Uropathogenic Escherichia coli (UPEC) are the leading cause of urinary tract infections (UTIs) globally. These strains can form biofilms and biofilm-like intracellular bacterial communities (IBCs) that protect against host defence systems and antimicrobials. The ability to form biofilms contributes not only to hospital acquired urinary tract infections (HAUTIs), the most common type of hospital acquired infection, but to chronic re-infections.
Here, we use transposon directed insertion site sequencing (TraDIS) to identify genes in the uropathogenic E. coli strain UTI89 that are essential for growth and survival in rich medium, and under biofilm forming conditions at varying temperatures. We compared the essential genome to other UPEC and laboratory E. coli strains to identify genes that were unique and essential in UTI89. In addition, we examined the effects of temperature on the essential genome of a mature biofilm and compared our results to studies of temporal and growth medium effects on biofilm essential genomes.
In our library, we identified 413 essential genes, 173 of which were not essential in TraDIS libraries for the uropathogenic E. coli strain EC958, or the laboratory K-12 E. coli strain BW25113. There were 18 essential genes that were only present in UTI89, while 155 were conserved but non-essential in other strains.
We further identified 177 genes essential for biofilm formation at both room (25°C) and physiological (37°C) temperatures. We found that genes involved in the production and regulation of fimbriae and flagella, as well as capsular synthesis and chemotaxis response systems were essential in both temperature conditions. However, an additional 109 and 70 genes were essential when grown at 25°C and 37°C, respectively. The biofilm grown at a 25°C required more genes involved in mitigating oxidative stress, while genes only essential at 37°C were critical for regulating ß-galactosidase and glycerol-3-phosphate metabolic pathways.
This work investigates the differences between essential genomes of UPEC and provides insight into the role of temperature on genes required for biofilm formation.