Project description:Introduction: Tuberculosis (TB) is a serious human disease caused by the bacterium Mycobacterium tuberculosis (Mtb). One third of the world’s population is estimated to be latently infected with Mtb. Exact mechanisms and properties of latent TB infection (LTBI) are not fully elucidated. In essence, the pathogen can enter a dormant or latent state characterized by limited growth and metabolism, resulting in absence of clinical symptoms in the host, and most importantly by increased phenotypic tolerance to the commonly used medications, thereby allowing indefinite persistence in the human body. This persistence is the main reason why the current treatment of new-onset pulmonary TB is very long, consisting of a six months therapy of four antibiotics (rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months, and only rifampicin and isoniazid for the last four months). Current state of the art: To fight TB globally and more efficiently, it is essential to shorten the treatment for TB with new drugs that are efficient also against LTBI. To facilitate discovery of such drugs, in vitro models for LTBI can be used for high throughput screening of chemical libraries. Current in vitro models such as nutrient starvation (Betts et al. 2002), nutrient depletion (Hampshire et al. 2004; Rifat, Bishai, and Karakousis 2009), progressive hypoxia (Wayne and Hayes 1996), nitric oxide treatment (Martin I. Voskuil et al. 2003) and multiple stress (Deb et al. 2009) mimic the dormant state of Mtb, but the technical settings and equipment required for these models obstruct high throughput applications. Proposed model: The streptomycin (STR)-starved 18b model (SS18b) is a simple and drug discovery efficient Mtb latency model successfully applicable to both in vitro and in vivo settings (Zhang et al. 2012). It is based on the Mtb strain 18b, which is a STR-dependent mutant that enters a viable but nonreplicating state in the absence of STR (Hashimoto 1955). Despite the successful model, we know very little about 18b. How well does SS18b mimic the bacterial response to the complex host-pathogen interactions underlying LTBI, and how does the SS18b response compare to that of other dormancy models are still open questions. In this work we analyse the complete genome of 18b and describe the transcriptomic response of 18b to STR depletion.

Project description:Introduction: Tuberculosis (TB) is a serious human disease caused by the bacterium Mycobacterium tuberculosis (Mtb). One third of the worldâs population is estimated to be latently infected with Mtb. Exact mechanisms and properties of latent TB infection (LTBI) are not fully elucidated. In essence, the pathogen can enter a dormant or latent state characterized by limited growth and metabolism, resulting in absence of clinical symptoms in the host, and most importantly by increased phenotypic tolerance to the commonly used medications, thereby allowing indefinite persistence in the human body. This persistence is the main reason why the current treatment of new-onset pulmonary TB is very long, consisting of a six months therapy of four antibiotics (rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months, and only rifampicin and isoniazid for the last four months). Current state of the art: To fight TB globally and more efficiently, it is essential to shorten the treatment for TB with new drugs that are efficient also against LTBI. To facilitate discovery of such drugs, in vitro models for LTBI can be used for high throughput screening of chemical libraries. Current in vitro models such as nutrient starvation (Betts et al. 2002), nutrient depletion (Hampshire et al. 2004; Rifat, Bishai, and Karakousis 2009), progressive hypoxia (Wayne and Hayes 1996), nitric oxide treatment (Martin I. Voskuil et al. 2003) and multiple stress (Deb et al. 2009) mimic the dormant state of Mtb, but the technical settings and equipment required for these models obstruct high throughput applications. Proposed model: The streptomycin (STR)-starved 18b model (SS18b) is a simple and drug discovery efficient Mtb latency model successfully applicable to both in vitro and in vivo settings (Zhang et al. 2012). It is based on the Mtb strain 18b, which is a STR-dependent mutant that enters a viable but nonreplicating state in the absence of STR (Hashimoto 1955). Despite the successful model, we know very little about 18b. How well does SS18b mimic the bacterial response to the complex host-pathogen interactions underlying LTBI, and how does the SS18b response compare to that of other dormancy models are still open questions. In this work we analyse the complete genome of 18b and describe the transcriptomic response of 18b to STR depletion. 12 samples were analyzed. Four biological replicates were sampled during the exponential growth phase, in presence of streptomycin. Four biological replicates derived after 2 weeks of streptomycin depletion, and two biological replicates derive after 4 weeks of streptomycin depletion. Two replicates derive from the resubmission of streptomycin after four weeks of depletion.

