Abstract
Microorganisms thrive in extreme environments and are known for synthesizing valuable metabolites. Salt-loving microorganisms can flourish in saline environments which inhibit the growth of other microbial life, and they possess the potential to produce stable and novel biomolecules for the use in biotechnological applications, including anticancer compounds. Sambhar Lake is the largest inland soda lake in India and is an appropriate habitat for halophilic bacterial and archaeal strains in terms of diversity and potential production of bioactive compounds. In the present study, a moderately halo-alkaliphilic bacterial strain C12A1 was isolated from Sambhar Lake, located in Rajasthan, India. C12A1 was gram-positive, motile, rod-shaped, formed oval endospores, produced carotenoids, and exhibited optimal growth at 37 °C in 10–15% NaCl (pH 8). C12A1 was found to be able to hydrolyze skimmed milk, gelatin, and Tween 80 but unable to hydrolyze starch and carboxymethylcellulose. C12A1 showed 98.87% and 98.50% identity in 16S rRNA gene sequence to P. halophilus and P. salipiscarius, respectively. Nevertheless, C12A1 was clustered within the clade consisting of P. salipiscarius strains, but it showed a distinct lineage. Thus, C12A1 was designated as Piscibacillus sp. Cell proliferation assay results showed that C12A1 broth extract (BEP) decreased cell viability in breast cancer MDA-MB-231 cells, which was confirmed by the MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. Induction of cell toxicity was visualized by microscopy. Reverse Transcriptase PCR (RT-PCR) analysis demonstrated that BEP inhibited the expression of proliferative B-cell lymphoma-extra large (Bcl-xL) and cell cycle marker Cyclin-dependent kinase 2 (CDK2) at transcript levels. Similarly, cell migration and colony formation along with mesenchymal marker vimentin and stem cell marker BMI transcripts were found to be inhibited when cells were treated with the BEP. The anti-breast cancer potential of C12A1 indicates that microorganisms inhabiting saline-alkaline habitats, with Piscibacillus sp. in particular, are a promising source for discovery of novel bioactive substances.
Highlights
Diverse halophilic microorganisms inhabit hypersaline and alkaline environments such as pond brines and natural salt lakes [1]
Halophilic bacteria have attracted more attention due to their adaptability in adverse conditions for growth. They produce varied natural bioactive compounds such as compatible solutes, antitumor and antimicrobial substances, enzymes, polymers, and pigments [5,6]. Halophilic bacteria such as Halobacterium sp.TM, Salinibacter, Halobacillus halophilus, Pseudomonas halophila and Haloferax mediterranei have been isolated from varied habitat [7,8,9,10,11]
The colonies of isolated halo-alkaliphilic bacterium strain C12A1 were circular in shape, convex, Mtriacnrosolrugacneisnmts-s2m01o8,o6t,hx aFOndR PcEreEaRmREtVoIEyWellow in color (Figure 1a)
Summary
Diverse halophilic microorganisms inhabit hypersaline and alkaline environments such as pond brines and natural salt lakes [1]. Halophilic bacteria have attracted more attention due to their adaptability in adverse conditions for growth They produce varied natural bioactive compounds such as compatible solutes, antitumor and antimicrobial substances, enzymes, polymers, and pigments [5,6]. Halophilic bacteria such as Halobacterium sp.TM, Salinibacter, Halobacillus halophilus, Pseudomonas halophila and Haloferax mediterranei have been isolated from varied habitat [7,8,9,10,11]. Considering the vastness of Sambhar Lake and an appropriate habitat of halophilic bacterial and archaeal strains in terms of diversity and potential production of bioactive compounds, the present study was undertaken to isolate and characterize strains from Sambhar Lake (a soda lake) to determine if any exhibit anti-breast cancer activity. We successfully purified C12A1, belonging to Piscibacillus sp., and investigated its anticancer activity against the MDA-MB-21 breast cancer cell line
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