Abstract
Bacterial motility is thought to play an important role in virulence. We have previously shown that proficient bacterial swimming and swarming in vitro is correlated with the persistent intramammary infection phenotype observed in cattle. However, little is known about the gene regulation differences important for different motility phenotypes in Escherichia coli. In this work, three E.coli strains that cause persistent bovine mastitis infections were grown in three media that promote different types of motility (planktonic, swimming, and swarming). Using whole-transcriptome RNA sequencing, we identified a total of 935 genes (~21% of the total genome) that were differentially expressed in comparisons of the various motility-promoting conditions. We found that approximately 7% of the differentially expressed genes were associated with iron regulation. We show that motility assays using iron or iron chelators confirmed the importance of iron regulation to the observed motility phenotypes. Because of the observation that E.coli strains that cause persistent infections are more motile, we contend that better understanding of the genes that are differentially expressed due to the type of motility will yield important information about how bacteria can become established within a host. Elucidating the mechanisms that regulate bacterial motility may provide new approaches in the development of intervention strategies as well as facilitate the discovery of novel diagnostics and therapeutics. IMPORTANCE Bacteria can exhibit various types of motility. It is known that different types of motilities can be associated with virulence. In this work, we compare gene expression levels in bacteria that were grown under conditions that promoted three different types of E.coli motility. Better understanding of the mechanisms of how bacteria can cause an infection is an important first step to better diagnostics and therapeutics.
Highlights
Animal Disease Center, Agricultural Research Service (ARS), United States Department of Agriculture (USDA), Ames, Iowa, USAc
The three Mammary-pathogenic Escherichia coli (MPEC) strains were used as the biological replicates under each growth condition to determine significant gene expression changes between the three motility phenotypes
Based on the finding of a large number of differentially expressed genes associated with the ferric uptake regulator (Fur), we explored the effects of iron on motility
Summary
Differential gene expression of three mastitis-causing Escherichia coli strains grown under planktonic, swimming, and swarming culture conditions. We compare gene expression in bacteria that are grown in conditions that force three types of bacterial motility. Bacteria can exhibit various types of motility. We compare gene expression levels in bacteria that were grown under conditions that promoted three different types of E. coli motility. Two of the best-described types of bacterial motility are swimming and swarming. Swimming motility is defined as that exhibited by individual bacteria propelled by rotating flagella in liquid or semisolid media. Swarming represents the coordinated motility of a dense group of bacteria [2, 3] and, like swimming, is mediated by flagella. Swarming bacteria can demonstrate inVolume 1 Issue 4 e00064-16 msystems.asm.org 1
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