The School of Molecular and Cellular Biology at the University of Illinois at Urbana-Champaign

My research program involves investigation of two novel aspects of microbial metabolism. The first project involves the development and application of genetic techniques for analysis of the methane-producing members of the so-called "third form of life", the Archaea. The second project involves an investigation of the largely unexplored metabolism of reduced phosphorus compounds, a class of compounds that possess unique biological properties, and which are now known to be widespread in nature. Although these studies are conducted with microbial model systems, both projects address fundamental research questions in new areas of biology and, as such, may possess widespread relevance.

Genetic analysis of methanogenic Archaea
Methanogenesis is critically important to a number of human-related problems including the production of alternative fuels from biological materials, waste treatment, and global warming (via production of a key greenhouse gas). Each year an estimated 5 x 1014 g of biologically produced methane is released into the atmosphere. Depending on your viewpoint, this represents a staggering untapped renewable energy source and/or a frightening contribution to global warming. Methanogenesis also plays an essential role in the global carbon cycle, is relevant to agriculture due to its role in ruminant nutrition and is a required step in the processing of waste in sewage treatment facilities and landfills. In addition, methanogens comprise one of the few experimentally tractable groups among the Archaea and, thus, provide outstanding model organisms for the study of this so-called "third form of life".
A major focus of research in my laboratory has been the development of genetic methods for use in the methanogenic archaeon Methanosarcina. Over the past five years, we have developed a collection of genetic tools and methods for use in Methanosarcina that are unsurpassed among methanoarchaea. These tools include; plasmid shuttle vectors, very high efficiency transformation, in vivo transposon mutagenesis, multiple selectable markers and an anaerobic incubator for large-scale growth on solid media. More recently, we have applied these methods to study the metabolism and physiology of Methanosarcina species. We showed that directed mutagenesis of specific genes is possible in two Methanosarcina species and have constructed dozens of mutant strains with lesions in over 15 different genes. Significantly, many of these strains have mutations in genes required for methanogenesis. The study of these mutants has revealed novel aspects of the methanogenic process. We have also adapted reporter gene fusions for use in Methanosarcina and shown that genes required for specific methanogenic pathways are transcriptionally regulated by availability of their substrate.

Microbial metabolism of reduced phosphorus compounds
The second project underway in my laboratory involves characterizing of the microbial metabolism of reduced phosphorus compounds. Phosphorus plays a central role in the metabolism of all living organisms and is a required nutrient. Despite the ubiquitous role of P in biology, the biochemistry of P containing compounds is generally considered to be quite simple, consisting almost entirely of phosphate-ester formation and hydrolysis. However, it is increasingly apparent that other types of P biochemistry are important as well. Some of these reactions involve compounds in which P is at a lower valence state, suggesting that previously unsuspected P redox reactions may be important in the metabolism of this element.

We have focused our studies on the metabolism of two reduced P compounds, phosphite and hypophosphite using of a combined approach that includes genetic, molecular and biochemical techniques. Surprisingly, organisms with metabolic pathways that allow oxidation of these compounds are quite common, with ca. 1% of all microorganisms being able to oxidize phosphite. We have isolated numerous microorganisms that are capable of oxidizing both hypophosphite and phosphite. Examination of these bacteria revealed at least three previously unknown pathways for oxidation of reduced P compounds, each of which is currently under study in my laboratory. Two novel phosphorus-oxidizing enzymes have been discovered and characterized during the course of this work. Interestingly, one of these has great potential as a cofactor-regenerating enzyme for use in biocatalysis. Preliminary data suggests that additional novel pathways are present among our isolates. In addition to these studies on phosphorus oxidation, we have recently begun genetic studies on phosphonate biosynthesis in Streptomyces. We hope that these studies will expand our concept of P metabolism and shed new light on the biochemical and physiological properties of reduced P compounds.