Biology subjects

Mobley, H. L.

Publications and source records attributed to Mobley, H. L..

2 recordsLinked to original sources

bioRxiv2026

Selective Sugar Transport Supports Proteus mirabilis Fitness in the Urinary Tract

Proteus mirabilis is a leading cause of complicated urinary tract infections (UTIs). Prior work showed P. mirabilis metabolizes sugars during experimental UTI, yet the role of sugar import systems in pathogenesis remains poorly defined. To investigate this, we generated a panel of 47 targeted mutants in predicted sugar transporter genes and assessed their growth in vitro and fitness in vivo. Growth screening in nutrient-rich and minimal media revealed carbon source-dependent defects in several phosphotransferase system (PTS) mutants, including ptsH and ptsI. Pooled insertion sequencing (In-seq) identified xapB, ptsH, and ptsI as in vivo fitness factors, with validation in a traditional murine co-challenge model. Functional studies showed that xapB, annotated as a xanthosine permease, did not support xanthosine or guanosine uptake in P. mirabilis, suggesting misannotation. Dissection of the PTS network revealed that a triple mutant lacking scrA, ulaC, and ptsG recapitulated the ptsH phenotype in vivo. To evaluate whether increased sugar availability exacerbates these defects, we modeled glucosuria using the SGLT2 inhibitor dapagliflozin in CBA/J mice. Dapagliflozin treatment significantly increased urinary glucose and enhanced P. mirabilis colonization. There was an inverse correlation between colonization and urinary glucose, but only in untreated mice. These findings reveal limitations in genome-based transporter annotation, establish a functional link between sugar import and P. mirabilis fitness during UTI, and demonstrate that host metabolic conditions such as glucosuria can influence the severity of infection. AUTHOR SUMMARYAll living organisms require nutrients to grow, survive, and cause disease. Bacteria like Proteus mirabilis, which causes urinary tract infections, rely on specialized systems to import and metabolize sugars available in the host environment. In this study, we systematically disrupted 47 genes predicted to encode sugar transporters in P. mirabilis and tested their contribution to infection in a mouse model. We identified three key genes (xapB, ptsH, and ptsI) that were critical for colonization. Further analysis showed that many sugar transporters in P. mirabilis were misannotated, and predicted substrates like sucrose and cellobiose were not utilized by the bacterium. We also demonstrated that high sugar conditions, mimicking diabetic urine using the drug dapagliflozin, worsened infection and increased disease severity. These results highlight the importance of carbohydrate acquisition for P. mirabilis during infection and emphasize the need to experimentally validate gene function rather than rely on predictions based on other bacteria like E. coli.

microbiology↗

bioRxiv2022

The ADP-heptose biosynthesis enzyme GmhB is a conserved Gram-negative bacteremia fitness factor

Klebsiella pneumoniae is a leading cause of Gram-negative bacteremia, which is a major source of morbidity and mortality worldwide. Gram-negative bacteremia requires three major steps: primary site infection, dissemination to the blood, and bloodstream survival. Since K. pneumoniae is a leading cause of healthcare-associated pneumonia, the lung is a common primary infection site leading to secondary bacteremia. K. pneumoniae factors essential for lung fitness have been characterized, but those required for subsequent bloodstream infection are unclear. To identify K. pneumoniae genes associated with dissemination and bloodstream survival, we performed insertion site sequencing (InSeq) using a pool of >25,000 transposon mutants in a murine model of bacteremic pneumonia. This analysis revealed the gene gmhB as important for either dissemination from the lung or bloodstream survival. In Escherichia coli, GmhB is a partially redundant enzyme in the synthesis of ADP-heptose for the lipopolysaccharide (LPS) core. To characterize its function in K. pneumoniae, an isogenic knockout strain ({Delta}gmhB) and complemented mutant were generated. During pneumonia, GmhB did not contribute to lung fitness and did not alter normal immune responses. However, GmhB enhanced bloodstream survival in a manner independent of serum susceptibility, specifically conveying resistance to spleen-mediated killing. In a tail-vein injection of murine bacteremia, GmhB was also required by K. pneumoniae, E. coli and Citrobacter freundii for optimal bloodstream survival. Together, this study identifies GmhB as a conserved Gram-negative bacteremia fitness factor that acts through LPS-mediated mechanisms to enhance bloodstream survival. IMPORTANCEKlebsiella pneumoniae frequently causes healthcare-associated infections including pneumonia and bacteremia. This is particularly concerning due to emerging antimicrobial resistance and the propensity for bacteremia to initiate sepsis, which has high mortality and is the most expensive hospital-treated condition. Defining mechanisms of bloodstream survival is critical to understanding the pathology of bacteremia and identifying novel targets for future therapies. In this study, we identified the K. pneumoniae enzyme GmhB as a bloodstream-specific fitness factor that enables the bacteria to survive in the spleen but is dispensable in the lung. Furthermore, GmhB is also needed by the related bacterial pathogens Escherichia coli and Citrobacter freundii to cause bacteremia. Conserved bacteremia fitness factors such a GmhB could be the basis for future therapeutics that would alleviate significant disease caused by from multiple diverse pathogens.

microbiology↗