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Genetic and Structural Characterization of the Core Region of the Lipopolysaccharide from Serratia marcescens N28b (Serovar O4). Núria Coderch, 2004.The gene cluster (waa) involved in Serratia marcescens N28b core lipopolysaccharide (LPS) biosynthesis was identified, cloned, and sequenced . Complementation analysis of known waa mutants from Escherichia coli K-12, Salmonella enterica, and Klebsiella pneumoniae led to the identification of five genes coding for products involved in the biosynthesis of a shared inner core structure: [L,D-HeppIII  (1 7)-L,D-HeppII(13)-L,D-HeppI(15)-KdopI(4 2)KdopII]
(L,D-Hepp,
L-glycero-D-manno-heptopyranose;
Kdo, 3-deoxy-D-manno-oct-2-ulosonic
acid) . Complementation and/or chemical analysis of several nonpolar
mutants within the S . marcescens waa gene cluster suggested
that in addition, three waa genes were shared by S . marcescens
and K . pneumoniae, indicating that the core region of the LPS
of S . marcescens and K . pneumoniae possesses additional
common features . Chemical and structural analysis of the major
oligosaccharide from the core region of LPS of an O-antigen-deficient
mutant of S . marcescens N28b as well as complementation
analysis led to the following proposed structure: ß-Glc-(16)--Glc-(14))--D-GlcN-(14)--D-GalA-[(21)--D,D-Hep-(21)--Hep]-(13)--L,D-Hep[(71)--L,D-Hep]-(13)--L,D-Hep-[(41)-ß-D-Glc]-(15)-Kdo .
The D configuration of the ß-Glc,
-GclN,
and
-GalA
residues was deduced from genetic data and thus is tentative .
Furthermore, other oligosaccharides were identified by ion cyclotron
resonance-Fourier-transformed electrospray ionization mass spectrometry,
which presumably contained in addition one residue of D-glycero-D-talo-oct-2-ulosonic
acid (Ko) or of a hexuronic acid . Several ions were identified
that differed from others by a mass of +80 Da, suggesting a
nonstoichiometric substitution by a monophosphate residue . However,
none of these molecular species could be isolated in substantial
amounts and structurally analyzed . On the basis of the structure
shown above and the analysis of nonpolar mutants, functions are
suggested for the genes involved in core biosynthesis .
Novel Developmental Genes, fruCD, of Myxococcus xanthus: Involvement of a Cell Division Protein in Multicellular Development. Takuya Akiyama, 2003.Myxococcus xanthus is a gram-negative soil bacterium that undergoes multicellular development upon nutrient starvation . In the present study, two novel developmental genes, fruC and fruD, of M . xanthus were identified and characterized . The FruD protein has significant amino acid sequence similarity to the DivIVA proteins of many bacteria including Bacillus subtilis . Vegetative cells of the fruD mutant exhibited a filamentous phenotype . The fruC and fruD mutants displayed similar delayed-development phenotypes . The formation of tightly aggregated mounds by fruC and fruD mutants was slower than that by the wild-type strain . Spore formation by the fruC and fruD mutants initiated after 30 h poststarvation, whereas wild-type M . xanthus initiated spore formation after 18 h . The fruCD genes were constitutively expressed as an operon during vegetative growth and development . S1 mapping revealed that transcription initiation sites of the fruCD operon were located 114 (P1) and 55 bp (P2) upstream of the fruC initiation codon . Only the P1 promoter was active during vegetative growth, while both the P1 and P2 promoters were active during development . The FruD protein was produced as a cytoplasmic protein and formed an oligomer during vegetative growth and development . SRI-286, a Thiosemicarbazole, in Combination with Mefloquine and Moxifloxacin for Treatment of Murine Mycobacterium avium Complex Disease. Luiz E. Bermudez, 2004.Treatment of Mycobacterium avium disease remains challenging when macrolide resistance develops . We infected C57 beige mice and treated them with mefloquine, SRI-286, and moxifloxacin . SRI-286 (80 mg/kg) was bactericidal in the liver . Mefloquine plus moxifloxacin or mefloquine plus SRI-286 were better than mefloquine alone .
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