Genetic analysis of the Rhizobium meliloti bacA gene: functional interchangeability with the Escherichia coli sbmA gene and phenotypes of mutants

Ichige, Asao; Walker, Graham C.

doi:10.1128/jb.179.1.209-216.1997

Cited by 70 publications

(110 citation statements)

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“…In E. coli, deletion of the bacA isofunctional homolog, sbmA, produces increased resistance to microcins B17 and J25, bleomycin, and Bac7, which is an antimicrobial peptide of mammalian origin (96,113). Similarly, the bacA mutants of S. meliloti and B. abortus show increased resistance to bleomycin relative to the wild type (74,100). Thus, BacA may play a role in the transport of modified peptides across the inner membrane (64).…”

Section: Bacamentioning

confidence: 99%

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Molecular Determinants of a Symbiotic Chronic Infection

2008

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Rhizobial bacteria colonize legume roots for the purpose of biological nitrogen fixation. A complex series of events, coordinated by host and bacterial signal molecules, underlie the development of this symbiotic interaction. Rhizobia elicit de novo formation of a novel root organ within which they establish a chronic intracellular infection. Legumes permit rhizobia to invade these root tissues while exerting control over the infection process. Once rhizobia gain intracellular access to their host, legumes also strongly influence the process of bacterial differentiation that is required for nitrogen fixation. Even so, symbiotic rhizobia play an active role in promoting their goal of host invasion and chronic persistence by producing a variety of signal molecules that elicit changes in host gene expression. In particular, rhizobia appear to advocate for their access to the host by producing a variety of signal molecules capable of suppressing a general pathogen defense response.

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Section: Bacamentioning

confidence: 99%

“…Generally, the loss of bacA function has been associated with an increased resistance to certain antimicrobial peptides (74,96,113). In E. coli, deletion of the bacA isofunctional homolog, sbmA, produces increased resistance to microcins B17 and J25, bleomycin, and Bac7, which is an antimicrobial peptide of mammalian origin (96,113).…”

Section: Bacamentioning

confidence: 99%

Molecular Determinants of a Symbiotic Chronic Infection

2008

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“…BacA is required for intracellular infections during Sinorhizobium meliloti plant symbiosis and Brucella abortus animal pathogenesis (64). BacA is also necessary for differentiation of Sinorhizobium meliloti into nitrogen-fixing differentiated cells (bacteroids) (109). Only when active promoters are inserted in the promoter trap will the bacA gene be expressed, resulting in the differentiation process.…”

Section: Selection Strategies In Ivetmentioning

confidence: 99%

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

Rediers

Rainey

Vanderleyden

et al. 2005

Microbiol Mol Biol Rev

140

120

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A major challenge for microbiologists is to elucidate the strategies deployed by microorganisms to adapt to and thrive in highly complex and dynamic environments. In vitro studies, including those monitoring genomewide changes, have proven their value, but they can, at best, mimic only a subset of the ensemble of abiotic and biotic stimuli that microorganisms experience in their natural habitats. The widely used gene-to-phenotype approach involves the identification of altered niche-related phenotypes on the basis of gene inactivation. However, many traits contributing to ecological performance that, upon inactivation, result in only subtle or difficult to score phenotypic changes are likely to be overlooked by this otherwise powerful approach. Based on the premise that many, if not most, of the corresponding genes will be induced or upregulated in the environment under study, ecologically significant genes can alternatively be traced using the promoter trap techniques differential fluorescence induction and in vivo expression technology (IVET). The potential and limitations are discussed for the different IVET selection strategies and system-specific variants thereof. Based on a compendium of genes that have emerged from these promoter-trapping studies, several functional groups have been distinguished, and their physiological relevance is illustrated with follow-up studies of selected genes. In addition to confirming results from largely complementary approaches such as signature-tagged mutagenesis, some unexpected parallels as well as distinguishing features of microbial phenotypic acclimation in diverse environmental niches have surfaced. On the other hand, by the identification of a large proportion of genes with unknown function, these promoter-trapping studies underscore how little we know about the secret lives of bacteria and other microorganisms

