Shabreen Banu, Shivakiran Alva, Prathiksha J Prabhu, Sreedharan Krishnan, Madhu K Mani
Multi-modular enzyme complexes known as non-ribosomal peptide synthetases (NRPSs) and polyketide synthetases (PKSs) have been widely reported in bacteria that produce secondary bioactive metabolites such as non-ribosomal peptides (NRPs) and polyketides (PKs), respectively. These NRPS/PKS pathways contribute to synthesizing several antibiotics, such as vancomycin, rifamycin, and bleomycin, which are vital in human medicine. The present study aimed to isolate gut-associated bacteria from mud crab , and detect NRPS and PKS gene clusters associated with it. This study included 36 bacterial isolates from five mud crab gut samples. Biosynthetic gene clusters (NRPS and PKS), were detected by PCR using degenerative primers specific to these genes. Three isolates (FKP2-4, FKP4-1, and FKP2-16) were positive for NRPS and two for PKS (FKP2-4 and FKP4-1) genes. The isolates were subjected to 16S rRNA gene amplification and sequenced. In silico analysis of the sequences using the Basic Local Alignment Search Tool (BLAST) identified the isolates FKP2-4, FKP4-1, and FKP2-16 as and , respectively, after comparing with the existing sequences available in the National Center for Biotechnology Information (NCBI) database. Compared to the control, it was observed that these isolates exhibited intriguing antagonistic activities against and . However, these isolates failed to show significant activity against . Exopolysaccharide production by the isolated organisms was tested using Zobell marine agar (ZMA) with 5% sucrose, but none of the colonies were mucoid or slimy.
