BioS, a Biotin-Induced, Stationary-Phase, and Possible LysR-Type Regulator in <i>Sinorhizobium meliloti</i>

Heinz, Elke B.; Phillips, Donald A.; Streit, Wolfgang R.

doi:10.1094/mpmi.1999.12.9.803

Cited by 23 publications

(43 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our microarray analysis indicated that CbrA affects the expression of eight regulatory proteins and may therefore be situated at the top of a complex regulatory network (Table 2). For instance, the cbrA::Tn5 mutant exhibits decreased expression of bioS (Table 2), which encodes a LysRlike transcription factor whose expression increases in response to biotin addition and during the transition from exponential growth to stationary phase growth (37,79). While BioS autoregulation was found to contribute to biotin-dependent induction of bioS, the factor required for stationary phase regulation of bioS was not identified previously.…”

Section: Resultsmentioning

confidence: 96%

The Symbiosis Regulator CbrA Modulates a Complex Regulatory Network Affecting the Flagellar Apparatus and Cell Envelope Proteins

et al. 2007

View full text Add to dashboard Cite

Sinorhizobium meliloti participates in a nitrogen-fixing symbiosis with legume plant host species of the genera Medicago, Melilotus, and Trigonella. We recently identified an S. meliloti two-component sensory histidine kinase, CbrA, which is absolutely required to establish a successful symbiosis with Medicago sativa (K. E. Gibson, G. R. Campbell, J. Lloret, and G. C. Walker, J. Bacteriol. 188:4508-4521, 2006). In addition to having a symbiotic defect, the cbrA::Tn5 mutant also has free-living phenotypes that suggest a cell envelope perturbation. Because the bases for these phenotypes are not well understood, we undertook an identification of CbrA-regulated genes. We performed a microarray analysis and compared the transcriptome of the cbrA::Tn5 mutant to that of the wild type. Our global analysis of gene expression identified 162 genes that are differentially expressed in the cbrA::Tn5 mutant, including those encoding proteins involved in motility and chemotaxis, metabolism, and cell envelope function. With regard to those genes with a known role in symbiosis, we observed increased expression of nine genes with overlapping functions in bacterial invasion of its host, which suggests that the mutant could be competent for invasion. Since these CbrA-repressed genes are vital to the invasion process, it appears that down-regulation of CbrA activity is important at this stage of nodule development. In contrast, our previous work showed that CbrA is required for bacteria to establish themselves within the host as nitrogen-fixing symbionts. Therefore, we propose a model in which CbrA functions as a developmental switch during symbiosis.As a model system for studying methods that invasive bacteria employ to transition from a free-living environment to their niche within the host, we explored how the gram-negative bacterium Sinorhizobium meliloti establishes a nitrogen-fixing symbiosis within the roots of leguminous plants such as Medicago sativa.

show abstract

Section: Resultsmentioning

confidence: 96%

The Symbiosis Regulator CbrA Modulates a Complex Regulatory Network Affecting the Flagellar Apparatus and Cell Envelope Proteins

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Two additional genes possibly linked to synthesis of biotin are present on pNGR234b: one encodes an 8-amino-7-oxononanoate synthase (NGR_b10670, a possible bioF homologue), while the other, a possible bioA homologue (NGR_b06270), encodes an adenosylmethionine-8-amino-7-oxononanoate aminotransferase. Furthermore, genes involved in biotin transport (bioMNY [NGR_c05050, NGR_c05060, and NGR_c05040]) and BioS (NGR_c13770) a sensor/regulator protein (36,37) were identified. Intriguingly, BioS proteins have only been found in strains NGR234 and 1021 (37).…”

