Date Published: May 22, 2018
Publisher: Springer Berlin Heidelberg
Author(s): Jia Wu, Guoqiang Xu, Yangyang Jin, Cong Sun, Li Zhou, Guodong Lin, Rong Xu, Ling Wei, Hui Fei, Dan Wang, Jianqing Chen, Zhengbing Lv, Kuancheng Liu.
The abuse of antibiotics and following rapidly increasing of antibiotic-resistant pathogens is the serious threat to our society. Natural products from microorganism are regarded as the important substitution antimicrobial agents of antibiotics. We isolated a new strain, Bacillus sp. GFP-2, from the Chiloscyllium plagiosum (Whitespotted bamboo shark) intestine, which showed great inhibitory effects on the growth of both Gram-positive and Gram-negative bacteria. Additionally, the growth of salmon was effectively promoted when fed with inactivated strain GFP-2 as the inhibition agent of pathogenic bacteria. The genes encoding antimicrobial peptides like LCI, YFGAP and hGAPDH and gene clusters for secondary metabolites and bacteriocins, such as difficidin, bacillibactin, bacilysin, surfactin, butirosin, macrolactin, bacillaene, fengycin, lanthipeptides and LCI, were predicted in the genome of Bacillus sp. GFP-2, which might be expressed and contribute to the antimicrobial activities of this strain. The gene encoding β-1,3-1,4-glucanase was successfully cloned from the genome and this protein was detected in the culture supernatant of Bacillus sp. GFP-2 by the antibody produced in rabbit immunized with the recombinant β-1,3-1,4-glucanase, indicating that this strain could express β-1,3-1,4-glucanase, which might partially contribute to its antimicrobial activities. This study can enhance a better understanding of the mechanism of antimicrobial activities in genus Bacillus and provide a useful material for the biotechnology study in antimicrobial agent development.
The studies of antibiotics started with the discovery of penicillin in 1928. With the discoveries of different antibiotics, many effective therapeutic strategies toward incurable or obstinate disease have been developed. However, accompany with the widely usage of antibiotics, the emerging of antibiotic-resistant pathogens is increasing rapidly, suggesting that, without urgent actions, we are heading for a “post-antibiotic era” (Mahlapuu et al. 2016). To solve this threat, many new and non-conventional anti-infective therapies have been developed (or identified) (Czaplewski et al. 2016). Over the past 10 years, many marine natural products were isolated and showed important effects in the aforementioned therapies. Due to the structural diversities of these natural products, researchers have paid high attention to expanding their studies from sponges, corals to microorganisms, among which, marine microorganisms are regarded as major sources of antimicrobial agents (Ng et al. 2015).
In this study, a new strain Bacillus sp. GFP-2 was isolated from the intestine of Whitespotted bamboo shark and could effectively inhibit the growth of Gram-positive and Gram-negative strains, showing around 50–70% inhibition ability of ampicillin. In addition, when fed additionally with strain GFP-2, as the inhibition agents of pathogenic bacteria, the growth of salmon (Oncorhynchus mykiss) can be greatly promoted, indicating that strain GFP-2 can effectively inhibit the growth of pathogenic bacteria in the intestine of other fishes besides shark.