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Steady-State Pharmacokinetics of a Double-Boosting Regimen of Saquinavir Soft Gel plus Lopinavir plus Minidose Ritonavir in Human Immunodeficiency Virus-Infected Adults. Esteban Ribera, 2004. Lactic Acid Bacteria as a Potential Source of Enzymes for Use in Vinification. Angela Matthews, 2004. Listeria monocytogenes relA and hpt Mutants Are Impaired in Surface-Attached Growth and Virulence. Clare M. Taylor, 2002.We describe here the identification and characterization of two Listeria monocytogenes (Tn917-LTV3) relA and hpt transposon insertion mutants that were impaired in growth after attachment to a model surface . Both mutants were unable to accumulate (p)ppGpp in response to amino acid starvation, whereas the wild-type strain accumulated (p)ppGpp within 30 min of stress induction . The induction of transcription of the relA gene after adhesion was demonstrated, suggesting that the ability to mount a stringent response and undergo physiological adaptation to nutrient deprivation is essential for the subsequent growth of the adhered bacteria . The absence of (p)ppGpp in the hpt mutant, which is blocked in the purine salvage pathway, is curious and suggests that a functional purine salvage pathway is required for the biosynthesis of (p)ppGpp . Both mutants were avirulent in a murine model of listeriosis, indicating an essential role for the stringent response in the survival and growth of L . monocytogenes in the host . Taken as a whole, this study provides new information on the role of the stringent response and the physiological adaptation of L . monocytogenes for biofilm growth and pathogenesis . Lateral Flagellar Gene System of Vibrio parahaemolyticus. Bonnie J. Stewart, 2003.Vibrio parahaemolyticus possesses dual flagellar systems adapted for movement under different circumstances . A single polar flagellum propels the bacterium in liquid (i.e., swimming) with a motor that is powered by the sodium motive force . Multiple proton-driven lateral flagella enable translocation over surfaces (i.e., swarming) . The polar flagellum is produced continuously, while production of lateral flagella is induced when the organism is grown on surfaces . This work describes the isolation of mutants with insertions in the structural and regulatory laf genes . A Tn5-based lux transcriptional reporter transposon was constructed and used for mutagenesis and subsequent transcriptional analysis of the laf regulon . Twenty-nine independent insertions were distributed within 16 laf genes . DNA sequence analysis identified 38 laf genes in two loci . Among the mutants isolated, 11 contained surface-induced lux fusions . A hierarchy of laf gene expression was established following characterization of the laf::lux transcriptional fusion strains and by mutational and primer extension analyses of the laf regulon . The laf system is like many enteric systems in that it is a proton-driven, peritrichous flagellar system; however, laf regulation was different from the Salmonella-Escherichia coli paradigm . There is no apparent flhDC counterpart that encodes master regulators known to control flagellar biosynthesis and swarming in many enteric bacteria . A potential  54-dependent regulator, LafK, was demonstrated to control expression of early genes, and a lateral-specific
28 factor controls late flagellar gene expression . Another notable feature was the discovery of a gene encoding a MotY-like product, which previously had been associated only with the architecture of sodium-type polar flagellar motors .
Survival and Growth of Francisella tularensis in Acanthamoeba castellanii. Hadi Abd, 2003.Francisella tularensis is a highly infectious, facultative intracellular bacterium which causes epidemics of tularemia in both humans and mammals at regular intervals . The natural reservoir of the bacterium is largely unknown, although it has been speculated that protozoa may harbor it . To test this hypothesis, Acanthamoeba castellanii was cocultured with a strain of F . tularensis engineered to produce green fluorescent protein (GFP) in a nutrient-rich medium . GFP fluorescence within A . castellanii was then monitored by flow cytometry and fluorescence microscopy . In addition, extracellular bacteria were distinguished from intracellular bacteria by targeting with monoclonal antibodies . Electron microscopy was used to determine the intracellular location of F . tularensis in A . castellanii, and viable counts were obtained for both extracellular and intracellular bacteria . The results showed that many F . tularensis cells were located intracellularly in A . castellanii cells . The bacteria multiplied within intracellular vacuoles and eventually killed many of the host cells . F . tularensis was found in intact trophozoites, excreted vesicles, and cysts . Furthermore, F . tularensis grew faster in cocultures with A . castellanii than it did when grown alone in the same medium . This increase in growth was accompanied by a decrease in the number of A . castellanii cells . The interaction between F . tularensis and amoebae demonstrated in this study indicates that ubiquitous protozoa might be an important environmental reservoir for F . tularensis .
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