Regulation of flagellar motility during biofilm formation

Abstract

Many bacteria swim in liquid or swarm over solid surfaces by synthesizing rotary flagella. The same bacteria that are motile also commonly form non-motile multicellular aggregates held together by an extracellular matrix called biofilms. Biofilms are an important part of the lifestyle of pathogenic bacteria and it is assumed that there is a motility-to-biofilm transition wherein the inhibition of motility promotes biofilm formation. The transition is largely inferred from regulatory mutants that reveal the opposite regulation of the two phenotypes. Here we review the regulation of motility during biofilm formation in Bacillus, Pseudomonas, Vibrio, and Escherichia, and we conclude that the motility-to-biofilm transition, if necessary, likely involves two steps. In the short term, flagella are functionally regulated to either inhibit rotation or modulate the basal flagellar reversal frequency. Over the long term, flagellar gene transcription is inhibited and in the absence of de novo synthesis, flagella are likely diluted to extinction through growth. Both short term and long term control is likely important to the motility-to-biofilm transition to stabilize aggregates and optimize resource investment. We emphasize the newly discovered classes of flagellar functional regulators and speculate that others await discovery in the context of biofilm formation.

Genomic sequencing-based mutational enrichment analysis identifies motility genes in a genetically intractable gut microbe

“…The N terminus of Ea2157 has homology to the YcgR family of proteins, which in enteric bacteria control chemotaxis and swimming velocity by interacting directly with stator proteins (25,31). These findings confirm the important role of c-di-GMP in the regulation of flagellar motility in Firmicutes (32). In addition to GGDEF and EAL domains, Ea2862 also has a PAS domain that is predicted to sense small molecules such as metabolites and gases (33).…”

How methylglyoxal kills bacteria: An ultrastructural study

“…In addition, flagella provide a propulsion system for bacteria and consequently bacteria can swim in liquids and swarm over surfaces [18]. The fimbriae and the flagella have been identified as important drug targets as inhibition of genes associated with functioning and/or synthesis of structural proteins will result in decreased bacterial mobility, ability to adhere to innate and cellular surfaces and this will reduce virulence and prevent biofilm formation.…”

Type III secretion systems: the bacterial flagellum and the injectisome

“…A key player in this switch is the small cytoplasmic signal molecule cyclic-di-GMP (c-di-GMP) [65][66][67]), which itself may be influenced by the cell cycle, linking flagellar biosynthesis to cell division. In general, high c-di-GMP levels lead to downregulation of flagellar transcription [68,69]. For the injectisome, a related transcription hierarchy exists.…”