ... more Biofouling is a panic issue in the marine environment where the major perpetrator is the biofilm forming microbial cells like bacterial groups. Hence, the present study was focused to study the diversity and density of marine biofilm forming bacteria on different experimental panels immersed in Palk Bay region. The results are inferred that the density and distribution of biofilm forming bacterial groups were significantly (P>0.05) varied, where as the Pseudomonas spp. (15.78–22.22%) had maximum distribution in the immersed all the test panels. The current antifouling paints create toxic effects on non-target organisms. Oflate, natural products were replaced with current toxic antifouling problems. Int he present study,the four marine plants viz. two sea weeds (Sarconema furcellatum, Sargassum wightii) species and two seagrasses (Syringodium isoetifolium, Cymodocea serrulata) species were selected to screen their antimicrofouling activity.From this, the crude acetone extract of S. furcellatum exhibited the good antimicrofouling activity over the other marine plant extracts against test microfoulers ; anti-
bacterial (770.16to1370.26 mm) with least concentration of MIC and MBC values (12.5–25 mg/ml and 25–50 mg/ml), antimicroalgal (50–300 mg/ml) and Artemia cytotoxicity (LC50 133.88 mg/ml; P>0.001) and anticrustacen activity was significantly (P>0.05) increased mortality with increasing test concentrations of crude extracts. Also, phytochemical studies of the four marine plants revealed the presence of
chemical constituents such as flavanoids, alkaloids, phenols and sugars. Further studies on the purification and identification of active compounds from S. furcellatum might help to characterize the nature of eco-friendly antifouling compounds filed study.

Journal of Polymers and the Environment

ACS Sustainable Chemistry & Engineering

In the present study, evaluation of antimicrobial, antioxidant, phytochemical constituents and to... more In the present study, evaluation of antimicrobial, antioxidant, phytochemical constituents and toxicological properties of six coastal medicinal plants (CMP's) such as Ipomea biloba, Cantharanthus roseus, Cymbopogon citratus, Vitex negundo, Thespesia populnea and Pandanus tectorius was done. The maximum antimicrobial activity was recorded by methanolic extracts of V. negundo and T. populnea against bacterial and fungal pathogens. Similarly, methanolic extracts of V. negundo and T. populnea evidenced highest antioxidant properties. The extract of T. populnea showed the maximum cytotoxicity against Artemia salina with the LC 50 value of 478.11 mg/ml. The hemolytic property of CMP's extracts was V. negundo (8.91%), T. populnea (21%) and C. citratus (64%) also the hemolytic index did not show any hemolysis of human erythrocytes. Furthermore, the TLC separation of V. negundo and T. populnea extracts exhibited the presence of Flavonoids (Rf-0.74) and Terpenoids (Rf-0.64). The present findings propose the promising clinical applications of selected CMP's.

A simple eco-friendly approach for the hasty synthesis of stable, potent and benign silver nanopa... more A simple eco-friendly approach for the hasty synthesis of stable, potent and benign silver nanoparticles (AgNPs) using seagrass, Syringodium isoetifolium was proposed and described here. The UV-Vis, DLS, XRD, AFM, FESEM, EDX and HRTEM analysis highly characterized and confirmed the presence of polydispersed (2-50 nm) spherical and stable AgNPs. FT-IR and phytochemical analysis suggested that the proteins act as reducing and also as capping agent. A hypothetical approach using bioinformatics tools revealed that the Phytochrome B protein of S. isoetifolium might be responsible for the biosynthesis of NPs. Furthermore, biosynthesized AgNPs showed magnificent antibacterial activity against thirteen clinical bacterial pathogens with maximum zone of inhibition of 14.3 AE 0.12 mm due to their smaller size and longer stability even at minimal nanomolar (nM) concentration. In addition, the MIC and MBC values also suggested the same. Moreover, the percentage of haemolysis (8.49 AE 3.10 to 73.34 AE 1.79%) and haemolytic index revealed the satisfactory biocompatibility of AgNPs that showed less/no haemolysis up to 3 nM concentration. Further, the toxicity effect of biosynthesized AgNPs against the brine shrimp, Artemia salina exhibited significantly increasing mortality (13 AE 4.7 to 100%) with LC 50 value at 4 nM concentration. Thus, the optical property, crystal structure, size, shape, stability, bactericidal activity, cytotoxicity, and biocompatibility apparently proved that the biologically synthesized AgNPs have typical properties of nanomaterials.

