title: Amino acid-dependent growth of Campylobacter jejuni: key roles for aspartase (AspA) under microaerobic and oxygen-limited conditions and identification of AspB (Cj0762), essential for growth on glutamate.
abstract: Amino acids are key carbon and energy sources for the asaccharolytic food-borne human pathogen Campylobacter jejuni. During microaerobic growth in amino acid rich complex media, aspartate, glutamate, proline and serine are the only amino acids significantly utilized by strain NCTC 11168. The catabolism of aspartate and glutamate was investigated. An aspartase (aspA) mutant (unable to utilize any amino acid except serine) and a Cj0762c (aspB) mutant lacking aspartate:glutamate aminotransferase (unable to utilize glutamate), were severely growth impaired in complex media, and an aspA sdaA mutant (also lacking serine dehydratase) failed to grow in complex media unless supplemented with pyruvate and fumarate. Aspartase was shown by activity and proteomic analyses to be upregulated by oxygen limitation, and aspartate enhanced oxygen-limited growth of C. jejuni in an aspA-dependent manner. Stoichiometric aspartate uptake and succinate excretion involving the redundant DcuA and DcuB transporters indicated that in addition to a catabolic role, AspA can provide fumarate for respiration. Significantly, an aspA mutant of C. jejuni 81-176 was impaired in its ability to persist in the intestines of outbred chickens relative to the parent strain. Together, our data highlight the dual function of aspartase in C. jejuni and suggest a role during growth in the avian gut.
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Edward
authors.initials: E
authors.lastname: Guccione
authors.forename: Maria del Rocio
authors.initials: Mdel R
authors.lastname: Leon-Kempis
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Pearson
authors.forename: Edward
authors.initials: E
authors.lastname: Hitchin
authors.forename: Francis
authors.initials: F
authors.lastname: Mulholland
authors.forename: Pauline M
authors.initials: PM
authors.lastname: van Diemen
authors.forename: Mark P
authors.initials: MP
authors.lastname: Stevens
authors.forename: David J
authors.initials: DJ
authors.lastname: Kelly
mesh_terms: D000332:Aerobiosis; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001219:Aspartate Aminotransferases / Q000235:genetics / Q000378:metabolism*; D001220:Aspartate Ammonia-Lyase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways; D002169:Campylobacter Infections / Q000382:microbiology / Q000662:veterinary; D016123:Campylobacter jejuni / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D002645:Chickens; D003470:Culture Media / Q000737:chemistry; D029382:Dicarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism; D005650:Fumarates / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009154:Mutation; D010100:Oxygen / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D003470:Culture Media; D029382:Dicarboxylic Acid Transporters; D005650:Fumarates; D001224:Aspartic Acid; D018698:Glutamic Acid; D001219:Aspartate Aminotransferases; D001220:Aspartate Ammonia-Lyase; D010100:Oxygen