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Elife. 2017 Jul 11;6. pii: e26938. doi: 10.7554/eLife.26938.

A broadly distributed toxin family mediates contact-dependent antagonism between gram-positive bacteria.

Author information

1
Department of Microbiology, University of Washington School of Medicine, Seattle, United States.
2
Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle, United Kingdom.
3
Department of Genome Sciences, University of Washington, Seattle, United States.
4
Michael DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Canada.
5
Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada.
6
Experimental Systems Group, Advanced Light Source, Berkeley, United States.
7
Northwestern Proteomics Core Facility, Northwestern University, Chicago, United States.
8
Department of Medicine, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Canada.
9
Department of Computer Science and Engineering, University of Washington, Seattle, United States.
10
Santa Fe Institute, Santa Fe, United States.
11
Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, United States.

Abstract

The Firmicutes are a phylum of bacteria that dominate numerous polymicrobial habitats of importance to human health and industry. Although these communities are often densely colonized, a broadly distributed contact-dependent mechanism of interbacterial antagonism utilized by Firmicutes has not been elucidated. Here we show that proteins belonging to the LXG polymorphic toxin family present in Streptococcus intermedius mediate cell contact- and Esx secretion pathway-dependent growth inhibition of diverse Firmicute species. The structure of one such toxin revealed a previously unobserved protein fold that we demonstrate directs the degradation of a uniquely bacterial molecule required for cell wall biosynthesis, lipid II. Consistent with our functional data linking LXG toxins to interbacterial interactions in S. intermedius, we show that LXG genes are prevalent in the human gut microbiome, a polymicrobial community dominated by Firmicutes. We speculate that interbacterial antagonism mediated by LXG toxins plays a critical role in shaping Firmicute-rich bacterial communities.

KEYWORDS:

Firmicute; infectious disease; microbiology; polymorphic; type VII secretion

PMID:
28696203
PMCID:
PMC5555719
DOI:
10.7554/eLife.26938
[Indexed for MEDLINE]
Free PMC Article

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