Substrate preferences, phylogenetic and biochemical properties of proteolytic bacteria present in the digestive tract of Nile tilapia (<i>Oreochromis niloticus</i>)

Abstract

&lt;abstract&gt; &lt;p&gt;Vertebrate intestine appears to be an excellent source of proteolytic bacteria for industrial and probiotic use. We therefore aimed at obtaining the gut-associated proteolytic species of Nile tilapia (&lt;italic&gt;Oreochromis niloticus&lt;/italic&gt;). We have isolated twenty six bacterial strains from its intestinal tract, seven of which showed exoprotease activity with the formation of clear halos on skim milk. Their depolymerization ability was further assessed on three distinct proteins including casein, gelatin, and albumin. All the isolates could successfully hydrolyze the three substrates indicating relatively broad specificity of their secreted proteases. Molecular taxonomy and phylogeny of the proteolytic isolates were determined based on their 16S rRNA gene barcoding, which suggested that the seven strains belong to three phyla viz. Firmicutes, Proteobacteria, and Actinobacteria, distributed across the genera &lt;italic&gt;Priestia&lt;/italic&gt;, &lt;italic&gt;Citrobacter&lt;/italic&gt;, &lt;italic&gt;Pseudomonas&lt;/italic&gt;, &lt;italic&gt;Stenotrophomonas&lt;/italic&gt;, &lt;italic&gt;Burkholderia&lt;/italic&gt;, &lt;italic&gt;Providencia&lt;/italic&gt;, and &lt;italic&gt;Micrococcus&lt;/italic&gt;. The isolates were further characterized by a comprehensive study of their morphological, cultural, cellular and biochemical properties which were consistent with the phylogenetic annotations. To reveal their proteolytic capacity alongside substrate preferences, enzyme-production was determined by the diffusion assay. The &lt;italic&gt;Pseudomonas&lt;/italic&gt;, &lt;italic&gt;Stenotrophomonas&lt;/italic&gt; and &lt;italic&gt;Micrococcus&lt;/italic&gt; isolates appeared to be most promising with maximum protease production on casein, gelatin, and albumin media respectively. Our findings present valuable insights into the phylogenetic and biochemical properties of gut-associated proteolytic strains of Nile tilapia.&lt;/p&gt; &lt;/abstract&gt;

Dietary Curcumin Supplementation Could Improve Muscle Quality, Antioxidant Enzyme Activities and the Gut Microbiota Structure of Pelodiscus sinensis

“…The principal microorganisms influenced by CM, as evidenced in prior research, encompass Proteobacteria, Firmicutes, Actinobacteria, and Fusobacteria [ 51 , 52 ]. In addition, dietary CM treatment also increased the abundance of Pseudomonas and Stenotrophomonas genus, which are identified as the main protease-producing bacteria [ 53 , 54 ]. Notably, the increased richness of Lactobacillus and Flavobacterium were detected in the CM4 group.…”

Antipathogenic Action and Antibiotic Sensitivity Pattern of the “Borhani”-Associated Lactic Acid Bacterium Weissella Confusa Lab-11

“…Samples were also spread on the MRS media without cysteine-supplementation and incubated aerobically. All colonies with unique morphological appearances were selected, picked by a sterile tooth-pick and streaked on MRS agar medium two to three times in succession to obtain pure cultures preserved as glycerol stocks at -80°C as described by Hossain et al (2011) and Hossain et al (2021). The isolates were revived in MRS broth before use, and subsequently transferred and maintained in the MRS medium at 37℃.…”

“…Taxonomic assignment of the isolate was based on (1) percent identity of its 16S rRNA gene sequence to that of other bacteria in GenBank (Hossain et al, 2018) and (2) the number of hits produced against various phylotypes in BLAST result (Hossain et al, 2021). BLAST was run with default setting except that the "Max target sequences" was set to 100 (default), 250, 500, 1,000 or 5,000.…”