Oklahoma State University

Gilbert H. John, Ph.D.

(405) 744-7914

FAX (405) 744-6790

307 Life Science East

Stillwater, OK 74078

E-mail: ghjohn@okstate.edu


Research Interest

Study the ability of intestinal microflora to metabolize xenobiotics. Specific area of interest involves studying the molecular and biochemical aspects of cytochrome P450-like proteins in microflora.

Develop biological sensors using microbial and mammalian enzymes to specifically detect toxin compounds.



Colorado State University, Fort Collins, CO B.S. 1985 Microbiology

Colorado State University, Fort Collins, CO Ph.D. 1990 Microbiology


Special Training and Previous Position

Associate Professor, Oklahoma State University, Department of Microbiology and Molecular Genetics, Stillwater, OK, 2001-present.

Assistant Professor, Oklahoma State University, Department of Microbiology and Molecular Genetics, Stillwater, OK, 1995-2001

Assistant Research Scientist, University of Arizona, Department of Pharmacology and Toxicology, Tucson, AZ, 1992-1995

Associate Adjunct Faculty, Microbiology Instructor, Pima Community College, Tucson, AZ, 1994-1995

Postdoctoral Fellow, Centers for Disease Control, Division of Molecular Biology, Lyme Disease Section, Fort Collins, CO, 1990-1992

Teaching Adjunct Faculty, Microbiology Instructor, Front Range Community College, Fort Collins, CO, 1992

Assistant for Microbiology 200, Colorado State University, 1989

Current Research

We are interested in the function of P450-like cytochromes, particularly in microbial systems. To this end, we have pursued three research areas. First, we have investigated the presence of P450-like cytochromes, an enzyme involved in the metabolism of xenobiotics, in Eubacterium, and Bifidobacterium species, using a combination of molecular biology, microbiology and biochemistry techniques. Secondly, we have investigated the interaction of intestinal microbes with various xenobiotics (surfactants, oral drugs). Lastly, the normal physiological processes associated with cytochrome P450 have been exploited in terms of developing a biological sensor for xenobioitic detection.


Recent Publications


  1. John, G.H., J.O. Carlson, C.V. Kimberling and R.P. Ellis. Polymerase Chain Reaction Amplification of the Constant and Variable Regions of the Bacteroides nodosus Fimbrial Gene. J. of Clin. Microbiol. 28:2456-2461, 1990.
  2. John, G.H., J.A. Hasler, Y. He, and J.R. Halpert. E. coli Expression and Characterization of Cytochromes P450 2B11, 2B1, and 2B5. Arch. Biochem. Biophys. 314:367-375, 1994.

  1. Hasler, J.A., G.R. Harlow, G.D. Szklarz, G.H. John, K.M. Kedzie, V.L. Burnett, Y. He, L.S. Kaminsky and J.R. Halpert. Site-directed Mutagenesis of Putative Substrate Recognition Sites in Cytochrome P450 2B11. Importance of Amino Acid Residues 114, 290, and 363 for Substrate Specificity. Mol. Pharmacol. 46:338-345, 1994.
  2. Born, S.L., G.H. John, G.R. Harlow and J.R. Halpert. Characterization of the Progesterone 21-hydroxylase Activity of Cytochrome P450 PBD-2/P450 2B11 Through Reconstitution, Heterologous Expression, and Site-directed Mutagenesis. Drug Metab. Dispos., 23:702-707, 1994.
  3. John, G.H., Smith, R., Abraham, K.J., and Ellis, R.P. Identification and grouping of Dichelobacter nodosus, using PCR and sequence analysis. Molecular and Cellular Probes, 13:61-65, 1999.


  1. Udeh, P., Veenstra, J., Abraham, K.J., and John, G.H. Quantitative Polymerase Chain Reaction (QPCR) using the mimic approach to estimate Cryptosporidium parvum oocysts (an intestinal pathogen) in municiple water treatment sludge samples. Molecular and Cellular Probes, 14:121-126, 2000.
  2. John, G.H., Walls, S., Goodfox-Jones, J., Keith, R., and Abraham, K.J. The presence of a P450-like protein in the human intestinal microflora, Eubacterium aerofaciens. Microbial Ecology in Health and Disease, 13:3-8, 2001.

  4. John, G. H. and Keith, R. Induction of a stress protein in Eubacterium biforme by the surfactant CTAB. Microbial Ecology in Health and Disease, In press, 2001.
  5. Tucker, K., Keith, R. Jacobs, D. and John, G.H. Metabolism of Phenobarbital by Bifidobacterium species. Anaerobe, Accepted pending revisions, 2001.

  7. Walls, S. and John, G.H. Phenobarbital induced proteins from Streptococcus intestinalis. Anaerobe, In preparation.