Transcriptome Changes in Mycoplasma hyopneumoniae during Infection

Abstract

Mycoplasma hyopneumoniae causes swine pneumonia and contributes significantly to the porcine respiratory disease complex. The mechanisms of pathogenesis are difficult to address, since there is a lack of genetic tools, but microarrays are available and can be used to study transcriptional changes that occur during disease as a way to identify important virulence-related genes. Mycoplasmas were collected from bronchial alveolar lavage samples and compared to broth-grown cells using microarrays. Bronchial alveolar lavage was performed on pigs 28 days postinfection, and mycoplasmas were isolated by differential centrifugation. Mycoplasma RNAenriched preparations were then obtained from total RNA by subtracting eucaryotic ribosomal and messenger RNAs. Labeled cDNAs were generated with mycoplasma open reading frame-specific primers. Nine biological replicates were analyzed. During lung infection, our analysis indicated that 79 M. hyopneumoniae genes were differentially expressed (P < 0.01), at a false-discovery rate of <2. The reactions that invading pathogens have toward host responses determine their ability to colonize and cause disease. Most bacteria have inducible regulons whose products enhance colonization and assist in the disease process. With mycoplasmas, the simplest of bacterial pathogens, the story of virulence factors and their regulation has been poorly studied and is less well known. Some mycoplasma species can generate high rates of diversity in selected genes or gene families through small sequence changes and recombination events resulting in changes at the genetic level (32). This variation is usually expressed by the generation of new chimeric surface molecules with high rates of antigenic diversity that are thought to help evade the host immune system. Phase switching may result when variation occurs within poly(A) tracts in promoter regions or in structural gene sequences or by DNA inversion. The generation of chimeric genes by intragenic recombination also occurs. This variation is carried through subsequent generations. There is no evidence that any of these mechanisms are operative in Mycoplasma hyopneumoniae, however. Some surface molecules in M. hyopneumoniae undergo posttranslational modification through proteolytic processing as a form of variation identifiable by immunoblotting (4, 7).Previous studies have shown that gene regulation does occur in M. hyopneumoniae in regard to heat shock (13), iron deprivation (14), and exposure to hydrogen peroxide (23). Since these growth conditions only partially mimic those found in vivo, we wanted to determine how exposure to the host during disease alters the transcriptional profiles of M. hyopneumoniae. Thus, we obtained organisms from infected pig lungs and compared their transcriptome with that from organisms grown in the laboratory using microarray technology. This provided a "global" snapshot of the steady-state concentrations of mRNAs, a good indicator of gene expression. Surprisingly, our results indicate that more genes are down-regulated d...

Comprehensive RNA-Seq Profiling to Evaluate the Sheep Mammary Gland Transcriptome in Response to Experimental Mycoplasma agalactiae Infection

“…Gene expression profiling has been intensively used for several mycoplasma species to study host-pathogen interactions. In this context, the transcriptomes of either the host or the pathogen were investigated to gain further insights into mycoplasma-induced pathogenesis [40–44]. To the best of our knowledge this is a singular study in many aspects.…”

Global transcriptional analysis of Mycoplasma hyopneumoniae following exposure to norepinephrine

“…When comparing the direction of regulation of differentially expressed genes in norepinephrine-exposed M. hyopneumoniae to those genes shown to be differentially expressed under heat shock (Madsen et al, 2006a), iron deprivation (Madsen et al, 2006b), oxidation conditions (Schafer et al, 2007) and in vivo growth (Madsen et al, 2008), an interesting correlation was observed. Genes upregulated during norepinephrine exposure were generally downregulated under the other conditions, if at all (Supplementary Table S1).…”

“…There is also a large group of transport-related proteins that might be involved and serve as receptors. Finally, given the diversity of genes regulated under different environmental conditions such as heat shock (Madsen et al, 2006a), iron deprivation (Madsen et al, 2006b), oxidative stress (Schafer et al, 2007) and the pig lung (Madsen et al, 2008), transcription in M. hyopneumoniae must involve multiple factors and mechanisms. We are only beginning to decipher those components and their mechanisms of action (Chang et al, 2008).…”

Comparative proteomic analysis of pathogenic and non-pathogenic strains from the swine pathogen Mycoplasma hyopneumoniae

“…However, these studies were unable to identify genes specifically related to virulence, even when analysing the infection conditions [13]. The M. hyopneumoniae proteomic studies performed thus far were mainly prospective.…”