|
|
|
|
|
|
 -Glutamyltranspeptidase,
but Not YwrD, Is Important in Utilization of Extracellular Glutathione as a
Sulfur Source in Bacillus subtilis.Hiromichi Minami, 2004. -Glutamyltranspeptidase
(EC 2.3.2.2) of Bacillus subtilis, which is an extracellular
enzyme, hydrolyzes the
-glutamyl
linkage of glutathione . YwrD, which is homologous to
-glutamyltranspeptidase,
was speculated to have a similar physiological role . It was
shown that
-glutamyltranspeptidase,
but not YwrD, is important in utilizing glutathione as the sole
sulfur source in Bacillus subtilis .
Inhibition of Antibiotic Efflux in Bacteria by the Novel Multidrug Resistance Inhibitors Biricodar (VX-710) and Timcodar (VX-853). Steve Mullin, 2004.Inhibitors of mammalian multidrug efflux, such as the plant alkaloid reserpine, are also active in potentiating antibiotic activity by inhibiting bacterial efflux . Based on this precedent, two novel mammalian multiple drug resistance inhibitors, biricodar (VX-710) and timcodar (VX-853), were evaluated for activity in a variety of bacteria . Both VX-710 and VX-853 potentiated the activity of ethidium bromide (EtBr), a model efflux substrate, against three clinically significant gram-positive pathogens: Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae . Similar to reserpine, VX-710 and VX-853 directly blocked EtBr efflux in S . aureus . Furthermore, these compounds were effective in lowering the MICs of several clinically used antibiotics, including fluoroquinolones, suggesting that VX-710 and VX-853 are representatives of a new class of bacterial efflux inhibitors with the potential for use in combination therapy . Expression and Immunogenicity of a Recombinant Diphtheria Toxin Fragment A in Streptococcus gordonii. Chiang W. Lee, 2004.A nontoxic mutant diphtheria toxin fragment A (DTA) was genetically fused in single, double, or triple copy to the major surface protein antigen P1 (SpaP) and surface expressed in Streptococcus gordonii DL-1 . The expression was verified by Western immunoblotting . Mouse antisera raised against the recombinant S . gordonii recognized the native diphtheria toxinm suggesting the recombinant DTA was immunogenic . When given intranasally to mice with cholera toxin subunit B as the adjuvant, the recombinant S . gordonii expressing double copies of DTA (SpaP-DTA2) induced a mucosal immunoglobulin A response and a weak systemic immunoglobulin G response . S . gordonii SpaP-DTA2 was able to orally colonize BALB/c mice for a 15-week period and elicited a mucosal response, but a serum immunoglobulin G response was not apparent . The antisera failed to neutralize diphtheria toxin cytotoxicity in a Vero cell assay . Microarray Analysis of Global Gene Expression in Mucoid Pseudomonas aeruginosa. Aaron M. Firoved, 2003.Pseudomonas aeruginosa is the dominant pathogen causing chronic respiratory infections in cystic fibrosis (CF) . After an initial phase characterized by intermittent infections, a chronic colonization is established in CF upon the conversion of P . aeruginosa to the mucoid, exopolysaccharide alginate-overproducing phenotype . The emergence of mucoid P . aeruginosa in CF is associated with respiratory decline and poor prognosis . The switch to mucoidy in most CF isolates is caused by mutations in the mucA gene encoding an anti-sigma factor . The mutations in mucA result in the activation of the alternative sigma factor AlgU, the P . aeruginosa ortholog of Escherichia coli extreme stress sigma factor  E . Because of the global nature of the regulators of mucoidy, we have hypothesized that other genes, in addition to those specific for alginate production, must be induced upon conversion to mucoidy, and their production may contribute to the pathogenesis in CF . Here we applied microarray analysis to identify on the whole-genome scale those genes that are coinduced with the AlgU sigmulon upon conversion to mucoidy . Gene expression profiles of AlgU-dependent conversion to mucoidy revealed coinduction of a specific subset of known virulence determinants (the major protease elastase gene, alkaline metalloproteinase gene aprA, and the protease secretion factor genes aprE and aprF) or toxic factors (cyanide synthase) that may have implications for disease in CF . Analysis of promoter regions of the most highly induced genes (>40-fold, P
 10-4) revealed a previously unrecognized, putative AlgU promoter upstream of the osmotically inducible gene osmE . This newly identified AlgU-dependent promoter of osmE was confirmed by mapping the mRNA 5' end by primer extension . The recognition of genes induced in mucoid P . aeruginosa, other than those associated with alginate biosynthesis, reported here revealed the identity of previously unappreciated factors potentially contributing to the morbidity and mortality caused by mucoid P . aeruginosa in CF .
Interactions of Insecticidal Toxin Gene Products from Xenorhabdus nematophilus PMFI296. Martin Sergeant, 2003.Four genes on a genomic fragment from Xenorhabdus nematophilus PMFI296 were shown to be involved in insecticidal activity towards three commercially important insect species . Each gene was expressed individually and in combinations in Escherichia coli, and the insecticidal activity of the lysates was determined . The combined four genes (xptA1, xptA2, xptB1, and xptC1), in E . coli, showed activity towards Pieris brassicae, Pieris rapae, and Heliothis virescens . The genes xptA1, xptB1, and xptC1 were involved in expressing activity towards P . rapae and P . brassicae, while the genes xptA2, xptB1, and xptC1 were needed for activity towards H . virescens . When each of these three genes was expressed individually in E . coli and the cell lysates were used in insect assays or mixed and then used, insecticidal activity was detected at a very low level . If the genes xptB1 and xptC1 were expressed in the same E . coli cell and this cell lysate was mixed with cells expressing xptA1, activity was restored to P . rapae and P . brassicae . Similarly mixing XptB1/C1 lysate with XptA2 lysate restored activity towards H . virescens. Individual gene disruptions in X . nematophilus PMFI296 reduced activity to insects; this activity was restored by complementation with cells expressing either xptA1 or xptA2 for their respective disruptions or E . coli expressing both xptB1 and xptC1 for individual disruptions of either of these genes . The genes xptA2, xptC1, and xptB1 were expressed as an operon in PMFI296 and inactivation of xptA2 or xptC1 resulted in silencing of downstream gene(s), while xptA1 was expressed as a single gene . Therefore, the two three gene product combinations interact with each other to produce good insecticidal activity .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
