Pharmacological properties of marine macroalgae-associated heterotrophic bacteria

The rich diversity of marine macroalgae and their associated bacterial flora represent a potential reservoir of bioactive compounds with valuable biotechnological and pharmaceutical use. Heterotrophic bacteria associated with the intertidal macroalgae were isolated and evaluated for their pharmacological properties using various in vitro models. Among 148 cultivable isolates, more than 50% were dominated by γ-Proteobacteria and Firmicutes, wherein 53 of them showed consistent antibacterial activity against a broad spectrum of clinically significant pathogens. The bacteria were characterized by extensive microbiological, molecular and chemical identification tools. The heterotrophs Bacillus amyloliquefaciens MTCC 12716 and Shewanella algae MTCC 12715 isolated from a red marine macroalga Hypnea valentiae exhibited potential anti-infective properties against multidrug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis (minimum inhibitory concentration of 6.25-12.5 µg/mL). The organic extract of B. amyloliquefaciens displayed significantly greater antioxidative properties (IC₉₀ < 1 mg/mL) and the activities showed considerable positive correlation (r² > 0.8, P < 0.05) with the inhibitory activities against angiotensin converting enzyme-I, pro-inflammatory cyclooxygenases and 5-lipoxygenase, dipeptidyl peptidase-4 and hydroxymethylglutaryl coenzyme A reductase, which were associated with hypertension, inflammation, diabetes, and hypercholesterolemia, respectively. The applications of nuclear magnetic resonance-based fingerprinting to analyze the characteristic signals in the solvent extracts and to correlate them with the pharmaceutical properties were underlined. The heterotrophic bacterium B. amyloliquefaciens MTCC 12716 might, therefore, serve as a potential therapeutic candidate to develop products with wide pharmaceutical applications.