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Deep sea bacterial communities demonstrate remarkable adaptability to high-pressure environments coupled with low temperatures which has sparked curiosity about their diversity and exceptional metabolic pathways. Additionally, bacteria in the deep sea exert a substantial influence over various biogeochemical processes. To date, we have relatively very little information about the deep-sea bacterial communities and, they remain largely unexplored. We investigated the variability in the physicochemical conditions, heavy metals and their influence on deep-sea bacterial community structure across three different depths in the Bay of Bengal. The structural and metabolic diversity of deep-sea sediment microbial communities were examined through culture-based sequencing of 16S rRNA genes, ecto-enzymatic studies, and community-level physiological profiling. Bacillota was the most dominant phylum representing 61% of the cultured bacterial isolates, while the remaining belonged to Actinomycetota and Pseudomonodata. Five potential novel species belonging to the genera Fictibacillus, Lysinibacillus, Salinicola, Robertmurraya and Blastococcus were identified. The extracellular enzymatic activity was positive for >50% of the bacterial isolates, wherein the genera Bacillus and Micromonospora exhibited versatile profiles. High metabolic diversity was recorded through the carbon substrate utilization profiles indicating that microbial communities are active participants in biogeochemical cycles in the deep sea. The most prominently utilized carbon substrates were a-cyclodextrin, glucose-1-phosphate, D-xylose, glycogen, and 2-hydroxy benzoic acid which serve as organic substrates for microbial metabolism, facilitating the decomposition of organic matter and, recycling carbon in deep-sea ecosystems. Multivariate statistical analyses confirmed that the environmental variables had a profound influence on the bacterial community. The findings shed light on spatial variability in the bacterial community structure, enzyme activity and metabolic profiles, and enhance our understanding of Bay of Bengal deep-sea sedimentary microbial ecology. [ABSTRACT FROM AUTHOR]

Aquatic pathogens contribute to the most severe economic loss in fishes. Nanoparticles are being developed as potent antimicrobial agents against various pathogens. The bacteria Aeromonas caviae is one of the most common aquatic pathogens that infects the majority of economically important fishes causing significant losses to the aquaculture industry. This study involved synthesizing and characterizing of a novel chitosan‐selenium nanoflower employing multiple spectroscopic and microscopic approaches. The UV‐vis spectra obtained at 265 nm indicated the formation of the Chitosan‐selenium nanoflower. The particle size analysis revealed the size of the nanoflowers to be 186.3 nm. The transmission electron micrographs revealed a unique nanoflower-like morphology. XRD spectrum revealed amorphous nature. The Raman spectrum showed a strong resonance peak at 254 cm−1 which is a characteristic absorption band for monoclinic Se and α‐Se. Cytotoxicity analysis of the synthesized nanoflowers against isolated fish pathogen Aeromonas caviae showed increasing toxicity in a dose‐dependent manner with maximum cytotoxicity of 75.06% at 1000 µg/mL. The DCFDA assay was conducted to estimate the increase in reactive oxygen species (ROS) production, and the highest percentage increase in ROS of 96.02% was observed at 1000 µg/mL. The lipid peroxidation assay was performed by quantification of the lipid oxidation product malondialdehyde (MDA). The highest percentage of lipid peroxidation was found to occur at a dose of 500 µg/mL. As a result, the synthesized chitosan‐selenium nanoflowers can be exploited as a promising antibacterial treatment against the fish pathogen Aeromonas caviae. [ABSTRACT FROM AUTHOR]

Marine invertebrates, particularly ascidians, constitute an important source of potential active and biofunctional natural products. The microbial diversity associated with ascidians is little recognized, although these microorganisms play a vital role in marine ecosystems. The objective of this study was to investigate bacterial population diversity in four ascidian samples: Phallusia nigra, Phallusia fumigata, Eudistoma viride, and Rhopalaea macrothorax, collected from the North Bay, Andaman and Nicobar Islands. Microbial strains identified up to the species level revealed 236 distinct species/ribotypes out of 298 bacterial strains. Of 298 ascidian-associated bacteria, 72 isolates belong to the class Gammaproteobacteria and the genus Endozoicomonas. The results from this investigation will contribute a broaden knowledge of microbial diversity associated to marine ascidians, and as a promising source for the discovery of new natural products. [ABSTRACT FROM AUTHOR]

