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J. Bacteriol., 02 1997, 1013-1022, Vol 179, No. 4
D Walter, M Ailion and J Roth
Salmonella typhimurium is able to catabolize 1,2-propanediol for use as the
sole carbon and energy source; the first enzyme of this pathway requires
the cofactor adenosyl cobalamin (Ado-B12). Surprisingly, Salmonella can use
propanediol as the sole carbon source only in the presence of oxygen but
can synthesize Ado-B12 only anaerobically. To understand this situation, we
have studied the pdu operon, which encodes proteins for propanediol
degradation. A set of pdu mutants defective in aerobic degradation of
propanediol (with exogenous vitamin B12) defines four distinct
complementation groups. Mutations in two of these groups (pduC and pduD)
eliminate propanediol dehydratase activity. Based on mutant phenotypes, a
third complementation group (pduG) appears to encode a cobalamin adenosyl
transferase activity. No function has been assigned to the pduJ
complementation group. Propionaldehyde dehydrogenase activity is eliminated
by mutations in any of the four identified complementation groups,
suggesting that this activity may require a complex of proteins encoded by
the operon. None of the mutations analyzed affects either of the first two
genes of the operon (pduA and pduB), which were identified by DNA sequence
analysis. Available data suggest that the pdu operon includes enough DNA
for about 15 genes and that the four genetically identified genes are the
only ones required for aerobic use of propanediol.
Copyright © 1997, American Society for Microbiology
Genetic characterization of the pdu operon: use of 1,2-propanediol in Salmonella typhimurium
Department of Biology, University of Utah, Salt Lake City 84112, USA.
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