In the natural setting, and within the human host, microbes seldom encounter conditions that are propitious for unrestricted growth. Rather, they must survive in environments where most of the time they are faced with limiting amounts of essential nutrients and stressful stimuli. The myriad of survival strategies that microorganisms have evolved to cope with starvation is reflected in the richness of diversity found in the microbial world. Our laboratory studies several of these microbial survival strategies. Two of the current projects are: the study of surface-associated microbial communities known as biofilms and the ways in interspecies interactions influence microbial development in communities. In addition, the laboratory is interested in bacterial genome evolution and is approaching this topic through comparative genomic studies of multiple isolates of the same species.
Bacterial Biofilms. It appears that most bacteria a capable and most likely prefer to exist in surface associated communities (biofilms). Biofilm formation is a complex developmental process which is regulated by environmental signals and bears many similarities to the development of multicellular organisms. Single motile planktonic cells can differentiate into non-motile cell that are members of a sessile community. A trademark of a mature biofilm is that the cells are encased in an extracellular matrix, that can be composed of polysaccharides, proteins and even nucleic acids. Currently, we are focusing our attention on several key questions regarding the matrix: What genes are involved in matrix production? How is matrix production regulated? What functions are played by protein components of the matrix? How does the matrix assist in the spatio-temporal organization of the biofilm?
Interspecies Interactions. On a global scale, the interactions between microbes of different species, be they prokaryotes or eukaryotes, far out-number microbial interactions with humans. Contacts amongst microbes have certainly influenced the evolution of numerous aspects of microbial physiology, including developmental strategies such as the ability to form biofilms. In fact, it has been proposed that in opportunistic pathogens, which are predominantly found in the environment, many of the virulence factors that are important in human infections may have been selected because they provide a selective advantage to bacteria in their interactions with non-mammalian, microscopic eukaryotes. Based on this hypothesis, our laboratory has developed a number of dual species model systems in which to study the molecular mechanisms that underlie diverse microbial interactions.
Comparative Genomics. Very recently we have begun a concerted effort at genome wide comparative analyses among strains of the same species. The amazing diversity observed in even the first examples of two or more completed genomes of the same species has prompted us to ask questions such as: What is the extent of diversity within a microbial species? What selective conditions drive the evolution of genomes in different species? Are there geographically-selected differences in genome structure among bacteria? What is the structure of natural microbial populations with regards to genomic diversity?
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References:
- Hogan, D.A, Å. Vik, and R. Kolter. 2004. A Pseudomonas aeruginosa quorum-sensing molecule influences Candida albicans morphology. Mol. Microbiol. 54:1212-1223.
- Kearns, D.B., F. Chu, S.S. Branda, R. Kolter and R. Losick. 2005. A master regulator for biofilm formation by Bacillus subtilis. Mol. Microbiol. 55:739-749.
- Romano, J.D. and R. Kolter. 2005. Pseudomonas-Saccharomyces Interactions: Influence of fungal metabolism on bacterial physiology and survival. J. Bacteriol. 187:940-948.
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