ROLE OF MECHANOSENSITIVE CHANNELS FOR BACTERIAL RECOVERY FROM SEVERE THERMAL STRESS

BUTTIGLIERO LV; MORAN BARRIO J; VIALE AM

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiología General; 2012

Sociedad Argentina de Microbiología General

Enterobacterial species such as Escherichia coli sustain growth over a temperature range of 40 ºC, i.e., between 15 and 49 ºC. Higher temperatures promote cell death to a magnitude that depends on heat intensity and duration, and are therefore defined as severe or extreme. The cellular targets responsible for cell death exposed to severe heat stress are not clearly defined, but protein aggregation, membrane alterations and ribosome melting are thought as main targets of severe heat stress. Here, we report that mechanosensitive channels (MSC) are required for E. coli survival from upon severe heat exposure. Cell death curves indicated that bacterial mutants deficient in main MSC are more sensitive to severe heat stress at 50 ºC than isogenic parental cells. Expression in these mutants the msc genes from plasmids restores the wt phenotype, discarding pleiotropic effects of the mutation. Protein aggregation and cell buoyant density analyses in Percoll gradients indicate that the severe heat stress provoked a hyposmotic-like response, probably as the result of the massive cytoplasmatic protein denaturation and concomitant hydration of previously buried protein sectors to the surrounding aqueous environment. Thus MSCs are seemingly necessary to relieve the increase in cell turgor resulting from the severe heat stress allowing cell recovery after the thermal stress recedes.