Unknown,Transcriptomics,Genomics,Proteomics

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Actinobacillus pleuropneumoniae during a natural infection in pigs

ABSTRACT: Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, a respiratory disease which causes great economic losses worldwide. Many virulence factors are involved in the pathogenesis, namely capsular polysaccharides, RTX toxins, LPS and many iron acquisition systems. In order to identify genes that are expressed in vivo during a natural infection, we undertook transcript profiling experiments with an A. pleuropneumoniae DNA microarray, after recovery of bacterial mRNAs from serotype 5b-infected porcine lungs. Comparative Genomic Hybridizations between Actinobacillus pleuropneumoniae serotype 5b strain L20 (ref) and serotype 5b fresh field isolate 896-07, recovered from infected pig lung tissues following natural acute infection. Two condition transcript profiling experiments : infectious 5b field strain isolated directly from lungs of naturally deceased pigs after acute infection vs infectious 5b field strain grown in BHI broth to an OD600 of 0.300.

ORGANISM(S): Actinobacillus pleuropneumoniae

SUBMITTER: Martine Denicourt

PROVIDER: E-GEOD-15911 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Bacteria can use host hormones as environment cue to modulate their pathogenic processes, which was discovered to play essential role in disease development. Actinobacillus pleuropneumoniae is one of the most important porcine respiratory pathogens causing great economic losses in the pig industry worldwide. Stress factors were found to contribute to the outcome of A. pleuropneumoniae infection. To test whether A. pleuropneumoniae could respond to host stress hormone catecholamines, the gene expression profiles after epinephrine (Epi) and norepinephrine (NE) treatment were compared with the untreated bacteria using microarray. Although the bacterial growth was not affected in the conditions tested, 157 and 104 genes associated with various function categories including many virulence factors were differentially expressed by Epi and NE treatment. 18 common genes were regulated by the two hormones, these genes included genes encoding virulence factors and potential responsors of Epi and NE. Further investigations on virulence traits demonstrated that cytotoxic activity was enhanced by Epi but repressed by NE in accordance with the regulations on apxIA. Biofilm formation was not affected by the two hormones despite that the biofilm formation gene pgaB was affected. Adhesion to host cells was induced by NE but not by Epi, possibly involving other putative adhesins affected by the hormones in addition to the autotransporter adhesin (APL_0443). Our study demonstrated that A. pleuropneumoniae could actively respond to catecholamines to control its virulence traits. The different regulated genes and effects caused by Epi and NE suggested A. pleuropneumoniae may have multiple responsive systems to sense different type of catecholamine hormones. Transcriptional profiles were analyzed using microarray to compared the epinephrine (Epi) or norepinephrine(NE) treated and untreated A. pleuropneumoniae. All samples were harvested from middle exponential phase (4 hours after sub-culture) at the OD600=1.435M-BM-10.065 for control, OD600=1.461M-BM-10.019 for Epi treated strain and OD600=1.545M-BM-10.115 for NE treated strain. Three biological replicates were conducted for each treatment. The total RNA were extracted and hybridized with the whole genome microarray of A. pleuropneumoniae. The signal intensities were normalized and transformed into log2 values. The genes with fold change M-bM-^IM-% 1.5 and P < 0.05 were selected as differentially expressed.

Project description:Actinobacillus pleuropneumoniae is an important porcine respiratory pathogen causing great economic losses in the pig industry worldwide. Oxygen deprivation is a stress that A. pleuropneumoniae will encounter during both early infection and the later, persistent stage. To understand modulation of A. pleuropneumoniae gene expression in response to the stress caused by anaerobic conditions, gene expression profiles under anaerobic and aerobic conditions were compared in this study. The microarray results showed that 631 genes (27.7% of the total ORFs) were differentially expressed in anaerobic conditions. Many genes encoding proteins involved in glycolysis, carbon source uptake systems, pyruvate metabolism, fermentation and the electron respiration transport chain were up-regulated. These changes led to an increased amount of pyruvate, lactate, ethanol and acetate in the bacterial cells as confirmed by metabolite detection. Genes encoding proteins involved in cell surface structures, especially biofilm formation, peptidoglycan biosynthesis and lipopolysaccharide biosynthesis were up-regulated as well. Biofilm formation was significantly enhanced under anaerobic conditions. These results indicate that induction of central metabolism is important for basic survival of A. pleuropneumoniae after a shift to an anaerobic environment. Enhanced biofilm formation may contribute to the persistence of this pathogen in the damaged anaerobic host tissue and also in the early colonization stage. These discoveries give new insights into adaptation mechanisms of A. pleuropneumoniae in response to environmental stress. Transcriptional profiles were analyzed using microarray to compare the gene expressions of A. pleuropneumoniae cultured under aerobic and anaerobic condition. The bacteria was cultured under aerobic condition to mid-log phase (3 hours) and then divided into two separate groups, one group was continually cultured under aerobic condition for 1 hour (OD600nm = 0.417 M-BM-1 0.008) and the other group was cultured under anaerobic condition for 1 hour (OD600nm = 0.333 M-BM-1 0.015). Three independent biological replicates were performed. The total RNA were extracted and hybridized with the whole genome microarray of A. pleuropneumoniae. The signal intensities were normalized and transformed into log2 values. The genes with P-value < 0.05 were selected as differentially expressed genes.

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Actinobacillus pleuropneumoniae during a natural infection in pigs

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