Hope A. Johnson, Ph.D., Stanford University
Assistant Professor of Biology
Personal Web Site: Coming Soon
Our lab is interested in the many ways bacteria interact with metals, specifically bacteria that oxidize manganese. Bacteria require trace amounts of metals for many of their enzymes, yet metals in high amounts can be toxic. Therefore, bacteria have evolved many ways to control the level of metals within the cell. In addition, bacteria can also take advantage of the redox properties of many metals and use them as a source or sink for electrons. In fact, some bacteria can breathe with metals just as we breathe with oxygen. In the case of manganese, we do not fully understand how or why bacteria oxidize this metal. Techniques in microbial physiology, molecular biology, and biochemistry will be used to answer this question. An understanding of how bacteria oxidize manganese will not only give us insight into the striking diversity of microbial life but can also give us important tools for bioremediation.
An additional area of interest is in bacterial protein function. For a given microbial genome, approximately 15-30% of the genes encode for hypothetical proteins – proteins of unknown function. For a genome of 3000 genes, thatÕs 500 to 900 proteins that we donÕt understand at all even though many of them may have an important, possibly novel function. ThereÕs a lot we do not know about supposedly simple organisms with small genomes! We will employ ligand binding techniques, bioinformatics, and biochemical and cellular assays to identify the function of these proteins. WeÕre specifically interested in those proteins that may be involved in bacterial interactions with metals.
Dick, G.J., Podell, S., Johnson, H.A., Rivera-Espinoza, Y., Bernier-Latmani, R., McCarthy, J.K., Torpey, J.W., Clement, B.G., Gaasterland, T., and Tebo, B. M. Genomic insights into Mn(II) oxidation by the marine a-proteobacterium Aurantimonas sp. strain SI85-9A1. Submitted to Applied and Environmental Microbiology.
Johnson, H.A. and Tebo, B.M. In vitro studies indicate a quinone is involved in bacterial Mn(II) oxidation. Archives of Microbiology. 189: 59-69. 2008.
Tebo, B.M., Johnson, H.A., McCarthy, J. Templeton, A.S. Geomicrobiology of manganese(II) oxidation. TRENDS in Microbiology, 13: 421-428. 2005.