Pharmacological potential of seaweed-associated heterotrophic Firmicutes.

Seaweed-associated bacterial symbionts are sources of potential pharmacological properties. The present study resulted in the culture-dependent isolation of bioactive heterotrophs belonging to the bacterial phylum Firmicutes, which were dominated more than 30% of the 127 cultivable isolates, amongst which 23 of them showed potential antimicrobial activities against a wide range of pathogens. The symbionts isolated from the seaweed Sargassum wightii showed significant bioactivity. Those were characterized as Bacillus safensis MTCC13040, B. valismortis MTCC13041, B. velezensis MTCC13044, B. methylotrophicus MTCC13042, Oceanobacillus profundus MTCC13045, B. tequilensis MTCC13043, and B. altitudinis MTCC13046. The organic extracts of the studied isolates showed potential antimicrobial properties against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci (minimum inhibitory concentration 6·25-12·5 µg ml-1 ). The organic extract of B. altitudinis MTCC13046 displayed significantly greater radical quenching ability (IC90 133 µg ml-1 , P < 0·05) other than attenuating hydroxymethyl glutaryl coenzyme A reductase (IC90 10·21 µg ml-1 , P < 0·05) and angiotensin-converting enzyme-1 (IC90 498 µg ml-1 , P < 0·05) relative to other studied heterotrophs. The organic extract of B. tequilensis MTCC13043 displayed significantly greater attenuation potential against pro-inflammatory 5-lipooxygenase (IC90 5·94 µg ml-1 , P < 0·05) and dipeptidyl peptidase-4 (IC90 271 µg ml-1 , P < 0·05). The seaweed-associated B. altitudinis MTCC13046 and B. tequilensis MTCC13043 could be used to develop promising pharmacological leads.