Preferential catabolism of l- vs d-serine by Proteus mirabilis contributes to pathogenesis and catheter-associated urinary tract infection.

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 those for 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 the hierarchical utilization of amino acids may be a critical component of P. mirabilis colonization and pathogenesis within the urinary tract.

Metabolic interplay between Proteus mirabilis and Enterococcus faecalis facilitates polymicrobial biofilm formation and invasive disease.

Polymicrobial biofilms play an important role in the development and pathogenesis of CAUTI. Proteus mirabilis and Enterococcus faecalis are common CAUTI pathogens that persistently co-colonize the catheterized urinary tract and form biofilms with increased biomass and antibiotic resistance. In this study, we uncover the metabolic interplay that drives biofilm enhancement and examine the contribution to CAUTI severity. Through compositional and proteomic biofilm analyses, we determined that the increase in biofilm biomass stems from an increase in the protein fraction of the polymicrobial biofilm matrix. We further observed an enrichment in proteins associated with ornithine and arginine metabolism in polymicrobial biofilms compared to single-species biofilms. We show that L-ornithine secretion by E. faecalis promotes arginine biosynthesis in P. mirabilis, and that disruption of this metabolic interplay abrogates the biofilm enhancement we see in vitro and leads to significant decreases in infection severity and dissemination in a murine CAUTI model.

How to Use a Mutant Library to Identify Genes Required for Biofilm Formation in the Pathogenic Fungus Candida albicans.

With over 1 billion infections and the causative agents showing critical diseases such as pancreatic cancer, the study of pathogenic fungi has never been more critical. In 2017, the United States spent $7.2 billion on fungal diseases. $4.5 billion was allocated to 75,055 hospitalizations, while $2.6 billion went to 8,993,230 outpatient visits. For Candida infections specifically, the cost was $1.4 billion. Currently, there are few classes of antifungals available, and resistance is growing. The identification of genes required for biofilm formation is essential for new antifungal development. This review details how to identify, verify, and characterize defective biofilm formation mutants in C. albicans. This includes how to run an in vitro biofilm formation assay, how to create clean deletions using the modified CRISPR-Cas9 system, how to assay to identify the potential causes of the defect, and how to create complementation strains to confirm the mutant defect.

Genome Sequences of Microbacteriophages Zada and Ioannes.

Microbacteriophages Zada and Ioannes were isolated from soil and characterized. Genomes were then sequenced and annotated. This was done using the host bacterium Microbacterium foliorum Zada and Ioannes are both lytic phages with a Siphoviridae morphotype.