MECHANOSENSITIVE CHANNELS ARE REQUIRED FOR BACTERIAL SURVIVAL FROM SEVERE THERMAL STRESS

BUTTIGLIERO, LV; MORAN BARRIO, J; VIALE, AM

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual SAIB; 2011

Mesophilic bacteria, such as Escherichia coli, can sustain growth in a temperature range between 15 and 49 ºC. Higher temperatures (> 50 ºC) promote cell death and are therefore defined as severe or extreme. The cellular targets responsible for cell death are still obscure, but ribosome melting, protein aggregation, and denaturation of membrane proteins are thought to represent main targets of extreme temperature exposure. The cellular mechanisms that contribute to bacterial survival and/or recovery from severe heat stress (SHS) are still ill-defined. Here, we present evidence that mechanosensitive channels (MSC) are required for bacterial survival from SHS. Cell death curves indicated that E. coli mutants lacking major MSC were much more sensitive to SHS at 50 ºC than isogenic wild-type (wt) cells. Expression in the mutants of the corresponding msc genes from plasmids restored the wt SHS resistant phenotype, discarding pleiotropic effects due to the mutation. Protein aggregation and cell buoyant density analyses using wt cells indicated that the SHS provoked a hyposmotic-like stress, most probably resulting from the massive cytoplasmatic protein denaturation and exposure of buried protein sectors to the solvent. We propose that MSC are thus necessary to relieve the increase in cell turgor resulting from the SHS allowing survival and cell recovery when extreme temperatures recede.