title: Selective utilization of exogenous amino acids by Dehalococcoides ethenogenes strain 195 and its effects on growth and dechlorination activity.
abstract: Bacteria of the genus Dehalococcoides are important members of bioremediation communities because of their ability to detoxify chloroethenes to the benign end product ethene. Genome-enabled studies conducted with Dehalococcoides ethenogenes 195 have revealed that two ATP-binding cassette (ABC)-type amino acid transporters are expressed during its exponential growth stages. In light of previous findings that Casamino Acids enhanced its dechlorination activity, we hypothesized that strain 195 is capable of importing amino acids from its environment to facilitate dechlorination and growth. To test this hypothesis, we applied isotopomer-based dilution analysis with (13)C-labeled acetate to differentiate the amino acids that were taken up by strain 195 from those synthesized de novo and to determine the physiological changes caused by the significantly incorporated amino acids. Our results showed that glutamate/glutamine and aspartate/asparagine were almost exclusively synthesized by strain 195, even when provided in excess in the medium. In contrast, phenylalanine, isoleucine, leucine, and methionine were identified as the four most highly incorporated amino acids, at levels >30% of respective proteinogenic amino acids. When either phenylalanine or all four highly incorporated amino acids were added to the defined mineral medium, the growth rates, dechlorination activities, and yields of strain 195 were enhanced to levels similar to those observed with supplementation with 20 amino acids. However, genes for the putative ABC-type amino acids transporters and phenylalanine biosynthesis exhibited insignificant regulation in response to the imported amino acids. This study also demonstrates that using isotopomer-based metabolite analysis can be an efficient strategy for optimizing nutritional conditions for slow-growing microorganisms.
authors: Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, USA.
authors: Wei-Qin
authors: WQ
authors: Zhuang
authors: Shan
authors: S
authors: Yi
authors: Xueyang
authors: X
authors: Feng
authors: Stephen H
authors: SH
authors: Zinder
authors: Yinjie J
authors: YJ
authors: Tang
authors: Lisa
authors: L
authors: Alvarez-Cohen
mesh_terms: D000085:Acetates / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism; D041862:Chloroflexi / Q000254:growth & development* / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D005030:Ethylenes / Q000378:metabolism*; D006843:Hydrocarbons, Chlorinated / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods
chemical_list: D000085:Acetates; D000596:Amino Acids; D002247:Carbon Isotopes; D003470:Culture Media; D005030:Ethylenes; D006843:Hydrocarbons, Chlorinated; C036216:ethylene