Reductions in bacterial viability stimulate the production of Extra-intestinal Pathogenic Escherichia coli (ExPEC) cytoplasm-carrying Extracellular Vesicles (EVs)

Min Jiang; Zhongxing Wang; Fufang Xia; Zhe Wen; Rui Chen; Dongyu Zhu; Min Wang; Xiangkai Zhuge; Jianjun Dai

doi:10.1371/journal.ppat.1010908

Reductions in bacterial viability stimulate the production of Extra-intestinal Pathogenic Escherichia coli (ExPEC) cytoplasm-carrying Extracellular Vesicles (EVs)

PLoS Pathog. 2022 Oct 19;18(10):e1010908. doi: 10.1371/journal.ppat.1010908. eCollection 2022 Oct.

Authors

Min Jiang^{1

2}, Zhongxing Wang^{1

2}, Fufang Xia^{1

2}, Zhe Wen^{1

2}, Rui Chen^{1

2}, Dongyu Zhu^{1

2}, Min Wang², Xiangkai Zhuge², Jianjun Dai^{1

3}

Affiliations

¹ MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
² Department of Nutrition and Food Hygiene, School of Public Health, Nantong University, Nantong, China.
³ College of Pharmacy, China Pharmaceutical University, Nanjing, China.

Abstract

Extra-intestinal Pathogenic Escherichia coli (ExPEC) is defined as an extra-intestinal foodborne pathogen, and several dominant sequence types (STs) ExPEC isolates are highly virulent, with zoonotic potential. Bacteria extracellular vesicles (EVs) carry specific subsets of molecular cargo, which affect various biological processes in bacteria and host. The mechanisms of EVs formation in ExPEC remains to be elucidated. Here, the purified EVs of ExPEC strains of different STs were isolated with ultracentrifugation processes. A comparative analysis of the strain proteomes showed that cytoplasmic proteins accounted for a relatively high proportion of the proteins among ExPEC EVs. The proportion of cytoplasm-carrying vesicles in ExPEC EVs was calculated with a simple green fluorescent protein (GFP) expression method. The RecA/LexA-dependent SOS response is a critical mediator of generation of cytoplasm-carrying EVs. The SOS response activates the expression of prophage-associated endolysins, Epel1, Epel2.1, and Epel2.2, which triggered cell lysis, increasing the production of ExPEC cytoplasm-carrying EVs. The repressor LexA controlled directly the expression of these endolysins by binding to the SOS boxes in the endolysin promoter regions. Reducing bacterial viability stimulated the production of ExPEC EVs, especially cytoplasm-carrying EVs. The imbalance in cell division caused by exposure to H2O2, the deletion of ftsK genes, or t6A synthesis defects activated the RecA/LexA-dependent SOS response, inducing the expression of endolysins, and thus increasing the proportion of cytoplasm-carrying EVs in the total ExPEC EVs. Antibiotics, which decreased bacterial viability, also increase the production of ExPEC cytoplasm-carrying EVs through the SOS response. Changes in the proportion of cytoplasm-carrying EVs affected the total DNA content of ExPEC EVs. When macrophages are exposed to a higher proportion of cytoplasm-carrying vesicles, ExPEC EVs were more cytotoxic to macrophages, accompanied with more-severe mitochondrial disruption and a higher level of induced intrinsic apoptosis. In summary, we offered comprehensive insight into the proteome analysis of ExPEC EVs. This study demonstrated the novel formation mechanisms of E. coli cytoplasm-carrying EVs.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cytoplasm / metabolism
Escherichia coli / genetics
Escherichia coli Proteins* / genetics
Escherichia coli Proteins* / metabolism
Extracellular Vesicles* / metabolism
Extraintestinal Pathogenic Escherichia coli* / genetics
Hydrogen Peroxide / metabolism
Membrane Proteins / metabolism
Microbial Viability*

Substances

Escherichia coli Proteins
FtsK protein, E coli
Hydrogen Peroxide
Membrane Proteins

Grants and funding

This study was supported by the National Natural Science Foundation of China (grant no. 31872479, to J.D., and 31702252, to X.Z.), the Jiangsu Province Key Research and Development Program (Modern Agriculture) Project (grant no. BE2022329, to X.Z.), and the Jiangsu Agricultural Science and Technology Innovation Fund (grant no. CX [21]3126, to X.Z.). The funding bodies had no role in the study design, data collection or interpretation, or the decision to submit the work for publication.