Bacillus subtilis Cold Adaptation

PEDRIDO M.E., GRAU R.

Mar del Plata

Congreso; SAIB; 2007

SAIB

Spore development in Bacillus subtilis is governed by the master transcription factor Spo0A. Although B. subtilis is a soil bacterium, and hence T changes would constitute a common environmental stress, in the past poor attention was devoted to this situation. Our group, nonetheless, recently reported that spo0A was dramatically induced after a temperature downshift. This stress correlated with increments in the level and activity of Spo0A and higher cellular survival rates. Here; using deletion mutants, beta-galactosidase reporter-essays and transcriptional fusions to fluorescent proteins; we investigated the circuit that result in the cold-induced upregulation of spo0A. We show that cold-induction of spo0A depends on its phosphorylation state and the integrity of the phosphorelay signal transduction system. Moreover, similar to what happens at 37° C, KinA retains an important role during cold adaptation, but interestingly we found that the sporulation efficiency of a kinB mutant, even in the presence of KinA, is reduced 200 fold respect to the wild type. Moreover, the expression of key developmental genes (i.e. spoIIG and spoIIA) was decreased and delayed in the kinB mutant during growth at low T. Since KinB is an integral membrane histidine kinase that lacks of a “periplasmic” sensor domain we propose and discuss a novel role of KinB as a “sporulation thermosensor”.