|
|
|
|
|
|
DNA Binding by the Meningococcal RdgC Protein, Associated with Pilin Antigenic Variation. Timothy Moore, 2004.The RdgC protein of Neisseria gonorrhoeae is required for efficient pilin antigenic variation, although its precise role has yet to be established . We demonstrate that the nearly identical RdgC from Neisseria meningitidis binds DNA with little specificity for sequence or structure, like the Escherichia coli protein . We also show that neither protein is able to constrain torsional tension in relaxed DNA . These data exclude several possible roles for RdgC in pilin antigenic variation and suggest that RdgC performs a similar function in both E . coli and the Neisseria spp . The Trypanocide Diminazene Aceturate Is Accumulated Predominantly through the TbAT1 Purine Transporter: Additional Insights on Diamidine Resistance in African Trypanosomes. Harry P. de Koning, 2004.Resistance to diminazene aceturate (Berenil) is a severe problem in the control of African trypanosomiasis in domestic animals . It has been speculated that resistance may be the result of reduced diminazene uptake by the parasite . We describe here the mechanisms by which [3H]diminazene is transported by Trypanosoma brucei brucei bloodstream forms . Diminazene was rapidly accumulated through a single transporter, with a Km of 0.45 ± 0.11 µM, which was dose dependently inhibited by pentamidine and adenosine . The Ki values for these inhibitors were consistent with this transporter being the P2/TbAT1 adenosine transporter . Yeast expressing TbAT1 acquired the ability to take up [3H]diminazene and [3H]pentamidine . TbAT1-null mutants had lost almost all capacity for [3H]diminazene transport . However, this cell line still displayed a small but detectable rate of [3H]diminazene accumulation, in a nonsaturable manner . We conclude that TbAT1 mediates [3H]diminazene transport almost exclusively and that this explains the observed diminazene resistance phenotypes of TbAT1-null mutants and field isolates . Novel Cassette-Based Shuttle Vector System for Gram-Positive Bacteria. Emmanuelle Charpentier, 2004.Our understanding of staphylococcal pathogenesis depends on reliable genetic tools for gene expression analysis and tracing of bacteria . Here, we have developed and evaluated a series of novel versatile Escherichia coli-staphylococcal shuttle vectors based on PCR-generated interchangeable cassettes . Advantages of our module system include the use of (i) staphylococcal low-copy-number, high-copy-number, thermosensitive and theta replicons and selectable markers (choice of erythromycin, tetracycline, chloramphenicol, kanamycin, or spectinomycin); (ii) an E . coli replicon and selectable marker (ampicillin); and (iii) a staphylococcal phage fragment that allows high-frequency transduction and an SaPI fragment that allows site-specific integration into the Staphylococcus aureus chromosome . The staphylococcal cadmium-inducible Pcad-cadC and constitutive PblaZ promoters were designed and analyzed in transcriptional fusions to the staphylococcal ß-lactamase blaZ, the Vibrio fischeri luxAB, and the Aequorea victoria green fluorescent protein reporter genes . The modular design of the vector system provides great flexibility and variety . Questions about gene dosage, complementation, and cis-trans effects can now be conveniently addressed, so that this system constitutes an effective tool for studying gene regulation of staphylococci in various ecosystems . Nisin-Producing Lactococcus lactis Strains Isolated from Human Milk. Shea S. Beasley, 2004. Effects of Litter Addition on Ectomycorrhizal Associates of a Lodgepole Pine (Pinus contorta) Stand in Yellowstone National Park. Kenneth W. Cullings, 2003.Increasing soil nutrients through litter manipulation, pollution, or fertilization can adversely affect ectomycorrhizal (EM) communities by inhibiting fungal growth . In this study, we used molecular genetic methods to determine the effects of litter addition on the EM community of a Pinus contorta stand in Yellowstone National Park that regenerated after a stand-replacing fire . Two controls were used; in unmodified control plots nothing was added to the soil, and in perlite plots perlite, a chemically neutral substance, was added to maintain soil moisture and temperature at levels similar to those under litter . We found that (i) species richness did not change significantly following perlite addition (2.6 ± 0.3 species/core in control plots, compared with 2.3 ± 0.3 species/core in perlite plots) but decreased significantly (P < 0.05) following litter addition (1.8 ± 0.3 species/core); (ii) EM infection was not affected by the addition of perlite but increased significantly (P < 0.001) in response to litter addition, and the increase occurred only in the upper soil layer, directly adjacent to the added litter; and (iii) Suillus granulatus, Wilcoxina mikolae, and agaricoid DD were the dominant organisms in controls, but the levels of W . mikolae and agaricoid DD decreased significantly in response to both perlite and litter addition . The relative levels of S . granulatus and a fourth fungus, Cortinariaceae species 2, increased significantly (P < 0.01 and P < 0.05, respectively) following litter addition . Thus, litter addition resulted in some negative effects that may be attributable to moisture-temperature relationships rather than to the increased nutrients associated with litter . Some species respond positively to litter addition, indicating that there are differences in their physiologies . Hence, changes in the EM community induced by litter accumulation also may affect ecosystem function . Diversity and Structure of Bacterial Communities in Arctic versus Antarctic Pack Ice. Robin Brinkmeyer, 2003.A comprehensive assessment of bacterial diversity and community composition in arctic and antarctic pack ice was conducted through cultivation and cultivation-independent molecular techniques . We sequenced 16S rRNA genes from 115 and 87 pure cultures of bacteria isolated from arctic and antarctic pack ice, respectively . Most of the 33 arctic phylotypes were >97% identical to previously described antarctic species or to our own antarctic isolates . At both poles, the  - and
 -proteobacteria and the
Cytophaga-Flavobacterium group were the dominant
taxonomic bacterial groups identified by cultivation as well as by
molecular methods . The analysis of 16S rRNA gene clone libraries from
multiple arctic and antarctic pack ice samples revealed a high
incidence of closely overlapping 16S rRNA gene clone and isolate
sequences . Simultaneous analysis of environmental samples with
fluorescence in situ hybridization (FISH) showed that
 95% of 4',6'-diamidino-2-phenylindole
(DAPI)-stained cells hybridized with the general bacterial probe
EUB338 . More than 90% of those were further assignable.
Approximately 50 and 36% were identified as
-proteobacteria in arctic and antarctic samples,respectively . Approximately 25% were identified as
-proteobacteria, and 25% were identified as belonging
to the Cytophaga-Flavobacterium group . For the
quantification of specific members of the sea ice community, new
oligonucleotide probes were developed which target the genera
Octadecabacter, Glaciecola, Psychrobacter,
Marinobacter, Shewanella, and Polaribacter.
High FISH detection rates of these groups as well as high viable counts
corroborated the overlap of clone and isolate sequences . A terrestrial
influence on the arctic pack ice community was suggested by the
presence of limnic
phylotypes .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
