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Synthesis and Localization of the Salmonella SPI-1 Type III Secretion Needle Complex Proteins PrgI and PrgJ. Anand Sukhan, 2003.An essential component of type III secretion systems (TTSS) is a supramolecular structure termed the needle complex . In Salmonella enterica, at least four proteins make up this structure: InvG, PrgH, PrgK, and PrgI . Another protein, PrgJ, is thought to play a role in the assembly of this structure, but its function is poorly understood . We have analyzed the expression and localization of PrgJ and the needle protein PrgI in different S . enterica serovar Typhimurium mutant strains . We found that the levels of PrgI and PrgJ were significantly reduced in a TTSS-deficient invA mutant strain and that the decreased levels were due to protein instability . In addition, we found that PrgJ, although associated with the needle complex in wild-type S . enterica serovar Typhimurium, was absent from needle complexes obtained from an invJ mutant strain, which exhibits very long needle substructures . We suggest that PrgJ is involved in capping the needle substructure of the needle complex . Influence of Biosurfactants from Probiotic Bacteria on Formation of Biofilms on Voice Prostheses. Lígia Rodrigues, 2004. An AraC/XylS Family Member at a High Level in a Hierarchy of Regulators for Phenol-Metabolizing Enzymes in Comamonas testosteroni R5. Maki Teramoto, 2002.Comamonas testosteroni strain R5 expresses a higher level of phenol-oxygenating activity than any other bacterial strain so far characterized . The expression of the operon encoding multicomponent phenol hydroxylase (mPH), which is responsible for the phenol-oxygenating activity, is controlled by two transcriptional regulators, PhcS and PhcR, in strain R5 . In this study, we identified a third transcriptional regulator for the mPH operon (PhcT) that belongs to the AraC/XylS family . While the disruption of phcT in strain R5 significantly reduced the expression of the mPH operon, it did not eliminate the expression . However, the disruption of phcT in strain R5 increased the expression of phcR . The phenol-oxygenating activity was abolished by the disruption of phcR, indicating that PhcT alone was not sufficient to activate the expression of the mPH operon . The disruption of phcS has been shown in our previous study to confer the ability of strain R5 to express the mPH operon in the absence of the genuine substrate for mPH . PhcT was not involved in the gratuitous expression . Strain R5 thus possesses a more elaborate mechanism for regulating the mPH operon expression than has been found in other bacteria . Detecting Protein-Protein Interactions in the Intact Cell of Bacillus subtilis (ATCC 6633). Michael S. Winters, 2003.The salt bridge, paired group-specific reagent cyanogen (ethanedinitrile; C2N2) converts naturally occurring pairs of functional groups into covalently linked products . Cyanogen readily permeates cell walls and membranes . When the paired groups are shared between associated proteins, isolation of the covalently linked proteins allows their identity to be assigned . Examination of organisms of known genome sequence permits identification of the linked proteins by mass spectrometric techniques applied to peptides derived from them . The cyanogen-linked proteins were isolated by polyacrylamide gel electrophoresis . Digestion of the isolated proteins with proteases of known specificity afforded sets of peptides that could be analyzed by mass spectrometry . These data were compared with those derived theoretically from the Swiss Protein Database by computer-based comparisons (Protein Prospector; http://prospector.ucsf.edu) . Identification of associated proteins in the ribosome of Bacillus subtilis strain ATCC 6633 showed that there is an association homology with the association patterns of the ribosomal proteins of Haloarcula marismortui and Thermus thermophilus . In addition, other proteins involved in protein biosynthesis were shown to be associated with ribosomal proteins . Compound-Specific Isotopic Fractionation Patterns Suggest Different Carbon Metabolisms among Chloroflexus-Like Bacteria in Hot-Spring Microbial Mats. Marcel T. J. van der Meer, 2003.Stable carbon isotope fractionations between dissolved inorganic carbon and lipid biomarkers suggest photoautotrophy by Chloroflexus-like organisms in sulfidic and nonsulfidic Yellowstone hot springs . Where co-occurring, cyanobacteria appear to cross-feed Chloroflexus-like organisms supporting photoheterotrophy as well, although the relatively small 13C fractionation associated with cyanobacterial sugar biosynthesis may sometimes obscure this process .
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