January
2003
, Volume
16
, Number
1
Pages
65
-
73
Authors
Olivia J.
Jahn
,
1
Guillermo
Davila
,
2
David
Romero
,
3
and
K. Dale
Noel
1
Affiliations
1Department of Biology, Marquette University, Milwaukee, WI 53233, U.S.A. 2Programas de Evolución Molecular and 3Genética Molecular de Plásmidos Bacterianos, Centro de Investigación sobre Fijación de Nitrógeno, Cuernavaca, Morelos, Mexico
Go to article:
RelatedArticle
Accepted 20 September 2002.
Abstract
Rhizobium etli CFN42 bacteroids from bean nodules possessed an abundant 16-kDa protein (BacS) that was found in the membrane pellet after cell disruption. This protein was not detected in bacteria cultured in tryptone-yeast extract. In minimal media, it was produced at low oxygen concentration but not in a mutant whose nifA was disrupted. N-terminal sequencing of the protein led to isolation of a bacS DNA fragment. DNA hybridization and nucleotide sequencing revealed three copies of the bacS gene, all residing on the main symbiotic plasmid of strain CFN42. A stretch of 304 nucleotides, exactly conserved upstream of all three bacS open reading frames, had very close matches with the NifA and sigma 54 consensus binding sequences. The only bacS homology in the genetic sequence databases was to three hypothetical proteins of unknown function, all from rhizobial species. Mutation and genetic complementation indicated that each of the bacS genes gives rise to a BacS polypeptide. Mutants disrupted or deleted in all three genes did not produce the BacS polypeptide but were Nod+ and Fix+ on Phaseolus vulgaris.
JnArticleKeywords
Page Content
ArticleCopyright
© 2003 The American Phytopathological Society