Browsing by Subject "Tryptophan synthase"

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    Beyond Tryptophan Synthase: Identification of Genes That Contribute to Chlamydia trachomatis Survival during Gamma Interferon-Induced Persistence and Reactivation
    (American Society for Microbiology, 2016-09-19) Muramatsu, Matthew K.; Brothwell, Julie A.; Steinman, Barry D.; Putman, Timothy E.; Rockey, Daniel D.; Nelson, David E.; Department of Microbiology & Immunology, IU School of Medicine
    Chlamydia trachomatis can enter a viable but nonculturable state in vitro termed persistence. A common feature of C. trachomatis persistence models is that reticulate bodies fail to divide and make few infectious progeny until the persistence-inducing stressor is removed. One model of persistence that has relevance to human disease involves tryptophan limitation mediated by the host enzyme indoleamine 2,3-dioxygenase, which converts l-tryptophan to N-formylkynurenine. Genital C. trachomatis strains can counter tryptophan limitation because they encode a tryptophan-synthesizing enzyme. Tryptophan synthase is the only enzyme that has been confirmed to play a role in interferon gamma (IFN-γ)-induced persistence, although profound changes in chlamydial physiology and gene expression occur in the presence of persistence-inducing stressors. Thus, we screened a population of mutagenized C. trachomatis strains for mutants that failed to reactivate from IFN-γ-induced persistence. Six mutants were identified, and the mutations linked to the persistence phenotype in three of these were successfully mapped. One mutant had a missense mutation in tryptophan synthase; however, this mutant behaved differently from previously described synthase null mutants. Two hypothetical genes of unknown function, ctl0225 and ctl0694, were also identified and may be involved in amino acid transport and DNA damage repair, respectively. Our results indicate that C. trachomatis utilizes functionally diverse genes to mediate survival during and reactivation from persistence in HeLa cells.
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    How Chlamydia trachomatis conquered gut microbiome-derived antimicrobial compounds and found a new home in the eye
    (National Academy of Sciences, 2019-06-18) Banerjee, Arkaprabha; Nelson, David E.; Microbiology and Immunology, School of Medicine
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    The identification and characterization of novel persistence genes in chlamydia trachomatis
    (2016-11-30) Muramatsu, Matthew Kazuyuki; Nelson, David E.; Batteiger, Byron E.; Serezani, C. Henrique; Spinola, Stanley M.; Sullivan, William J., Jr.
    Chlamydia trachomatis is an obligate intracellular bacterial pathogen that can infect the eyes, genital tract, and disseminate to lymph nodes in humans. Many C. trachomatis infections are clinically asymptomatic and can become chronic if left untreated. When humans are infected with C. trachomatis, a cytokine that is produced is interferon-gamma (IFN-γ). In vitro, IFN-γ stimulates expression of the host enzyme indoleamine 2,3-dioxygenase. This enzyme converts free intracellular tryptophan to N-formylkynurenine. Tryptophan starvation induces C. trachomatis to enter a viable-but-nonculturable state termed persistence, which has been proposed to play a key role in chronic Chlamydial disease. To circumvent host induced tryptophan depletion, urogenital strains of C. trachomatis encode a functional tryptophan synthase (TS). TS synthesizes tryptophan from indole and serine, allowing Chlamydia to reactivate from persistence. Transcriptomic analysis revealed C. trachomatis differentially regulates hundreds of genes in response to tryptophan starvation. However, genes that mediate entry, survival, and reactivation from persistence remain largely unknown. Using a forward genetic screen, we identified six Susceptible to IFN-γ mediated Persistence (Sip) mutants that have diminished capacities to reactivate from persistence with indole. Mapping the deleterious persistence alleles in three of the Sip mutants revealed that only one of the mutants had a mutation in TS. The two other Sip mutants mapped had mutations in CTL0225, a putative integral membrane protein, and CTL0694, a putative oxidoreductase. Neither of these genes plays a known role in tryptophan synthesis. However, amino acid (AA) competitive inhibition assays suggest that CTL0225 may be involved in the transport of leucine, isoleucine, valine, cysteine, alanine, and serine. Additionally, metabolomics analysis indicates that all free amino acids are depleted in response to IFN-γ, making this amino acid transporter essential during persistence. Taken together we have identified two new chlamydial persistence genes that may play a role in chronic chlamydial disease.