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Enzymatic Detachment of Staphylococcus epidermidis Biofilms. Jeffrey B. Kaplan, 2004.The gram-positive bacterium Staphylococcus epidermidis is the most common cause of infections associated with catheters and other indwelling medical devices . S . epidermidis produces an extracellular slime that enables it to form adherent biofilms on plastic surfaces . We found that a biofilm-releasing enzyme produced by the gram-negative periodontal pathogen Actinobacillus actinomycetemcomitans rapidly and efficiently removed S . epidermidis biofilms from plastic surfaces . The enzyme worked by releasing extracellular slime from S . epidermidis cells . Precoating surfaces with the enzyme prevented S . epidermidis biofilm formation . Our findings demonstrate that biofilm-releasing enzymes can exhibit broad-spectrum activity and that these enzymes may be useful as antibiofilm agents . Syntrophic-Methanogenic Associations along a Nutrient Gradient in the Florida Everglades. Ashvini Chauhan, 2004.Nutrient runoff from the Everglades Agricultural Area resulted in a well-documented gradient of phosphorus concentrations in soil and water, with concomitant ecosystem-level changes, in the northern Florida Everglades . It was recently reported that sulfate-reducing prokaryote assemblage composition, numbers, and activities are dependent on position along the gradient (H . Castro, K . R . Reddy, and A . Ogram, Appl . Environ . Microbiol . 68:6129-6137, 2002) . The present study utilized a combination of culture- and non-culture-based approaches to study differences in composition of assemblages of syntrophic and methanogenic microbial communities in eutrophic, transition, and oligotrophic areas along the phosphorus gradient . Methanogenesis rates were much higher in eutrophic and transition regions, and sequence analysis of 16S rRNA gene clone libraries constructed from samples taken from these regions revealed differences in composition and activities of syntroph-methanogen consortia . Methanogens from eutrophic and transition regions were almost exclusively composed of hydrogenotrophic methanogens, with approximately 10,000-fold-greater most probable numbers of hydrogenotrophs than of acetotrophs . Most cultivable strains from eutrophic and transition regions clustered within novel lineages . In non-culture-based studies to enrich syntrophs, most bacterial and archaeal clones were either members of novel lineages or closely related to uncultivated environmental clones . Novel cultivable Methanosaeta sp . and fatty acid-oxidizing bacteria related to the genera Syntrophomonas and Syntrophobacter were observed in microcosms containing soil from eutrophic regions, and different lines of evidence indicated the existence of novel syntrophic association in eutrophic regions . ArgR-Independent Induction and ArgR-Dependent Superinduction of the astCADBE Operon in Escherichia coli. Alexandros K. Kiupakis, 2002.For Escherichia coli, growth in the absence of ammonia is termed nitrogen limited and results in the induction of genes that assimilate other nitrogen sources, a response mediated by  54 and nitrogen regulator I (NRI, also called NtrC) . The astCADBE operon, which is required for growth with arginine as the sole nitrogen source, is moderately expressed during general nitrogen limitation and maximally expressed in the presence of arginine . The operon is also induced in stationary phase . Primer extension analysis of E . coli revealed the presence of a
54-dependent promoter utilized in exponential phase during nitrogen limitation and a
S-dependent promoter active during stationary phase . We used an ast-lacZ fusion to show that arginine stimulates expression, that ArgR, the arginine repressor, enhances expression from both promoters but is not essential, and that transcription by the two forms of the RNA polymerase is competitive and mutually exclusive . We demonstrated the binding of RNA polymerase holoenzymes, NRI, and ArgR to the promoter region in vitro . We also reconstituted transcription from both promoters with purified components, which confirmed the accessory role of ArgR for the
54-dependent promoter . Thus, the ast operon exhibits nitrogen source-specific induction that is unique for an NRI-dependent gene . The transcriptional regulation of the ast operon in E . coli differs from that in Salmonella enterica serovar Typhimurium, in which ArgR is required for ast operon expression .
Internal and External Mycoflora of the American Dog Tick, Dermacentor variabilis (Acari: Ixodidae), and Its Ecological Implications. Jay A. Yoder, 2003.Scopulariopsis brevicaulis, the anamorph of Microascus brevicaulis (Microascaceae, Ascomycota), has been identified in the body contents of the tick Dermacentor variabilis . After topical application of the fungal inoculum, tick mortality was marked . This is the first account describing the internal mycoflora of D . variabilis with a novel technique used to recover potential biological control agents .
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