Biology subjects

Guariglia-Oropeza, V.

Publications and source records attributed to Guariglia-Oropeza, V..

2 recordsLinked to original sources

bioRxiv2024

The Streptococcus pyogenes mannose phosphotransferase system (Man-PTS) influences antimicrobial activity and niche-specific nasopharyngeal infection

Streptococcus pyogenes is a human-adapted pathogen that causes a variety of infections including pharyngitis and skin infections, and although this bacterium produces many virulence and host colonization factors, how S. pyogenes competes with the host microbiota is not well understood. Here we detected antimicrobial activity produced from S. pyogenes MGAS8232 that was able to prevent the growth of Micrococcus luteus. This activity was produced when cells were grown in 5% CO2 and in M17 media supplemented with galactose; however, evaluation of the phenotype with the addition of alternative sugars coupled with genome sequencing experiments revealed the antimicrobial phenotype was not related to classical bacteriocins. To further determine genes involved in the production of this activity, a transposon mutant library in S. pyogenes MGAS8232 was generated. The transposon screen identified the mannose phosphotransferase system (Man-PTS), a major sugar transporter in S. pyogenes, as important for the antimicrobial phenotype. Additional loss-of-function transposon mutants linked to the antimicrobial activity were identified to also be involved in alternative sugar utilization and additionally, the Man-PTS was also further identified from a secondary mutation in a bacteriocin operon mutant. Sugar utilization profiles in all the Man-PTS mutants demonstrated that galactose, mannose, and N-acetylglucosamine utilization was impaired in different Man-PTS mutants. In vitro RNA-seq experiments in high and low glucose concentrations further identified the Man-PTS as a glucose transporter; however, there was no transcriptional regulators or virulence factors affected with the loss of the Man-PTS. A clean deletion in the Man-PTS demonstrated defects in a mouse model of nasopharyngeal infection. Overall, the ability of S. pyogenes to utilize alternative sugars presented by glycans seems to play a role in acute infection and interactions with the endogenous microbial population existing in the nasopharynx. IMPORTANCEStreptococcus pyogenes causes a wide range of infections and is responsible for over 500,000 deaths per year due to invasive infections and post-infection sequelae. The most common clinical manifestation of S. pyogenes however are acute infections such as pharyngitis or impetigo. S. pyogenes can adapt to its environment through alternative sugar metabolism and in this study, we identified an antimicrobial phenotype that was not bacteriocin-related but a by-product of alternative sugar metabolism. Evidently, the mannose phosphotransferase system, a well-studied sugar transporter, was involved in production of the antimicrobial, and was also important for S. pyogenes to utilize alternative sugars and establish nasopharyngeal infection, but not skin infection. Overall, this study identified potential strategies used by S. pyogenes for interactions with the endogenous microbiota and further elucidated the importance of sugar metabolism in acute infection.

microbiology↗

bioRxiv2021

Heme-dependent siderophore utilization promotes iron-restricted growth of the Staphylococcus aureus hemB small colony variant

The ability to acquire iron is essential for Staphylococcus aureus to cause infection. Respiration deficient S. aureus small colony variants (SCVs) frequently cause persistent infections, which necessitates they too acquire iron. How SCVs obtain iron remains unknown and so here we addressed this outstanding question by creating a stable hemB mutant in S. aureus USA300 strain LAC. The mutant, auxotrophic for hemin, was assessed for its ability to grow under iron- restriction and with various iron sources. The hemB SCV utilizes exogenously supplied heme but was attenuated for growth under conditions of iron starvation. RNA-seq analyses showed that both WT S. aureus and the hemB mutant sense and respond to iron starvation, however, growth assays show that the hemB mutant is defective for siderophore-mediated iron acquisition. Indeed, the hemB SCV demonstrates limited utilization of endogenous staphyloferrin B or exogenously provided staphyloferrin A, Desferal, and epinephrine, which enabled the SCV to sustain only minimal growth in iron deplete media. Direct measurement of intracellular ATP in hemB and WT S. aureus revealed that both strains can generate comparable levels of ATP during exponential growth suggesting defects in ATP production cannot account for the inability to efficiently utilize siderophores. Defective siderophore utilization by hemB bacteria was also evident in vivo. Indeed, the administration of Desferal failed to promote hemB bacterial growth in vivo, in contrast to WT, in every organ analyzed except for the murine kidney where growth was enhanced. In support of the hypothesis that S. aureus accesses heme in kidney abscesses, in vitro analyses revealed that increased heme availability enables hemB bacteria to utilize siderophores for growth when iron availability is restricted. Taken together, our data support the conclusion that heme is not only used as an iron source itself, but as a nutrient that promotes utilization of siderophore-iron complexes. Author summaryS. aureus small colony variants (SCVs) represent a difficult to treat subpopulation of bacteria that are associated with chronic recurrent infection and worsened clinical outcome. Indeed, SCVs persist within the host despite appropriate administration of antibiotics. This study yields insight into the mechanisms by which S. aureus SCVs acquire iron which, during infection of a host, is a difficult-to-acquire metal nutrient. Under heme limited conditions, hemB S. aureus is severely impaired for siderophore-dependent growth and, in agreement, murine infection indicates that hemin-deficient SCVs meet their nutritional requirement for iron through utilization of heme in vivo. Importantly, we demonstrate that hemB SCVs rely upon heme as a nutrient to promote siderophore utilization. Therefore, perturbation of heme biosynthesis and/or utilization represents a viable to strategy to mitigate the ability of SCV bacteria to acquire siderophore- bound iron during infection.

microbiology↗