Isolation of Marine Bacillus sp. with Antagonistic and Organic-Substances-Degrading Activities and Its Potential Application as a Fish Probiotic

Abstract

We report on the isolation and characterization of an acid- and bile-tolerant bacterial strain, Bacillus sp. YB1701 with antibacterial and quorum-quenching activity. Strain YB1701 was isolated from coastal sediment samples and characterized by biochemical tests and 16S rRNA sequencing. In vitro study indicated that strain YB1701 can survive at pH 2.0 for up to 3 h and tolerate bile up to 2.0% concentration even after 12 h of exposure. Strain YB1701 showed antimicrobial activity against fish pathogens Aeromonas hydrophila and Vibrio parahemolyticus using an agar well diffusion assay. The trial test showed dietary supplementation of YB1701 significantly improved the resistance of Carassius auratus gibelio against A. hydrophila challenge. The safety assessment revealed that the isolate Bacillus sp. YB1701 was not cytotoxic to Carassius auratus gibelio or mice and did not exhibit hemolytic activity on rabbit blood agar plate. Disc-diffusion assays using a panel of antibiotics listed by the European Food Safety Authority (EFSA) showed that YB1701 was susceptible to selected antibiotics. Under laboratory conditions, the degradation rate of organic waste (predominately fish excrement) for 14 days by YB1701 was 79.69%. Results from the present study suggest that strain YB1701 is a potential probiotic strain and can be used in aquaculture for degrading organic waste and improving disease resistance of fish against bacterial infection. Further study is needed to assess the utility of strain YB1701 on a commercial scale.

Isolation and identification of proteolytic, amylolytic, lipolytic, and chitinolytic bacteria from shrimp waste

“…These results agree with those reported by other authors for amylolytic capacity from different Vibrio species (Raghul Subin & Bhat 2011). Like our results, the genus Bacillus has been reported with amylolytic capacity (Zhou et al 2018). In addition, several bacteria including B.…”

Quorum Quenching Properties and Probiotic Potentials of Intestinal Associated Bacteria in Asian Sea Bass Lates calcarifer

“…The 16S rDNA sequence analysis of Bacillus sp. QQ4 showed 99.76% similarity to B. subtilis, B. velezensis and B. amyloliquefaciens, an observation that is very similar to the findings of Zhou et al (2018) [33]. Although Bacillus strains were already reported for QQ activity in various aquatic animals, here autochthonous Bacillus spp., able to degrade common AHLs belonging to Vibrio pathogens in fish, were isolated from the gastrointestinal tract of L. calcalifer for the first time.…”

“…Bacillus spp. have a high potential to produce functional enzymes that break down biological macromolecules, supply vitamins and fatty acids as well as degrade organic materials [33,46]. Thus, apart from endogenous digestive enzymes, there is a distinct microbial source of several exoenzymes in the intestine that might participate in and enhance the digestive process of aquatic animals.…”

Planococcus maritimus ML1206 Isolated from Wild Oysters Enhances the Survival of Caenorhabditis elegans against Vibrio anguillarum

“…Several marine bacterial strains, which might inhibit V. anguillarum damage to C. elegans , were isolated from healthy intestines of oysters and perch, and were tested on the C. elegans model. The experiments of acid and bile salt tolerance are both considered indispensable steps in screening probiotics [ 43 ]. In this study, strain ML1206, with good tolerance of acid and bile salt, and antibacterial function, was selected out of 20 marine bacterial strains as a potential probiotic candidate for further experiments.…”