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Isolation, Screening and Evaluation of Antifouling Activity of Mangrove Associated Bacterium, Bacillus subtilis subsp. subtilis RG

Ramasubburayan, R., Prakash, S., Iyapparaj, P., Sumathi, S., Titus, Susan, Immanuel, G., Palavesam, A.
Proceedings of the National Academy of Sciences, India, Section B: biological sciences 2017 v.87 no.3 pp. 1015-1024
Artemia franciscana, Perna, antifouling activities, bacteria, ethyl acetate, fouling, larvae, lethal concentration 50, median effective concentration, microalgae, minimum inhibitory concentration, mussels, rhizosphere, ribosomal RNA, screening, sequence analysis, soil, toxicity, India
In the present study, an attempt has been made to explore the antifouling activity of bacterial strains isolated from the root and rhizosphere soil of Pichavaram mangroves, India. Altogether, 14 different mangrove associated bacterial strains (MAB1–14) were isolated and screened for antagonistic activity against fouling bacterial strains. Screening results inferred that, five (35.71 %) out of 14 MAB isolates exhibited antagonistic activity. Among them, MAB6 showed notable growth inhibitory activity and it was identified as Bacillus subtilis subsp. subtilis through 16S rRNA gene sequencing. The crude ethyl acetate extract of B. subtilis subsp. subtilis RG strongly inhibited (8–13 mm) the growth of fouling bacterial strains. Minimum inhibitory concentration (MIC) of extract against fouling bacterial strains was ranged between 25 and 50 µg/ml; whilst minimum bactericidal concentration was ranged from 50 to 100 µg/ml, respectively. This extract has also effectively inhibited the growth of fouling microalgal strains with the MIC range of 50–100 µg/ml, respectively. Anticrustacean assay using Artemia franciscana larvae showed the LC₅₀ value of 264.89 µg/ml. Further, the lower EC₅₀ value (63.46 µg/ml) than the LC₅₀ value (156.32 µg/ml) and 100 % recovery of mussel Perna indica in toxicity assay inferred the non-toxic nature of the extract.