Molecular mechanism of acid stress response of A. acidoterrestris DSM 3922T under sublethal pH environment

Acid-responsive proteome expression profiles of Alicyclobacillus acidoterrestris (A. acidoterrestris) were analysed using label-free quantitative mass spectrometry to investigate its acid resistance mechanism at sublethal pH. Totally, 325 differential expression proteins were identified during acid stress at pH2.5 condition for 15 min, of which the expressions of 83 proteins were up-regulated and the other 242 proteins expressions were down-regulated. Differentially expressed proteins were mainly involved in organic nitrogen compounds metabolism, small molecule metabolism, organic acid metabolism and signal transduction. Overall, they were mapped into 97 metabolic pathways. Combination of KEGG pathway analysis and protein functional analysis suggested that the pH homeostasis system, changes in metabolic pathways, cell membrane permeability and DNA repair are the main acid resistance mechanisms of A. acidoterrestris at sublethal pH conditions. It is speculated that A. acidoterrestris may sense and transmit pH signals from the external environment through the nhaB protein which holds histidine-dependent acid resistance system, initiating a series of acid tolerance reactions. Our study demonstrated global physiological response of A. acidoterrestris to sublethal pH, which provided a better understanding of acid adaption mechanism of A. acidoterrestris.