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Characterization of Salmonella enterica Subspecies I Genovars by Use of Microarrays. S. Porwollik, 2004.Subspecies 1 of Salmonella enterica is responsible for almost all Salmonella infections of warm-blooded animals . Within subspecies 1 there are over 2,300 known serovars that differ in their prevalence and the diseases that they cause in different hosts . Only a few of these serovars are responsible for most Salmonella infections in humans and domestic animals . The gene contents of 79 strains from the most prevalent serovars were profiled by microarray analysis . Strains within the same serovar often differed by the presence and absence of hundreds of genes . Gene contents sometimes differed more within a serovar than between serovars . Groups of strains that share a distinct profile of gene content can be referred to as "genovars" to distinguish them from serovars . Several misassignments within the Salmonella reference B collection were detected by genovar typing and were subsequently confirmed serologically . Just as serology has proved useful for understanding the host range and pathogenic manifestations of Salmonella, genovars are likely to further define previously unrecognized specific features of Salmonella infections . The Putative Response Regulator BaeR Stimulates Multidrug Resistance of Escherichia coli via a Novel Multidrug Exporter System, MdtABC. Satoshi Nagakubo, 2002.Overproduction of the response regulator BaeR confers resistance to novobiocin and bile salts in a  acrAB mutant by stimulating drug exporter gene expression . The mdtABC (multidrug transporter ABC, formerly known as yegMNO) genes, which encode a resistance-nodulation-cell division (RND) drug efflux system, are responsible for resistance . The MdtABC system comprises the transmembrane MdtB/MdtC heteromultimer and MdtA membrane fusion protein . MdtAC also confers bile salt, but not novobiocin, resistance . This indicates that the evolution from an MdtC homomultimer to an MdtBC heteromultimer contributed to extend the drug resistance spectrum . A BLAST search suggested that such a heteromultimer-type RND exporter constitutes a unique family among gram-negative organisms .
The DnaK Chaperone Is Necessary for  -Complementation of ß-Galactosidase in Escherichia coli.Nicolas Lopes Ferreira, 2002.We show here the involvement of the molecular chaperone DnaK from Escherichia coli in the in vivo -complementation of the ß-galactosidase . In the dnaK756(Ts) mutant,
-complementation occurs when the organisms are grown at 30°C but not at 37 or 40°C, although these temperatures are permissive for bacterial growth . Plasmid-driven expression of wild-type dnaK restores the
-complementation in the mutant but also stimulates it in a dnaK+ strain . In a mutant which contains a disrupted dnaK gene ( dnaK52::Cmr),
-complementation is also impaired, even at 30°C . This observation provides an easy and original phenotype to detect subtle functional changes in a protein such as the DnaK756 chaperone, within the physiologically relevant temperature .
Acetic Acid Increases Stability of Silage under Aerobic Conditions. H. Danner, 2003.The effects of various compounds on the aerobic stability of silages were evaluated . It has been observed that inoculation of whole-crop maize with homofermentative lactic acid bacteria leads to silages which have low stability against aerobic deterioration, while inoculation with heterofermentative lactic acid bacteria, such as Lactobacillus brevis or Lactobacillus buchneri, increases stability . Acetic acid has been proven to be the sole substance responsible for the increased aerobic stability, and this acid acts as an inhibitor of spoilage organisms . Therefore, stability increases exponentially with acetic acid concentration . Only butyric acid has a similar effect . Other compounds, like lactic acid, 1,2-propanediol, and 1-propanol, have been shown to have no effect, while fructose and mannitol reduce stability .
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