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The present study probed the antimicrobial potential of a rare mangrove associated actinomycetes against an array of aquatic bacterial pathogens causing disease outbreak in fin and shellfish. Antibacterial activity results implied that the mangrove associated actinomycetes RAS7 exhibited striking inhibitory activity against the tested aquatic bacterial pathogens. Identification of strain RAS7 through polyphasic and 16S rRNA sequencing affirmed that the strain belongs to Rhodococcus sp. Optimization of culture conditions for antibacterial activity by Rhodococcus sp. inferred that it grew well and exerted notable antagonistic activity in medium supplied with 1% galactose and peptone as carbon and nitrogen sources. Similarly, the strain grown in 0.1% tyrosine, 1% NaCl, pH 7.5 and temperature 35 °C recorded maximum bioactivity against the test pathogens. The crude ethyl acetate extract of Rhodococcus sp. at 200  μg/ml recorded markedly pronounced growth inhibitory activity ranged between 14 and 29 mm. The cytotoxic effect of crude extract against brine shrimp Artemia salina nauplii registered LC 50 value of 134.294 μg/ml after 24 h of exposure. The secondary metabolite was separated using Ethyl acetate: Methanol (7:3) as solvent system through TLC. The TLC autobiogram mapped the active spot in TLC with Rf value of 0.84. Analysis of chemical constituents and FT-IR spectral analysis substantiated that the active principle in bioassay guided fraction was sterol-glycosides., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Coral mucus is one of the key localization in the coral holobiont, as this serves as an energy rich substrate for a wide range of abundant, diverse and multifunctional microbiota. However, very little is known about the functional role of bacterial communities in their associations with corals. In the present study, a total of 48 isolates were obtained from Porites lutea wherein the genus of Bacillus sp. and Vibrio sp. were predominant. Bio-prospecting the coral mucus revealed the existence of (10.42%) antagonistic bacteria against the tested bacterial pathogens. Molecular taxonomy (16S rRNA) proved the identity of these antagonistic bacteria belong to Enterobacter cloacae (CM1), Bacillus subtilis (CM2), Bacillus sp. (CM11) and Bacillus marisflavi (CM12). The secondary screening emphasized that the ethyl acetate extract of B. subtilis showed strong antagonistic effect, followed by the chloroform extract of E. cloacae and ethyl acetate extract of B. marisflavi. The antagonistic activity was statistically confirmed by Principal Component Analysis and Hierarchical Cluster Analysis. The privileged coral mucus associated bacterial (CMAB) solvent extracts inhibited the bacterial pathogens at 100 μg/ml (MIC) and ceased the growth at 200 μg/ml (MBC). The hemolytic and brine shrimp lethality assays disclosed the non-toxic nature of solvent extracts of CMAB. Altogether, the present investigation brought out the diversity of bacteria associated with the mucus of P. lutea. In addition, bio-prospecting corroborated the CMAB as the potential source of pharmacologically important bioactive compounds against a wide range of bacterial pathogens., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Silver nanoparticle was green synthesized involving the unripe fruit extracts of Solanum nigrum (Sn-AgNPs). The synthesized Sn-AgNPs was bio-physically characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM). UV-Vis recorded the absorbance spectra at 443 nm. XRD analysis clearly demonstrated the crystalline nature of Sn-AgNPs with Bragg's reflection peaks at 111, 200, 220 and 311 lattice planes. The FTIR spectrum of Sn-AgNPs showed strong bands at 3432, 1555, 1455, 862 and 406 cm -1 which corresponds at O-H, C-H, C-C, C-OH and C-N groups respectively. TEM exhibited the spherical shape of Sn-AgNPs with particle size between 20 and 30 nm. The antibacterial effects of Sn-AgNPs were tested on clinically important biofilm forming Gram positive (Bacillus pumulis and Enterococcus faecalis) and Gram negative (Proteus vulgaris and Vibrio parahaemolyticus) bacteria. The greater inhibition of B. pumulis and E. faecalis was observed at 100 μg mL -1 of Sn-AgNPs compared to P. vulgaris and V. parahaemolyticus. The biofilm inhibition potential of Sn-AgNPs was greater against Gram positive bacteria than that of Gram negative bacteria. Furthermore, Sn-AgNPs effectively degraded the industrial effluent methyl orange dye by photocatalysis. It is concluded that Sn-AgNPs could be used as an effective therapeutics against the biofilm of clinically important bacteria. The green synthesized Sn-AgNPs can be employed to degrade dye effluents and prevent environmental pollution as well., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In the recent years, synthesis of nanomaterials using seaweeds and their diverse applications is escalating research in modern era. Among the noble metals, platinum nanoparticles (PtNPs) are of great importance owing to their catalytic property and less toxicity. The significance of this work is a simple one-step synthesis of PtNPs using aqueous extract of Indian brown seaweed Padina gymnospora and their catalytic activity with a polymer Polyvinylpyrrolidone (PVP) as PVP/PtNPs nanocomposite towards antimicrobial, haemolytic, cytotoxic (Artemia salina) and antioxidant properties. Fourier Transform Infrared (FT-IR) spectrum results showed diversified functional groups (biomoeities such as carbohydrates and proteins) present in the seaweed extract is responsible for the reduction of platinum ions (Pt + ) to PtNPs. The seaweed mediated PtNPs was characterized by UV-vis spectrophotometer, X-ray diffraction (XRD) pattern, Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy Dispersive X-ray (EDX) spectroscopy and High Resolution Transmission Electron Microscopy (HRTEM) analysis. The synthesized PtNPs was found to be truncated octahedral in shape with the range of 5-50nm. Crystalline nature of the nanoparticles was evidenced by Selected Area Electron Diffraction (SAED) pattern with bright circular spots corresponding to (111), (200), (220) and (311) Bragg's reflection planes. The size of the PtNPs was further evidenced by Dynamic Light Scattering (DLS) analysis and it is originate to be stable at -22.5mV through Zeta Potential (ZP) analysis. The present study shows that the catalytic behavior of PtNPs as polymer/metal nanocomposite (PVP/PtNPs) preparation for an antibacterial activity against seven disease causing pathogenic bacterial strains with the maximum activity against Escherichia coli (15.6mm) followed by Lactococcus lactis (14.8mm) and Klebsiella pneumoniae (14.4mm). But no haemolytic activity was seen at their effective bactericidal concentration, whereas increase in the haeomyltic activity was seen only in higher concentrations (600, 900 and 1200μgmL -1 ). On the other hand, PVP/PtNPs nanocomposite has shown cytotoxic activity at 100±4μgmL -1 (LC 50 ) against Artemia salina nauplii. Furthermore, PVP/PtNPs nanocomposite showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide, nitric oxide and hydroxyl radicals., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Green synthesis of nanoparticles using seaweeds are fascinating high research attention nowadays and also gaining center of attention in biomedical applications. In this work, we have synthesized biocompatible and functionalized silver nanoparticles using an aqueous extract of seaweed Enteromorpha compressa as a reducing as well as stabilizing agent and their efficient antimicrobial and anticancer activity are reported here. The UV-vis spectra of AgNPs showed the characteristics SPR absorption band at 421 nm. The chemical interaction and crystalline nature of the AgNPs were evaluated by FT-IR and XRD studies. The XRD result of AgNPs shows typical Ag reflection peaks at 38.1°, 44.2°, 64.4° and 77.1° corresponding to (111), (200), (220) and (311) Bragg's planes. The surface morphology and composition of the samples were observed by HRTEM, EDS and SAED pattern analyses. Spherical shaped Ag nano structures were observed in the size ranges between 4 and 24 nm with clear lattice fringes in the HRTEM image. This report reveals that seaweed mediated synthesis of AgNPs and sustained delivery of Ag ions to the bacterial and fungal surface have been reducing their growth rate which was evaluated by well diffusion assay. The synthesized AgNPs showed favorable cytotoxicity against Ehlrich Ascites Carcinoma (EAC) cells with IC 50 value was recorded at 95.35 μg mL -1 . This study showed cost effective silver nanoparticles synthesis with excellent biocompatibility and thus could potentially be utilized in biomedical and pharmaceutical applications.

