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The Bacillus subtilis Acyl Lipid Desaturase Is a  5
Desaturase.Silvia G. Altabe, 2003.Bacillus subtilis was recently reported to synthesize unsaturated fatty acids (UFAs) with a double bond at positions 5,
7,
and
9
(M . H . Weber, W . Klein, L . Muller, U . M . Niess, and M . A . Marahiel,
Mol . Microbiol . 39:1321-1329, 2001) . Since this finding would have
considerable importance in the double-bond positional specificity
displayed by the B . subtilis acyl lipid desaturase, we
have attempted to confirm this observation . We report that the double
bond of UFAs synthesized by B . subtilis is located
exclusively at the
5
position, regardless of the growth temperature and the length chain
of the fatty acids .
Identification of Virulence Genes in a Pathogenic Strain of Pseudomonas aeruginosa by Representational Difference Analysis. Ji Young Choi, 2002.Pseudomonas aeruginosa is an opportunistic pathogen that may cause severe infections in humans and other vertebrates . In addition, a human clinical isolate of P . aeruginosa, strain PA14, also causes disease in a variety of nonvertebrate hosts, including plants, Caenorhabditis elegans, and the greater wax moth, Galleria mellonella . This has led to the development of a multihost pathogenesis system in which plants, nematodes, and insects have been used as adjuncts to animal models for the identification of P . aeruginosa virulence factors . Another approach to identifying virulence genes in bacteria is to take advantage of the natural differences in pathogenicity between isolates of the same species and to use a subtractive hybridization technique to recover relevant genomic differences . The sequenced strain of P . aeruginosa, strain PAO1, has substantial differences in virulence from strain PA14 in several of the multihost models of pathogenicity, and we have utilized the technique of representational difference analysis (RDA) to directly identify genomic differences between P . aeruginosa strains PA14 and PAO1 . We have found that the pilC, pilA, and uvrD genes in strain PA14 differ substantially from their counterparts in strain PAO1 . In addition, we have recovered a gene homologous to the ybtQ gene from Yersinia, which is specifically present in strain PA14 but absent in strain PAO1 . Mutation of the ybtQ homolog in P . aeruginosa strain PA14 significantly attenuates the virulence of this strain in both G . mellonella and a burned mouse model of sepsis to levels comparable to those seen with PAO1 . This suggests that the increased virulence of P . aeruginosa strain PA14 compared to PAO1 may relate to specific genomic differences identifiable by RDA . Bacterial Chemotaxis: a New Player in Response Regulator Dephosphorylation. John S. Parkinson, 2003. Isolation and Molecular Characterization of pMG160, a Mobilizable Cryptic Plasmid from Rhodobacter blasticus. Masayuki Inui, 2003.A 3.4-kb cryptic plasmid was obtained from a new isolate of Rhodobacter blasticus . This plasmid, designated pMG160, was mobilizable by the conjugative strain Escherichia coli S17.1 into Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas palustris . It replicated in the latter strains but not in Rhodospirillum rubrum, Rhodocyclus gelatinosus, or Bradyrhizobium species . Plasmid pMG160 was stably maintained in R . sphaeroides for more than 100 generations in the absence of selection but showed segregational instability in R . palustris . Instability in R . palustris correlated with a decrease in plasmid copy number compared to the copy number in R . sphaeroides . The complete nucleotide sequence of plasmid pMG160 contained three open reading frames (ORFs) . The deduced amino acid sequences encoded by ORF1 and ORF2 showed high degrees of homology to the MobS and MobL proteins that are involved in plasmid mobilization of certain plasmids . Based on homology with the Rep protein of several other plasmids, ORF3 encodes a putative rep gene initiator of plasmid replication . The functions of these sequences were demonstrated by deletion mapping, frameshift analysis, and analysis of point mutations . Two 6.1-kb pMG160-based E . coli-R . sphaeroides shuttle cloning vectors were constructed and designated pMG170 and pMG171 . These two novel shuttle vectors were segregationally stable in R . sphaeroides growing under nonselective conditions .
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