Differential mRNA stability of the vapAICD operon of the facultative intracellular pathogen Rhodococcus equi.

The gene encoding virulence associated protein A (VapA) is clustered with three vapA homologues (vapICD) within the pathogenicity island of the virulence plasmid of Rhodococcus equi. Northern blot analysis showed a vapA transcript of c. 700 nucleotides (nt) suggesting that vapA is a monocistronic transcript.

Transcriptional regulation of the virR operon of the intracellular pathogen Rhodococcus equi.

The virR operon, located on the virulence plasmid of the intracellular pathogen Rhodococcus equi, contains five genes, two of which (virR and orf8) encode transcriptional regulators. The first gene of the operon (virR), encoding a LysR-type transcriptional regulator, is transcribed at a constitutive low level, whereas the four downstream genes are induced by low pH and high growth temperature. Differential regulation of the virR operon genes could not be explained by differential mRNA stability, as there were no major differences in mRNA half-lives of the transcripts representing each of the five genes within the virR operon.

Versatile Rhodococcus equi-Escherichia coli shuttle vectors.

Rhodococcus equi is an intracellular pathogen of macrophages, causing disease in young foals, humans, and sporadically other animals. Although R. equi is easy to grow and manipulate, the analysis of virulence is hampered by a lack of molecular tools.

The LysR-type transcriptional regulator VirR is required for expression of the virulence gene vapA of Rhodococcus equi ATCC 33701.

The virulence of the intracellular pathogen Rhodococcus equi in foals is dependent on the presence of an 81-kb virulence plasmid encoding the virulence protein VapA. Expression of this protein is induced by exposure to oxidative stress, high temperatures, and low pHs, which reflect the conditions encountered by R. equi when it enters the host environment.