Role of general stress-response alternative sigma factors σS (RpoS) and σB (SigB) in bacterial heat resistance as a function of treatment medium pH

► sigB and rpoS deletion greatly decreased microbial heat resistance. ► Influence of rpoS deletion was constant under all conditions (54-60 °C, pH 4.0-7.0). ► Influence of sigB deletion was constant under all conditions, except at pH 4.0. ► Protection on cell envelopes exerted by RpoS was greater than that by SigB. ► Avoiding sigma factor expression might be a key for improving heat treatments.