scholarly journals Regulatory Role of Rhizobium etli CNPAF512 fnrN during Symbiosis

2004 ◽  
Vol 70 (3) ◽  
pp. 1287-1296 ◽  
Author(s):  
Martine Moris ◽  
Bruno Dombrecht ◽  
Chuanwu Xi ◽  
Jos Vanderleyden ◽  
Jan Michiels
Keyword(s):  
Sigma Factor ◽  
Rhizobium Etli ◽  
Wild Type ◽  
Free Living ◽  
Severe Reduction ◽  
Fixation Capacity ◽  
Additional Level ◽  
Microaerobic Conditions ◽  
Related Proteins

ABSTRACT The Rhizobium etli CNPAF512 fnrN gene was identified in the fixABCX rpoN 2 region. The corresponding protein contains the hallmark residues characteristic of proteins belonging to the class IB group of Fnr-related proteins. The expression of R. etli fnrN is highly induced under free-living microaerobic conditions and during symbiosis. This microaerobic and symbiotic induction of fnrN is not controlled by the sigma factor RpoN and the symbiotic regulator nifA or fixLJ, but it is due to positive autoregulation. Inoculation of Phaseolus vulgaris with an R. etli fnrN mutant strain resulted in a severe reduction in the bacteroid nitrogen fixation capacity compared to the wild-type capacity, confirming the importance of FnrN during symbiosis. The expression of the R. etli fixN, fixG, and arcA genes is strictly controlled by fnrN under free-living microaerobic conditions and in bacteroids during symbiosis with the host. However, there is an additional level of regulation of fixN and fixG under symbiotic conditions. A phylogenetic analysis of the available rhizobial FnrN and FixK proteins grouped the proteins in three different clusters.

scholarly journals Role of the Helicobacter hepaticus Flagellar Sigma Factor FliA in Gene Regulation and Murine Colonization

2008 ◽  
Vol 190 (19) ◽  
pp. 6398-6408 ◽  
Author(s):  
Torsten Sterzenbach ◽  
Lucie Bartonickova ◽  
Wiebke Behrens ◽  
Birgit Brenneke ◽  
Jessika Schulze ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Sigma Factor ◽  
Intestinal Inflammation ◽  
Gall Stone ◽  
Helicobacter Hepaticus ◽  
Intestinal Colonization ◽  
Wild Type ◽  
Chronic Intestinal Inflammation ◽  
Flagellar Genes

ABSTRACT The enterohepatic Helicobacter species Helicobacter hepaticus colonizes the murine intestinal and hepatobiliary tract and is associated with chronic intestinal inflammation, gall stone formation, hepatitis, and hepatocellular carcinoma. Thus far, the role of H. hepaticus motility and flagella in intestinal colonization is unknown. In other, closely related bacteria, late flagellar genes are mainly regulated by the sigma factor FliA (σ28). We investigated the function of the H. hepaticus FliA in gene regulation, flagellar biosynthesis, motility, and murine colonization. Competitive microarray analysis of the wild type versus an isogenic fliA mutant revealed that 11 genes were significantly more highly expressed in wild-type bacteria and 2 genes were significantly more highly expressed in the fliA mutant. Most of these were flagellar genes, but four novel FliA-regulated genes of unknown function were identified. H. hepaticus possesses two identical copies of the gene encoding the FliA-dependent major flagellin subunit FlaA (open reading frames HH1364 and HH1653). We characterized the phenotypes of mutants in which fliA or one or both copies of the flaA gene were knocked out. flaA_1 flaA_2 double mutants and fliA mutants did not synthesize detectable amounts of FlaA and possessed severely truncated flagella. Also, both mutants were nonmotile and unable to colonize mice. Mutants with either flaA gene knocked out produced flagella morphologically similar to those of wild-type bacteria and expressed FlaA and FlaB. flaA_1 mutants which had flagella but displayed reduced motility did not colonize mice, indicating that motility is required for intestinal colonization by H. hepaticus and that the presence of flagella alone is not sufficient.

