Preferential catabolism of L- vs D-serine by Proteus mirabilis contributes to pathogenesis and catheter-associated urinary tract infection

Abstract

Proteus mirabilis is a common cause of urinary tract infection, especially in catheterized individuals. Amino acids are the predominant nutrient for bacteria during growth in urine, and our prior studies identified several amino acid import and catabolism genes as fitness factors for P. mirabilis catheter-associated urinary tract infection (CAUTI), particularly D- and L-serine. In this study, we sought to determine the hierarchy of amino acid utilization by P. mirabilis and to examine the relative importance of D- vs L-serine catabolism for critical steps in CAUTI development and progression. Herein, we show that P. mirabilis preferentially catabolizes L-serine during growth in human urine, followed by D-serine, threonine, tyrosine, glutamine, tryptophan, and phenylalanine. Independently disrupting catabolism of either D- or L-serine has minimal impact on in vitro phenotypes while completely disrupting both pathways decreases motility, biofilm formation, and fitness due to perturbation of membrane potential and cell wall biosynthesis. In a mouse model of CAUTI, loss of either serine catabolism system decreased fitness, but disrupting L-serine catabolism caused a greater fitness defect than disrupting D-serine catabolism. We therefore conclude that hierarchical utilization of amino acids may be a critical component of P. mirabilis colonization and pathogenesis within the urinary tract.

Metabolic interplay betweenProteus mirabilisandEnterococcus faecalisfacilitates polymicrobial biofilm formation and invasive disease

“…When grown in pooled human urine, the speF mutant grew similarly to wild-type while viability of the argF mutant stopped increasing after ~3 hours (Figure 3 J). This corresponds to the timing of a ~50% reduction in the arginine concentration of urine (from ~134 µM to ~60 µM) by wild-type P. mirabilis (35), which is notable as a prior study observed that growth of an E. coli arginine auxotroph became limited when the concentration of arginine decreased below 60 µM (36,37). Importantly, growth of argF in human urine could again be rescued by supplementation with L-citrulline, much like growth in minimal medium (Figure 3 J).…”

“…We therefore sought to determine the contribution of E. faecalis L-ornithine secretion and P. mirabilis arginine biosynthesis to the successful establishment of polymicrobial catheter biofilms as well as promoting dissemination to the kidneys and bloodstream and overall disease severity. To address this hypothesis, we utilized the E. faecalis arcD mutant and the P. mirabilis argF mutant to examine the specific contribution of ornithine export and arginine biosynthesis to pathogenesis in the well-established murine CAUTI model (35,40,41). Female CBA/J mice aged 6-8 weeks were transurethrally inoculated with 10 5 CFUs of either wild type P. mirabilis, the argF mutant, wild-type E. faecalis, the arcD mutant, or polymicrobial mixtures, and a 4mm silicone catheter segment was placed in the bladder during inoculation.…”