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Two Tandem Mechanisms Control Bimodal Expression of the Flagellar Genes in Salmonella enterica

Lookup NU author(s): Dr Phillip AldridgeORCiD


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Copyright © 2020 American Society for Microbiology. Flagellar gene expression is bimodal in Salmonella enterica Under certain growth conditions, some cells express the flagellar genes whereas others do not. This results in mixed populations of motile and nonmotile cells. In the present study, we found that two independent mechanisms control bimodal expression of the flagellar genes. One was previously found to result from a double negative-feedback loop involving the flagellar regulators RflP and FliZ. This feedback loop governs bimodal expression of class 2 genes. In this work, a second mechanism was found to govern bimodal expression of class 3 genes. In particular, class 3 gene expression is still bimodal, even when class 2 gene expression is not. Using a combination of experimental and modeling approaches, we found that class 3 bimodality results from the σ28-FlgM developmental checkpoint.IMPORTANCE Many bacterial use flagella to swim in liquids and swarm over surface. In Salmonella enterica, over 50 genes are required to assemble flagella. The expression of these genes is tightly regulated. Previous studies have found that flagellar gene expression is bimodal in S. enterica, which means that only a fraction of cells express flagellar genes and are motile. In the present study, we found that two separate mechanisms induce this bimodal response. One mechanism, which was previously identified, tunes the fraction of motile cells in response to nutrients. The other results from a developmental checkpoint that couples flagellar gene expression to flagellar assembly. Collectively, these results further our understanding of how flagellar gene expression is regulated in S. enterica.

Publication metadata

Author(s): Wang X, Koirala S, Aldridge PD, Rao CV

Publication type: Article

Publication status: Published

Journal: Journal of Bacteriology

Year: 2020

Volume: 202

Issue: 13

Print publication date: 09/06/2020

Online publication date: 09/06/2020

Acceptance date: 13/04/2020

ISSN (print): 0021-9193

ISSN (electronic): 1098-5530

Publisher: American Society for Microbiology


DOI: 10.1128/JB.00787-19

PubMed id: 32312744


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