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"Divisional control during genetically programmed competence in Bacillus subtilis"

by
Kenneth Briley Jr.
Interdisciplinary Biomedical Sciences Program
B.S. 2003, Monmouth University



Thesis Advisor: David Dubnau, Ph.D.
Professor
Department of Microbiology & Molecular Genetics

Thursday, November 11, 2010
ICPH Seminar Room, 1:00 p.m.


Abstract

Certain bacteria are capable of undergoing several stationary-phase developmental processes. These developmental states, which include genetic competence, sporulation, and biofilm production, arm these microbes with additional tools that aid in survivability during times of stress. These stressors can include those encountered in the environment, such as changes in temperature, ultraviolet light, nutrient availability, and in the case of pathogenic bacteria, host-immune defense systems. These environmental hurdles can occasionally be overcome however, through the genetic induction of one of the aforementioned developmental states. For example, the human pathogen, Nesseria gonnhorea, is capable of entering into a state of genetic competence, or the ability to internalize exogenous DNA, during which time, it has the capacity to acquire genes (termed transformation) presumably helpful for pathogenesis. In this case, genetic competence is medically important, represents a potential target for antimicrobials and warrants further study to elucidate the generalized mechanism by which it occurs. Because many bacteria use similar systems to enter this physiological state, data gathered while studying one specific bacterial species, can sometimes be applied to others.
Bacillus subtilis is a Gram-positive, soil dwelling bacteria capable of undergoing genetic competence. Due to its ease of cultivability and induction of competence, B. subtilis has long been used as a model organism to study both the regulation of naturally-occurring competence and the genes that facilitate the uptake of exogenous DNA. In this study, we have used a combination of genetic and biochemical approaches to describe the requirements of the B. subtilis competence-induced comG operon for the binding and transport of exogenous DNA. We have focused this work on the first gene in this operon, comGA, where we have characterized its` requirements in the binding and uptake of transforming DNA, and have proposed a revised model for the transport of exogenous DNA.
We have also investigated the competence-induced divisional control system, partially requiring comGA. In the course of this work, we have identified a key competence protein, Maf, that operates with ComGA along the divisional program, during the transition out of competence. We also provide evidence that ComGA and Maf may have a role(s) in the segregation of the nucleoid. Using a targeted screen to identify divisional proteins that bind to Maf, we have proposed a model for this divisional control mechanism.


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