Mutations That Stimulate
            <i>flhDC</i>
            Expression in Escherichia coli K-12

Fahrner, Karen; Berg, Howard C.

doi:10.1128/jb.00455-15

Cited by 38 publications

(38 citation statements)

References 91 publications

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“…One explanation for the NPEC-F strains and the faster derivatives of the NPEC-S strains is that their movement employs flagella. Several mutations can stimulate expression of flhDC , which specifies the master regulator of flagella synthesis, including insertions in the promoter region of the flhDC operon (27–29). Such an insertion increased flhDC expression 2.7-fold and resulted in 32-fold and 65-fold increases in fliA and flhB expression, respectively (29).…”

Section: Resultsmentioning

confidence: 99%

FIMBRIAE AND FLAGELLA MEDIATED SURFACE MOTILITY AND THE EFFECT OF GLUCOSE ON NONPATHOGENIC AND UROPATHOGENICESCHERICHIA COLI

Ambagaspitiye¹,

Sudarshan²,

Hogins³

et al. 2019

Preprint

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word count: 223 15 Text word count (including abstract and importance): 3965 16 17 2ABSTRACT 18 We characterized the surface motility of nonpathogenic and pathogenic E. coli strains 19 with respect to the appendage requirement, flagella versus fimbriae, and the glucose requirement. 20 Nonpathogenic lab strains exhibited either slow or fast surface movement. The slow strains 21 required type 1 fimbriae for movement, while the fast strains required flagella and had an 22 insertion in the flhDC promoter region. Surface movement of three uropathogenic E. coli 23 (UPEC) strains was fast and required flagella, but these strains did not have an insertion in the 24 flhDC promoter region. We assessed swimming motility as an indicator of flagella synthesis and 25 found that glucose inhibited swimming of the slow nonpathogenic strains but not of the fast 26 nonpathogenic or pathogenic strains. Fimbriae-based surface motility requires glucose, which 27 inhibits cyclic-AMP (cAMP) and flagella synthesis; therefore, we examined whether surface 28 motility required cAMP. The surface motility of a slow, fimbriae-dominant, nonpathogenic strain 29 did not require cAMP, which was expected because fimbriae synthesis does not require cAMP. 30In contrast, the surface motility of a faster, flagella-dominant, UPEC strain required cAMP, 31 which was unexpected because swarming was unaffected by the presence of glucose. Electron 32 microscopy verified the presence or absence of fimbriae or flagella. In summary, surface 33 motilities of the nonpathogenic and uropathogenic E. coli strains of this study differed in the 34 appendage used and the effects of glucose on flagella synthesis. 35 36 IMPORTANCE 37Uropathogenic Escherichia coli strains cause 80-90% of community-acquired urinary 38 tract infections, and recurrent urinary tract infections, which can last for years, and often become 39 antibiotic resistant. Urinary tract infections can be associated with intra-vesical lesions extending 40 3 from localized trigonitis/cystitis to widely distributed pancystitis: motility may be a factor that 41 distinguishes between these infection patterns. Nonpathogenic and uropathogenic E. coli were 42 shown to exhibit fimbriae-and flagella-dependent surface motility, respectively, and the 43 difference was attributed to altered control of flagella synthesis by glucose. Uropathogenic E. 44 coli strains grow more rapidly in urine than nonpathogenic strains, which implies differences in 45 metabolism. Understanding the basis for glucose-insensitive control of flagella-dependent 46 motility could provide insight into uropathogenic E. coli metabolism and virulence. 47 48 49 Escherichia coli is an extraordinarily successful pathogen which causes a variety of 50 diseases, including urinary tract infections (1). Uropathogenic E. coli (UPEC) is the predominant 51 cause of acute and recurrent urinary tract infections, which can become antibiotic resistant and 52 persist for years (2, 3). In women with recurrent urinary tract infections (rUTIs), the cla...

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Section: Resultsmentioning

confidence: 99%

FIMBRIAE AND FLAGELLA MEDIATED SURFACE MOTILITY AND THE EFFECT OF GLUCOSE ON NONPATHOGENIC AND UROPATHOGENICESCHERICHIA COLI

Ambagaspitiye¹,

Sudarshan²,

Hogins³

et al. 2019

Preprint

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“…IS1 refers to the IS1 elements that was described by Lee and Park [13] at −303 pb. IS refers to the IS5 described by Fahrner and Berg as the most distal (−476) IS element that had a positive effect on flhD expression [14]. b contains the 1 kb ladder (Amresco, Solon OH) and 14 lanes of PCR products: lanes 1 & 2, MC1000; lanes 3 & 4, JS81; lanes 5 & 6, JS45; lanes 7 & 8, JS56; lanes 9 & 10, JS87; lanes 11 & 12, JS44; lanes 13 and 14, JS43.…”

Section: Resultsmentioning

confidence: 99%

“…As mechanism, we propose that the location of the mutation within the flhD operon determines whether the effect on motility is positive or negative. All the previously published E. coli K-12 biofilm isolates had increased motility [11–14]. Barker and coworkers postulated that the positive effect on flhD expression of these insertions may be due to interference with some of the negative regulators ( e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Relative to the transcription start site, two IS5 elements inserted 315 and 166 bp upstream, while one IS1 inserted 303 bp upstream [13]. The final study that identified insertion elements in the flhD promoter is by Fahrner and Berg, who found IS elements up to 476 bp from the transcriptional start that still had stimulating effects on expression of the flhD operon [14]. The authors concluded that a large upstream region is involved in the topology of flhD expression.…”

