Abstract

ANTI-PROLIFERATIVE ACTIVITY OF SECONDARY METABOLITES FROM HALOALKALIPHILIC BREVIBACILLUS LATEROSPORUS

David Njenga*, James Mbaria, Romano Mwirichia, Joseph Nguta, Sospeter Njeru

ABSTRACT

Background. Secondary metabolites from actinomyces have been a rich source of antibiotics. Extremophile microbes may produce unique metabolites that can be exploited as antimicrobials to mitigate against antimicrobial resistance and as anticancer agents. Methodology. We studied secondary metabolites from an extremophile Brevibacillus laterosporus recovered from the hypersaline Lake Magadi. The microbe was selected among 10 isolates, displaying high bioactivity. Secondary metabolites were extracted from the broth production media using ethyl acetate. Results. The isolate exhibited antibacterial activities against a wide range of pathogens, with MICs ranging from 6.25 μg/mL in B. subtilis and E. coli to 50 μg/mL in S. aureus and MBCs ranging from 12.5 μg/mL in B. subtilis and E. coli to 100 μg/mL in S. aureus. Notably, the MBC was twice the MIC across allthe pathogens tested. The crude extract displayed antiproliferative activity (IC50 60.63 μg ml-1) against HELA cells and cytotoxicity (CC50 of 89.52 μg ml-1) against Vero 199 cells. The isolate thrived at pH 9, temperature > 40 ℃, and 5 % salinity. The isolate also showed high positivity for the secretion of cellulase, amylase, lipase, and lyase enzymes. The major constituents in the ethyl acetate crude extract of Brevibacillus laterosporus were hydrocinnamic acid, 4-hydroxy-benzene propanoic acid, n-hexadecanoic acid, and (E)-9-octadecenoic acid. Fatty acid and fatty acid esters were also identified. Conclusion. B. laterosporus produces metabolites with antimicrobial and antiproliferative activity. These compounds can be exploited for therapeutic use. Significance and impact of the study Drug resistance is a public health threat; therefore, it is necessary to develop novel drugs. Our findings highlight the potential of antimicrobial compounds from Brevibacillus brevis for pharmaceutical use.

Keywords: Secondary metabolites, actinomycetes, antiproliferative activity, cytotoxicity.