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 several categories: (1) The regulation of gene expression by environmental factors such as light and oxygen (2) Origin of photosynthesis and the survival and growth of bacteria in extreme environments (3) 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.

Origin of photosynthesis and the survival of bacteria in extreme environments: To obtain a better understanding on the origin and evolution of photosynthesis we have undertaken an extensive analysis of photosynthesis genes that are present in ancient, deeply divergent, species of photosynthetic microorganisms. This includes analysis of photosynthesis genes from the gram-positive bacterium Heliobacillus mobilus, and the green gliding bacterium Chloroflexus aurantiacus. Phylogenetic analysis of chlorophyll biosynthesis genes as well as apoproteins of the photosystem should shed light on early evolutionary events that gave rise to photosynthesis.   More recently, we have been identifying microbial species that are present in a series of hypersaline and alkaline lakes that are presenting Warner Valley Oregon.   The habitat is thought to closely mimic the habitat hat was present in early earth history.    We are attempting isolate various photosynthetic species from this unique environment.

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
Swem, L. R., X. Gong, C.-A. Yu & C. E Bauer. 2006.  RegB controls a diverse array of metabolic processes by monitoring the redox state of the ubiquinone pool. J. Biol. Chem.  281: 6768-6775.

Smart, J. L. & C. E. Bauer. 2006.   Tetrapyrrole biosynthesis in Rhodobacter capsulatus is transcriptionally regulated by a novel heme-binding regulatory protein, HbrL.   J. Bacteriol. 188: 1567-1576

Yuan, H., S. Masuda, V, Dragnea, S. Anderson, K. Moffat & C. E. Bauer. 2006.  Structure of the blue light photoreceptor, BluP (Slr1694) from Synechocystis PCC6803 reveals photoinduced alterations of a hydrogen bond network to FAD.  Biochemisty, In Press

Dragnea , V., M.   Waegelle, S.   Balascuta, C. E. Bauer and B. Dragnea 2005 Spectroscopic studies of the AppA blue-light receptor BLUF domain from Rb. sphaeroides in solution with time-resolved spectroscopy .   Biochemistry.   44:15978-15985

Anderson, S., V. Dragnea, V., S. Masuda, J. Ybe, K. Moffat & C. E. Bauer . 2005. Structure of a novel photoreceptor: the BLUF domain of AppA from Rhodobacter sphaeroides . Biochemistry. 44, 7998-8005

Evolution of photosynthesis
Xiong, J. & C. E. Bauer.   2002. A cytochrome b  origin  of photosynthetic reaction centers. J. Mol. Biol.   322,  1025-1037.

Xiong, J., & C. E. Bauer. 2002.   Complex  evolution of photosynthesis.   Ann Rev.  Plant Physiol.   53, 503-521.

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).