Seaweeds rich in polysaccharides are considered commercially important because of their wide range of industrial applications. In this study, the red seaweed Kappaphycus alvarezii was used for bioplastic film production. Plasticizer polyethylene glycol (PEG) to seaweed biomass ratio was optimized and a thin bioplastic film with higher tensile strength was produced. The films obtained were characterized by its thickness, tensile strength, colour (L, a, b), elongation at break (EAB), water vapour transmission rate (WVTR) and oxygen transmission rate (OTR). TG-DSC, AFM, SEM and FTIR spectroscopy analysis were performed to assess the composition, phase transitions and chemical reaction capabilities of the film. The bioplastic film obtained from 4% K. alvarezii (whole seaweed) showed better physical and mechanical properties, whereas TG-DSC, FTIR and AFM showed similar kind of bioplastic properties in all the concentrations. Decrease in OTR was observed against decreasing wall thickness of the film. The present study suggests that the seaweed would be a potential alternate source for bioplastic production which may reduce the usage of non-degradable plastics. [ABSTRACT FROM AUTHOR]

The diversity of actinobacteria associated with marine ascidian Phallusia nigra from Andaman Islands was investigated. A total of 10 actinobacteria were isolated and based on the biochemical and molecular characterization, the isolates were assigned to 7 different actinobacterial genera. Eight putatively novel species belonging to genera Rhodococcus, Kineococcus, Kocuria, Janibacter, Salinispora and Arthrobacter were identified based on 16S rDNA sequence similarity with the NCBI database. The organic extracts of ten isolates displayed considerable bioactivity against test pathogens, which were Gram-positive and Gram-negative in nature. PCR-based screening for type I and type II polyketide synthases (PKS-I, PKS-II) and nonribosomal peptide synthetases (NRPS) revealed that, 10 actinobacterial isolates encoded at least one type of polyketide synthases biosynthesis gene. Majority of the isolates found to produce industrially important enzymes; amylase, protease, gelatinase, lipase, DNase, cellulase, urease, phosphatase and l-asparaginase. The present study emphasized that, ascidians are a prolific resource for novel bioactive actinobacteria with potential for novel drug discovery. This result expands the scope to functionally characterize the novel ascidian associated marine actinobacteria and their metabolites could be a source for the novel molecules of commercial interest. [ABSTRACT FROM AUTHOR]

Membrane biofouling remains a significant challenge in the application of ultrafiltration (UF) pretreatment systems in desalination and water industries. Bacterial biofilms produce extracellular polymeric substances, which contain alginate as a major component. There has been an ongoing search to look for passive/non-chemical means of mitigating this problem. We present a method based on immobilization of a polysaccharide-degrading enzyme, alginate lyase (Alg L), onto cellulose acetate membrane to control biofilm formation. Various parameters like Alg L concentration, cross-linker concentration and pH were optimized. Two immobilization procedures were adopted and the Alg L immobilization efficiency of each method was compared. Activation of membrane with a cross-linking agent, followed by Alg L immobilization was found to be relatively more effective. Immobilization was confirmed by determining the activity of the immobilized enzyme; viscosity decrease corresponding to enzymatic degradation of the substrate was observed. The immobilization protocol was found to be highly reproducible. The ability of the test membrane to mitigatePseudomonas aeruginosabiofilm formation was confirmed by scanning electron microscopy. The results show that Alg L immobilization on UF membrane can be used for controlling polysaccharide fouling on membrane filters used in advanced water purification techniques. [ABSTRACT FROM PUBLISHER]

Surfactin is a lipopeptide, composed of one β-hydroxy fatty acid, a long fatty acid moiety, and seven amino acids. In this study, the biosurfactant biosynthesis genes; 4′-pantetheinyl transferase ( sfp), phosphopantetheinyl transferase ( sfpO), and surfactin synthetase ( srfA) have been characterized from the marine sponge-associated Bacillus licheniformis NIOT-06 from the Andaman and Nicobar Islands. The purified recombinant biosurfactant revealed excellent emulsification activity with crude oil and kerosene. Reverse-phase high-performance liquid chromatography resolved the purified recombinant biosurfactant into several fractions and one of which had significant surface tension reducing property. Fourier transform infrared spectroscopy spectrum also revealed the presence of C-N-N, alkenes, and N-H as the functional groups, and a similar overlapping pattern was observed with that of standard lipopeptide surfactin. The diversity and phylogeny of sfp, sfpO, and srfA gene sequences were compared with other eubacteria. The sfp, sfpO, and srfA gene sequences obtained from Bacillus licheniformis NIOT-06 were diverse and appeared to be partially conserved when compared with the GenBank reported sequences of several eubacteria. [ABSTRACT FROM AUTHOR]

