Antimicrobial profiling of coral reef and sponge associated bacteria from southeast coast of India.

Culturable bacteria associated with marine sponges and coral mucus (collected from Gulf of Mannar and Palk Bay) were screened for their prospective antimicrobial compounds against 9 bacterial pathogens (Bacillus megaterium, B. cereus, Salmonella typhimurium, Staphylococcus aureus, Proteus vulgaris, Klebsillla pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii) and a fungal pathogen (Candida albicans). Of the 263 bacterial isolates obtained during this study, 52 isolates displayed antimicrobial activity against one or more pathogens. 16S rRNA gene sequencing revealed that these 52 strains affiliated to 14 genera from three phyla Proteobacteria, Firmicutes and Actinobacteria. Sponge associated bacterial strains F-04, I-23, I-33 and G-03 inhibited the growth of all the bacterial pathogens tested in this study and significantly the former 2 strains inhibited the growth of fungal pathogen also. Majority of the potential strains (88.4% out of 52 strains) inhibited the growth of Bacillus cereus. Interestingly, an actinomycete strain F-04 (isolated from sponge Orina sagittaria) inhibited the growth of methicillin resistant Staphylococcus aureus. In total, 10 volatile organic compounds were determined from the ethyl acetate and hexane extract of the strain F-04 using GC-MS. Overall, marine bacteria isolated during this study demonstrate the potential for the development of broad spectrum antibiotics.

Prokaryotic Diversity in Oxygen Depleted Waters of the Bay of Bengal Inferred Using Culture-Dependent and -Independent Methods.

There are regions in the world oceans where oxygen saturation is at its lowest, evident at depths between shelf to upper bathyal zone. These regions are known as Oxygen Minimum Zones (OMZs), which reportedly support phylogenetically diverse microbes. In this study, we aimed to characterize prokaryotic diversity in the water samples collected from 43, 200 and 1000 m depth of the Bay of Bengal Time Series location (BoBTS-18.0027°N, 89.0174°E) in the OMZ region. Illumina sequencing generated 3,921,854 reads of 16S rRNA gene amplicons, which corresponded to 5778 operational taxonomic units. The distribution of bacteria at class level varied with depth and oxygen concentration. α-Proteobacteria was found in abundance in 43 m and 1000 m depth water samples. γ-Proteobacteria was prominently detected in oxygen-depleted depths of 200 m and 1000 m. AB16 (Marine Group A, originally SAR406) was restricted at dissolved oxygen concentration of 1.5 µM at 200 m. Archaeal members were observed in low abundance (2%), with a high occurrence of phylum Euryarchaeota at 43 m, while Crenarchaeota was detected only at 200 m depth. Select bacterial cultures were screened for their ability to reduce nitrate in vitro, to obtain insights into their possible role in the nitrogen cycle. A total of 156 bacterial isolates clustered majorly with Alcanivorax, Bacillus, Erythrobacter, Halomonas, Idiomarina and Marinobacter. Among them, 11 bacterial genera showed positive nitrate reduction in the Griess test. A large percentage (63.55%) of 16S rRNA gene amplicons corresponded to unidentified OTUs at genus or higher taxonomic levels, suggesting a greater undiscovered prokaryotic diversity in this oxygen depleted region.

Improved Sprouting and Growth of Mung Plants in Chromate Contaminated Soils Treated with Marine Strains of Staphylococcus Species.

Marine bacteria possess a wide variety of bioremediation potential which is beneficial environmentally and economically. In this study, bacterial isolates from marine waters were screened for tolerance and growth in high concentrations of chromate (Cr6+). Two isolates, capable of tolerating Cr6+ concentrations 300 µg mL-1 or higher, and found to completely reduce 20 µg mL-1 Cr6+ were grown in Cr6+ (50 and 100 mg kg-1) spiked garden soil. Notably, both facilitated normal germination and growth of mung (Vigna radiata) seeds, which could hardly germinate in Cr6+ spiked garden soil without either of these bacteria. In fact, large percent of mung seeds failed to sprout in the Cr6+ spiked garden soil and could not grow any further. Apparently, chromate detoxification by marine bacterial isolates and the ability of mung plants to deal with the reduced form appear to work complementarily. This study provides an insight into marine bacterial abilities with respect to chromium and potential applications in promoting growth of leguminous plants-similar to mung in particular-in Cr6+ contaminated soil.

Phylogenetic analyses and nitrate-reducing activity of fungal cultures isolated from the permanent, oceanic oxygen minimum zone of the Arabian Sea.

