Biology subjects

Odom John, A.

Publications and source records attributed to Odom John, A..

3 recordsLinked to original sources

bioRxiv2026

The cellular esterase FrmB controls metabolic homeostasis and small colony variant formation in Staphylococcus aureus

Staphylococcus aureus is a gram-positive bacterium that commonly colonizes the nasal passage, axilla, groin, and gastrointestinal tract of adults and adolescents. Although frequently nonpathogenic, S. aureus can infect most tissue types with clinical outcomes ranging from mild to fatal. The ability of S. aureus to persist and infect multiple body sites is driven largely by its metabolism. S. aureus can metabolize a wide range of niche-specific carbon sources, which contributes significantly to its persistence. Specifically, the utilization of glycolytic intermediates and pyruvate are associated with S. aureus bacterial burden and survival in the host. In this study, we establish the biological role of a serine hydrolase, FrmB, and evaluate its impact on S. aureus carbon metabolism. Using targeted metabolomics on S. aureus strains with and without FrmB, we find that FrmB is required for central carbon metabolic homeostasis. Mechanistically, we find that FrmB controls the enzymatic activity of the crucial rate-limiting enzyme, pyruvate dehydrogenase, which links glycolysis to the downstream tricarboxylic acid (TCA) cycle. Importantly, we find that the metabolic derangements in the absence of FrmB impact the ability of S. aureus to utilize pyruvate as a primary carbon source and reduce fitness. Finally, we demonstrate that FrmB is important for the formation of small colony variants (SCVs), a clinically relevant metabolic transition that is associated with chronic infection and antibiotic resistance.

microbiology↗

bioRxiv2023

Volatile profiling distinguishes Streptococcus pyogenes from other respiratory streptococcal species

Sore throat is one of the most common complaints encountered in the ambulatory clinical setting. Rapid, culture-independent diagnostic techniques that do not rely on pharyngeal swabs would be highly valuable as a point-of-care strategy to guide outpatient antibiotic treatment. Despite the promise of this approach, efforts to detect volatiles during oropharyngeal infection have yet been limited. In our research study, we sought to evaluate for specific bacterial volatile organic compounds (VOC) biomarkers in isolated cultures in vitro, in order to establish proof-of-concept prior to initial clinical studies of breath biomarkers. A particular challenge for diagnosis of pharyngitis due to Streptococcus pyogenes is the likelihood that many metabolites may be shared by S. pyogenes and other related oropharyngeal colonizing bacterial species. Therefore, we evaluated whether sufficient metabolic differences are present that distinguish the volatile metabolome of Group A streptococci from other streptococcal species that also colonize the respiratory mucosa, such as S. pneumoniae and S. intermedius. In this work, we identify candidate biomarkers that distinguish S. pyogenes from other species, and establish highly produced VOCs that indicate presence of S. pyogenes in vitro, supporting future breath-based diagnostic testing for streptococcal pharyngitis. IMPORTANCEAcute pharyngitis accounts for approximately 15 million ambulatory care visits in the USA. The most common and important bacterial cause of pharyngitis is Streptococcus pyogenesis, accounting for 15% to 30% of pediatric pharyngitis. Distinguishing between bacterial and viral pharyngitis is key to management in US practice. Culture of a specimen obtained by throat swab is the standard laboratory procedure for the microbiologic confirmation of pharyngitis, however this method is time consuming which delays appropriate treatment. If left untreated, S. pyogenes pharyngitis may lead to local and distant complications. In this study, we characterized the volatile metabolomes of S. pyogenes and other related oropharyngeal colonizing bacterial species. We identify candidate biomarkers that distinguish S. pyogenes from other species and provides evidence to support future breath-based diagnostic testing for streptococcal pharyngitis.

microbiology↗

bioRxiv2019

Modification of an atypical clathrin-independent AP-2 adaptin complex of Plasmodium falciparum reduces susceptibility to artemisinin

The efficacy of current antimalarial drugs is threatened by reduced susceptibility of Plasmodium falciparum to artemisinin. In the Mekong region this is associated with mutations in the kelch propeller-encoding domain of pfkelch13, but variants of other parasite proteins are also thought to modulate the response to drug. Evidence from human and rodent studies suggests that the -subunit of the AP-2 adaptin trafficking complex is one such protein of interest. We generated transgenic Plasmodium falciparum parasites encoding the I592T variant of pfap2, orthologous to the I568T mutation associated with in vivo artemisinin resistance in P. chabaudi. When exposed to a four-hour pulse of dihydroartemisin in the ring-stage survival assay, two P. falciparum clones expressing AP-2 I592T displayed significant and reproducible survival of 8.0% and 10.3%, respectively, compared to <2% for the 3D7 parental line (P = 0.0011 for each clone). In immunoprecipitation and localisation studies of HA-tagged AP-2, we identified interacting partners including AP-2, AP-1/2{beta}, AP-2{sigma} and a kelch-domain protein encoded on chromosome 10 of P. falciparum, K10. Conditional knockout indicates that the AP-2 trafficking complex in P. falciparum is essential for the fidelity of merozoite biogenesis and membrane organisation in the mature schizont. We also show that while other heterotetrameric AP-complexes and secretory factors interact with clathrin, AP-2 complex subunits do not. Thus, the AP-2 complex may be diverted from a clathrin-dependent endocytic role seen in most eukaryotes into a Plasmodium-specific function. These findings represent striking divergences from eukaryotic dogma and support a role for intracellular traffic in determining artemisinin sensitivity in vitro, confirming the existence of multiple functional routes to reduced ring-stage artemisinin susceptibility. Therefore, the utility of pfkelch13 variants as resistance markers is unlikely to be universal, and phenotypic surveillance of parasite susceptibility in vivo may be needed to identify threats to our current combination therapies.

microbiology↗