Studies were carried out for the optimization and production of novel extracellular glutaminase-free l-asparaginase from Nocardiopsis alba NIOT-VKMA08. Among the tested carbon and nitrogen sources, maximum l-asparaginase production was observed with a combination of l-asparagine and maltose (1.5 %) and twofold increase in yield (18.47 IU mL) was observed with newly optimized NIOT-asparaginase medium. Activity of the purified enzyme was moderately inhibited by various divalent cations and thiol group blocking reagents, with K and V of 0.127 mM and 5.50 U µg. Optimum pH and temperature of purified l-asparaginase for the hydrolysis of l-asparagine was 8.0 and 37 °C, respectively. The enzyme inhibited polyacrylamide formation in 10 % solution and it was very specific for its natural substrate l-asparagine. Partial glutaminase activity was not detected, which could reduce the possibility of side effects during cancer therapy. l-Asparaginase biosynthesis gene ( ansA) was cloned and transformed in E. coli JM109. The ansA gene sequence reported in this study contains several base substitutions with that of reported sequences in GenBank, resulting in altered amino acid sequences of the translated protein. [ABSTRACT FROM AUTHOR]

The architecture of testicular lobules, morphology of spermatozoa, and spermatophore in the mud crab, Scylla serrata, are described for the first time employing atomic force microscopy (AFM). A fast and simple squash preparation protocol was followed using crustacean physiological saline without distorting the natural structure. Observations provided new insight into the arrangement of lobules and morphology of testicular assembly. It consists of a close network of lobules of different sizes in a radial manner on radially branching basal tubules. Budding of new lobules is another distinguishable feature noted in the network of testicular organization. A thin membranous envelope of the lobule with undulating processes offered indirect evidence on the possible storage of sperm cells within the lumen of the lobule. Spermatozoa of S. serrata were of different shapes and sizes, and, depending on the maturational status, they displayed changes in the acrosome vesicle with a significant amount of cytoplasm. Vertical constrictions found in the testicular lobules suggest propulsive extrusion of spermatophoric masses into the central lumen. These observations necessitate further study using AFM and involving molecular probes to elucidate the polymorphic nature of male germinal cells, mechanisms of spermatophore formation, and the phylogenetic relationship among crustaceans in general. [ABSTRACT FROM AUTHOR]

Thraustochytrids are the most promising microbial source for the commercial production of docosahexaenoic acid (DHA) for its application in the human health, aquaculture, and nutraceutical sectors. The present study isolated 127 thraustochytrid strains from mangrove habitats of the south Andaman Islands, India to study their diversity, polyunsaturated fatty acids (PUFAs), and biotechnological potential. The predominant strains were identified as belonging to two major genera (Thraustochytrium, Aurantiochytrium) based on morphological and molecular characteristics. The strain ANVKK-06 produced the maximum biomass of 5.42 g·L−1, while ANVKK-03 exhibited the maximum total lipid (71.03%). Omega-3 PUFAs such as eicosapentaenoic acid (EPA) accumulated up to 11.03% in ANVKK-04, docosapentaenoic acid (DPA) up to 8.65% in ANVKK-07, and DHA up to 47.19% in ANVKK-06. ANVKK-06 showed the maximum scavenging activity (84.79 ± 2.30%) while ANVKK-03 and ANVKK-10 displayed the highest antibacterial activity against human and fish pathogens, S. aureus (18.69 ± 1.2 mm) and V. parahaemolyticus (18.31 ± 1.0 mm), respectively. All strains were non-toxic as evident by negative blood agar hemolysis, thus, the thraustochytrids are suggested to be a potential source of DHA for application in the health care of human and fish. [ABSTRACT FROM AUTHOR]

Marine actinobacteria are known to be a rich source for novel metabolites with diverse biological activities. In this study, a potential extracellular L-asparaginase was characterised from the Streptomyces griseus NIOT-VKMA29. Box-Behnken based optimization was used to determine the culture medium components to enhance the L-asparaginase production. pH, starch, yeast extract and L-asparagine has a direct correlation for enzyme production with a maximum yield of 56.78 IU mL−1. A verification experiment was performed to validate the experiment and more than 99% validity was established. L-Asparaginase biosynthesis gene (ansA) from Streptomyces griseus NIOT-VKMA29 was heterologously expressed in Escherichia coli M15 and the enzyme production was increased threefold (123 IU mL−1) over the native strain. The ansA gene sequences reported in this study encloses several base substitutions with that of reported sequences in GenBank, resulting in altered amino acid sequences of the translated protein. [ABSTRACT FROM AUTHOR]