Cyclic-di-GMP signaling in Bacillus subtilis.

Abstract

In many bacteria, bis-(3',5')-cyclic dimeric guanosine monophosphate (c-di-GMP) plays an important role in bacterial physiology. Much of the earlier studies focused on the characterization of the GGDEF and EAL domain proteins. However, a great deal of its signaling pathway remains unsolved. We employed the use of Bacillus subtilis which contains only six GGDEF/EAL domain proteins involved in c-di-GMP metabolism to gain more insights. In this study, we report the enzymatic activity of the four GGDEF domain proteins, YhcK, YdaK, YtrP and YkoW, as well as the cellular localization of YuxH and YkoW during exponential and sporulation phases. Out of the four GGDEF domain proteins, only YkoW displayed diguanylate cyclase activity. Furthermore, YkoW also exhibited phosphodiesterase activity. Although YhcK and YtrP lack enzymatic activity, they were found to have c-di-GMP binding ability. On the other hand, YdaK presented lack of enzymatic activity as well as no nucleotide binding ability. However, YdaK contains a conserved RXXD I-site which may function as a site for protein-protein interaction. Fluorescence tagging reveals a decrease in YuxH-GFP fluorescence signal intensity in spore forming cells. YkoW-YFP was also found to be implicated in sporulation during which higher YFP fluorescence signal intensity was detected.