Plasmid replicons of Rhizobium

2005 ◽  
Vol 33 (1) ◽  
pp. 157-158 ◽  
Author(s):  
L.C. Crossman
Keyword(s):  
Short Review ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
Free Living ◽  
Leguminous Plants ◽  
Symbiotic Plasmid ◽  
Rhizobium Spp ◽  
Plasmid Replicons ◽  
Rhizobium Sp

Rhizobium spp. are found in soil. They are both free-living and found symbiotically associated with the nodules of leguminous plants. Traditionally, studies have focused on the association of these organisms with plants in nitrogen-fixing nodules, since this is regarded as the most important role of these bacteria in the environment. Rhizobium sp. are known to possess several replicons. Some, like the Rhizobium etli symbiotic plasmid p42d and the plasmid pNGR234b of Rhizobium NGR234, have been sequenced and characterized. The plasmids from these organisms are the focus of this short review.

scholarly journals The Staphylococcal Ferritins Are Differentially Regulated in Response to Iron and Manganese and via PerR and Fur

2004 ◽  
Vol 72 (2) ◽  
pp. 972-979 ◽  
Author(s):  
Julie A. Morrissey ◽  
Alan Cockayne ◽  
Kirsty Brummell ◽  
Paul Williams
Keyword(s):  
Oxidative Stress ◽  
Staphylococcus Aureus ◽  
Staphylococcus Epidermidis ◽  
Oxidative Stress Response ◽  
Metal Availability ◽  
Wild Type ◽  
Additional Level ◽  
Alkyl Hydroperoxidase ◽  
Iron And Manganese

ABSTRACT Staphylococcus aureus and Staphylococcus epidermidis ferritin (FtnA and SefA, respectively) homologues are antigenic and highly conserved. A previous study showed that ftnA is a component of the S. aureus PerR regulon with its transcription induced by elevated iron and repressed by PerR, which functions as a manganese-dependent transcriptional repressor. We have further investigated the role of iron and Fur in the regulation of PerR regulon genes ftnA (ferritin), ahpC (alkyl-hydroperoxidase), and mrgA (Dps homologue) and shown that iron has a major role in the regulation of the PerR regulon and hence the oxidative stress response, since in the presence of both iron and manganese, transcription of PerR regulon genes is induced above the repressed levels observed with manganese alone. Furthermore the PerR regulon genes are differentially regulated by metal availability and Fur. First, there is an additional level of PerR-independent regulation of ftnA under low-iron conditions which is not observed with ahpC and mrgA. Second, there is a differential response of these genes to Fur as ftnA expression is constitutive in a fur mutant, while ahpC expression is constitutive under low-Fe/Mn conditions but some repression of ahpC still occurs in the presence of manganese, whereas mrgA expression is still repressed in the fur mutant as in wild-type S. aureus, although there is a decrease in the overall level of mrgA transcription. These studies have also shown that FtnA expression is regulated by growth phase, but maximal transcription of ftnA differs dependent on the growth medium. Moreover, there are significant regulatory differences between the S. aureus and S. epidermidis ferritins, as sefA expression in contrast to that of ftnA is derepressed under low-Fe/Mn ion conditions.

scholarly journals Role of TonB1 in Pyoverdine-Mediated Signaling in Pseudomonas aeruginosa

2009 ◽  
Vol 191 (18) ◽  
pp. 5634-5640 ◽  
Author(s):  
Matt Shirley ◽  
Iain L. Lamont
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Sigma Factor ◽  
Phenylacetic Acid ◽  
Cytoplasmic Membrane ◽  
Receptor Protein ◽  
Wild Type ◽  
Membrane Spanning ◽  
Signaling Process

ABSTRACT Pyoverdines are siderophores secreted by Pseudomonas aeruginosa. Uptake of ferripyoverdine in P. aeruginosa PAO1 occurs via the FpvA receptor protein and requires the energy-transducing protein TonB1. Interaction of (ferri)pyoverdine with FpvA activates pyoverdine gene expression in a signaling process involving the cytoplasmic-membrane-spanning anti-sigma factor FpvR and the sigma factor PvdS. Here, we show that mutation of a region of FpvA that interacts with TonB1 (the TonB box) prevents this signaling process, as well as inhibiting bacterial growth in the presence of the iron-chelating compound ethylenediamine-di(o-hydroxy-phenylacetic acid). Signaling via wild-type FpvA was also eliminated in strains lacking TonB1 but was unaffected in strains lacking either (or both) of two other TonB proteins in P. aeruginosa, TonB2 and TonB3. An absence of pyoverdine-mediated signaling corresponded with proteolysis of PvdS. These data show that interactions between FpvA and TonB1 are required for (ferri)pyoverdine signal transduction, as well as for ferripyoverdine transport, consistent with a mechanistic link between the signaling and transport functions of FpvA.

scholarly journals Differential Regulation of Two Divergent Sinorhizobium meliloti Genes for HPII-Like Catalases during Free-Living Growth and Protective Role of Both Catalases during Symbiosis

1999 ◽  
Vol 181 (8) ◽  
pp. 2634-2639 ◽  
Author(s):  
Samuel Sigaud ◽  
Vanessa Becquet ◽  
Pierre Frendo ◽  
Alain Puppo ◽  
Didier Hérouart
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Protective Role ◽  
Transcription Level ◽  
Dramatic Decrease ◽  
Free Living ◽  
Gene Encoding ◽  
Fixation Capacity ◽  
Minimum Medium

