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Sequence Analysis of the Mobile Genome Island pKLC102 of Pseudomonas aeruginosa C. Jens Klockgether, 2004.The Pseudomonas aeruginosa plasmid pKLC102 coexists as a plasmid and a genome island in clone C strains . Whereas the related plasmid pKLK106 reversibly recombines with P . aeruginosa clone K chromosomes at one of the two tRNALys genes, pKLC102 is incorporated into the tRNALys gene only close to the pilA locus . Targeting of the other tRNALys copy in the chromosome is blocked by a 23,395-bp mosaic of truncated PAO open reading frames, transposons, and pKLC102 homologs . Annotation and phylogenetic analysis of the large 103,532-bp pKLC102 sequence revealed that pKLC102 is a hybrid of plasmid and phage origin . The plasmid lineage conferred oriV and genes for replication, partitioning, and conjugation, including a pil cluster encoding type IV thin sex pili and an 8,524-bp chvB glucan synthetase gene that is known to be a major determinant for host tropism and virulence . The phage lineage conferred integrase, att, and a syntenic set of conserved hypothetical genes also observed in the tRNAGly-associated genome islands of P . aeruginosa clone C chromosomes . In subgroup C isolates from patients with cystic fibrosis, pKLC102 was irreversibly fixed into the chromosome by the insertion of the large 23,061-bp class I transposon TNCP23, which is a composite of plasmid, integron, and IS6100 elements . Intramolecular transposition of a copy of IS6100 led to chromosomal inversions and disruption of plasmid synteny . The case of pKLC102 in P . aeruginosa clone C documents the intraclonal evolution of a genome island from a mobile ancestor via a reversibly integrated state to irreversible incorporation and dissipation in the chromosome . Addition of Aromatic Substrates Restores Trichloroethylene Degradation Activity in Pseudomonas putida F1. Yuki Morono, 2004.The rate of trichloroethylene (TCE) degradation by toluene dioxygenase (TDO) in resting cells of Pseudomonas putida F1 gradually decreased and eventually stopped within 1.5 h, as in previous reports . However, the subsequent addition of toluene, which is the principal substrate of TDO, resulted in its immediate degradation without a lag phase . After the consumption of toluene, degradation of TCE restarted at a rate similar to its initial degradation, suggesting that this degradation was mediated by TDO molecules that were present before the cessation of TCE degradation . The addition of benzene and cumene, which are also substrates of TDO, also caused restoration of TCE degradation activity: TCE was degraded simultaneously with cumene, and a larger amount of TCE was degraded after cumene was added than after toluene or benzene was added . But substrates that were expected to supply the cells with NADH or energy did not restore TCE degradation activity . This cycle of pseudoinactivation and restoration of TCE degradation was observed repeatedly without a significant decrease in the number of viable cells, even after six additions of toluene spread over 30 h . The results obtained in this study demonstrate a new type of restoration of TCE degradation that has not been previously reported . Widespread Occurrence of a Novel Division of Bacteria Identified by 16S rRNA Gene Sequences Originally Found in Deep Marine Sediments. Gordon Webster, 2004. Characterization of a Spontaneous Nonmagnetic Mutant of Magnetospirillum gryphiswaldense Reveals a Large Deletion Comprising a Putative Magnetosome Island. Sabrina Schübbe, 2003.Frequent spontaneous loss of the magnetic phenotype was observed in stationary-phase cultures of the magnetotactic bacterium Magnetospirillum gryphiswaldense MSR-1 . A nonmagnetic mutant, designated strain MSR-1B, was isolated and characterized . The mutant lacked any structures resembling magnetosome crystals as well as internal membrane vesicles . The growth of strain MSR-1B was impaired under all growth conditions tested, and the uptake and accumulation of iron were drastically reduced under iron-replete conditions . A large chromosomal deletion of approximately 80 kb was identified in strain MSR-1B, which comprised both the entire mamAB and mamDC clusters as well as further putative operons encoding a number of magnetosome-associated proteins . A bacterial artificial chromosome clone partially covering the deleted region was isolated from the genomic library of wild-type M . gryphiswaldense . Sequence analysis of this fragment revealed that all previously identified mam genes were closely linked with genes encoding other magnetosome-associated proteins within less than 35 kb . In addition, this region was remarkably rich in insertion elements and harbored a considerable number of unknown gene families which appeared to be specific for magnetotactic bacteria . Overall, these findings suggest the existence of a putative large magnetosome island in M . gryphiswaldense and other magnetotactic bacteria . The Membrane Domain of SpoIIIE Is Required for Membrane Fusion during Bacillus subtilis Sporulation. Marc D. Sharp, 2003.During Bacillus subtilis sporulation, SpoIIIE is required for both postseptational chromosome segregation and membrane fusion after engulfment . Here we demonstrate that SpoIIIE must be present in the mother cell to promote membrane fusion and that the N-terminal membrane-spanning segments constitute a minimal membrane fusion domain, as well as direct septal localization .
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