Bacterial Fight Club: Two-Component Signaling Cascades and Type VI Secretion System Cross-Interactions Benefit Bacterial Fitness

Indianapolis, IN

Uropathogenic E.coli (UPEC) account for the majority of urinary tract infections (UTIs) and part of their infection cycle includes the formation of biofilms. Bacterial two-component systems (TCSs) and type-VI secretion systems (T6SSs) are known to be involved in biofilm formation and virulence. In UPEC, the QseBC TCS is located within a T6SS gene cluster and also atypically interacts with another TCS, PmrAB. We hypothesize that PmrAB-QseBC-T6SS interactions confer a fitness advantage to UPEC, and that interfering with these interactions will negatively affect bacterial fitness, T6SS function, and virulence. To test this hypothesis, this project used bacterial fight clubs  in which the fitness of TCS- and T6SS-mutants were evaluated in competition assays. Bacterial counts were used to measure survival rates in each case. Our results showed that ΔqseC and ΔqseCΔpmrA are outcompeted by WT UPEC and that UPEC has two functional T6SS gene clusters, Hcp gene clusters 1 and 3. Our findings suggest that these interactions confer a fitness advantage to WT UPEC, and that interfering with said interactions could potentially attenuate virulence.