Section: Introductionmentioning

confidence: 99%

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Spontaneous mutations in the flhD operon generate motility heterogeneity in Escherichia coli biofilm

et al. 2016

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BackgroundHeterogeneity and niche adaptation in bacterial biofilm involve changes to the genetic makeup of the bacteria and gene expression control. We hypothesized that i) spontaneous mutations in the flhD operon can either increase or decrease motility and that ii) the resulting motility heterogeneity in the biofilm might lead to a long-term increase in biofilm biomass.ResultsWe allowed the highly motile E. coli K-12 strain MC1000 to form seven- and fourteen-day old biofilm, from which we recovered reduced motility isolates at a substantially greater frequency (5.4 %) than from a similar experiment with planktonic bacteria (0.1 %). Biofilms formed exclusively by MC1000 degraded after 2 weeks. In contrast, biofilms initiated with a 1:1 ratio of MC1000 and its isogenic flhD::kn mutant remained intact at 4 weeks and the two strains remained in equilibrium for at least two weeks. These data imply that an ‘optimal’ biofilm may contain a mixture of motile and non-motile bacteria.Twenty-eight of the non-motile MC1000 isolates contained an IS1 element in proximity to the translational start of FlhD or within the open reading frames for FlhD or FlhC. Two isolates had an IS2 and one isolate had an IS5 in the open reading frame for FlhD. An additional three isolates contained deletions that included the RNA polymerase binding site, five isolates contained point mutations and small deletions in the open reading frame for FlhC. The locations of all these mutations are consistent with the lack of motility and further downstream within the flhD operon than previously published IS elements that increased motility. We believe that the location of the mutation within the flhD operon determines whether the effect on motility is positive or negative.To test the second part of our hypothesis where motility heterogeneity in a biofilm may lead to a long-term increase in biofilm biomass, we quantified biofilm biomass by MC1000, MC1000 flhD::kn, and mixtures of the two strains at ratios of 1:1, 10:1, and 1:10. After 3 weeks, biofilm of the mixed cultures contained up to five times more biomass than biofilm of each of the individual strains.ConclusionMutations in the flhD operon can exert positive or negative effects on motility, depending on the site of the mutation. We believe that this is a mechanism to generate motility heterogeneity within E. coli biofilm, which may help to maintain biofilm biomass over extended periods of time.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0878-1) contains supplementary material, which is available to authorized users.

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“…In addition to prewired regulation, genetic mutations can also lead to activation of genes that are otherwise silenced, but the dynamics of such events under changing environments are much less understood. In the case of motility gene expression, a wide array of mutations have been found upstream of flhDC in both wild and laboratory isolates of E. coli K-12 strains (11)(12)(13). In particular, many strains, including several sequenced MG1655 variants, such as CGSC 7740, carry different insertion sequence (IS) elements that perturb the regulation of flhDC expression, leading to dramatic differences in the ability to become motile under conditions that are typically used to study motility (11,14,15).…”

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confidence: 99%

Rapid Accumulation of Motility-Activating Mutations in Resting Liquid Culture of Escherichia coli

Parker

Demetçi

2019

J Bacteriol

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Expression of motility genes is a potentially beneficial but costly process in bacteria. Interestingly, many isolate strains of Escherichia coli possess motility genes but have lost the ability to activate them under conditions in which motility is advantageous, raising the question of how they respond to these situations. Through transcriptome profiling of strains in the E. coli single-gene knockout Keio collection, we noticed drastic upregulation of motility genes in many of the deletion strains compared to levels in their weakly motile parent strain (BW25113). We show that this switch to a motile phenotype is not a direct consequence of the genes deleted but is instead due to a variety of secondary mutations that increase the expression of the major motility regulator, FlhDC. Importantly, we find that this switch can be reproduced by growing poorly motile E. coli strains in nonshaking liquid medium overnight but not in shaking liquid medium. Individual isolates after the nonshaking overnight incubations acquired distinct mutations upstream of the flhDC operon, including different insertion sequence (IS) elements and, to a lesser extent, point mutations. The rapidity with which genetic changes sweep through the populations grown without shaking shows that poorly motile strains can quickly adapt to a motile lifestyle by genetic rewiring. IMPORTANCE The ability to tune gene expression in times of need outside preordained regulatory networks is an essential evolutionary process that allows organisms to survive and compete. Here, we show that upon overnight incubation in liquid medium without shaking, populations of largely nonmotile Escherichia coli bacteria can rapidly accumulate mutants that have constitutive motility. This effect contributes to widespread secondary mutations in the single-gene knockout library, the Keio collection. As a result, 49/71 (69%) of the Keio strains tested exhibited various degrees of motility, whereas their parental strain is poorly motile. These observations highlight the plasticity of gene expression even in the absence of preexisting regulatory programs and should raise awareness of procedures for handling laboratory strains of E. coli.

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Mutations That Stimulate flhDC Expression in Escherichia coli K-12

Cited by 38 publications

References 91 publications

FIMBRIAE AND FLAGELLA MEDIATED SURFACE MOTILITY AND THE EFFECT OF GLUCOSE ON NONPATHOGENIC AND UROPATHOGENICESCHERICHIA COLI

FIMBRIAE AND FLAGELLA MEDIATED SURFACE MOTILITY AND THE EFFECT OF GLUCOSE ON NONPATHOGENIC AND UROPATHOGENICESCHERICHIA COLI

Spontaneous mutations in the flhD operon generate motility heterogeneity in Escherichia coli biofilm

Rapid Accumulation of Motility-Activating Mutations in Resting Liquid Culture of Escherichia coli

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