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 (2-50nm) 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±0.12mm 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±3.10 to 73.34±1.79%) and haemolytic index revealed the satisfactory biocompatibility of AgNPs that showed less/no haemolysis up to 3nM concentration. Further, the toxicity effect of biosynthesized AgNPs against the brine shrimp, Artemia salina exhibited significantly increasing mortality (13±4.7 to 100%) with LC 50 value at 4nM 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., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

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 478.11μg/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., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

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.

Contraceptive properties of seaweeds are still stands as lacuna; in this context, the screening of in vitro male contraceptive properties of crude ethanolic extract of Indian seaweeds against normal human sperm is carried out. In total, twelve seaweeds were screened for in vitro spermicidal activity. Among these twelve seaweeds, Halimeda gracilis showed 100% inhibition of human spermatozoa at 10 mg ml(-1) concentration in 20 s and its EC50 value was 2.05 mg ml(-1) in 20 s. Further, dose- and time-dependent spermicidal assay revealed that the sperm was completely immobilised for 20 s. Plasma membrane of sperm was damaged due to the exposure of H. gracilis extract. MTT assay with H. gracilis extract showed 88.5% of cytotoxic incidence. H. gracilis extract tested for cytotoxicity against Artemia salina recorded LC50 value of 34.8 μg ml(-1) . Phytochemical analysis of H. gracilis extract evidenced the presence of alkaloids, flavonoids, proteins and sugars. Results of this study clearly inferred that the synergistic effect of active principles reside within the H. gracilis extract had shown better contraceptive activity., (© 2013 Blackwell Verlag GmbH.)

