Stimulating anaerobic respiration primes anaerobically grown Listeria monocytogenes for intracellular growth

Title

Stimulating anaerobic respiration primes anaerobically grown Listeria monocytogenes for intracellular growth

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Listeria monocytogenes (Listeria) is a Gram positive facultative organism whose lifestyle ranges from a saprophyte to an enteric intracellular pathogen. Listeria is generally ingested from contaminated food products, and as it transmits through the gastrointestinal tract its environment becomes increasingly anoxic. Currently it is not clear how Listeria adaptations to the fluctuating oxygen levels contribute to its pathogenesis. Therefore, we set out to understand what role anaerobic respiration plays in Listeria pathogenesis. Previous work in our lab has shown that anaerobically cultured Listeria has decreased intracellular growth in a tissue culture infection model using RAW264.7 macrophages. We hypothesized that this may be due to anaerobically cultured Listeria taking longer to switch from fermentation to aerobic respiration. This hypothesis was supported by the observation that, compared to an aerobic inoculum, an anaerobic inoculum exhibited an extended lag phase during aerobic growth in vitro. Using a tetrazolium reduction assay, we confirmed that anaerobically cultured Listeria have decreased reducing power, indicating decreased electron transport chain (ETC) activity. To determine whether the reduced ETC activity under anaerobic conditions is an important factor in Listeria pathogenesis, we supplemented the cultures with fumarate as an alternative electron acceptor to stimulate ETC activity and measured listeriolysin O (LLO) production as well as intracellular growth. When we supplied exogenous fumarate to Listeria, we noticed an increase in the reducing power as well as LLO production in anaerobically grown Listeria, compared to no fumarate controls. Moreover, fumarate supplementation restored the intracellular growth of anaerobically grown Listeria to the same level of aerobically grown Listeria inside macrophages. These findings point to the crucial role of anaerobic respiration in Listeria anaerobic virulence regulation.

Publication Date

4-18-2018

Project Designation

Graduate Research

Primary Advisor

Yvonne Y Sun

Primary Advisor's Department

Biology

Keywords

Stander Symposium poster

Comments

Presenter: Nathan C Wallace

Stimulating anaerobic respiration primes anaerobically grown Listeria monocytogenes for intracellular growth

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