Pathways for the utilization of N-acetyl-galactosamine and galactosamine in Escherichia coli.
Among enteric bacteria, the ability to grow on N-acetyl-galactosamine (GalNAc or Aga) and on D-galactosamine (GalN or Gam) differs. Thus, strains B, C and EC3132 of Escherichia coli are Aga+ Gam+ whereas E. coli K-12 is Aga- Gam-, similarly to Klebsiella pneumoniae KAY2026, Klebsiella oxytoca M5a1 and Salmonella typhimurium LT2. The former strains carry a complete aga/kba gene cluster at 70.5 min of their gene map. These genes encode an Aga-specific phosphotransferase system (PTS) or IIAga (agaVWE) and a GalN-specific PTS or IIGam (agaBCD). Both PTSs belong to the mannose-sorbose family, i.e. the IIB, IIC and IID domains are encoded by different genes, and they share a IIA domain (agaF). Furthermore, the genes encode an Aga6P-deacetylase (agaA), a GalN6P deaminase (agaI), a tagatose-bisphosphate aldolase comprising two different peptides (kbaYZ) and a putative isomerase (agaS), i.e. complete pathways for the transport and degradation of both amino sugars. The genes are organized in two adjacent operons (kbaZagaVWEFA and agaS kbaYagaBCDI) and controlled by a repressor AgaR. Its gene agaR is located upstream of kbaZ, and AgaR responds to GalNAc and GalN in the medium. All Aga- Gam- strains, however, carry a deletion covering genes agaW' EF 'A; consequently they lack active IIAga and IIGam PTSs, thus explaining their inability to grow on the two amino sugars. Remnants of a putative recombination site flank the deleted DNA in the various Aga- Gam- enteric bacteria. Derivatives with an Aga+ Gam- phenotype can be isolated from E. coli K-12. These retain the DeltaagaW' EF 'A deletion and carry suppressor mutations in the gat and nag genes for galactitol and N-acetyl-glucosamine metabolism, respectively, that allow growth on Aga but not on GalN.
Brinkkötter
A
A
Universität Osnabrück, Fachbereich Biologie/Chemie, D-49069 Osnabrück, Germany.
Klöss
H
H
Alpert
C
C
Lengeler
J W
JW
D000116:Acetylgalactosamine / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism; D005688:Galactosamine / Q000378:metabolism*; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism; D018085:Regulon; D017422:Sequence Analysis, DNA
D003470:Culture Media; D005688:Galactosamine; D010770:Phosphotransferases; D005634:Fructose-Bisphosphate Aldolase; D000116:Acetylgalactosamine