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Identification and Characterization of CAMP Cohemolysin as a Potential Virulence Factor of Riemerella anatipestifer. Karen C. Crasta, 2002.Riemerella anatipestifer is responsible for exudative septicemia in ducks . The genetic determinant of the CAMP cohemolysin, cam, from a strain of R . anatipestifer was cloned and expressed in Escherichia coli. Chromosomal DNA from serotype 19 strain 30/90 was used to construct a gene library in pBluescript II SK(-) vector in E . coli XL-1-Blue strain . The clones containing recombinant plasmids were screened for the CAMP reaction with Staphylococcus aureus . Those that showed cohemolysis were chosen for further analysis by sequencing . One of these clones, JFRA8, was subcloned to identify the smallest possible DNA fragment containing the CAMP cohemolysin determinant, which was located on a 3,566-bp BamHI-BstXI fragment which specified a 1,026-bp open reading frame . Clones containing recombinant plasmids carrying cam obtained by PCR cloning into E . coli M15 strain secreted an active CAMP cohemolysin . Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses confirmed that the recombinant strain expressed a protein with a molecular mass of 37 kDa and that strains from serotypes 1, 2, 3, 5, 6, and 19 expressed the cohemolysin . The deduced amino acid sequence showed high homology to those of O-sialoglycoprotein endopeptidases . Hydrolysis of radioiodinated glycophorin A confirmed that Cam is a sialoglycoprotease . Soil Type Is the Primary Determinant of the Composition of the Total and Active Bacterial Communities in Arable Soils. Martina S. Girvan, 2003.Degradation of agricultural land and the resulting loss of soil biodiversity and productivity are of great concern . Land-use management practices can be used to ameliorate such degradation . The soil bacterial communities at three separate arable farms in eastern England, with different farm management practices, were investigated by using a polyphasic approach combining traditional soil analyses, physiological analysis, and nucleic acid profiling . Organic farming did not necessarily result in elevated organic matter levels; instead, a strong association with increased nitrate availability was apparent . Ordination of the physiological (BIOLOG) data separated the soil bacterial communities into two clusters, determined by soil type . Denaturing gradient gel electrophoresis and terminal restriction fragment length polymorphism analyses of 16S ribosomal DNA identified three bacterial communities largely on the basis of soil type but with discrimination for pea cropping . Five fields from geographically distinct soils, with different cropping regimens, produced highly similar profiles . The active communities (16S rRNA) were further discriminated by farm location and, to some degree, by land-use practices . The results of this investigation indicated that soil type was the key factor determining bacterial community composition in these arable soils . Leguminous crops on particular soil types had a positive effect upon organic matter levels and resulted in small changes in the active bacterial population . The active population was therefore more indicative of short-term management changes .
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