Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cells of Escherichia coli undergo a metabolic switch associated with the production and utilization of acetate. During exponential growth on tryptone broth, these cells excrete acetate via the phosphotransacetylase-acetate kinase (Pta-AckA) pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. This metabolic switch depends upon the induction of Acs. As part of our effort to dissect the mechanism(s) underlying induction and to identify the signal(s) that triggers that induction, we sought the sigma factor most responsible for acs expression. Using isogenic strains that carry a temperature sensitivity allele of the gene that encodes sigma(70) and either a wild-type or null allele of the gene that encodes sigma(S), we determined by immunoblotting, reverse transcriptase PCR, and acs::lacZ transcriptional fusion analyses that sigma(70) is the sigma factor primarily responsible for the acs transcription that cells induce during mid-exponential phase. In contrast, sigma(S) partially inhibits that transcription as cells enter stationary phase.
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PMID:sigma(70) is the principal sigma factor responsible for transcription of acs, which encodes acetyl coenzyme A synthetase in Escherichia coli. 1062 11

Stenoxybacter acetivorans is a newly described, obligately microaerophilic beta-proteobacterium that is abundant in the acetate-rich hindgut of Reticulitermes. Here we tested the hypotheses that cells are located in the hypoxic, peripheral region of Reticulitermes flavipes hindguts and use acetate to fuel their O(2)-consuming respiratory activity in situ. Physical fractionation of R. flavipes guts, followed by limited-cycle PCR with S. acetivorans-specific 16S rRNA gene primers, indicated that cells of this organism were indeed located primarily among the microbiota colonizing the hindgut wall. Likewise, reverse transcriptase PCR of hindgut RNA revealed S. acetivorans-specific transcripts for acetate-activating enzymes that were also found in cell extracts (acetate kinase and phosphotransacetylase), as well as transcripts of ccoN, which encodes the O(2)-reducing subunit of high-affinity cbb(3)-type cytochrome oxidases. However, S. acetivorans strains did not possess typical enzymes of the glyoxylate cycle (isocitrate lyase and malate synthase A), suggesting that they may use an alternate pathway to replenish tricarboxylic acid cycle intermediates or they obtain such compounds (or their precursors) in situ. Respirometric measurements indicated that much of the O(2) consumption by R. flavipes worker larvae was attributable to their guts, and the potential contribution of S. acetivorans to O(2) consumption by extracted guts was about 0.2%, a value similar to that obtained for other hindgut bacteria examined. Similar measurements obtained with guts of larvae prefed diets to disrupt major members of the hindgut microbiota implied that most of the O(2) consumption observed with extracted guts was attributable to protozoans, a group of microbes long thought to be "strict anaerobes."
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PMID:Physiological ecology of Stenoxybacter acetivorans, an obligate microaerophile in termite guts. 1782 35