Role of lipids in the activation of sigma E factor during the sporulation in Bacillus subtilis.

DIEZ VERÓNICA; SCHUJMAN GUSTAVO E.; DE MENDOZA DIEGO.

Carlos Paz

Congreso; XLIV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

During sporulation in B. subtilis an asymmetrical division creates two compartments, a larger one (mother cell) and a smaller one (prespore). The sE factor is proteolitically activated only in the mother cell by the membrane protease SpoIIGA. For this process is required the prespore protein SpoIIR. We have previously shown that inhibition of fatty acid biosynthesis precludes sE activation. To establish the role of lipids in sE activation, we analyzed the effect of cerulenin (a fatty acid biosynthesis inhibitor) in sporulation frequency of mixed cultures of spoIIR and spoIIGA mutants, finding that lipids are required for SpoIIR translocation or its interaction with SpoIIGA. Using a mutant version of SpoIIR (IIRDSec) we found that translocation of SpoIIR is essential for SpoIIGA activity during exponential growth. Expression of the transcription factor Spo0A (the master sporulation regulator) in exponential phase prevents IIRDSec-mediated sE activation, suggesting the existence of a Spo0A-dependent inhibitor mechanism. Conversely, in the presence of SpoIIR, induction of Spo0A bypassed the lipid synthesis requirement. Finally, we analyzed sE activation in a conditional mutant for phospholipid biosynthesis and found that fatty acid but not phospholipid biosynthesis is essential for sE activation. Together, our results highlight the role of lipids in bacterial differentiation.