Reports on the active role of fungi as denitrifiers in terrestrial ecosystems have stimulated an interest in the study of the role of fungi in oxygen-deficient marine systems. In this study, the culturable diversity of fungi was investigated from 4 stations within the permanent, oceanic, oxygen minimum zone of the Arabian Sea. The isolated cultures grouped within the 2 major fungal phyla Ascomycota and Basidiomycota; diversity estimates in the stations sampled indicated that the diversity of the oxygen-depleted environments is less than that of mangrove regions and deep-sea habitats. Phylogenetic analyses of 18S rRNA sequences revealed a few divergent isolates that clustered with environmental sequences previously obtained by others. This is significant, as these isolates represent phylotypes that so far were known only from metagenomic studies and are of phylogenetic importance. Nitrate reduction activity, the first step in the denitrification process, was recorded for isolates under simulated anoxic, deep-sea conditions showing ecological significance of fungi in the oxygen-depleted habitats. This report increases our understanding of fungal diversity in unique, poorly studied habitats and underlines the importance of fungi in the oxygen-depleted environments.

A role for antioxidants in acclimation of marine derived pathogenic fungus (NIOCC 1) to salt stress.

Salinity tolerance a key factor helps in understanding the ionic homeostasis in general, which is a fundamental cellular phenomenon in all living cells. Here, a marine derived pathogenic fungus was examined for its adaptation under salt stress using antioxidant properties. The aqueous extracts of halophilic fungus exhibited different levels of antioxidant activity in all the in vitro tests such as α,α-diphenyl-ß-picrylhydrazyl (DPPH(·)), Hydroxyl Radical Scavenging Assay (HRSA), Metal chelating assay and ß-carotene-linoleic acid model system. The antioxidant capacity of marine fungus exposed to high salt condition showed an increase in activity. In addition, the production of intra and extracellular antioxidant enzymes of the fungus at various salt stresses were analyzed and discussed for their possible role in the stress mechanism. The marine derived fungus was identified as Phialosimplex genus, which is associated with infections in dogs. Thus the present study elucidates that the scavenging activity is one of the protective mechanisms developed in the fungus to avoid the deleterious effect of salt stress. In addition, the study also helps in understanding how the pathogenic fungus tackles the oxidative burst i.e. hypersensitivity reaction performed by host to kill the pathogens.

Profiling of a few immune responsive genes expressed in postlarvae of Fenneropenaeus indicus challenged with Vibrio harveyi D3.

We identified 38 genes and eight hypothetical proteins by sequencing of 1200 clones from a Vibrio harveyi challenged Fenneropenaeus indicus subtracted cDNA library. Based on physiological roles and functions these genes were categorized into 10 groups with ∼29% of the sequences having no matches in the databases. Immune related transcripts in the library were carboxypeptidase B, ferritin, translationally controlled tumor proteins (TCTP), hemocyanin, chitinase and serine carboxy peptidase. Remarkably, qPCR results imply 4.15, 3.45 and 1.86-fold rises in expression of ferritin, TCTP and hemocyanin transcripts respectively. Additionally, minor upregulation of other immune relevant genes lectin, penaeidin, crustin, MnSOD was observed in the challenged postlarvae.

Distribution of butyltins in waters and sediments of the Mandovi and Zuari estuaries, west coast of India.

Butyltins (TBT, DBT, MBT) were measured in water and sediment samples collected from various locations in the Mandovi (ten stations) and Zuari (nine stations) estuaries during November 2007. The total butyltin (TB) in water samples varied between approximately 12 and 73 and from 0.5 to 77 ng Sn l(-1), whereas for the sediments, it varied from approximately 15 to 118 and 6 to 119 ng Sn g(-1) dry weight for the Mandovi and the Zuari estuaries, respectively. The average TB concentration in the sediments from the Zuari estuary was higher as compared to the Mandovi estuary, whereas for the water samples, it was vice versa. For both the water and sediment samples, MBT was generally the most predominant butyltin in these two estuaries. This suggests that the butyltin contamination was not freshly derived. Fairly good relationships between the concentrations of TB and organic carbon in water and sediment samples of these estuaries implicate the importance of adsorption/desorption processes in controlling the levels of TB in these estuaries.

Seasonal variation in organotins in the waters of the Dona Paula Bay, west coast of India.

Surface seawaters from the Dona Paula Bay, were collected at weekly intervals during March 2007 to March 2008, and analyzed for butyltins (BT) such as tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT) using a GC-MS system. The mean concentrations of TBT, DBT, MBT and total BT varied from <1-37, 4-19, 6-28 and 21-84 ng Sn L(-1), respectively. Highest levels of BTs were recorded during May followed by April 2007 and March 2007 probably because the shipping and tourism activities are very high during these months.

Distribution of butyltins in the waters and sediments along the coast of India.

Water and surface sediment samples were analyzed for butyltins (TBT, DBT, MBT) from various ports along the east and west coast of India. The total butyltin (TB) in water samples varied between ~1.7 and 342 ng S nl⁻¹, whereas for sediments it varied between below detection limit to 14861 ng S ng⁻¹ dry weight of sediment. On an average Chennai port recorded the highest level of butyltins in the sediments while Paradip recorded the highest level of butylins in the waters. A fairly good relationship between the TB in the sediment and overlying water samples, as well as between organic carbon and TB, implicates the importance of adsorption/desorption process in controlling the levels of TBT in these port areas. In India the data on organotin pollution is very sparse; most of the port areas have been surveyed for butyltins for the first time during this study.