Project description:This study uses microarray analyses to examine gene expression profiles for Mycobacterium tuberculosis (Mtb) induced by exposure in vitro to bovine lung surfactant preparations that vary in apoprotein content: (i) whole lung surfactant (WLS) containing the complete mix of endogenous lipids and surfactant proteins (SP)-A, -B, -C, and -D; (ii) extracted lung surfactant (CLSE) containing lipids plus SP-B and -C; (iii) column-purified surfactant lipids (PPL) containing no apoproteins, and (iv) purified human SP-A. Exposure to WLS evoked a multitude of transcriptional responses in Mtb, with 52 genes up-regulated and 23 genes down-regulated at 30 min exposure, plus 146 genes up-regulated and 27 genes down-regulated at 2 h. Notably, WLS rapidly induced several membrane-associated lipases that presumptively act on surfactant lipids as substrates, and a large number of genes involved in the synthesis of phthiocerol dimycocerosate (PDIM), a cell wall component known to be important in macrophage interactions and Mtb virulence. Exposure of Mtb to CLSE, PPL, or purified SP-A caused a substantially weaker transcriptional response (â¤ 20 genes were induced) suggesting that interactions among multiple lipid-protein components of WLS may contribute to its effects on Mtb transcription. Whole lung surfactant (WLS) was obtained by centrifugation of lavage fluid (0.15M NaCl) from the intact lungs of freshly killed calves (ONY, Inc, Amherst, NY). Centrifugation was done at 12,000 x g at room temperature to pellet the active large aggregate surfactant fraction. CLSE was prepared by extraction of WLS into chloroform-methanol by the method of Bligh and Dyer (1959), as described in our prior work (Notter et al. 2002). CLSE is conceptually identical to the substance of the clinical surfactant InfasurfÂ®. The composition of CLSE by weight was approximately 94% phospholipid, 4.5% cholesterol, and 1.5% protein (a mixture of SP-B and SP-C) as defined previously (Notter et al. 2002). Mixed lung surfactant phospholipids (PPL) were isolated from CLSE by column chromatography with an elution solvent of 1:1 (v/v) chloroform-methanol plus 5% 0.1 N HCl. Two passes through a Sephadex LH-20 column (Pharmacia-LKB Biotechnology, Piscataway, NJ) separated phospholipids away from hydrophobic surfactant apoproteins and neutral lipids. Acid remaining in PPL fractions was removed by a second chloroform-methanol extraction. Final PPL had a protein content below the limits of detection of both the Folin-phenol assay of Lowry et al. (1951) and the amido black assay of Kaplin and Pedersen (1989) modified by the addition of 15% sodium dodecyl sulfate (SDS) to allow accurate quantitation in the presence of lipid. Human SP-A was a gift from Dr. J. R. Wright at Duke University, and was isolated from bronchoalveolar lavage from patients with alveolar proteinosis as described previously (Wright et al. 1987). For exposure studies with Mtb, amounts of WLS, CLSE, and PPL used per experiment were 3.3 mg in a total volume of 4 ml. In preliminary studies, this concentration was shown to induce a transcriptional response in Mtb without affecting viability after a 2 h treatment as determined by serial dilutions compared to untreated Mtb. SP-A was studied at a level of 0.165 mg based on its putative concentration of approximately 5% in endogenous surfactant. To determine the effects of lung surfactant on the transcriptional response of Mtb, preparations of WLS, CLSE, or PPL (in 650 Âµl PBS) were initially coated onto the bottom surface of a 25 cm2 cell culture flask for 30 min at 37oC to mimic a surfactant layer. A minimum of two independent biological replicates were studied for each surfactant preparation. Purified human SP-A was also examined for its effects on Mtb transcription, and phosphate buffered saline (PBS) was used as a âno treatmentâ control. In experiments with SP-A (in 650 Âµl PBS), the pure apoprotein was either pre-coated on the flask as done with the surfactant preparations, or was directly added and incubated with Mtb during study. Mtb was added to the flask in 3.35 ml of DMEM (supplemented with 2% FCS and 5 mM HEPES) and exposed to coated surfactant/SP-A or PBS control for 30 min or 2h at 37oC, followed by RNA isolation as detailed by Rohde et al. (2008). GTC lysis/stabilization buffer was added, and pelleted Mtb were washed and then digested with lysozyme. TRIzol (Invitrogen) was added, and organisms were disrupted using glass beads in a Mini-Bead Beater (BioSpec Products, Inc. Bartlesville, OK). After extraction of Mtb lysates with chloroform, ethanol was added to the aqueous phase before loading samples onto RNeasy mini columns (Qiagen, Valencia, CA). Subsequent steps were then performed according to the manufacturerâs instructions. Following elution with RNase-free water, the RNA samples were treated with DNase (Turbo DNAfree, Applied Biosystems, Foster City, CA), and stored at -70oC until analysis. The MessageAmpTMII-Bacteria system (Applied Biosystems) was used to amplify mycobacterial RNA for all samples [16]. Total RNA was reverse transcribed to yield double-stranded amino-allyl modified aRNA, which was labeled with Alexa Fluor 555 and Alexa Fluor 647 (Invitrogen). Excess reactive dyes were removed with a Mega Clear purification kit (Applied Biosystems). Next, Alexa-labeled aRNA from paired samples was dried using a Speedvac, and re-suspended in hybridization buffer (5x SSC, 25% formamide, 0.15% SDS, and 25 Î¼g salmon sperm DNA). The mixed samples were denatured by being heated to 95oC for and then cooled to 50oC prior to loading them onto microarrays. The arrays were hybridized for approximately 15 h at 45oC, washed and then dried by centrifugation. Fluorescence intensity data from each array were collected with a GenePix 4000B scanner (Axon Instruments, Union City, CA) using GenePixPro3.0 software (Axon Instruments). Image analysis, i.e. spot identification, background measurements, quality assessment and flagging were conducted with Imagene software (Version 6.0, BioDiscovery, Inc., El Segundo, CA). Poor quality spots were filtered and removed from the analysis. Subsequent normalization, statistical analysis (i.e. t-test), and visualization of array data was conducted using Genespring (Version 7, Agilent Technologies, Palo Alto, CA).

			Action	DRS
	SRR11564400_1.fastq.gz	Fastqsanger.gz
	SRR11564400_2.fastq.gz	Fastqsanger.gz
	SRR11564500_1.fastq.gz	Fastqsanger.gz
	SRR11564500_2.fastq.gz	Fastqsanger.gz
	SRR11564600_1.fastq.gz	Fastqsanger.gz

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Mycobacterium tuberculosis

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