Marine bionanotechnology is one of the most promising areas of research in modern science and tec... more Marine bionanotechnology is one of the most promising areas of research in modern science and technology. Although there are multitude methods for the synthesis of nanoparticles (NPs), there is an increasing attention in developing high-yield, low-cost, non-toxic and eco-friendly procedures. The vital advantages of greener synthesis are cost-effective, reduced usage of toxic chemicals and abundant availability of resources. During the last ten years, there have been many biological entities used to elevate novel, greener and affordable methods for the metal NPs synthesis. Rate of synthesis and stability are higher for plant material mediated NPs. However, in comparison with terrestrial resources, marine resources have not been fully explored for synthesis of noble metal NPs. Our present review is designed to speculate the importance of usage of vast marine resources and its mediated NPs synthesis, in particular seaweed-mediated NPs synthesis to overcome the limitations involved in physical and chemical methods. Finally, recent advancements in greener synthesis of metal NPs, their size, distribution, morphology and applications such as antimicrobial, antifouling and anticancer potentials are briefly described along with portraying the prospective scope of research in this field without any negative impact on the environment.

A novel green route has approached for the synthesis of silver doped fluor-hydroxyapatite/␤-cyclo... more A novel green route has approached for the synthesis of silver doped fluor-hydroxyapatite/␤-cyclodextrin composite by the assistance of fluorine-based ionic liquid. The selected [BMIM]BF 4 ionic liquid for this work plays a dual role as fluoride source and templating agent. It helps to improve the crystalline structures and the shape of the composites. The crystallinity, surface morphology, topographical studies of the synthesized composite were validated. The XRD results of the composite show typical Ag reflection peaks at 38.1 • , 44.2 • and 63.4 • . The ionic liquid assisted composite displayed the hexagonal shaped HA particles, which are surrounded by spherical nano-Ag particles and these particles are uniformly dispersed in the ␤-cyclodextrin matrix in both horizontal and cross sections from surface morphology observations. The Ionic liquid assisted silver doped fluor-hydroxyapatite/␤-cyclodextrin composite exhibited very good antibacterial activities against Escherichia coli, Salmonella typhi, Klebsiella pneumonia and Serratia liquefaciens pathogens. The antibacterial proficiencies were established using Confocal Laser Scanning Microscopic developed biofilms images and bacterial growth curve analysis. The cytotoxicity results of the ionic liquid assisted composite analyzed by cell proliferation in vitro studies using human osteosarcoma cell line (MG-63) and this study has shown excellent biocompatibility. (S. M.). phate primarily nano-hydroxyapatite (69%), it could be natural or synthetic has given an excellent biocompatibility with bones, teeth, skin and muscles .

A novel biomimetic f-HAp/PVP/Ag nanocomposite was synthesized under the ionic liquid medium, whic... more A novel biomimetic f-HAp/PVP/Ag nanocomposite was synthesized under the ionic liquid medium, which was composed of inorganic and organic nanofillers like fluor-hydroxyapatite, silver nanoparticles and polyvinyl pyrrolidone. In composite synthesis, the first time we were used fluorine based ionic liquid for the fluorine contents on the fluor-hydroxyapatite nanoparticles which were resulting in very good crosslinking and interfacial bonding with the PVP and Ag nanoparticles. Ionic liquid has assisted good morphological structure of both inorganic materials. The chemical interaction and crystallinity changes of the nanocomposite were evaluated by FTIR and XRD studies. The surface morphology and composition of the samples were observed by FE-SEM, HR-TEM and EDS analyses. This report reveals that the greener approach for synthesis of fluor-hydroxyapatite nanocomposite and sustained delivery of silver and fluorine ions from the fluor-hydroxyapatite surface to the bacterial surface have been reducing the bacterial growth rate which was evaluated by different pathogenic bacterial strains via different methods and it also favourable cytotoxicity effect with human osteosarcoma (MG-63) cells.

