|
|
|
|
|
|
Stable Carbon Isotopic Fractionations Associated with Inorganic Carbon Fixation by Anaerobic Ammonium-Oxidizing Bacteria. Stefan Schouten, 2004.Isotopic analyses of Candidatus "Brocadia anammoxidans," a chemolithoautotrophic bacterium that anaerobically oxidizes ammonium (anammox), show that it strongly fractionates against 13C; i.e., lipids are depleted by up to 47  versus CO2 . Similar results were obtained for the anammox bacterium Candidatus "Scalindua sorokinii," which thrives in the anoxic water column of the Black Sea, suggesting that different anammox bacteria use identical carbon fixation pathways, which may be either the Calvin cycle or the acetyl coenzyme A pathway .
groEL Expression in gyrB Mutants of Borrelia burgdorferi. Janet Alverson, 2002.GroEL protein and groEL mRNA transcript were up-regulated in gyrB mutants of Borrelia burgdorferi, a causative agent of Lyme disease . Furthermore, the protein and transcript levels in gyrB mutants were greater than those in experimentally heat-shocked cultures of wild-type B . burgdorferi . Circular DNA in the gyrB mutants was more relaxed than in wild-type cells, although groEL is on the linear chromosome of B . burgdorferi . To our knowledge, this is the first evidence, albeit indirect, for the effect of DNA topology on gene expression from a linear DNA molecule in a bacterium . An Extracytoplasmic-Function Sigma Factor Is Involved in a Pathway Controlling ß-Exotoxin I Production in Bacillus thuringiensis subsp . thuringiensis Strain 407-1. Sylvain Espinasse, 2004.ß-Exotoxin I is an insecticidal nucleotide analogue secreted by various Bacillus thuringiensis strains . In this report, we describe the characterization and transcriptional analysis of a gene cluster, designated sigW-ecfX-ecfY, that is essential for ß-exotoxin I production in B . thuringiensis subsp . thuringiensis strain 407-1 . In this strain, the disruption of the sigW cluster resulted in nontoxic culture supernatants . sigW encodes a protein of 177 residues that is 97 and 94% identical to two putative RNA polymerase extracytoplasmic-function-type sigma factors from Bacillus anthracis strain Ames and Bacillus cereus strain ATCC 14579, respectively . It is also 50, 30, and 26% identical to SigW from Clostridium perfringens and SigW and SigX from Bacillus subtilis, respectively . EcfX, encoded by the gene following sigW, significantly repressed the expression of sigW when both genes were overtranscribed, suggesting that it could be the anti-sigma factor of SigW . Following the loss of its curable cry plasmid, strain 407 became unable to synthesize crystal toxins, in contrast to the mutant strain 407-1(Cry–)(Pig+), which overproduced this molecule in the absence of this plasmid . Transcriptional analysis of sigW indicated that this gene was expressed during the stationary phase and only in the 407-1(Cry–)(Pig+) mutant . This suggests that in the wild type-407(Cry+) strain, ß-exotoxin I was produced from determinants located on a cry gene-bearing plasmid and that sigW is able to induce ß-exotoxin I production in B . thuringiensis in the absence of cry gene-bearing plasmids . Although the signal responsible for this activation is unknown, these results indicate that ß-exotoxin I production in B . thuringiensis can be restored or induced via an alternative pathway that requires sigW expression .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
