Temperature dependence of mycosubtilin homologue production in Bacillus subtilis ATCC6633

TL;DR

This study shows that lower growth temperatures significantly increase mycosubtilin production and alter homologue composition in Bacillus subtilis, without changing gene expression, likely due to enhanced enzyme turnover and fatty acid synthesis shifts.

Contribution

It reveals how temperature modulates mycosubtilin synthesis and homologue distribution, providing insights into optimizing production conditions for this antifungal compound.

Findings

Mycosubtilin production increases 30-fold at 25°C compared to 37°C.

Lower temperature shifts fatty acid homologues toward odd-numbered chains.

Gene expression levels of synthetase remain unchanged across temperatures.

Abstract

Bacillus subtilis ATCC6633 produces mycosubtilin, a non-ribosomally synthesized lipopeptide of the iturin family which presents antagonistic activities toward various phytopathogens. Different homologues with fatty acid moiety varying from C 15 to C 17 are usually co-produced, with their biological activities increasing with the number of carbons in the fatty acid chain. In the present report, we highlight that growth temperature modulates both the extent of mycosubtilin production and the relative abundance of the different homologues. A 30-fold increase in mycosubtilin production was observed when the temperature was decreased from 37 C to 25 C for both strain ATCC6633 and its derivative BBG100, a constitutive mycosubtilin overproducer. However, no significant difference in either the expression of the mycosubtilin synthetase encoding genes or in the intracellular synthetase concentration could be found, suggesting that the observed phenotype originated from a higher mycosubtilin synthetase turnover at lower temperature. We also point out that lower growth temperature leads to an increased proportion of odd-numbered fatty acid homologues as a consequence of de novo synthesis of C 17 anteiso fatty acid following cell adaptation to low temperatures.