Title: Arms race drives evolution of metabolic diversity

Presenter: Jim Spain

University: Georgia Institute of Technology, the USA

Time: 10:30-11:30, April 10, 2015

Venue: Room A203, Institute of Microbiology, Chinese Academy of Sciences

Abstract: Microorganisms have evolved a wide variety of strategies for the biodegradation of natural and synthetic chemicals, pesticides and antibiotics. The synthetic chemicals have only been in the biosphere for the past century- yet most simple synthetic organic compounds are now biodegradable. In many instances the enzymes involved in the catabolic pathways are closely related to the enzymes involved in degradation of natural compounds. Millions of natural organic chemicals are produced and degraded in natural ecosystems. Therefore, there is a huge reservoir of unexplored metabolic diversity among bacteria that catalyze the biodegradation.

Within a few years after new chemicals, pesticides or antibiotics enter the biosphere, pathways evolve to allow the compounds to support growth of bacteria. Often the chemicals must be modified to make them less susceptible to biodegradation if they are to remain effective. There seems to be a similar arms race in natural ecosystems among the organisms that engage in chemical communication and defense. Plants produce allelopathic chemicals to suppress competing species or pathogens. Once bacteria evolve the ability to degrade such chemicals their effectiveness would be reduced. Allelopathic plants often produce multiple analogs of the active chemicals which suggests the operation of an arms race among the plants, the target species and the bacteria. Stilbenes such as resveratrol are antifungal compounds produced by a variety of plants including peanuts and grapes. In peanuts resveratrol is accompanied by up to 20 different homologs. We found that resveratrol is readily biodegraded by a diverse community of bacteria in the rhizosphere. The initial enzyme has very limited activity toward the most common homologs of resveratrol which suggests they are more recently evolved and less susceptible to biodegradation. Such an arms race could account for many of the myriad small organic compounds produced in the biosphere. Understanding the ecological roles of bacterial catabolic pathways could provide the basis for interventions to limit the spread of invasive plants or improve the defenses of agriculturally important crops.

Introduction:

Jim Spain received his PhD in microbiology from The University of Texas at Austin and a BS in Biology from the University of Texas at Arlington. He studied the biodegradation of pesticides in the marine environment for five years as a post doctoral fellow and research scientist at the U.S. Environmental Protection Agency Marine Environmental Research Laboratory. Prior to joining Georgia Tech Dr. Spain directed the Environmental Biotechnology research program at the Air Force Research Laboratory in Panama City, Florida where he studied the biodegradation of synthetic organic compounds in the environment. His research interests in environmental biotechnology include: discovery and construction of bacteria for degradation of substituted aromatic compounds; physiological and ecological factors controlling microbial processes; and discovery of biocatalysts for green chemistry synthesis of novel materials. He works at the interface between basic microbiology research and practical applications to solve environmental problems.

Dr. Spain is a former editor for Applied and Environmental Microbiology and has published over 150 peer reviewed papers, several books, and numerous book chapters on the biodegradation and biosynthesis of organic compounds. He has served on review committees for the EPA, DoE, NIEHS, and DoD and on the editorial boards of a variety of journals.