PREreviews of “Breaching the cell-envelope barriers of gram-positive and fungal microbes by a type VI secretion system in Acidovorax citrulli” | PREreview

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Breaching the cell-envelope barriers of gram-positive and fungal microbes by a type VI secretion system in Acidovorax citrulli

by Tong-Tong Pei, Yumin Kan, Zeng-Hang Wang, Ming-Xuan Tang, Hao Li, Shuangquan Yan, Yang Cui, Hao-Yu Zheng, Han Luo, and Tao G. Dong

Posted: May 31, 2021
Server: bioRxiv
DOI: 10.1101/2021.05.31.446370

Abstract

The type VI secretion system (T6SS) is a double-tubular toxin-injection nanomachine widely found in gram-negative human and plant pathogens. The current model depicts that the T6SS spear-like Hcp tube is powered by the contraction of an outer sheath to drill through the envelope of a neighboring cell, achieving cytosol to cytosol delivery. However, gram-positive bacteria seem to be impenetrable to such T6SS action. Here we report that a plant pathogen Acidovorax citrulli (AC) deploys a highly potent T6SS to kill a range of bacteria including Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Mycobacterium smegmatis as well as fungal species including Candida albicans and Pichia pastoris. Using bioinformatic and biochemical assays, we identified a group of T6SS effectors and characterized one effector RhsB that is critical for interspecies interaction. We report that RhsB contains a conserved YD-repeat domain and a C-terminal nuclease domain. Toxicity of RhsB was neutralized by its downstream immunity proteins through direct interaction. RhsB was cleaved at the C-terminal end and a catalytic mutation within the internal aspartic protease abolished such cleavage. Collectively, the T6SS of AC displays potent activities to penetrate the cell envelope barriers of gram-positive and fungal species, highlighting the greatly expanded capabilities of T6SS in modulating microbiome compositions in complex environments.

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by Khaki Chameleon

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Are the results likely to lead to future research?	100%	0%	0%	0%
Is sufficient detail provided to allow reproduction of the study?	100%	0%	0%	0%
Are the methods and statistics appropriate for the analysis?	0%	0%	0%	100%
Are the principal conclusions supported by the data and analysis?	100%	0%	0%	0%
Does the manuscript discuss limitations?	0%	0%	0%	100%
Have the authors adequately discussed ethical concerns?	0%	0%	100%	0%
Does the manuscript include new data?	100%	0%	0%	0%
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PREreview by Khaki Chameleon

Authored by Khaki Chameleon

In this short manuscript by Pei et al., authors describe that a plant pathogen, Acidovorax citrulli, uses a T6SS to compete with Gram-positive bacterial and fungal species. A brief characterization of a new effector (named RhsB) is described, which belongs to the nuclease superfamily PD-(D/E)XK.…

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