Section: Resultsmentioning

confidence: 99%

Rhizobium sp. Strain NGR234 Possesses a Remarkable Number of Secretion Systems

Schmeisser

Liesegang²,

Krysciak

et al. 2009

Appl Environ Microbiol

Self Cite

152

143

View full text Add to dashboard Cite

Rhizobium sp. strain NGR234 is a unique alphaproteobacterium (order Rhizobiales) that forms nitrogenfixing nodules with more legumes than any other microsymbiont. We report here that the 3.93-Mbp chromosome (cNGR234) encodes most functions required for cellular growth. Few essential functions are encoded on the 2.43-Mbp megaplasmid (pNGR234b), and none are present on the second 0.54-Mbp symbiotic plasmid (pNGR234a). Among many striking features, the 6.9-Mbp genome encodes more different secretion systems than any other known rhizobia and probably most known bacteria. Altogether, 132 genes and proteins are linked to secretory processes. Secretion systems identified include general and export pathways, a twin arginine translocase secretion system, six type I transporter genes, one functional and one putative type III system, three type IV attachment systems, and two putative type IV conjugation pili. Type V and VI transporters were not identified, however. NGR234 also carries genes and regulatory networks linked to the metabolism of a wide range of aromatic and nonaromatic compounds. In this way, NGR234 can quickly adapt to changing environmental stimuli in soils, rhizospheres, and plants. Finally, NGR234 carries at least six loci linked to the quenching of quorum-sensing signals, as well as one gene (ngrI) that possibly encodes a novel type of autoinducer I molecule.Diverse soil bacteria interact with plants in ways that range from symbiotic to pathogenic. Symbiotic Eubacteria (both alpha-and betaproteobacteria, collectively called rhizobia) form nitrogen-fixing associations of tremendous environmental importance (41, 66). Although some rhizobia are able to reduce atmospheric nitrogen to ammonia under saprophytic, free-living conditions, the reduced oxygen tensions found within the intracellular environment of specialized organs called nodules, maximizes this process (16). As legume roots penetrate the soil, they come in contact with rhizobia. Symbiotic interactions are initiated by the exchange of diverse molecules between the partners. Among them, plants liberate flavonoids into the rhizosphere that upregulate rhizobial genes. As a result, lipo-chito-oligo-saccharidic Nod factors are produced that trigger the nodulation pathway in susceptible legumes. Then, in many hosts, rhizobia enter the roots through root hairs, make their way to the cortex, multiply and fill the intracellular spaces of mature nodules. Centripetal progression of rhizobia into the plant and their maturation into nitrogen-fixing symbiosomes depends on the continued exchange of diverse signals.Many, but not all of these signals have been identified; one sure way to take stock of what is necessary for effective symbiosis is to sequence the partners. We began this work by assembling overlapping sets of cosmids (contigs) of the microsymbiont Rhizobium sp. strain NGR234 (hereafter NGR234) (63), which enabled us to elucidate the nucleotide sequence of the symbiotic (pNGR243a) plasmid (29). Similar techniques permitted the assembly of sections of th...

show abstract

“…The production of succinoglycan is regulated by the ExoS/ChvI two-component regulatory system (7), the exoR gene (45), the LysR-type transcriptional regulator gene syrM (52), and other genes, including syrA (2), exoX, and exoD (44,46,61). The involvement of the S. meliloti bioS gene in perceiving plant signals which regulate S. meliloti biotin production is one of the most recent examples of a LysR family transcriptional regulator involved in the S. meliloti-alfalfa signal exchange (20).…”

mentioning

confidence: 99%

Two NewSinorhizobium melilotiLysR-Type Transcriptional Regulators Required for Nodulation

et al. 2005

View full text Add to dashboard Cite

The establishment of an effective nitrogen-fixing symbiosis between Sinorhizobium meliloti and its legume host alfalfa (Medicago sativa) depends on the timely expression of nodulation genes that are controlled by LysR-type regulators. Ninety putative genes coding for LysR-type transcriptional regulators were identified in the recently sequenced S. meliloti genome. All 90 putative lysR genes were mutagenized using plasmid insertions as a first step toward determining their roles in symbiosis. Two new LysR-type symbiosis regulator genes, lsrA and lsrB, were identified in the screening. Both the lsrA and lsrB genes are expressed in free-living S. meliloti cells, but they are not required for cell growth. An lsrA1 mutant was defective in symbiosis and elicited only white nodules that exhibited no nitrogenase activity. Cells of the lsrA1 mutant were recovered from the white nodules, suggesting that the lsrA1 mutant was blocked early in nodulation. An lsrB1 mutant was deficient in symbiosis and elicited a mixture of pink and white nodules on alfalfa plants. These plants exhibited lower overall nitrogenase activity than plants inoculated with the wild-type strain, which is consistent with the fact that most of the alfalfa plants inoculated with the lsrB1 mutant were short and yellow. Cells of the lsrB1 mutant were recovered from both pink and white nodules, suggesting that lsrB1 mutants could be blocked at multiple points during nodulation. The identification of two new LysR-type symbiosis transcriptional regulators provides two new avenues for understanding the complex S. meliloti-alfalfa interactions which occur during symbiosis.

show abstract

BioS, a Biotin-Induced, Stationary-Phase, and Possible LysR-Type Regulator in Sinorhizobium meliloti

Cited by 23 publications

References 24 publications

The Symbiosis Regulator CbrA Modulates a Complex Regulatory Network Affecting the Flagellar Apparatus and Cell Envelope Proteins

The Symbiosis Regulator CbrA Modulates a Complex Regulatory Network Affecting the Flagellar Apparatus and Cell Envelope Proteins

Rhizobium sp. Strain NGR234 Possesses a Remarkable Number of Secretion Systems

Two NewSinorhizobium melilotiLysR-Type Transcriptional Regulators Required for Nodulation

Contact Info

Product

Resources

About