Role of Mechanosensitive Channels for bacterial recovery from severe thermal stress

BUTTIGLIERO LAURA; MORÁN-BARRIO JORGELINA; ALEJANDRO M. VIALE

Mar del Paata

Congreso; VIII Congreso Argentino de Microbiología General; 2012

SOCIEDAD ARGENTINA DE MICROBIOLOGÍA GENERAL

Mechanosensitivechannels are required for bacterial survival from severe thermal stressLaura Buttigliero, Jorgelina Morán-Barrio, and Alejandro M.Viale IBR, CONICET ? Fac. Cs Bioq y Farm, U.N.R.Suipacha531, S2002LRK Rosario, Argentina. E.mail:buttigliero@ibr.gov.ar Mesophilicbacteria, such as Escherichia coli, cansustain and/or grow 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 cellulartargets responsible for cell death are still obscure, but ribosome melting,protein aggregation, and denaturation of membrane proteins are thought torepresent main targets of extreme temperature exposure. The cellular mechanismsthat contribute to bacterial survival and/or recovery from severe heat stress(SHS) are still ill-defined.Here, wepresent evidence that mechanosensitive channels (MSC) are required forbacterial survival from SHS. Cell death curves indicated that E. coli mutants lacking major MSCs weremuch more sensitive to SHS at 50 ºC than isogenic wild-type (wt) cells. Expression in themutants of the corresponding mscgenes from plasmids restored the wt SHS resistant phenotype, discardingpleiotropic effects due to the mutations. Protein aggregation andcell buoyant density analysesusing wt cells indicated that SHS provoked a hyposmotic-likestress, most probably resulting from the massive cytoplasmatic proteindenaturation and exposure of buried protein sectors to the solvent. We proposethat MSC are necessary to relieve the increases in cell turgor resulting fromthe SHS, thus allowing cell survival and recovery when extreme temperaturesrecede.