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In Vitro Activity and Potency of an Intravenously Injected Antimicrobial Peptide and Its DL Amino Acid Analog in Mice Infected with Bacteria. Amir Braunstein, 2004.We report that intravenous injection (3 mg/kg of body weight twice daily) of a diastereomer (containing 33% D amino acids) of an antimicrobial peptide, K6L9 (LKLLKKLLKKLLKLL-NH2), but not the all-L-amino-acid parental peptide, cures neutropenic mice infected with gentamicin-sensitive Pseudomonas aeruginosa and gentamicin-resistant Acinetobacter baumannii bacteria . Various biophysical experiments suggest a membranolytic-like effect . A New Black Aspergillus Species, A . vadensis, Is a Promising Host for Homologous and Heterologous Protein Production. Ronald P. de Vries, 2004.A new species of the group of black aspergilli, Aspergillus vadensis, was analyzed for its potential as a host for homologous and heterologous protein production . Unlike the other black aspergilli, this strain does not acidify the culture medium when nitrate is the nitrogen source and only produces very low levels of extracellular proteases, mainly serine metalloproteases . The stability of A . tubingensis feruloyl esterase A (FaeA) was compared upon production in wild-type A . vadensis, A . tubingensis, and an A . niger strain in which the three main protease-encoding genes were disrupted . The production of FaeA in A . vadensis resulted in larger amounts of intact protein than production in A . tubingensis and was similar to production in an A . niger protease disruptant, confirming in vivo the low proteolytic activity of A . vadensis . The protoplast formation and transformation efficiencies of A . vadensis were much higher than those of A . niger . These characteristics make A . vadensis a very promising candidate for homologous, and possibly heterologous, protein production . Identification of Two Quorum-Sensing Systems in Sinorhizobium meliloti. Melanie M. Marketon, 2002.Sinorhizobium meliloti is a free-living soil bacterium which is capable of establishing a symbiotic relationship with the alfalfa plant (Medicago sativa) . This symbiosis involves a network of bacterium-host signaling, as well as the potential for bacterium-bacterium communication, such as quorum sensing . In this study, we characterized the production of N-acyl homoserine lactones (AHLs) by two commonly used S . meliloti strains, AK631 and Rm1021 . We found that AK631 produces at least nine different AHLs, while Rm1021 produces only a subset of these molecules . To address the difference in AHL patterns between the strains, we developed a novel screening method to identify the genes affecting AHL synthesis . With this screening method, chromosomal groEL (groELc) was shown to be required for synthesis of the AHLs that are unique to AK631 but not for synthesis of the AHLs that are made by both AK631 and Rm1021 . We then used the screening procedure to identify a mutation in a gene homologous to traM of Agrobacterium tumefaciens, which was able to suppress the phenotype of the groELc mutation . A traR homolog was identified immediately upstream of traM, and we propose that its gene product requires a functional groELc for activity and is also responsible for inducing the synthesis of the AHLs that are unique to AK631 . We show that the traR/traM locus is part of a quorum-sensing system unique to AK631 and propose that this locus is involved in regulating conjugal plasmid transfer . We also present evidence for the existence of a second quorum-sensing system, sinR/sinI, which is present in both AK631 and Rm1021 . Helicobacter pylori Expresses an Autolytic Enzyme: Gene Identification, Cloning, and Theoretical Protein Structure. Eleonora Marsich, 2002.Helicobacter pylori is an important pathogen of the gastric system . The clinical outcome of infection is thought to be correlated with some genetic features of the bacterium . However, due to the extreme genetic variability of this organism, it is hard to draw definitive conclusions concerning its virulence factors . Here we describe a novel H . pylori gene which expresses an autolytic enzyme that is also capable of degrading the cell walls of both gram-positive and gram-negative bacteria . We designated this gene lys . We found this gene and observed its expression in a number of unrelated clinical strains, a fact that suggests that it is well conserved in the species . A comparison of the nucleotide sequences of lys and the hypothetical gene HP0339 from H . pylori strain ATCC 26695 revealed almost total identity, except for the presence of an insertion consisting of 24 nucleotides in the lys sequence . The coding sequences of lys and HP0339 show a high degree of homology with the coding sequence of bacteriophage T4 lysozyme . Because of this similarity, it was possible to model the three-dimensional structures of both the lys and HP0339 products . mgr, a Novel Global Regulator in Staphylococcus aureus. Thanh T. Luong, 2003.The virulence determinants of Staphylococcus aureus are coordinately controlled by several unlinked chromosomal loci . Here, we report the identification of CYL5614, derived from strain Becker, with a mutation that affects the expression of type 8 capsular polysaccharide (CP8), nuclease, alpha-toxin, coagulase, protease, and protein A . This novel locus, named mgr, was linked by transposon Tn917 and mapped by three-factorial transduction crosses . The region containing the mgr locus was cloned and sequenced . Deletion mutagenesis and genetic complementation showed that the locus consisted of one gene, mgrA . Interestingly, mgrA-null mutants exhibited a phenotype opposite to that of CYL5614 . This was due to a T-to-C mutation upstream of mgrA that resulted in a four- to eightfold increase in mgrA transcription in strain CYL5614 . Thus, these results indicate that mgrA is an activator of CP8 and nuclease but a repressor of alpha-toxin, coagulase, protease, and protein A . In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses showed that the mgr locus profoundly affected extracellular protein production, suggesting that the locus may regulate many other genes as well . The translated MgrA protein has a region of significant homology, which includes the helix-turn-helix DNA-binding motif, with the Escherichia coli MarR family of transcriptional regulators . Northern slot blot analyses suggested that mgr affected CP8, alpha-toxin, nuclease, and protein A at the transcriptional level . Identification of New Genes Positively Regulated by Tri10 and a Regulatory Network for Trichothecene Mycotoxin Production. Andrew W. Peplow, 2003.Tri10, a regulatory gene in trichothecene mycotoxin-producing Fusarium species, is required for trichothecene biosynthesis and the coordinated expression of four trichothecene pathway-specific genes (Tri4, Tri5, Tri6, and Tri101) and the isoprenoid biosynthetic gene for farnesyl pyrophosphate synthetase (FPPS) . We showed that six more trichothecene genes (Tri3, Tri7, Tri8, Tri9, Tri11, and Tri12) are regulated by Tri10 . We also constructed a cDNA library from a strain of Fusarium sporotrichioides that overexpresses Tri10 (  Tri10) and used cDNA derived from the
Tri10 strain and a non-Tri10-expressing strain ( Tri10) to differentially screen macroarrays prepared from the cDNA library . This screen identified 15 additional Tri10-regulated transcripts . Four of these transcripts represent Tri1, Tri13, and Tri14 and a gene designated Tri15 . Three other sequences are putative orthologs of genes for isoprenoid biosynthesis, the primary metabolic pathway preceding trichothecene biosynthesis . The remaining eight sequences have been designated Ibt (influenced by Tri10) genes . Of the 26 transcripts now known to be positively regulated by Tri10, 22 are positively coregulated by Tri6, a gene that encodes a previously characterized trichothecene pathway-specific transcription factor . These 22 Tri10- and Tri6-coregulated sequences include all of the known Tri genes (except for Tri10), the FPPS gene, and the other three putative isoprenoid biosynthetic genes . Tri6 also regulates a transcript that is not regulated by Tri10 . Thus, Tri10 and Tri6 regulate overlapping sets of genes that include a common group of multiple genes for both primary and secondary metabolism .
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