|
|
|
|
|
|
Xenorhabdus nematophila Requires an Intact iscRSUA-hscBA-fdx Operon To Colonize Steinernema carpocapsae Nematodes. Eric C. Martens, 2003.An insertion between iscA and hscB of the Xenorhabdus nematophila iscRSUA-hscBA-fdx locus, predicted to encode Fe-S assembly machinery, prevented colonization of Steinernema carpocapsae nematodes . The insertion disrupted cotranscription of iscA and hscB, but did not reduce hscBA expression, suggesting that X . nematophila requires coordinated expression of the isc-hsc-fdx locus for colonization . Activities of Doripenem (S-4661) against Drug-Resistant Clinical Pathogens. Ronald N. Jones, 2004.Doripenem (formerly S-4661), a new 1-ß-methyl carbapenem, was challenged with a worldwide collection of 394 drug-refractory isolates . For endemic extended-spectrum ß-lactamase- and stably derepressed AmpC-producing enteric bacilli, the doripenem MICs at which 90% of the isolates were inhibited (MIC90s) were 0.03 to 0.5 µg/ml, generally lower than those of comparator carbapenems . A greater proportion of strains among carbapenem-resistant nonfermentative gram-negative bacilli were inhibited by doripenem at  4 µg/ml, and doripenem was the most active carbapenem (MIC90, 1 to 4 µg/ml) against penicillin-resistant streptococci .
Abundance of Dioxygenase Genes Similar to Ralstonia sp . Strain U2 nagAc Is Correlated with Naphthalene Concentrations in Coal Tar-Contaminated Freshwater Sediments. Hebe M. Dionisi, 2004.We designed a real-time PCR assay able to recognize dioxygenase large-subunit gene sequences with more than 90% similarity to the Ralstonia sp . strain U2 nagAc gene (nagAc-like gene sequences) in order to study the importance of organisms carrying these genes in the biodegradation of naphthalene . Sequencing of PCR products indicated that this real-time PCR assay was specific and able to detect a variety of nagAc-like gene sequences . One to 100 ng of contaminated-sediment total DNA in 25-µl reaction mixtures produced an amplification efficiency of 0.97 without evident PCR inhibition . The assay was applied to surficial freshwater sediment samples obtained in or in close proximity to a coal tar-contaminated Superfund site . Naphthalene concentrations in the analyzed samples varied between 0.18 and 106 mg/kg of dry weight sediment . The assay for nagAc-like sequences indicated the presence of (4.1 ± 0.7) x 103 to (2.9 ± 0.3) x 105 copies of nagAc-like dioxygenase genes per µg of DNA extracted from sediment samples . These values corresponded to (1.2 ± 0.6) x 105 to (5.4 ± 0.4) x 107 copies of this target per g of dry weight sediment when losses of DNA during extraction were taken into account . There was a positive correlation between naphthalene concentrations and nagAc-like gene copies per microgram of DNA (r = 0.89) and per gram of dry weight sediment (r = 0.77) . These results provide evidence of the ecological significance of organisms carrying nagAc-like genes in the biodegradation of naphthalene . Genes Coding for a New Pathway of Aerobic Benzoate Metabolism in Azoarcus evansii. Johannes Gescher, 2002.A new pathway for aerobic benzoate oxidation has been postulated for Azoarcus evansii and for a Bacillus stearothermophilus-like strain . Benzoate is first transformed into benzoyl coenzyme A (benzoyl-CoA), which subsequently is oxidized to 3-hydroxyadipyl-CoA and then to 3-ketoadipyl-CoA; all intermediates are CoA thioesters . The genes coding for this benzoate-induced pathway were investigated in the ß-proteobacterium A . evansii . They were identified on the basis of N-terminal amino acid sequences of purified benzoate metabolic enzymes and of benzoate-induced proteins identified on two-dimensional gels . Fifteen genes probably coding for the benzoate pathway were found to be clustered on the chromosome . These genes code for the following functions: a putative ATP-dependent benzoate transport system, benzoate-CoA ligase, a putative benzoyl-CoA oxygenase, a putative isomerizing enzyme, a putative ring-opening enzyme, enzymes for ß-oxidation of CoA-activated intermediates, thioesterase, and lactone hydrolase, as well as completely unknown enzymes belonging to new protein families . An unusual putative regulator protein consists of a regulator protein and a shikimate kinase I-type domain . A deletion mutant with a deletion in one gene (boxA) was unable to grow with benzoate as the sole organic substrate, but it was able to grow with 3-hydroxybenzoate and adipate . The data support the proposed pathway, which postulates operation of a new type of ring-hydroxylating dioxygenase acting on benzoyl-CoA and nonoxygenolytic ring cleavage . A ß-oxidation-like metabolism of the ring cleavage product is thought to lead to 3-ketoadipyl-CoA, which finally is cleaved into succinyl-CoA and acetyl-CoA . Repression of Phenazine Antibiotic Production in Pseudomonas aureofaciens Strain 30-84 by RpeA. Cheryl A. Whistler, 2003.Pseudomonas aureofaciens strain 30-84 is a biological control bacterium that utilizes a two-component GacS/GacA regulatory system interconnected with the PhzR/PhzI quorum sensing system to positively regulate biosynthesis of phenazine antibiotics that contribute to its association with plant hosts . To date, no negative regulators of phenazine production have been identified, nor has the role of repression been studied . Here we describe a novel repressor of secondary metabolism in P . aureofaciens strain 30-84, RpeA, whose deduced amino acid sequence is similar to those of a group of putative two-component regulatory systems of unknown function found in several animal and plant-pathogenic bacteria . In minimal medium where phenazine production is very low, inactivation of the rpeA gene enhanced phenazine biosynthetic gene expression and increased phenazine production but did not increase quorum sensing signal accumulation . Furthermore, RpeA functioned to block phenazine biosynthetic gene transcription in minimal medium even when quorum-sensing signals were at a level that was sufficient for induction of phenazine gene expression in rich medium . Additionally, in the absence of rpeA, the quorum sensor PhzR was not required for phenazine production . Although repression plays a critical role in phenazine regulation, the rpeA mutation could not bypass the requirement for a functional GacS/GacA system, demonstrating that activation is required even in the absence of the RpeA repressor . This study reinforces that multiple signals, including nutrition and population density, are integrated to control the appropriate expression of phenazine antibiotics .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
