Date of Award

9-6-2024

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Bioinformatics & Computational Biology

First Advisor

Catherine Putonti

Abstract

Bacterial species inhabit both the “healthy” and symptomatic female urinary tract. Lactobacillus species are frequently dominant members of the healthy urinary tract microbiota (urobiome), and thus have been associated with the lack of lower urinary tract symptoms (LUTS). In contrast, colonization by Escherichia coli is the most common cause of urinary tract infections (UTIs). Prior research has found that strains of Lactobacillus can inhibit the growth of uropathogens such as E. coli as well as vaginosis-associated pathogens. Investigations into the means by which lactobacilli inhibit pathogenic growth have primarily focused on their production of hydrogen peroxide (H2O2) and lactic acid, although other metabolites have been identified. This project explored how the secreted compounds of urinary strains of Lactobacillus species affect the growth of urinary E. coli. 53 different E. coli strains, isolated from urine samples of females with and without LUTS, were grown with the cell-free supernatant (CFS) of 42 different urinary lactobacilli strains. These lactobacilli included strains of the species L. crispatus, L. gasseri, L. jensenii, L. johnsonii, L. mulieris, and L. paragasseri. Three scenarios were observed: (1) the CFS had no effect on the growth of the E. coli, (2) the CFS reduced the growth of the E. coli, and (3) the CFS inhibited growth or killed the E. coli. At least half of the Lactobacillus CFS + E. coli pairs tested resulted in inhibited or reduced E. coli growth. To determine how the CFS was inhibiting or reducing E. coli growth, we further explored the role that pH and protein-based constituents of the CFS played. Evidence of phage induction caused by Lactobacillus CFS was found identifying a means in which lactobacilli can reduce or inhibit E. coli growth. To expand on these results, we tested L. mulieris UMB7784 CFS on another uropathogen, Aerococcus urinae. These experiments demonstrated evidence of this strain of Lactobacillus CFS negatively impacting the growth of A. mictus. This study furthers our understanding of interactions between microbes within the urinary microbiome.

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