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Fitness Cost of SCCmec and Methicillin Resistance Levels in Staphylococcus aureus. Miriam Ender, 2004.Transformation of a type I SCCmec element into Staphylococcus aureus yielded highly oxacillin-resistant transformants with a reduced growth rate . Faster-growing variants could again be selected at the cost of reduced resistance levels, demonstrating an inverse correlation between oxacillin resistance levels and growth rate . In Vivo Study of Trichoderma-Pathogen-Plant Interactions, Using Constitutive and Inducible Green Fluorescent Protein Reporter Systems. Zexun Lu, 2004.Plant tissue colonization by Trichoderma atroviride plays a critical role in the reduction of diseases caused by phytopathogenic fungi, but this process has not been thoroughly studied in situ . We monitored in situ interactions between gfp-tagged biocontrol strains of T . atroviride and soilborne plant pathogens that were grown in cocultures and on cucumber seeds by confocal scanning laser microscopy and fluorescence stereomicroscopy . Spores of T . atroviride adhered to Pythium ultimum mycelia in coculture experiments . In mycoparasitic interactions of T . atroviride with P . ultimum or Rhizoctonia solani, the mycoparasitic hyphae grew alongside the pathogen mycelia, and this was followed by coiling and formation of specialized structures similar to hooks, appressoria, and papillae . The morphological changes observed depended on the pathogen tested . Branching of T . atroviride mycelium appeared to be an active response to the presence of the pathogenic host . Mycoparasitism of P . ultimum by T . atroviride occurred on cucumber seed surfaces while the seeds were germinating . The interaction of these fungi on the cucumber seeds was similar to the interaction observed in coculture experiments . Green fluorescent protein expression under the control of host-inducible promoters was also studied . The induction of specific Trichoderma genes was monitored visually in cocultures, on plant surfaces, and in soil in the presence of colloidal chitin or Rhizoctonia by confocal microscopy and fluorescence stereomicroscopy . These tools allowed initiation of the mycoparasitic gene expression cascade to be monitored in vivo . Identification of Secretion Determinants of the Bordetella pertussis BrkA Autotransporter. David C. Oliver, 2003.The autotransporters comprise a functionally diverse family of gram-negative proteins that mediate their own export across the bacterial outer membrane . They consist of an amino-terminal passenger region called the "  -domain" and the structural hallmark of the autotransporter family, a carboxy-terminal transporter region usually referred to as the "ß-domain." The passenger region can be quite diverse and constitutes the effector functions of these proteins, whereas the C-terminal region is conserved and is responsible for translocating the passenger moiety across the outer membrane . BrkA is the 103-kDa autotransporter protein in Bordetella pertussis that is cleaved to yield a 73-kDa N-terminal
-domain and a 30-kDa C-terminal ß-domain . We have previously shown that a recombinant form of the ß-domain of BrkA is capable of forming channels in artificial membranes . Here, we define two additional secretion determinants of BrkA . N-terminal sequencing of the 73-kDa BrkA passenger from B . pertussis and Escherichia coli revealed that BrkA has a 42-amino-acid signal peptide . In addition, deletion analysis of BrkA identified a 31- to 39-amino-acid region found immediately upstream of the ß-domain that was essential for surface expression . This 31- to 39-amino-acid linker region, together with the ß-domain, defines the minimal BrkA translocation unit . The linker region may also serve to anchor the BrkA passenger to the bacterial surface .
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