Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling of S. meliloti BacA mutants

ABSTRACT: Expression profile in bacteria from infection threads

INSTRUMENT(S): Axon- GenePix4000B

ORGANISM(S): Sinorhizobium meliloti

SUBMITTER: Christine Bobik

PROVIDER: E-TABM-73 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Sinorhizobium meliloti differentiation during symbiosis with alfalfa: a transcriptomic dissection.

Capela Delphine D Filipe Cédric C Bobik Christine C Batut Jacques J Bruand Claude C

Molecular plant-microbe interactions : MPMI 20060401 4

Sinorhizobium meliloti is a soil bacterium able to induce the formation of nodules on the root of specific legumes, including alfalfa (Medicago sativa). Bacteria colonize nodules through infection threads, invade the plant intracellularly, and ultimately differentiate into bacteroids capable of reducing atmospheric nitrogen to ammonia, which is directly assimilated by the plant. As a first step to describe global changes in gene expression of S. meliloti during the symbiotic process, we used who ...[more]

PMID: 16610739

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Project description:Background: During gut colonization, the enteric pathogen C. jejuni has to surmount the toxic effects of reactive oxygen species produced by its own metabolism, by the host immune system and by the intestinal microflora. Elucidation of C. jejuni oxidative stress defense mechanisms is critical for understanding Campylobacter pathophysiology. Results: The mechanisms of oxidative stress defenses in Campylobacter jejuni were characterized by transcriptional profiling, genes mutagenesis, and phenotypic analysis. The transcriptome changes, in response to H2O2, cumene hydroperoxide, or menadione exposure, were found to be oxidant specific and revealed the differential expression of genes belonging to a variety of biological pathways, from the classical oxidative stress defense systems, to the heat shock response, DNA repair and metabolism, fatty acid and capsule biosynthesis, and multidrug efflux pumps. To define the peroxide sensing regulator PerR, an isogenic mutant was constructed and its transcriptome profile compared to the wild-type strain. Sixty-six genes were found to belong to the PerR regulon. PerR appear to regulate gene expression both dependently and independently of the presence of iron and/or H2O2. The perR mutant was affected in its motility and attenuated in the chick colonization model. Mutagenic and phenotypic studies of the superoxide disumutase SodB, the alkyl-hydroxyperoxidase AhpC, and the catalase KatA, revealed their role in oxidative stress defenses and chick gut colonization. Conclusion: This study reveals the interplay between PerR, the iron metabolism and the oxidative stress defenses and highlights their role in the colonization and/or survival of C. jejuni in the chick cecum. Keywords: Transcriptional response to 3 oxidants (H2O2, menadione and cumene hydroperoxide) and characterization of the perR regulon (comparison of the transciptomes from the wild-type and perR mutant). To investigate the transcriptional responses of C. jejuni to oxidant exposure, hydrogen peroxide (H2O2), cumene hydroperoxide (CHP), or menadione sodium bisulfite (MND) was added to the 50 ml broth at a final concentration of 1 mM. The same amount of water or DMSO was added to the bacterial culture that served as reference samples for the transcriptional profile study in response to H2O2, MND or CHP. Furthermore, to investigate the transcriptional response of C. jejuni to H2O2 exposure in the presence of excess iron, ferrous sulfate was added to the bacterial culture at a final concentration of 40 µM, 15 min prior to H2O2 exposure. Ten minutes after the addition of the oxidant, total RNA was extracted and processed for microarray hybridization. To identify the PerR regulon, the wild-type strain C. jejuni NCTC 11168 and the perR mutant were grown in 500 ml flasks containing 250 ml of MEMα medium. At mid-log phase, 50 ml of the cultures were transferred to 100 ml flasks and ferrous sulfate and/or H2O2 were added . Ten minutes following the addition of H2O2 the cells were collected and the total RNA extracted.

Project description:Innate immunity is expected to play a primary role in conferring resistance to novel infectious diseases, but few studies have attempted to examine its role in the evolution of resistance to emerging pathogens in wild vertebrate populations. Here we used experimental infections and cDNA microarrays to examine whether changes in the innate and/or acquired immune responses likely accompanied the emergence of resistance in house finches (Carpodacus mexicanus) in the eastern United States subject to a recent outbreak of conjunctivitis-causing bacterium (Mycoplasma gallisepticum- MG). Three days following experimental infection with MG, we observed differences in the splenic transcriptional responses between House Finches from eastern U.S. populations, with a 12-year history of MG exposure, versus western U.S. populations, with no history of exposure to MG. In particular, western birds down-regulated gene expression, while eastern finches showed no expression change relative to controls. Studies involving poultry have shown that MG can manipulate host immunity, and our observations suggest that pathogen manipulation occurred only in finches from the western populations, outside the range of MG. Fourteen days after infection, eastern finches, but not western finches, up-regulated genes associated with acquired immunity (cell-mediated immunity) relative to controls. These observations suggest population differences in the temporal course of the response to infection with MG, and imply that innate immune processes were targets of selection in response to MG in the eastern U.S. population. Birds were randomly selected to be kept either as controls or infected via ocular inoculation with 20 μl of culture containing 1 x 104 to 1 x 106 color changing units/ml of an early 2007 Auburn MG isolate. All infected birds were inoculated with precisely the same volume of the same culture. Control birds were sham infected using sterile SP4 medium (Whitcomb 1983). Infected birds were euthanized three days (N=6 from Arizona and N=11 from Alabama) and 14 days (N=11 from Arizona and N=12 from Alabama) after treatment. Control birds were euthanized 14 days after sham-inoculation; Control (N=11 birds from Arizona and 9 from Alabama) and infected birds were maintained under identical conditions, but in separate rooms of an aviary. Infected birds were euthanized three days (N=6 from Arizona and N=11 from Alabama) and 14 days (N=11 from Arizona and N=12 from Alabama) after treatment. Control birds were euthanized 14 days after sham-inoculation. We used a common reference design (Yang & Speed 2002), in which we pooled 2 to 6 spleens from birds from the same population in the same treatment to generate enough mRNA for microarray hybridizations and hybridized two pools for each treatment from each population.

Dataset Information

Transcription profiling of S. meliloti BacA mutants

Publications

Sinorhizobium meliloti differentiation during symbiosis with alfalfa: a transcriptomic dissection.

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