AUTHOR=Li Yanyan , Yan Xiaojun , Tao Zhen 

TITLE=Two Type VI Secretion DNase Effectors are Utilized for Interbacterial Competition in the Fish Pathogen Pseudomonas plecoglossicida

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.869278

DOI=10.3389/fmicb.2022.869278

ISSN=1664-302X

ABSTRACT=<p><italic>Pseudomonas plecoglossicida</italic> is a facultative fish pathogen that possesses three distinct type VI secretion systems (named T6SS-1, T6SS-2, and T6SS-3). Our previous work indicated that only T6SS-2 of <italic>P. plecoglossicida</italic> mediates interbacterial competition. However, the antibacterial T6SS effectors and their functions are unclear. Here, we reported two T6SS effectors that mediate antibacterial activity. We first identified four putative antibacterial effectors (denoted as Txe1, Txe2, Txe3, and Txe4) and their cognate immunity proteins encoded in <italic>P. plecoglossicida</italic> strain XSDHY-P by analyzing the regions downstream of three <italic>vgrG</italic> genes. We showed that the growth of <italic>Escherichia coli</italic> cells expressing Txe1, Txe2, and Txe4 was inhibited, and these three effectors exhibited nuclease activity <italic>in vivo</italic>. The interbacterial competition assays with single- or multi-effector deletion mutants as attackers revealed that Txe1 was the predominant T6SS toxin of <italic>P. plecoglossicida</italic> strain XSDHY-P mediating the interbacterial killing. This work contributes to our understanding of bacterial effectors involved in the interbacterial competition.</p>