Silver and gold nanoparticles were synthesized using an aqueous extract of the seaweed Turbinaria... more Silver and gold nanoparticles were synthesized using an aqueous extract of the seaweed Turbinaria conoides and their antibiofilm activity against marine biofilm forming bacteria is reported here. The UV-Vis spectra showed the characteristics SPR absorption band for Ag NPs at 421 and for Au NPs at 538 nm. Further, the synthesized nanoparticles were characterized using FT-IR, XRD, FESEM, EDX, and HRTEM analysis. Spherical and triangular nanostructures of the Ag and Au nanoparticles were observed between the size ranges of 2–17 nm and 2–19 nm, respectively. The synthesized Ag NPs are efficient in controlling the bacterial biofilm formation; however, Au NPs did not show any remarkable antibiofilm activity. The maximum zone of inhibition was recorded against E. coli (17.6 ± 0.42 mm), followed by Salmonella sp., S. liquefaciens, and A. hydrophila. The macrotube dilution method inferred the MIC (20–40 í µí¼‡L mL −1) and MBC (40–60 í µí¼‡L mL −1) of Ag NPs. The CLSM images clearly showed the weak adherence and disintegrating biofilm formation of marine biofilm bacterial strains treated with Ag NPs. The Artemia cytotoxicity assay recorded the LC 50 value of 88.914 ± 5.04 í µí¼‡L mL −1. Thus the present study proved the efficiency of Ag NPs as a potent antimicrofouling agent and became the future perspective for the possible usage in the biofouling related issues in the aquaculture installations and other marine systems.

Environmental Monitoring and Assessment, 2015

The present study was undertaken to investigate the diversity of mangrove-associated bacterial ge... more The present study was undertaken to investigate the diversity of mangrove-associated bacterial genera at Manakudy estuary, Southwest coast of India. The root and rhizosphere sediments of both mangrove and their associated plants were collected from chosen area. Results inferred that the maximum nutrients, THB density, and diversity indices were recorded in rhizosphere and root sample of Avicennia officinalis. Altogether, 258 bacterial strains were isolated from the chosen mangrove samples and screened for nitrogen fixing and phosphate solubilizing ability. Screened result inferred that, 36.43 % isolates had nitrogen fixing and 29.45 % isolates had phosphate solubilizing ability. Here, the genus Bacillus spp. (21.71 %) was the most dominant genera. The bacterial diversity indices, i.e., univariate analysis showed remarkable variation between the chosen samples; however, maximum diversity indices was registered by rhizosphere and root sample of A. officinalis. The 95 % confidence interval and ellipse showed that samples were well mendacious within AvTD and VarTD. Likewise, the multivariate analysis like similarity percentage was good discriminator from 16.64 to 100 % by Bray-Curtis dissimilarity. The prinicipal component analysis (PCA) showed marked variation between the tested bacterial communities. Cluster analysis and non-metric multi-dimensional scaling (MDS) were grouped by Bray-Curtis similarity index which strongly evidence that the rhizosphere and root samples of A. officinalis were highly diversified in the study area.

In shallow coastal regions, bacteria are believed to play an important role in the recycling of m... more In shallow coastal regions, bacteria are believed to play an important role in the recycling of matter. A study concerning total heterotrophic bacteria and phosphate solubilizing bacterial populations in the water and sediment samples of the Karangadu and Devipattinam, Palk Strait, Southeast coast of India were carried out from July 2008-May 2009. THB and PSB were high in November month. THB was ranged between 5.23-9.75x10 5 cells ml -1 and 2.36-11.21x10 5 cells g -1 and PSB was fluctuated between 0.98-5.6x10 3 cells ml -1 and 1.12-6.84x10 3 cells g -1 from water and sediment samples respectively. Among all the PSB isolates, twenty proficient PSB strains were selected for phosphatase activity and P solubilization efficiency under in vitro condition.

A total of 17 bacterial isolates including Azotobacter chroococcum (N=5), Azotobacter beijerincki... more A total of 17 bacterial isolates including Azotobacter chroococcum (N=5), Azotobacter beijerinckii (N=4), Pseudomonas aeruginosa (N=4), and Bacillus sp (N=4) were isolated and tested for siderophore, HCN, ammonia and indole acetic acid production in vitro. The bacterial cultures were positive for siderophore, HCN and ammonia. Among the isolates, The amount of IAA produced by Azotobacter chroococcum and Azotobacter beijerinckii were 23.6 and 17.6 µg ml -1 respectiviely, whereas the phosphate solubilizers Pseudomonas aeruginosa and Bacillus sp showed maximum IAA production of 26.5 and 19.8 µg ml -1 of IAA in Luria Bertani broth. The single inoculation effects of N 2 -fixing and PS bacteria on the growth, chlorophyll content, P and N content of black gram plants in green house experiments varied considerably between the treatments. The N contents in roots and shoots differed considerably among the treatments.

