Effects of cell-free culture fluids for the expression of putative acyltransferase in corynebacterium glutamicum

Abstract

Autoinduction is mediated by signaling molecules known as autoinducers (AIs) that are produced, released and detected by bacterium itself. We recently reported that Corynebacterium glutamicum possesses an autoinduction system which secretes autoinducers during the stationary-phase of growth, triggering the expression of acyltransferase gene. However, it is still not clear what may act as autoinducers for the autoinduction in C. glutamicum. In this study, we compared the inducing effects of cell-free culture fluids obtained from a number of microbes including Agrobacterium tumefaciens, Vibrio harveyi, and Escherichia coli. Fluids from A. tumefaciens did not increase the expression of acyltransferase, whereas fluids from V. harveyi BB120 (AI-1+, AI-2+) did. Interestingly, the expression was increased by the fluids obtained from the early exponential-phase culture of BB120. Furthermore, this induction was not observed by the fluids from autoinducer mutants of V. harveyi MM77 (AI-1-, AI-2-) and BB152 (AI-1-, AI-2+). Unlike the effect shown by BB152, fluids from E. coli (AI-1-, AI-2+) still induced the acyltransferase expression. Taken together, these results suggest that C. glutamicum autoinducers seem to be unidentified molecules which do not belong to AI-1 or AI-2. © 2012, The Microbiological Society of Korea.