title: Laboratory evolution of Geobacter sulfurreducens for enhanced growth on lactate via a single-base-pair substitution in a transcriptional regulator.
abstract: The addition of organic compounds to groundwater in order to promote bioremediation may represent a new selective pressure on subsurface microorganisms. The ability of Geobacter sulfurreducens, which serves as a model for the Geobacter species that are important in various types of anaerobic groundwater bioremediation, to adapt for rapid metabolism of lactate, a common bioremediation amendment, was evaluated. Serial transfer of five parallel cultures in a medium with lactate as the sole electron donor yielded five strains that could metabolize lactate faster than the wild-type strain. Genome sequencing revealed that all five strains had non-synonymous single-nucleotide polymorphisms in the same gene, GSU0514, a putative transcriptional regulator. Introducing the single-base-pair mutation from one of the five strains into the wild-type strain conferred rapid growth on lactate. This strain and the five adaptively evolved strains had four to eight-fold higher transcript abundance than wild-type cells for genes for the two subunits of succinyl-CoA synthase, an enzyme required for growth on lactate. DNA-binding assays demonstrated that the protein encoded by GSU0514 bound to the putative promoter of the succinyl-CoA synthase operon. The binding sequence was not apparent elsewhere in the genome. These results demonstrate that a single-base-pair mutation in a transcriptional regulator can have a significant impact on the capacity for substrate utilization and suggest that adaptive evolution should be considered as a potential response of microorganisms to environmental change(s) imposed during bioremediation.
authors: Department of Microbiology, University of Massachusetts Amherst, St Paul, MN, USA. zsummers@umn.edu
authors: Zarath M
authors: ZM
authors: Summers
authors: Toshiyuki
authors: T
authors: Ueki
authors: Wael
authors: W
authors: Ismail
authors: Shelley A
authors: SA
authors: Haveman
authors: Derek R
authors: DR
authors: Lovley
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000595:Amino Acid Sequence; D020029:Base Pairing; D001483:Base Sequence; D001673:Biodegradation, Environmental; D004269:DNA, Bacterial / Q000235:genetics; D019143:Evolution, Molecular; D045302:Geobacter / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D060587:Groundwater / Q000382:microbiology; D019344:Lactic Acid / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D019344:Lactic Acid