Professor
Ph.D., University of Illinois, 1986
Postdoctoral Fellow, E. I. du Pont de Nemours & Co.

Program Affiliation: Molecular Biology & Genetics | Microbiology | Plant Biology

Research Groups Affiliation: Biochemistry | Genetics | Microbiology | Plant Biology

NIH Research Career Development Award
American Society for Photobiology Young Investigator Award
Clyde Culbertson Endowed Professorship
ASM “Waksman Foundation Lecturer”

Phone: 812/855-6595
Fax: 812/855-6705
Email Carl

Bauer Lab web site

The laboratory interests fall into two categories:

1. The regulation of gene expression by environmental factors such as light and oxygen
2. Differentiation of bacteria into different cell types.

Regulation of photosynthesis gene expression by oxygen and light:
Photosynthetic bacteria suppress the development of their photosynthetic apparatus when in the presence of oxygen or high light intensity. Through the use of genetic approaches, we have isolated numerous regulatory mutants that exhibit an altered response to light and oxygen. Molecular genetic and biochemical analysis of several of these mutants has demonstrated that expression of photosynthesis genes is regulated by a complex set of regulatory circuits that is responsible for coordinating synthesis of pigments and polypeptide components of the photosystem. Recent data indicates that photosynthesis regulatory genes also control synthesis of other critical cellular processes involved in carbon and nitrogen fixation. We are currently utilizing a variety of recombinant DNA, genetic, biochemical and biophysical techniques to obtain a detailed understanding of the mechanisms of controlling gene expression by these environmental stimuli.

Photo Behavior of Rhodospirillum centenum:
Rhodospirillum centenum has a complex life cycle with three distinct cell types. Swim cells are vibroid in shape and motile in liquid medium by means of a single polar flagellum. Swarm cells are induced when R. centenum is grown on solid medium, and express multiple lateral flagella with an elongated cell body. Resting cells called cysts are formed when starved. Cyst cells are spherical with large granules of poly-hydroxy butyrate (PHB) stored in the cytoplasm and a thick outer coat that typically surrounds 4-5 cells. Cysts have increased resistance to environmental stresses such as heat and dessication. When returned to a nutrient rich medium, outgrowth of cyst cells ruptures the outer coat and the vegetative cell is regenerated, with the husk of the outer coat left behind.

Using transposon mutagenesis , we have isolated mutants that constitutively form cyst cells. Several of these disruptions map to a large and intriguing set of potential regulatory genes. Two genetically isolated histidine kinase genes and two distinct clusters of che -like genes have been identified through this screen. A previously identified operon, che1 , has been shown to control chemotaxis (see below). We are currently studying che2 and che3 to determine what affect these genes have on chemotaxis and development.

Gene Expression
Setterdahl, A., & C. E. Bauer. 2008. Regulation of Gene Expression in Response to Oxygen Tension. In Purple Photosynthetic Bacteria. Kluwer Academic Press. In Press.

Wu, J., & C. E. Bauer. 2008. RegB/RegA, A Global Redox-Responding Two-Component Regulatory System. In, Bacterial Signal Transduction: network and drug targets. Ryutaro Utsumi edt. pp 131-148, Landes Bioscience Eurekah, Georgetown, TX.

Yuan, H., & C. E. Bauer. 2008. PixE promotes Dark Oligomerization of the BLUF Photoreceptor PixD. Proc. Natl Acad. Sci. USA. In Press.

Willett, J., J. L. Smart & C. E. Bauer 2007. RegA in Controls Bacteriochlorophyll and Carotenoid Synthesis in Rhodobacter capsulatus. J. Bacteriol. 189, 7765-7773.

Prokaryotic Differentiation
Berleman, J., & C. E. Bauer 2005. A chemotaxis like signal transduction cascade controls a cyst developmental pathway in Rhodospirillum centenum . Mol . Microbiol. 55, 1390-1402.

Berelman, J. & C. E. Bauer. 2004.Characterization of the cyst cell formation in the purple photosynthetic bacterium Rhodospirillum centenum . Microbiology150, 383-390 (Featured on cover)

Berleman, J., B.  Hasselbring, & C. E. Bauer. 2004. Hypercyst Mutants in Rhodospirillum centenum Identify Regulatory Loci Involved in Cyst Cell Differentiation. J. Bacteriol. 186, 5834-5841 (Featured on cover).