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K-State Today

May 2, 2019

Division of Biology Seminar May 3

Submitted by Division of Biology

Craig Ellermeier, associate professor of microbiology and immunology at the University of Iowa, will present "Lysozyme Resistance in C. difficile" as part of the Division of Biology Seminar Series at 4 p.m. Friday, May 3, in 221 Ackert Hall.

Ellermeier will speak on Clostridioides difficile, like many pathogenic Gram-positive bacteria is highly resistant to lysozyme a component of the innate immune system that cleaves bacterial peptidoglycan. Ellermeier found that lysozyme resistance is partially controlled by the alternative sigma factor σV. σ factors are an essential component of RNA polymerase that recognize promoters for transcription. Alternative σ factors allow for expression of subsets of genes usually required for response to a stress. σV is required for transcribing lysozyme resistance genes. In the absence of lysozyme, σV is held inactive by the anti-σ factor, RsiV. In the presence of lysozyme RsiV is degraded via a series of proteases which results in the activation of σV. σV then helps RNA polymerase recognize the promoters and transcribe lysozyme resistance genes. His focus on understanding the mechanism of how the activity of σV is controlled by lysozyme. This process is initiated when RsiV binds to lysozyme which allows signal peptidase to cleave RsiV. We determined the X-ray crystal structure of the RsiV-lysozyme complex. Using the structure as a guide we constructed RsiV mutants that are unable to bind lysozyme and thus prevents degradation of RsiV and σV activation in response to lysozyme. While σV is required for maximum lyszoyme resistance even in the absence of σV, C. difficile is highly resistant to lysozyme. We used CRISPRi to knockdown expression of target genes to uncover additional lysozyme resistance genes in C. difficile.

If you would like to visit with Ellermeier, please contact Revathi Govind at rgovind@k-state.edu.