Deficiency of a Sinorhizobium meliloti BacA mutant in alfalfa symbiosis correlates with alteration of the cell envelope

J Bacteriol. 2002 Oct;184(20):5625-32. doi: 10.1128/JB.184.20.5625-5632.2002.

Abstract

The BacA protein is essential for the long-term survival of Sinorhizobium meliloti and Brucella abortus within acidic compartments in plant and animal cells, respectively. Since both the S. meliloti and B. abortus bacA mutants have an increased resistance to bleomycin, it was hypothesized that BacA was a transporter of bleomycin and bleomycin-like compounds into the bacterial cell. However, our finding that the S. meliloti bacA mutant also has an increased sensitivity to detergents, a hydrophobic dye, ethanol, and acid pH supported a model in which BacA function affects the bacterial cell envelope. In addition, an S. meliloti lpsB mutant that is defective at a stage in infection of the host similar to that found for a bacA mutant is also sensitive to the same agents, and the carbohydrate content of its lipopolysaccharide (LPS) is altered. However, analysis of crude preparations of the bacA mutant LPS suggested that, unlike that for LpsB, BacA function did not affect the carbohydrate composition of the LPS. Rather, we found that at least one function of BacA is to affect the distribution of LPS fatty acids, including a very-long-chain fatty acid thought to be unique to the alpha-proteobacteria, including B. abortus.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Cations, Divalent / pharmacology
  • Cell Membrane / chemistry*
  • Cell Membrane / metabolism
  • Fatty Acids / analysis
  • Hydrogen-Ion Concentration
  • Lipopolysaccharides / chemistry
  • Mannosyltransferases
  • Medicago sativa / microbiology*
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins*
  • Mutation*
  • Sinorhizobium meliloti / genetics*
  • Sinorhizobium meliloti / growth & development
  • Sinorhizobium meliloti / metabolism
  • Sinorhizobium meliloti / physiology
  • Symbiosis*
  • Zinc / pharmacology

Substances

  • Bacterial Proteins
  • Cations, Divalent
  • Fatty Acids
  • Lipopolysaccharides
  • Membrane Proteins
  • Membrane Transport Proteins
  • bacA protein, Rhizobium meliloti
  • LpsB protein, bacteria
  • Mannosyltransferases
  • Zinc