Differential expression of 10 sigma factor genes in Mycobacterium tuberculosis

Abstract

SummaryThe ability of Mycobacterium tuberculosis to adapt to different environments in the infected host is essential for its pathogenicity. Consequently, this organism must be able to modulate gene expression to respond to the changing conditions it encounters during infection. In this paper we begin a comprehensive study of M. tuberculosis gene regulation, characterizing the transcript levels of 10 of its 13 putative sigma factor genes. We developed a real-time RT-PCR assay using a family of novel fluorescent probes called molecular beacons to quantitatively measure the different mRNAs. Three sigma factor genes were identified that have increased mRNA levels after heat shock, two of which also responded to detergent stress. In addition, we also identified a sigma factor gene whose mRNA increased after mild cold shock and a second that responded to conditions of low aeration.

Implications of streamlining theory for microbial ecology

“…Thus, in principle, small genomes are likely to be found in organisms that occupy fundamental niches that are relatively invariant. Conversely, organisms that transition between aerobic and anaerobic environments (Manganelli et al, 1999), surface attachment (Ishimoto and Lory, 1989) and circadian rhythms (Yoshimura et al, 2007) require major shifts in metabolism and/or physiology. Global regulation of these processes is commonly encoded by s-factors.…”

The Mycobacterium tuberculosis serine/threonine kinases PknA and PknB: substrate identification and regulation of cell shape

“…The mRNA levels of sigA, whose expression is stable during exponential growth and decreases slightly in stationary phase (Manganelli et al 1999), were also measured in the same RNA samples. Transcription of pknB was stable from early through late log phase and then decreased 10-fold upon entry into stationary phase ( Supplementary Fig.…”

The use of microarray analysis to determine the gene expression profiles of Mycobacterium tuberculosis in response to anti-bacterial compounds

“…Also over-expressed after drug treatment (>3 drugs) were gltA1 (a probable citrate synthase) and icl (isocitrate lyase) similar to changes in metabolism seen under stress conditions 28 . RNA polymerase sigma factors A and B were also induced, together with serine/threonine protein kinases B and G. sigB has been implicated in the M. tuberculosis response to a number of stress conditions 29 . The product of pknG is predicted to be a soluble protein (the transcription of which may be controlled by the redox status of the cell) which may be involved in glutamine uptake and which may be up-regulated under nitrogen-limiting conditions 30 .…”