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.
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.
Guccione
Edward
E
Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Leon-Kempis
Maria del Rocio
Mdel R
Pearson
Bruce M
BM
Hitchin
Edward
E
Mulholland
Francis
F
van Diemen
Pauline M
PM
Stevens
Mark P
MP
Kelly
David J
DJ
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
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