DNA Uptake upon T6SS-Dependent Prey Cell Lysis Induces SOS Response and Reduces Fitness of Acinetobacter baylyi

Lin Lin,Peter David Ringel,Andrea Vettiger,Lara Dürr,Marek Basler

doi:10.1016/j.celrep.2019.09.083

Abstract

Certain Gram-negative bacteria use the type VI secretion system (T6SS) to kill and lyse competing bacteria. Here, we show that the T6SS-dependent lysis of prey cells by the naturally competent Acinetobacter baylyi results in the extensive filamentation of a subpopulation of A.baylyi cells. Filamentation is dependent on the release of DNA from the prey and its uptake by the competence system. The analysis of A.baylyi transcriptome and the response of transcriptional reporters suggest that the uptake of DNA results in the upregulation of the SOS response, which often leads to cell-division arrest. Long-term competition between competent and non-competent strains shows that the strain lacking the DNA uptake machinery outcompetes the parental strain only in the presence of the T6SS-dependent lysis of prey cells. Our data suggest that the cost of the induced SOS response may drive the selection of tight regulation or the loss of DNA uptake in bacteria capable of lysing their competitors.

Highlights

In natural environments, the microbial community often contains numerous different species, which compete or cooperate with one another
We show that the T6SS-dependent lysis of prey cells by the naturally competent Acinetobacter baylyi results in the extensive filamentation of a subpopulation of A. baylyi cells
The analysis of A. baylyi transcriptome and the response of transcriptional reporters suggest that the uptake of DNA results in the upregulation of the SOS response, which often leads to cell-division arrest

Summary

Introduction

The microbial community often contains numerous different species, which compete or cooperate with one another. The cooperative interactions are often mutually beneficial, providing fitness benefits to all of the species involved (Sachs et al, 2004). One example of the cooperative interactions is the biofilm formation, which involves bacterial cells adhering to one another as well as to non-biological surfaces (Hall-Stoodley et al, 2004; Lopez et al, 2010). The biofilm provides the cells in this structure with great advantages in nutrient capture as well as tolerance/resistance toward antimicrobials (Flemming et al, 2016). The competition, often involves the secretion of antimicrobial compounds such as colicins, pyocins, and antibiotics to the environment (Cascales et al, 2007; Michel-Briand and Baysse, 2002; Stubbendieck and Straight, 2016) or directly into the adjacent cells mediated by secretion systems, which require cell-cell contact. The type IV secretion system (T4SS) of Xanthomonas citri was shown to secrete a peptidoglycan hydrolase to kill other Gram-negative bacteria (Sgro et al, 2018; Souza et al, 2015)

Results

Discussion

Conclusion