The effects of low‐shear stress on Adherent‐invasive Escherichia coli

Abstract

The impact of low-shear stress (LSS) was evaluated on an Adherent-invasive Escherichia coli clinical isolate (AIEC strain O83:H1) from a Crohn's disease patient. High-aspect ratio vessels (HARVs) were used to model LSS conditions to characterize changes in environmental stress resistance and adhesion/invasive properties. Low-shear stress-grown cultures exhibited enhanced thermal and oxidative stress resistance as well as increased adherence to Caco-2 cells, but no changes in invasion were observed. An AIEC rpoS mutant was constructed to examine the impact of this global stress regulator. The absence of RpoS under LSS conditions resulted in increased sensitivity to oxidative stress while adherence levels were elevated in comparison with the wild-type strain. TnphoA mutagenesis and rpoS complementation were carried out on the rpoS mutant to identify those factors involved in the LSS-induced adherence phenotype. Mutagenesis results revealed that one insertion disrupted the tnaB gene (encoding tryptophan permease) and the rpoS tnaB double mutant exhibited decreased adherence under LSS. Complementation of the tnaB gene, or medium supplemented with exogenous indole, restored adhesion of the rpoS tnaB mutant under LSS conditions. Overall, our study demonstrated how mechanical stresses such as LSS altered AIEC phenotypic characteristics and identified novel functions for some RpoS-regulated proteins.

Induction of Attachment-Independent Biofilm Formation and Repression ofhfqExpression by Low-Fluid-Shear Culture of Staphylococcus aureus

“…However, when using a nutrient-rich medium in our studies, we noted an approximately 3-fold difference in the cell concentrations of MRSA strain N315 and a difference of more than 5-fold for the MSSA strain 8325. Additionally, in response to LSMMG culturing in minimal medium, E. coli ZK650 exhibited increased growth (19), whereas under the same conditions, E. coli strains AIEC 083:H1 and K-12 AMS6 displayed growth profiles similar to those of controls (3,71). Taken together, it is most likely that changes in growth kinetics in response to LSMMG culture conditions occur on a strain-specific basis.…”

“…For the microorganisms thus far examined, the effect of the LSMMG environment on growth kinetics is varied, including reports of the low-shear condition having no effect or resulting in higher concentrations of bacteria than in controls (3,5,49,62,73). When cultured under LSMMG conditions in a nutrient-rich broth, S. Typhimurium 3339 displayed nearly identical growth profiles to those of the control through the mid-log growth phase (49).…”

“…Mathematical modeling has demonstrated that the fluid shear level within the RWV is less than 1 dyne/cm 2 and that incremental increases in fluid shear levels in the RWV result in corresponding changes in the microbial response (46). As this level of fluid shear reflects the fluid shear levels previously described for the brush border of the intestine, the RWV has been proposed as a model for investigating the effects of low fluid shear levels that are similar to those in the intestine (3,26,47,49,58).…”

The IbeA Invasin of Adherent-Invasive Escherichia coli Mediates Interaction with Intestinal Epithelia and Macrophages

“…The primers were IbeA2-F and IbeA2-R. The cat PCR product flanked by 40 bases upstream and downstream homologous to ibeA was subsequently electroporated into RedϩGam-producing AIEC NRG857c (with plasmid pKM201) (26,28). The presence of the cat gene was further confirmed by PCR (see Fig.…”

The Effects of Modeled Microgravity on Growth Kinetics, Antibiotic Susceptibility, Cold Growth, and the Virulence Potential of aYersinia pestis ymoA-Deficient Mutant and Its Isogenic Parental Strain

“…In addition to S. Typhimurium, enterotoxigenic and enteropathogenic E. coli (Chopra et al, 2006), adherent-invasive E. coli (Allen et al, 2008), and P. aeruginosa (Crabbé et al, 2008(Crabbé et al, , 2011 have also been characterized following CR growth. Interestingly, all the aforementioned pathogens responded to CR growth by similarly exhibiting enhanced virulence potentials.…”