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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 ± 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 ± 3.10 to 73.34 ± 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 ± 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. [ABSTRACT FROM AUTHOR]

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, whereas 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. Of late, natural products were replaced with current toxic antifouling problems. In the present study, the four marine plants viz . two seaweeds ( 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; antibacterial (7±0.16 to 13±0.26 mm) with least concentration of MIC and MBC values (12.5–25 µg/ml and 25–50 µg/ml), antimicroalgal (50–300 µg/ml) and Artemia cytotoxicity (LC 50 133.88 µg/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. [ABSTRACT FROM AUTHOR]