Mechanism of the Potential Therapeutic Candidate Bacillus subtilis BSXE-1601 Against Shrimp Pathogenic Vibrios and Multifunctional Metabolites Biosynthetic Capability of the Strain as Predicted by Genome Analysis.

Dongdong Wang,Wenjun Wang,Weiming Zhu,Vikash Kumar,Shuanglin Dong,Haidong Li,Xiangli Tian,Guoliang Zhu,Wenwen Jiang,Jiahui Li,Kun Zhao

doi:10.3389/fmicb.2020.581802

Abstract

The global shrimp industry has suffered bacterial diseases caused mainly by Vibrio species. The typical vibriosis, acute hepatopancreatic necrosis disease (AHPND), has resulted in mass mortality and devastating economic losses. Thus, therapeutic strategies are highly needed to decrease the risk of vibriosis outbreaks. Herein, we initially identified that the growth of the causative agent of AHPND, Vibrio parahaemolyticus (VPAHPND) and other vibrios in Pacific white shrimp (Litopenaeus vannamei) was inhibited by a Bacillus subtilis strain BSXE-1601. The natural products amicoumacins A, B, and C were purified from the cell-free supernatant from the strain BSXE-1601, but only amicoumacin A was demonstrated to be responsible for this anti-Vibrio activity. Our discovery provided the first evidence that amicoumacin A was highly active against shrimp pathogens, including the representative strain VPAHPND. Furthermore, we elucidated the amicoumacin A biosynthetic gene cluster by whole genome sequencing of the B. subtilis strain BSXE-1601. In addition to amicoumacin A, the strain BSXE-1601 genome harbored other genes encoding bacillibactin, fengycin, surfactin, bacilysin, and subtilosin A, all of which have previously reported antagonistic activities against pathogenic strains. The whole-genome analysis provided unequivocal evidence in support of the huge potential of the strain BSXE-1601 to produce diverse biologically antagonistic natural products, which may facilitate further studies on the effective therapeutics for detrimental diseases in shrimp.

Highlights

The greatest challenge in the global shrimp industry is a disease that of bacterial origin and chief among these is Vibrio species (Ajadi et al, 2016; Hoseinifar et al, 2018)
The results revealed that amicoumacin A had good resistant activity against the tested bacterial pathogens of shrimp, especially VPAHPND 2S01, V. alginolyticus AR-1, V. harveyi SRTT9, V. vulnificus S01P2, even at a low concentration of 1.25 μg ml−1
The results may provide new insights into the possible mechanism of antagonistic activity of B. subtilis strain BSXE-1601 against the bacterial pathogens of shrimp

Summary

Introduction

The greatest challenge in the global shrimp industry is a disease that of bacterial origin and chief among these is Vibrio species (Ajadi et al, 2016; Hoseinifar et al, 2018). The acute hepatopancreatic necrosis disease (AHPND), formerly known as shrimp “early mortality syndrome” (EMS), is a newly emerging vibriosis that has caused severe mortality (up to 100%) and devastating economic effect in the global shrimp industry (Lightner et al, 2012; Joshi et al, 2014; Kongrueng et al, 2015; Boonsri et al, 2017). Besides AHPND, other vibrioses were frequently reported in farmed shrimp caused by Vibrio alginolyticus, Vibrio anguillarum, V. harveyi, Vibrio vulnificus, Vibrio splendidus, V. campbellii and Vibrio fischeri (Lavilla-Pitogo et al, 1990; Lightner, 1996; Lavilla-Pitogo et al, 1998; Chen et al, 2000; Jayasree et al, 2006; Longyant et al, 2008; Zheng et al, 2016; Chandrakala and Priya, 2017; Karnjana et al, 2019). Strategies that focus on restraining the growth or activity of pathogenic bacteria are highly needed

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Conclusion