[35]

The Effect of Low-Shear Modeled Microgravity on Adherent Invasive Escherichia coli Physiology and Virulence Potential. 

C.A. Allen, D.W. Niesel, and A.G. Torres. Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX.

   Adherent-invasive E. coli (AIEC) exhibit intrinsic adherent and invasive characteristics during host cell interactions and have been found to colonize the lesions of Crohn’s Disease (CD) patients. To date, little is known about the environmental triggers which induce changes in AIEC allowing it to persist in the gut and contribute to the chronic inflammation associated with CD.  AIEC strain O83:H1 was cultured under low-shear modeled microgravity (LSMMG) using high-aspect ratio vessels (HARVs) to examine the impact of this environment on AIEC physiology and virulence potential. Physiological assays revealed increases in both thermal stress resistance and in adherence to Caco-2 monolayers by AIEC O83:H1 after growth under LSMMG.  The alternative sigma factor and global stress response regulator RpoS was examined under LSMMG using an isogenic rpoS mutant.  The mutant exhibited similar characteristics as AIEC O83:H1 but with significantly increased thermal stress resistance and adherence.  Western blot analysis revealed no significant differences in RpoS expression in AIEC O83:H1 under LSMMG suggesting a potential regulatory role at the transcriptional level.  Transposon mutagenesis of the rpoS mutant produced two isolates with diminished adherence capabilities.  These results suggest a regulatory role for RpoS in AIEC adhesion under LSMMG conditions. Characterization of the transposon mutants is currently underway to identify putative adhesins/and or adherence-associated genes which play a key role in AIEC adherence under LSMMG conditions.  (Supported by NASA: 98-HEDS-02-291 and GSRP Fellowship 424490)