Laboratory evolution of Geobacter sulfurreducens for enhanced growth on lactate via a single-base-pair substitution in a transcriptional regulator

• Published in: The ISME Journal 2012-05, Vol.6 (5), p.975-983
• Main Authors: Summers, Zarath M, Ueki, Toshiyuki, Ismail, Wael, Haveman, Shelley A, Lovley, Derek R
• Format: Article
• Language: English
• Subjects: Adaptation, Biological - genetics; Amino Acid Sequence; Base Pairing; Base Sequence; Biodegradation, Environmental; Biomedical and Life Sciences; Bioremediation; Cell culture; Deoxyribonucleic acid; DNA; DNA, Bacterial - genetics; Ecology; Environmental changes; Enzymes; Evolution; Evolution, Molecular; Evolutionary Biology; Genomes; Geobacter; Geobacter - genetics; Geobacter - growth & development; Geobacter - metabolism; Geobacter sulfurreducens; Ground water; Groundwater; Groundwater - microbiology; Lactic acid; Lactic Acid - metabolism; Life Sciences; Metabolism; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Microorganisms; Molecular Sequence Data; Mutation; Nucleotide sequence; Operon; Operons; Organic compounds; Original; original-article; Promoter Regions, Genetic; Promoters; Sequence Analysis, DNA; Single-nucleotide polymorphism; succinyl-CoA synthase; Transcription
• ISSN: 1751-7362; 1751-7370
• DOI: 10.1038/ismej.2011.166

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.