ABSTRACT Two catalases, KatA and KatB, have been detected inSinorhizobium meliloti growing on rich medium. Here we characterize a new catalase gene encoding a third catalase (KatC). KatC activity was detectable only at the end of the stationary phase inS. meliloti growing in minimum medium, whereas KatA activity was found during the exponential phase. Analysis with akatC-lacZ fusion demonstrated that katCexpression is mainly regulated at the transcription level. An increase of catalase activity correlating with KatA induction was detected in bacteroids. A dramatic decrease of nitrogen fixation capacity in a katA katC double mutant was observed, suggesting that these catalases are very important for the protection of the nitrogen fixation process.

scholarly journals Interaction between NifL and NifA in the nitrogen-fixing Pseudomonas stutzeri A1501

Microbiology ◽  
2006 ◽  
Vol 152 (12) ◽  
pp. 3535-3542 ◽  
Author(s):  
Zhihong Xie ◽  
Yuetang Dou ◽  
Shuzheng Ping ◽  
Ming Chen ◽  
Guoying Wang ◽  
...  
Keyword(s):  
Nitrogenase Activity ◽  
Pseudomonas Stutzeri ◽  
Physical Interaction ◽  
Wild Type ◽  
Yeast Two Hybrid ◽  
Free Living ◽  
Yeast Two Hybrid System ◽  
Living State ◽  
Microaerobic Conditions ◽  
Two Hybrid

Pseudomonas stutzeri strain A1501 isolated from rice fixes nitrogen under microaerobic conditions in the free-living state. This paper describes the properties of nifL and nifA mutants as well as the physical interaction between NifL and NifA proteins. A nifL mutant strain that carried a mutation non-polar on nifA expression retained nitrogenase activity. Complementation with a plasmid containing only nifL led to a decrease in nitrogenase activity in both the wild-type and the nifL mutant, suggesting that NifL acts as an antiactivator of NifA activity. Using the yeast two-hybrid system and purified protein domains of NifA and NifL, an interaction was shown between the C-terminal domain of NifL and the central domain of NifA, suggesting that NifL antiactivator activity is mediated by direct protein interaction with NifA.

scholarly journals Regulation of Denitrification Genes in Neisseria meningitidis by Nitric Oxide and the Repressor NsrR

2006 ◽  
Vol 189 (3) ◽  
pp. 1138-1144 ◽  
Author(s):  
Jonathan D. Rock ◽  
Melanie J. Thomson ◽  
Robert C. Read ◽  
James W. B. Moir
Keyword(s):  
Nitric Oxide ◽  
Neisseria Meningitidis ◽  
Nitrite Reductase ◽  
Dependent Manner ◽  
Wild Type ◽  
Aerobic Conditions ◽  
Microaerobic Conditions ◽  
Denitrification Genes ◽  
Control Of Expression

ABSTRACT The human pathogen Neisseria meningitidis is capable of growth using the denitrification of nitrite to nitrous oxide under microaerobic conditions. This process is catalyzed by two reductases: nitrite reductase (encoded by aniA) and nitric oxide (NO) reductase (encoded by norB). Here, we show that in N. meningitidis MC58 norB is regulated by nitric oxide via the product of gene NMB0437 which encodes NsrR. NsrR is a repressor in the absence of NO, but norB expression is derepressed by NO in an NsrR-dependent manner. nsrR-deficient mutants grow by denitrification more rapidly than wild-type N. meningitidis, and this is coincident with the upregulation of both NO reductase and nitrite reductase even under aerobic conditions in the absence of nitrite or NO. The NsrR-dependent repression of aniA (unlike that of norB) is not lifted in the presence of NO. The role of NsrR in the control of expression of aniA is linked to the function of the anaerobic activator protein FNR: analysis of nsrR and fnr single and nsrR fnr double mutants carrying an aniA promoter lacZ fusion indicates that the role of NsrR is to prevent FNR-dependent aniA expression under aerobic conditions, indicating that FNR in N. meningitidis retains considerable activity aerobically.

scholarly journals Identification of Sigma Factor 54-Regulated Small Non-Coding RNAs by Employing Genome-Wide and Transcriptome-Based Methods in Rhizobium Strains

