C-Signal-Dependent Gene Expression in Myxococcus Xanthus

Michigan State University, East Lansing MI

Investigators

Abstract

In nature, bacteria often exist as members of communities called biofilms. The development of biofilms involves cells sending signals to each other and changing their gene expression in response. Understanding how bacteria regulate genes in response to cell-cell interactions during biofilm development is a fundamental challenge of great practical significance. Myxococcus xanthus provides a very attractive experimental system to address this challenge. When starved, cells move to aggregation centers and construct a nascent fruiting body. Within the fruiting body, rod-shaped cells differentiate into spherical, dormant spores. Signaling between cells is essential for this developmental process. Studies of C-signaling during M. xanthus development are establishing a new paradigm for how bacterial cells interact and regulate genes. C-signaling involves CsgA, a protein whose level rises in developing cells. CsgA becomes associated with the cell surface and mediates short-range signaling between cells. C-signaling induces several responses in recipient cells. It regulates cell movements, gene expression, and sporulation. The different responses to Csignaling require different levels of CsgA. The rising level of CsgA and the increased contacts between cells as they enter aggregates may ensure that the high level of C-signaling required for gene expression leading to sporulation only occurs within the fruiting body. The long-term goal of this project is to understand how differential gene expression in response to C-signaling regulates fruiting body development. Past support led to the discovery that C-signal-dependent genes are under combinatorial control of transcription factors. A recurring theme is the involvement of MrpC and FruA, but some genes require additional transcription factors. The aims of the project are 1) to determine the roles of MrpC and FruA at particular promoters, 2) to identify the direct targets of MrpC and FruA genome-wide, and 3) to discover additional transcription factors of C-signal-dependent genes. It is anticipated that the results of the project will provide paradigms for how bacteria might regulate genes and control cell behavior in response to signals in biofilms of practical importance, facilitating discovery of ways to manipulate biofilm growth. Also, the project will contribute to the development of human resources in science through the teaching and training of undergraduates, graduate, and postdoctoral students.