Dr. Heidi B. Kaplan
The University of Texas Health Science Center at Houston
McGovern Medical School
Department of Microbiology and Molecular Genetics
Cell-cell interactions and signal transduction pathways orchestrate development in all multicellular organisms. Our research focuses on the interactions and signaling pathways that direct the initiation of multicellular development in a simple model system, Myxococcus xanthus. M. xanthus is a gram-negative soil bacterium that exhibits social behaviors as it senses and responds to its environment and communicates with its neighbors. These abilities allow the cells to survive starvation by forming a mound-shaped structure termed a fruiting body in which about 100,000 rod-shaped cells differentiate into environmentally resistant spherical myxospores. This developmental program is initiated by starvation at high density. The starvation pathway senses nutrient limitation and the A signal transduction pathway senses cell density. The output of these pathways is integrated and controls the increase in the transcription of developmentally expressed genes such as 4521. Using molecular, genetic, and biochemical techniques we are identifying and characterizing the components of these signaling pathways, including sasS, sasR, sasN, which map to the sasB locus.
A second focus of our research is the analysis of cell motility. The M. xanthus fruiting body can be considered a single-species biofilm, similar to that of Pseudomonas aeruginosa, which causes persistent and chronic lung infections in cystic fibrosis patients. We are studying the cell-surface components necessary for the flagella-independent surface motility, termed social gliding, that initiates biofilm formation.
Currently, we are 1) continuing our structural and functional analysis of the transducer/regulators encoded by the sasB and other loci, 2) characterizing the function and regulation of 4521 and the other target genes of these pathways, and 3) analyzing the link between lipopolysaccharide O-antigen biosynthesis, 4521 gene expression, and social gliding motility.