Global gene expression by Bacillus anthracis during growth in mammalian blood
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ABSTRACT:
ORGANISM(S): Bacillus anthracis str. Sterne
SUBMITTER: Paul Carlson
PROVIDER: E-MTAB-3828 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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To further characterize the interactions between Salmonella and the gallbladder environment we compared the transcriptome of Salmonella cultures grown in LB or physiological murine bile. Our data showed that many genes involved in bacterial central metabolism are affected by bile, with the citric acid cycle being repressed and alternative respiratory systems being activated. Additionally, our study revealed a new aspect of Salmonella interactions with bile through the identification of phoP as a bile-responsive gene. Repression of phoP expression does not involve PhoPQ sensing of a bile component. Due to its critical role in Salmonella virulence, further studies in this area will likely reveal aspects of the interaction between Salmonella and bile that are relevant to disease. Salmonella enterica serovar Typhimurium LT2 glass slide microarrays were obtained through the NIAID’s Pathogen Functional Genomics Resource Center, managed and funded by Division of Microbiology and Infectious Diseases, NIAID, NIH, DHHS and operated by the J. Craig Venter Institute. Two independent cultures of Salmonella enterica serovar Typhimurium SL1344 were grown overnight in Luria-Bertani (LB) broth with streptomycin (100 μg/mL) at 37oC with shaking (225 RPM). Cells were pelleted by centrifugation and resuspended in sterile Dulbecco’s phosphate-buffered saline (PBS). These suspensions were further diluted 1:50 in PBS and used to inoculate 70 μL of either LB or physiological murine bile (in 0.65-mL tubes) at a 1:100 dilution. Cultures were incubated for 24 hours at 37oC with agitation (225 RPM). Then, samples were diluted in PBS and serial dilutions were plated on LB plates containing 100 μg/mL of streptomycin and incubated overnight at 37oC for bacterial growth and enumeration by colony counting. The remaining cells were used in the subsequent steps, as described below. RNA isolation began with the addition of 2 volumes of RNAprotect Bacteria Reagent (Qiagen, Hilden, Germany) to the bacterial cultures and incubation at room temperature for approximately 5 minutes. Cells were pelleted by centrifugation and RNA was isolated using the RNeasy Mini Kit (Qiagen) with the on-column DNase digestion, according to the manufacturer’s recommendations. Synthesis of cDNA was performed as described herein. The entire RNA sample (≥3 μg) was mixed with 6 μg of Random Primers (Invitrogen, Burlington, Canada) and 40 units of RNaseOUT recombinant ribonuclease inhibitor (Invitrogen, Burlington, Canada) in a total volume of 18.5 μL and incubated at 70oC for 10 minutes. Samples were incubated on ice for 30 seconds, centrifuged to bring down condensation and incubated with the following components (final concentrations; Invitrogen): First Strand Buffer (1X), dithiothreitol (DTT; 10 mM), dNTPs (dATP, dCTP, dGTP, dTTP; 0.5 mM each) and 100 units of SuperScript II reverse transcriptase in a total volume of 30 μL. The mixture was incubated at 42oC overnight and the reaction was stopped and the RNA degraded through the addition of 0.5 M EDTA and 1 M sodium hydroxide (10 μL each) and incubation at 65oC for 15 minutes. 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