Stress Resistance in the Thermo-acidophilic Microorganisms. The Case of the Genus Alicyclobacillus (pp. 175-198)
Authors: (Antonio Bevilacqua*, Milena Sinigaglia, and Maria Rosaria Corbo, University of Foggia, Via Napoli, Italy and others)
Abstract: At present, the genus Alicyclobacillus includes 20 species, isolated from various habits and environments and characterized by the ability to grow under thermo-acidophilic conditions and produce endospores; the species of concern in food microbiology is A. acidoterrestris. A. acidocaldarius is the type microorganism for the extraction of thermostable proteins. Traditionally Alicyclobacillus is described as a genus including microorganisms with ω-alicyclic fatty acids in the membrane: this definition has been put in a crisis by the recovery of A. pomorum and A. aeris, not possessing these fatty acids. However, the presence of these compounds is believed to play a fundamental role in their resistance to temperature and acidic conditions. Another key-point, that could explain why alicyclobacilli are so resistant to some environments, is the different structure of enzymes (i.e. distribution of charged, basic and acid residues, number of salt bridges, cavities, hydration water and content of proline). After a brief description of the genus, this chapter offers an overview of the possible reasons to explain stress-resistance in Alicyclobacillus, along with a short report on the most important approaches employed by food producers to reduce spore contamination.