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“…For example, it seemed unlikely that a reduction in the lipid A VLCFA content could account for the low-level bleomycin resistance phenotype of the S. meliloti bacA-null mutant, since deletion of the bacA homolog, sbmA, in Escherichia coli also gives rise to a similar phenotype (10), despite the fact that the lipid A of E. coli lacks VLCFA modifications (15). Thus, these data suggested that BacA might have additional effects on S. meliloti, resulting in increased sensitization of wild-type S. meliloti toward bleomycin relative to the S. meliloti bacA mutant.…”

mentioning

confidence: 99%

“…Although the precise function of BacA is unknown, S. meliloti and B. abortus bacAnull mutants display a range of phenotypes during growth in complex medium, including low-level resistance to bleomycin, a glycopeptide antibiotic, and increased sensitivity to detergents compared with their respective parent strains (7,10). The detergent sensitivity phenotype led to the discovery that BacA affects the unusual very-long-chain fatty acid (VLCFA) modifications, 27-OHC28:0, 27-OH(␤OMeC4:0)C28, and 29-OHC30:0, of the lipid A in both S. meliloti and B. abortus (5,7).…”

mentioning

confidence: 99%

BacA-Mediated Bleomycin Sensitivity in Sinorhizobium meliloti Is Independent of the Unusual Lipid A Modification

et al. 2006

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Sinorhizobium meliloti bacA mutants are symbiotically defective, deoxycholate sensitive, and bleomycin resistant. We show that the bleomycin resistance phenotype is independent of the lipid A alteration and that the changes giving rise to both phenotypes are likely to be involved in the inability of bacA mutants to persist within their hosts.The BacA protein is essential for Sinorhizobium meliloti, a legume symbiont, and Brucella abortus, a phylogenetically related mammalian pathogen, to establish chronic intracellular infections in their respective hosts (9,13). Although the precise function of BacA is unknown, S. meliloti and B. abortus bacAnull mutants display a range of phenotypes during growth in complex medium, including low-level resistance to bleomycin, a glycopeptide antibiotic, and increased sensitivity to detergents compared with their respective parent strains (7, 10). The detergent sensitivity phenotype led to the discovery that BacA affects the unusual very-long-chain fatty acid (VLCFA) modifications, 27-OHC28:0, 27-OH(␤OMeC4:0)C28, and 29-OHC30:0, of the lipid A in both S. meliloti and B. abortus (5, 7). Thus, in the absence of BacA, only ϳ50% of the lipid A molecules of S. meliloti and B. abortus become modified with a VLCFA, in contrast to their respective parent strains, whose lipid A molecules all contain a VLCFA modification (5). However, recent evidence suggests that the unusual lipid A modification observed during growth of wild-type S. meliloti in complex medium is important, but not essential, for the legume symbiosis (6). Thus, since additional VLCFA modifications of the lipid A occur during the symbiosis of Rhizobium leguminosarum with peas (11), and we observed a similar increase in S. meliloti lipopolysaccharide (LPS) hydrophobicity during the alfalfa symbiosis (6), we proposed a model whereby BacA could be involved in host-induced lipid A changes. These BacA-dependent lipid A changes could be essential for the chronic infection of their eukaryotic hosts by S. meliloti and B. abortus (6).Nevertheless, there also remained a formal possibility that additional lipid A-independent changes were occurring in the S. meliloti bacA-null mutant and that one or more of these changes could also be involved in the inability of bacA mutants to persist within their hosts. For example, it seemed unlikely that a reduction in the lipid A VLCFA content could account for the low-level bleomycin resistance phenotype of the S. meliloti bacA-null mutant, since deletion of the bacA homolog, sbmA, in Escherichia coli also gives rise to a similar phenotype (10), despite the fact that the lipid A of E. coli lacks VLCFA modifications (15). Thus, these data suggested that BacA might have additional effects on S. meliloti, resulting in increased sensitization of wild-type S. meliloti toward bleomycin relative to the S. meliloti bacA mutant.S. meliloti mutants completely lacking the lipid A VLCFA modification have increased sensitivity to bleomycin. Our recent discovery that the lipid A species produced by the S. m...

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Genetic analysis of the Rhizobium meliloti bacA gene: functional interchangeability with the Escherichia coli sbmA gene and phenotypes of mutants

Cited by 70 publications

References 50 publications

Molecular Determinants of a Symbiotic Chronic Infection

Molecular Determinants of a Symbiotic Chronic Infection

Unraveling the Secret Lives of Bacteria: Use of In Vivo Expression Technology and Differential Fluorescence Induction Promoter Traps as Tools for Exploring Niche-Specific Gene Expression

BacA-Mediated Bleomycin Sensitivity in Sinorhizobium meliloti Is Independent of the Unusual Lipid A Modification

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