REGULATION OF SPORE DEVELOPMENT UNDER ALCOHOL STRESS IN BACILLUS SUBTILIS

GOTTIG, NATALIA; SANTUCCI, NATALIA; MENDEZ, MARCELO

Villa Carlos Paz

Congreso; XXXVIII Reunión Nacional de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2002

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Here we report the mechanism by which sub-lethal concentrations of alcohols inhibit spore development in B. subtilis. We determined that the primary effect was to block Spo0A activation by the phosphorelay signaling system. Phosphorelay components that did not require Spo0A-P for their transcription were not affected by alcohol (i.e. KinA, KinB and Spo0B).By contrast transcription of Spo0A and Spo0F was abolished if ethanol  was added before the onset the stationary phase. Accordingly the transcription of SpoIIG, SpoIIA and SpoIIE was also abolished. Furthermore, the alcohol effect was independent of the activity of the general stress transcription factor sB but it was bypassed by IPTG-induction of the phosphorylation-independent form of Spo0A-Sad 67. Screening of a mini Tn10 insertional library revealed two types of suppressors: rapA and sinR. Deletion mutants of each one of these transition states regulator coding-genes restored a partial spo+ phenotype while sporulation in double mutants rapA-sinR- was completely unaffected by alcohol. Furthermore, alcohol stress induced the transcription of rapA and sinR while blocked the Spo0A-dependent induction of the sinR-antagonist sinI. Moreover, alcohol-treatment also blocked fatty acid synthesis, which is essential at later stages of development after cytokinesis. We present here a model where the blockage of sporulation at stage 0 constitutes a regulatory check-point that coordinates the alcohol-induction of the stress-protecting factor sB and the inhibition of spore development.