Responses of Staphylococcus aureus to Environmental Stresses (pp.509-546)
Authors: (Tone Mari Rode, Trond Møretrø, Solveig Langsrud, and Askild Holck, Norwegian Institute of Food, Fisheries and Aquaculture Research, As, Norway)
Abstract: Staphylococcus aureus can colonize and survive in a vide variety of environmental niches. It is often involved in nosocomial infections, andis a leading cause of gastroenteritis due to consumption of contaminated food. Staphylococcal food poisoning is due to the absorption of staphylococcal enterotoxins preformed in the food. Bacteria are exposed to several stress factors when present in food or in food production environments. Food preservation techniques like acidification, use of preservatives, heat treatment and high pressure all induce different types of stress responses in S. aureus. Compared with other food related bacteria S. aureus tolerates high levels of sodium chloride and shows a high heat tolerance. Several global gene expression studies have given valuable information on the different regulation pathways in S. aureus under stress. Some responses are invoked under a number of different stress conditions. For example, in response to both temperature and osmotic stress, and other stresses, the alternative sigma factor SigB (ζB) plays a central role and is involved in the regulation of hundreds of genes. Regarding acid stress, the growth patterns and genetic responses of S. aureus is highly dependent on the acid type and pH level, as weak organic acids are membrane-permeable, and the undissociated acids can enter the cell. An acid shock to pH 4.5 by hydrochloric acid will to a minor degree affect the growth pattern of exponentially growing S. aureus compared to permeant weak organic acids.
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