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Subpopulation Characteristics of Egg-Contaminating Salmonella enterica serovar Enteritidis as Defined by the Lipopolysaccharide O Chain. Jean Guard-Bouldin, 2004.Characterization of Salmonella enterica serovar Enteritidis was refined by incorporating new data from isolates obtained from avian sources, from the spleens of naturally infected mice, and from the United Kingdom into an existing lipopolysaccharide (LPS) O-chain compositional database . From least to greatest, the probability of avian isolates producing high-molecular-mass LPS O chain ranked as follows: pooled kidney, liver, and spleen; intestine; cecum; ovary and oviduct; albumen; yolk; and whole egg . Mouse isolates were most like avian intestinal samples, whereas United Kingdom isolates were most like those from the avian reproductive tract and egg . Non-reproductive tract organ isolates had significant loss of O chain . Isogenic isolates that varied in ability to make biofilm and to be orally invasive produced different O-chain structures at 25°C but not at 37°C . Hens infected at a 91:9 biofilm-positive/-negative colony phenotype ratio yielded only the negative phenotype from eggs . These results indicate that the environment within the hen applies stringent selection pressure on subpopulations of S . enterica serovar Enteritidis at certain points in the infection pathway that ends in egg contamination . The avian cecum, rather than the intestines, is the early interface between the environment and the host that supports emergence of subpopulation diversity . These results suggest that diet and other factors that alter cecal physiology should be investigated as a means to reduce egg contamination . Inhibition of Listeria monocytogenes in Fish and Meat Systems by Use of Oregano and Cranberry Phytochemical Synergies. Y. T. Lin, 2004. TrwD, the Hexameric Traffic ATPase Encoded by Plasmid R388, Induces Membrane Destabilization and Hemifusion of Lipid Vesicles. Cristina Machón, 2002.TrwD, a hexameric ATP hydrolase encoded by plasmid R388, is a member of the PulE/VirB11 protein superfamily of traffic ATPases . It is essential for plasmid conjugation, particularly for expression of the conjugative W pilus . In the present study, we analyzed the effects that TrwD produced on unilamellar vesicles consisting of cardiolipin and phosphatidylcholine in equimolar amounts . TrwD induced dose-dependent vesicle aggregation and intervesicular mixing of the lipids located in the outer monolayers in the presence of calcium . It also induced extensive leakage of the vesicular aqueous contents . A point mutant of TrwD with a mutation in the P loop of the nucleotide-binding region (K203Q) that lacks both ATPase activity and the ability to support conjugation showed the same behavior as native TrwD in all of these processes, which were independent of the presence of ATP . Structure prediction methods revealed a close similarity to Helicobacter pylori protein HP0525, another member of the PulE/VirB11 family, whose crystal structure is known . The interpretation of our data in the light of this structure is that TrwD interacts with the lipid bilayer through hydrophobic regions in its N-terminal domain, which leads to a certain degree of membrane destabilization . TrwD appears to be a part of the conjugation machinery that interacts with the membranous systems in order to facilitate DNA transfer in bacteria . Solar UV-B Radiation Inhibits the Growth of Antarctic Terrestrial Fungi. Kevin A. Hughes, 2003.We tested the effects of solar radiation, and UV-B in particular, on the growth of Antarctic terrestrial fungi . The growth responses to solar radiation of five fungi, Geomyces pannorum, Phoma herbarum, Pythium sp., Verticillium sp., and Mortierella parvispora, each isolated from Antarctic terrestrial habitats, were examined on an agar medium in the natural Antarctic environment . A 3-h exposure to solar radiation of >287 nm reduced the hyphal extension rates of all species relative to controls kept in the dark . Pythium sp . cultures exposed to solar radiation for 1.5 h on five consecutive days were most sensitive to radiation of >287 nm, but radiation of >313 nm also inhibited growth to a lesser extent . Radiation of >400 nm had no effect on hyphal growth relative to controls kept in the dark . Short-wave solar UV-B radiation of between 287 and 305 nm inhibited the growth of Pythium sp . hyphae on and below the surface of the agar medium after 24 h, but radiation of  345 nm only reduced the growth of surface hyphae . Similar detrimental effects of UV-B on surface and, to a lesser extent, submerged hyphae of all five fungi were shown in the laboratory by using artificial UV-B from fluorescent lamps . A comparison of growth responses to solar radiation and temperature showed that the species that were most resistant to UV radiation grew fastest at higher temperatures . These data suggest that solar UV-B reduces the growth of fungi on the soil surface in the Antarctic terrestrial environment .
Molecular Phylogenetic Exploration of Bacterial Diversity in a Bakreshwar (India) Hot Spring and Culture of Shewanella-Related Thermophiles. Dhritiman Ghosh, 2003.The bacterial diversity of a hot spring in Bakreshwar, India, was investigated by a culture-independent approach . 16S ribosomal DNA clones derived from the sediment samples were found to be associated with gamma-Proteobacteria, cyanobacteria, and green nonsulfur and low-GC gram-positive bacteria . The first of the above phylotypes cobranches with Shewanella, a well-known iron reducer . This phylogenetic correlation has been exploited to develop culture conditions for thermophilic iron-reducing microorganisms .
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