Phosphatase Producing Bacteria (PPB) and Inorganic Phosphate Solubilizing Bacteria (IPSB) are important to reef nutrition. These microbes and phosphate concentration play a significant role in the productivity of coral reef ecosystems. A study was conducted in Gulf of Mannar coral reef ecosystem to understand the diversity of these groups of bacteria and their competence in mineralizing the phosphate. The PPB isolates were identified under six genera i.e. Bacillus, Pseudomonas, Micrococcus, Vibrio, Arthrobacter and Brevibacterium. Likewise, the IPSB isolates were also identified that belong to six genera i.e. Bacillus, Arthrobacter, Pseudomonas, Flavobacterium, Flavomonas and Micrococcus. Among the PPB and IPSB strains, Bacillus represented more number of species than others. PPB exhibited maximum activity between pH 8 and 9 and the lowest was at pH 6. Among the phosphatase producers Bacillus cereus (546) showed maximum activity (0.333 mmol/l P) at pH 8. In general, the phosphatase activity in most of the Bacillus species varied with reference to different pH. The species Bacillus megaterium (573) showed highest phosphate solubilizing activity (0.906 mmol/l P) by producing 2-ketogluconic acid. The production of organic acids and phosphatase enzymes by these bacterial groups are responsible for the conversion of insoluble inorganic and organic phosphates into soluble forms which are available for the reef organisms., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bioluminescence is a biochemical process occurring in many organisms. Bacterial bioluminescence has been investigated extensively that lead to many applications of such knowledge. Quorum sensing in the bioluminescent bacteria is a chemical signal process to recognize the strength of its own population to start luminescence in harmony. There is a mechanism in these bacteria to also recognize inter-species strength. When there is a higher number of these bacteria, the possibility and frequency of cell-cell physical contact will be high. In this study, the physical proximity was artificially enhanced between cells and the effect on luminescence in the concentrated cells in the normal culture medium and in the presence of other non-bacterial cell-free supernatants was investigated. The role of such physical contact in the quorum sensing in the bioluminescence is not known. Increase in the luminescence of V. fischeri when concentrated shows that the presence of physical proximity facilitates the quorum sensing for their bioluminescence., (Copyright © 2009 John Wiley & Sons, Ltd.)

Microbiological studies in a modified extensive shrimp culture system at Nambuthalai, southeast coast of India were carried out fora period of 120 days. Population dynamics and distribution profile of luminous bacteria and total heterotrophic bacteria in the water sediment and animal samples were monitored. Luminous bacteria associated with exoskeleton, gills and gut were isolated and quantified. The total heterotrophic bacterial counts ranged from 1.3 x 10(4) to 25.3 x 10(4) CFU ml(-1) in water and 1.5 x 10(6) to 26.2 x 10(6) CFU g(-1) in sediment. The V. harveyi population density varied between 0.6 x 10(4) and 8.8 x 10(4) LCFU ml(-1) in water and from 1.2 x 10(6) to 10.4 x 10(6) LCFU g(-1) sediment respectively. The gut of the animal was found to harbor high density of V. harveyi than gills and exoskeleton. The total heterotrophic bacteria and V. harveyi population density showed increasing trend during the culture period. The high V harveyi density observed in this study at the end of the culture period correlated with the outbreak of white spot disease.

Investigation on physico-chemical parameters and bacteial characteristics of the coral reef environs of the Gulf of Mannar biosphere reserve was studied. The study found the influence of different physico-chemical parameters on one another and also on the distribution of the total heterotrophic bacteria (THB) in the coral reef areas. Nutrients exhibited considerable seasonal and spatial variations with influence on the bacterial population. Coral reef areas recorded higher bacterial population density both in water (3.5 to 18 x 10(5) CFU ml(-1)) and sediment (1 to 14 x 10(7) CFU g(-1)) samples than the non coral reef areas (3.4 to 10.5 x 10(4) CFU ml(-1) in water and 0.9 to 7 x 10(6) CFU g(-1)). The study also found the dominance of gram negative groups at all the three stations (64.73, 63,5 and 72.59%) with Pseudomonas contributing maximum number of strains in all the samples. In addition Vibrio, Aeromonas, Flavobacterium, Cytophaga, Enterobacter and Alcaligenes were also recorded. The gram positive group was represented by Bacillus, Micrococcus, Arthrobacter and Corynebacterium. The genetic composition of THB isolated from the coral mucus revealed the presence of Vibrio and Micrococcus in all the coral mucus.