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Molecular Characterization of Two Lactate Dehydrogenase Genes with a Novel Structural Organization on the Genome of Lactobacillus sp . Strain MONT4. Jennifer Weekes, 2004. A New Type IV Secretion System Promotes Conjugal Transfer in Agrobacterium tumefaciens. Lishan Chen, 2002.Two DNA transfer systems encoded by the tumor-inducing (Ti) plasmid have been previously identified in Agrobacterium tumefaciens . The virB operon is required for the transfer of transferred DNA to the plant host, and the trb system encodes functions required for the conjugal transfer of the Ti plasmid between cells of Agrobacterium . Recent availability of the genome sequence of Agrobacterium allowed us to identify a third system that is most similar to the VirB type IV secretion system of Bartonella henselae . We have designated this system avhB for Agrobacterium virulence homologue virB . The avhB loci reside on pAtC58 and encode at least 10 proteins (AvhB2 through AvhB11), 7 of which display significant similarity to the corresponding virulence-associated VirB proteins of the Ti plasmid . However, the AvhB system is not required for tumor formation; rather, it mediates the conjugal transfer of the pAtC58 cryptic plasmid between cells of Agrobacterium . This transfer occurs in the absence of the Ti plasmid-encoded VirB and Trb systems . Like the VirB system, AvhB products promote the conjugal transfer of the IncQ plasmid RSF1010, suggesting that these products comprise a mating-pair formation system . The presence of plasmid TiC58 or plasmid RSF1010 reduces the conjugal transfer efficiency of pAtC58 10- or 1,000-fold, respectively . These data suggest that complex substrate interactions exist among the three DNA transfer systems of Agrobacterium . Gene Transfer in Mycoplasma pulmonis. Amy M. Teachman, 2002.Experiments were undertaken to examine gene transfer in Mycoplasma pulmonis . Parent strains containing transposon-based tetracycline and chloramphenicol resistance markers were combined to allow transfer of markers . Two mating protocols were developed . The first consisted of coincubating the strains in broth culture for extended periods of time . The second protocol consisted of a brief incubation of the combined strains in a 50% solution of polyethylene glycol . Using either protocol, progeny that had acquired antibiotic resistance markers from both parents were obtained . Analysis of the progeny indicated that only the transposon and not flanking genomic DNA was transferred to the recipient cell . Gene transfer was DNase resistant and probably the result of conjugation or cell fusion . Identification of a Differentially Expressed Oligopeptide Binding Protein (OppA2) in Streptococcus uberis by Representational Difference Analysis of cDNA. D. L. Taylor, 2003.Streptococcus uberis is an increasingly significant cause of intramammary infection in the dairy cow, presently responsible for approximately 33% of all cases of bovine mastitis in the United Kingdom . Following experimentally induced infection of the lactating mammary gland, S . uberis is found predominantly in the luminal areas of secretory alveoli and ductular tissue, indicating that much of the bacterial growth occurs in residual and newly synthesized milk . With the objective of identifying potential virulence determinants in a clinical isolate of S . uberis, we have used representational difference analysis of cDNA to identify genes that show modified expression in milk . We have identified a number of differentially expressed genes that may contribute to the overall pathogenicity of the organism . Of these, a transcript encoding a putative oligopeptide binding protein (OppA) was further characterized . We have found that S . uberis possesses two oppA-like open reading frames, oppA1 and oppA2, which are up-regulated to different degrees following growth in milk . Mutants lacking either oppA1 or oppA2 are viable and have an increased resistance to the toxic peptide derivative aminopterin; however, only mutants lacking oppA1 display a lower rate of growth in milk . In addition, expression of the oppA genes appears to be coordinated by different mechanisms . We conclude that the oppA genes encode oligopeptide binding proteins, possibly displaying different specificities, required for the efficient growth of S . uberis in milk . Prokaryotic Utilization of the Twin-Arginine Translocation Pathway: a Genomic Survey. Kieran Dilks, 2003.The twin-arginine translocation (Tat) pathway, which has been identified in plant chloroplasts and prokaryotes, allows for the secretion of folded proteins . However, the extent to which this pathway is used among the prokaryotes is not known . By using a genomic approach, a comprehensive list of putative Tat substrates for 84 diverse prokaryotes was established . Strikingly, the results indicate that the Tat pathway is utilized to highly varying extents . Furthermore, while many prokaryotes use this pathway predominantly for the secretion of redox proteins, analyses of the predicted substrates suggest that certain bacteria and archaea secrete mainly nonredox proteins via the Tat pathway . While no correlation was observed between the number of Tat machinery components encoded by an organism and the number of predicted Tat substrates, it was noted that the composition of this machinery was specific to phylogenetic taxa . Recombinant Strain of Bacillus thuringiensis Producing Cyt1A, Cry11B, and the Bacillus sphaericus Binary Toxin. Hyun-Woo Park, 2003.A novel recombinant Bacillus thuringiensis subsp . israelensis strain that produces the B . sphaericus binary toxin, Cyt1Aa, and Cry11Ba is described . The toxicity of this strain (50% lethal concentration [LC50] = 1.7 ng/ml) against fourth-instar Culex quinquefasciatus was higher than that of B . thuringiensis subsp . israelensis IPS-82 (LC50 = 7.9 ng/ml) or B . sphaericus 2362 (LC50 = 12.6 ng/ml) .
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