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Temporal Global Changes in Gene Expression during Temperature Transition in Yersinia pestis. Vladimir L. Motin, 2004.DNA microarrays encompassing the entire genome of Yersinia pestis were used to characterize global regulatory changes during steady-state vegetative growth occurring after shift from 26 to 37°Cin the presence and absence of Ca2+ . Transcriptional profiles revealed that 51, 4, and 13 respective genes and open readingframes [ORFs] on pCD, pPCP, and pMT were thermoinduced and thatthe majority of these genes carried by pCD were downregulatedby Ca2+ . In contrast, Ca2+ had little effect on chromosomalgenes and ORFs, of which 235 were thermally upregulated and274 were thermally downregulated . The primary consequence ofthese regulatory events is profligate catabolism of numerousmetabolites available in the mammalian host. Genomic Approach to Identification of Mutations Affecting Caspofungin Susceptibility in Saccharomyces cerevisiae. Sarit Markovich, 2004.The antifungal agent caspofungin (CAS) specifically interferes with glucan synthesis and cell wall formation . To further study the cellular processes affected by CAS, we analyzed a Saccharomyces cerevisiae mutant collection (4,787 individual knockout mutations) to identify new genes affecting susceptibility to the drug . This collection was screened for increased CAS sensitivity (CAS-IS) or increased CAS resistance (CAS-IR) . MICs were determined by the broth microdilution method . Disruption of 20 genes led to CAS-IS (four- to eightfold reductions in the MIC) . Eleven of the 20 genes are involved in cell wall and membrane function, notably in the protein kinase C (PKC) integrity pathway (MID2, FKS1, SMI1, and BCK1), chitin and mannan biosynthesis (CHS3, CHS4, CHS7, and MNN10), and ergosterol biosynthesis (ERG5 and ERG6) . Four of the 20 genes (TPO1, VPS65, VPS25, and CHC1) are involved in vacuole and transport functions, 3 of the 20 genes (CCR4, POP2, and NPL3) are involved in the control of transcription, and 2 of the 20 genes are of unknown function . Disruption of nine additional genes led to CAS-IR (a fourfold increase of MIC) . Five of these nine genes (SLG1, ERG3, VRP1, CSG2, and CKA2) are involved in cell wall function and signal transduction, and two of the nine genes (VPS67 and SAC2) are involved in vacuole function . To assess the specificity of susceptibility to CAS, the MICs of amphotericin B, fluconazole, flucytosine, and calcofluor for the strains were tested . Seven of 20 CAS-IS strains (with disruption of FKS1, SMI1, BCK1, CHS4, ERG5, TPO1, and ILM1) and 1 of 9 CAS-IR strains (with disruption of SLG1) demonstrated selective susceptibility to CAS . To further explore the importance of PKC in CAS susceptibility, the activity of the PKC inhibitor staurosporine in combination with CAS was tested against eight Aspergillus clinical isolates by the microdilution assay . Synergistic or synergistic-to-additive activities were found against all eight isolates by use of both MIC and minimum effective concentration endpoints . Transcriptional Response of Pasteurella multocida to Nutrient Limitation. Michael L. Paustian, 2002.Bacteria often encounter environments where nutrient availability is limited, and they must adapt accordingly . To identify Pasteurella multocida genes that are differentially expressed during nutrient limitation, we utilized whole-genome microarrays to compare levels of gene expression during growth in rich and minimal media . Our analysis showed that the levels of expression of a total of 669 genes, representing approximately one-third of the genome, were detectably altered over the course of the experiment . A large number (n = 439) of genes, including those involved in energy metabolism, transport, protein synthesis, and binding, were expressed at higher levels in rich medium, suggesting that, upon exposure to a rich environment, P . multocida immediately begins to turn on many energy-intensive biosynthetic pathways or, conversely, turns these genes off when it is exposed to a nutrient-deficient environment . Genes with increased expression in minimal medium (n = 230) included those encoding amino acid biosynthesis and transport systems, outer membrane proteins, and heat shock proteins . Importantly, our analysis also identified a large number (n = 164) of genes with unknown functions whose expression was altered during nutrient limitation . Overall, the results of our study show that a wide repertoire of genes, many of which have yet to be functionally classified, undergo transcriptional regulation in P . multocida in response to growth in minimal medium and provide a strong foundation to investigate the transcriptional response of this multispecies pathogen to growth in a nutrient-limited environment . The ATPase FliI Can Interact with the Type III Flagellar Protein Export Apparatus in the Absence of Its Regulator, FliH. Tohru Minamino, 2003.Salmonella FliI is the ATPase that drives flagellar protein export . It normally exists as a complex together with the regulatory protein FliH . A fliH null mutant was slightly motile, with overproduction of FliI resulting in substantial improvement of its motility . Mutations in the cytoplasmic domains of FlhA and FlhB, which are integral membrane components of the type III flagellar export apparatus, also resulted in substantially improved motility, even at normal FliI levels . Thus, FliH, though undoubtedly important, is not essential .
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