Genetic regulatory networks and physiology of E. coli, Salmonella and Vibrio
Dr. John W. Foster, Professor, received his Ph.D. in Microbiology from Hahnemann University College of Medicine (now part of Drexel University) in Philadelphia in 1979 and carried out his postdoctoral studies at Georgetown University. Dr. Foster was honored in Who's Who in American Universities and Colleges in 1978, was named 1994 Hahnemann University Alumnus of the year, and received the 2007 Southeastern ASM branch “Robert Eagon Award” for accomplishments in microbial physiology. He has served in the American Society for Microbiology as the Chair of Division K (Microbial Physiology and Metabolism) and as an invited ad hoc member of the Microbial Physiology and Bacterial Pathogenesis Study Sections for the National Institutes of Health (NIH). His scholarly work includes over 100 peer-reviewed articles, a textbook on microbial physiology now in its 4th Edition (coauthored by Albert G. Moat), and a new textbook for undergraduate majors entitled "Microbiology: An Evolving Science" coauthored Joan Slonczewski, PhD, Kenyon College, Ohio (See link below). As of 2008, Dr. Foster has mentored 13 doctoral students and 16 post-doctoral fellows in studies designed to reveal the molecular strategies used by bacterial pathogens to survive stress.
Research summary
The enteric pathogens Salmonella enterica and E. coli 0157:H7 face daunting odds during their voyages in the natural environment and through an infected host. After ingestion, for example, they must be prepared to meet extremely acidic conditions in the stomach. The more acid resistant an organism is, the more likely it can survive passage through the gastric acid barrier and ultimately cause disease. Our laboratory has discovered critical adaptive responses used by Salmonella and E. coli to survive acidic environments found in the stomach. These responses are induced when cells are shifted to mild acid conditions (pH 5 to pH 6), but once engaged they protect the organisms against strong acid conditions (pH 2 to pH 3). We are investigating these responses at the biochemical, genetic and molecular levels and have discovered that each organism uses elaborate genetic regulatory networks to control acid resistance.
John W. Foster, Ph. D.A major question we are asking is how cells "sense" changes in proton concentration during adaptation, and subsequently transmit that signal to the transcriptional/translational machinery. The results of these studies will provide new insights into how cells control their internal pH, repair damage to macromolecules, and modulate gene expression upon recognizing imminent threats to survival.
In a separate project, we are examining the marine microbe Vibrio vulnificus and how it synthesizes and utilizes a growth factor. V. vulnificus is a pathogenic microbe commonly found in oysters. It can cause a severe, life-threatening disease in immunocompromised individuals who consume uncooked oysters. Work is underway to characterize the pathway used to synthesize this growth factor and to elucidate the molecular response to this compound.
Recent Publications
Mates, Aaron, Atef K. Sayad and John W. Foster. 2007. Products of the Escherichia coli Acid Fitness Island Attenuate Metabolite Stress at Extreme Low pH and Mediate a Cell Density-Dependent Acid Resistance. J. Bacteriol. 189:2659-2768
Sayed, A.K., C. Odom and JW. Foster. 2007. The Escherichia coli AraC-family regulatorsGadX and GadW activate gadE, the central activator of glutamate-dependent acid resistance. Microbiology 153: 2584-2592
Richard, H. and J.W. Foster. 2007. Sodium levels modulate the activities of the GadX and GadW regulators of Escherichia coli acid resistance. Microbiology 153:3154-3161
Foster, J.W. 2004. E. coli acid resistance: Tales of a amateur acidophile. Nat. Rev. Microbiol. 2:898-907.
Paul, B.J., M.B. Barker, W. Ross, D.A. Schneider, C.A. Webb, J.W. Foster, and R.L. Gourse. 2004. DksA: A critical component of the transcription initiation machinery that potentiates the regulation of rRNA promoters by ppGpp and the initiating NTP.
Cell 118:311-322.
Ma, Z, N. Masuda and J.W. Foster. 2004. Characterization of EvgAS-YdeO-GadE branched regulatory circuit governing glutamate-dependent acid resistance in Escherichia coli. J. Bacteriol. 186:7378-7389.
Gong, S, Z Ma, and J. W. Foster. 2004. The Era-like GTPase TrmE conditionally regulates gadE and glutamate-dependent acid resistance in Escherichia coli. Mol. Microbiol. 54:948-961.
Richard, H. and JW Foster. 2004. Escherichia coli glutamate- and arginine-dependent acid resistance systems increase internal pH and reverse transmembrane potential. J. Bacteriol. 186:6032-6041. Nominated to Faculty of 1000 by Herb Arst.
Ma, Z., H. Richard and J.W. Foster. 2003. pH-dependent modulation of cyclic AMP levels and GadW-dependent repression of RpoS affect synthesis of the GadX regulator and Escherichia coli acid resistance. J. Bacteriol. 185:6852-6859.
Ma, Z, S. Gong, H. Richard, D.L. Tucker, T.Conway, and J.W.Foster. 2003. GadE(YhiE) activates glutamate decarboxylase-dependent acid resistance in Escherichia coli. Mol. Microbiol. 49:1309-1320.
Richard, HT and JW Foster. 2003. Acid resistance in Escherichia coli. Adv. Appl Microbiol. 52:167-186.
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