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Nucleotide Sequence and Evolution of the Five-Plasmid Complement of the Phytopathogen Pseudomonas syringae pv . maculicola ES4326. John Stavrinides, 2004.Plasmids are transmissible, extrachromosomal genetic elements that are often responsible for environmental or host-specific adaptations . In order to identify the forces driving the evolution of these important molecules, we determined the complete nucleotide sequence of the five-plasmid complement of the radish and Arabidopsis pathogen Pseudomonas syringae pv . maculicola ES4326 and conducted an intraspecific comparative genomic analysis . To date, this is the most complex fully sequenced plasmid complement of any gram-negative bacterium . The plasmid complement comprises two pPT23A-like replicons, pPMA4326A (46,697 bp) and pPMA4326B (40,110 bp); a pPS10-like replicon, pPMA4326C (8,244 bp); and two atypical, replicase-deficient replicons, pPMA4326D (4,833 bp) and pPMA4326E (4,217 bp) . A complete type IV secretion system is found on pPMA4326A, while the type III secreted effector hopPmaA is present on pPMA4326B . The region around hopPmaA includes a shorter hopPmaA homolog, insertion sequence (IS) elements, and a three-element cassette composed of a resolvase, an integrase, and an exeA gene that is also present in several human pathogens . We have also identified a novel genetic element (E622) that is present on all but the smallest plasmid (pPMA4326E) that has features of an IS element but lacks an identifiable transposase . This element is associated with virulence-related genes found in a wide range of P . syringae strains . Comparative genomic analyses of these and other P . syringae plasmids suggest a role for recombination and integrative elements in driving plasmid evolution . Vanadium Respiration by Geobacter metallireducens: Novel Strategy for In Situ Removal of Vanadium from Groundwater. Irene Ortiz-Bernad, 2004. Sequencing of Flagellin Genes from Natrialba magadii Provides New Insight into Evolutionary Aspects of Archaeal Flagellins. Inna Serganova, 2002.We have determined the nucleotide sequence of a flagellin gene locus from the haloalkaliphilic archaeon Natrialba magadii, identified the gene products among proteins forming flagella, and demonstrated cotranscription of the genes . Based on the sequence analysis we suggest that different regions of the genes might have distinct evolutionary histories including possible genetic exchange with bacterial flagellin genes . Point Mutations in HpuB Enable Gonococcal HpuA Deletion Mutants To Grow on Hemoglobin. Ching-Ju Chen, 2002.Neisseria gonorrhoeae ordinarily requires both HpuA and HpuB to use hemoglobin (Hb) as a source of iron for growth . Deletion of HpuA resulted in reduced Hb binding and failure of growth on Hb . We identified rare Hb-utilizing colonies (Hb+) from an hpuA deletion mutant of FA1090, which fell into two phenotypic classes . One class of the Hb+ revertants required expression of both TonB and HpuB for growth on Hb, while the other class required neither TonB nor HpuB . All TonB/HpuB-dependent mutants had single amino acid alterations in HpuB, which occurred in clusters, particularly near the C terminus . The point mutations in HpuB did not restore normal Hb binding . Human serum albumin inhibited Hb-dependent growth of HpuB point mutants lacking HpuA but did not inhibit growth when expression of HpuA was restored . Thus, HpuB point mutants internalized heme in the absence of HpuA despite reduced binding of Hb . HpuA facilitated Hb binding and was important in allowing use of heme from Hb for growth . PCR Detection of Virulence Genes in Yersinia enterocolitica and Yersinia pseudotuberculosis and Investigation of Virulence Gene Distribution. P. Thoerner, 2003.PCR-based assays were developed for the detection of plasmid- and chromosome-borne virulence genes in Yersinia enterocolitica and Yersinia pseudotuberculosis, to investigate the distribution of these genes in isolates from various sources . The results of PCR genotyping, based on 5 virulence-associated genes of 140 strains of Y . enterocolitica, were compared to phenotypic tests, such as biotyping and serotyping, and to virulence plasmid-associated properties such as calcium-dependent growth at 37°C and Congo red uptake . The specificity of the PCR results was validated by hybridization . Genotyping data correlated well with biotype data, and most biotypes resulted in (nearly) homogeneous genotypes for the chromosomal virulence genes (ystA, ystB, and ail); however, plasmid-borne genes (yadA and virF) were detected with variable efficiency, due to heterogeneity within the bacterial population for the presence of the virulence plasmid . Of the virulence genes, only ystB was present in biotype 1A; however, within this biotype, pathogenic and apathogenic isolates could not be distinguished based on the detection of virulence genes . Forty Y . pseudotuberculosis isolates were tested by PCR for the presence of inv, yadA, and lcrF . All isolates were inv positive, and 88% of the isolates contained the virulence plasmid genes yadA and lcrF . In conclusion, this study shows that genotyping of Yersinia spp., based on both chromosome- and plasmid-borne virulence genes, is feasible and informative and can provide a rapid and reliable genotypic characterization of field isolates .
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