Journal of environmental biology / Academy of Environmental Biology, India, 2014

In this study, methanogenic consortia were isolated and characterized from eight different sedime... more In this study, methanogenic consortia were isolated and characterized from eight different sediment samples of mangrove ecosystem located in Ennore, Chennai. Out of eight samples, two consortia (SpR6 and SSS8) were consistent and good at methane production. The maximum methane (6.95%) was produced by the sample collected from the swampy sediments (SSS8) of mangrove environment on 5th day of incubation. The pure colonies of methanogenic consortia (SSS8) isolated in the roll tube produced maximum methane (5%) on 70th day. Further, all the isolated consortia produced methane when it was grown with and without gaseous (H2 and CO2) substrate and the maximum production of 15.1% (SSS8) on 12th day of incubation in the presence of gaseous substrate. Also, the methanogenic consortium isolated from the mangrove environment produced significant amount of methane in tyndallized cow dung (4.7%) than in raw cow dung. The fluorescence of isolated colony and individual cells of methanogenic consort...

Archives of Applied …, 2011

Samples of water and sediment were collected from July to December 2009 in Kottaipattinam coast (... more Samples of water and sediment were collected from July to December 2009 in Kottaipattinam coast (Palk Strait, Southeast coast of India). Kottaipattinam coast is one of the major fish landing centre in Palk Strait and receives a considerable amount of sewage and man made waste. Qualitative and quantitative analysis of the composition of the microbial flora were conducted on samples from three stations. The highest bacterial densities, in water and in sediment samples, were found in December and the lowest, in August. Among Gram-negative bacteria, the predominant genus was Pseudomonas; Aeromonas, Vibrio and Flavobacterium were also recorded. Gram-positive bacilli were abundant at all sampling points. Along with physico-chemical parameters were also monitored at every month of sampling.

Archives of Applied …, 2011

Water samples from the Karangadu coast, Palk Strait, Southeast coast of India were sampled bimont... more Water samples from the Karangadu coast, Palk Strait, Southeast coast of India were sampled bimonthly for enumeration of total heterotrophic bacteria as well as phosphate solubilizing bacteria between January and December 2008.THB was high in November month and PSB was also high in September and November months, population density of THB ranged from 4.25-8.25x10 6 cells ml -1 and phosphate solubilizing bacterial population from 2.02-2.6x10 3 cells ml -1 . A wide variation in the capacity to solubilize phosphorous by the isolates of PSB were observed. Further, all the isolates were able to secrete phytohormones like Indole acetic acid (IAA) and Gibberellic acid (GA 3 ) and also studied phosphatse activity by efficient PSB isolates under in vitro condition.

Biocatalysis and Agriculture Biotechnology, Nov 1, 2014

Biofouling is a panic issue in the marine environment where the major perpetrator is the biofilm ... more Biofouling is a panic issue in the marine environment where the major perpetrator is the biofilm forming microbial cells like bacterial groups. Hence, the present study was focused to study the diversity and density of marine biofilm forming bacteria on different experimental panels immersed in Palk Bay region. The results are inferred that the density and distribution of biofilm forming bacterial groups were significantly (P>0.05) varied, where as the Pseudomonas spp. (15.78–22.22%) had maximum distribution in the immersed all the test panels. The current antifouling paints create toxic effects on non-target organisms. Oflate, natural products were replaced with current toxic antifouling problems. Int he present study,the four marine plants viz. two sea weeds (Sarconema furcellatum, Sargassum wightii) species and two seagrasses (Syringodium isoetifolium, Cymodocea serrulata) species were selected to screen their antimicrofouling activity.From this, the crude acetone extract of S. furcellatum exhibited the good antimicrofouling activity over the other marine plant extracts against test microfoulers ; anti-
bacterial (770.16to1370.26 mm) with least concentration of MIC and MBC values (12.5–25 mg/ml and 25–50 mg/ml), antimicroalgal (50–300 mg/ml) and Artemia cytotoxicity (LC50 133.88 mg/ml; P>0.001) and anticrustacen activity was significantly (P>0.05) increased mortality with increasing test concentrations of crude extracts. Also, phytochemical studies of the four marine plants revealed the presence of
chemical constituents such as flavanoids, alkaloids, phenols and sugars. Further studies on the purification and identification of active compounds from S. furcellatum might help to characterize the nature of eco-friendly antifouling compounds filed study.