2021 ◽  
Author(s):  
Kasthuri Rajendran ◽  
Vikram Kumar ◽  
Ilamathi Raja ◽  
Manoharan Kumariah ◽  
Jebasingh Tennyson
Keyword(s):  
Nitrogen Fixation ◽  
Sigma Factor ◽  
Bradyrhizobium Japonicum ◽  
Symbiotic Association ◽  
Transcriptome Data ◽  
Free Living ◽  
Rhizobium Strains ◽  
Legume Symbiosis ◽  
Biological Nitrogen

Abstract Rhizobium-legume symbiosis is considered as the major contributor of biological nitrogen fixation. In the present study, we have identified sigma factor 54-regulated sRNAs from the genome of five Rhizobium strains and integrated with the free-living and symbiotic specific transcriptome data to identify the novel putative sRNAs that are over expressed during the regulation of nitrogen fixation. A total of 1059 sRNAs were predicted from each genome of the select set of Rhizobium strains and 1,375 sRNAs were predicted from the transcriptome data of Bradyrhizobium japonicum. Target mRNA analysis revealed the functional role of putative novel sRNAs from different free-living and symbiotic strains. Those novel sRNAs were inferred to target several nodulation and nitrogen fixation genes including nodC, nodJ, nodY, nodJ, nodM, nodW, nodZ, nifD, nifN, nifQ, fixK, fixL, Fdx, nolB, and several cytochrome proteins. Further, sRNAs of Bradyrhizobium japonicum which targeted the regulatory genes of nitrogen fixation were experimentally confirmed with semi-quantitative reverse transcription polymerase chain reaction. Predicted target mRNAs were functionally classified based on the COG analysis and GO annotations. Studies on this sigma factor 54-regulated sRNA identification could be a better method to relate the role of sRNAs in nitrogen metabolism during free-living and symbiotic association with legumes.

scholarly journals Vibrio cholerae O139 requires neither capsule nor LPS O side chain to grow inside Acanthamoeba castellanii

2009 ◽  
Vol 58 (1) ◽  
pp. 125-131 ◽  
Author(s):  
Hadi Abd ◽  
Amir Saeed ◽  
Andrej Weintraub ◽  
Gunnar Sandström
Keyword(s):  
Vibrio Cholerae ◽  
Acanthamoeba Castellanii ◽  
Side Chain ◽  
Wild Type ◽  
Intracellular Growth ◽  
Free Living ◽  
Growth And Survival ◽  
Free Living Amoeba ◽  
Vibrio Cholerae O139

Vibrio cholerae, the causative agent of cholera, has the ability to grow and survive in the aquatic free-living amoeba Acanthamoeba castellanii. The aim of the present study was to examine the ability of the clinical isolate V. cholerae O139 MO10 to grow in A. castellanii and to determine the effect of the bacterial capsule and LPS O side chain on intracellular growth. Results from co-cultivation, viable counts, a gentamicin assay, electron microscopy and statistical analysis showed that the association of V. cholerae O139 MO10 with A. castellanii did not inhibit growth of the amoeba, and enhanced growth and survival of V. cholerae O139 MO10 occurred. The wild-type V. cholerae O139 MO10 and a capsule mutant or capsule/LPS double mutant grew inside A. castellanii. Neither the capsule nor the LPS O side chain of V. cholerae O139 was found to play an important role in the interaction with A. castellanii, disclosing the ability of V. cholerae to multiply and survive inside A. castellanii, as well as the role of A. castellanii as an environmental host for V. cholerae.

scholarly journals Yeast peroxisomes multiply by growth and division

2007 ◽  
Vol 178 (3) ◽  
pp. 399-410 ◽  
Author(s):  
Alison M. Motley ◽  
Ewald H. Hettema
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
De Novo ◽  
Maturation Process ◽  
Wild Type ◽  
Related Proteins ◽  
Assay Conditions

Peroxisomes can arise de novo from the endoplasmic reticulum (ER) via a maturation process. Peroxisomes can also multiply by fission. We have investigated how these modes of multiplication contribute to peroxisome numbers in Saccharomyces cerevisiae and the role of the dynamin-related proteins (Drps) in these processes. We have developed pulse-chase and mating assays to follow the fate of existing peroxisomes, de novo–formed peroxisomes, and ER-derived preperoxisomal structures. We find that in wild-type (WT) cells, peroxisomes multiply by fission and do not form de novo. A marker for the maturation pathway, Pex3-GFP, is delivered from the ER to existing peroxisomes. Strikingly, cells lacking peroxisomes as a result of a segregation defect do form peroxisomes de novo. This process is slower than peroxisome multiplication in WT cells and is Drp independent. In contrast, peroxisome fission is Drp dependent. Our results show that peroxisomes multiply by growth and division under our assay conditions. We conclude that the ER to peroxisome pathway functions to supply existing peroxisomes with essential membrane constituents.

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