Abstract
Listeria monocytogenes is a foodborne human pathogen capable of causing life-threatening disease in susceptible populations. Previous proteomic analysis we performed demonstrated that different strains of L. monocytogenes initiate a stringent response when subjected to alkaline growth conditions. Here, using multidimensional protein identification technology (MudPIT), we show that in L. monocytogenes EGD-e this response involves an energy shift to anaerobic pathways in response to the extracellular pH environment. Importantly we show that this supports a reduction in relative lag time following an abrupt transition to low oxygen tension culture conditions. This has important implications for the packaging of fresh and ready-to-eat foods under reduced oxygen conditions in environments where potential exists for alkaline adaptation.
Highlights
Listeria monocytogenes is a physiologically robust food-borne human pathogen
We demonstrated that different strains of L. monocytogenes initiate a common stress proteome when subjected to alkaline growth conditions, and that this involves a shift to a survival or "stringent-response"-like state that was coupled to cell surface perturbations which could aid in attachment to surfaces [10,11]
Systems are mobilised that facilitate stabilisation of these and other regulatory proteins to prevent pH induced conformational changes that may lead to loss of function. This is coupled with an adaptive shift in energy metabolism that increases production of acidic by-products, ATP and reducing equivalents, to compensate for inhibition of other energy production pathways that are physically influenced by the extracellular pH environment
Summary
Listeria monocytogenes is a physiologically robust food-borne human pathogen. It is a facultative anaerobe, growing preferentially under microaerophilic conditions. Energy generation in L. monocytogenes is achieved by both fermentation and aerobic respiration. L. monocytogenes is able to generate energy by substrate-level phosphorylation alone (i.e. generation of ATP independent to electron acceptors or cellular respiration) and modulation of its energy generation source (i.e. oxidative versus substrate level phosphorylation) in response to growth conditions has been described (e.g. nutrient limitation) and appears to influence pathogenicity [4,7,8]. The ability of L. monocytogenes to grow at low oxygen tensions represents a risk for fresh and ready-to-eat food manufacturers, given its association with pathogenicity The ability of L. monocytogenes to grow at low oxygen tensions represents a risk for fresh and ready-to-eat food manufacturers, given its association with pathogenicity (e.g. [4])
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