|
|
|
|
|
|
Dynamics of Fruiting Body Morphogenesis. Dale Kaiser, 2004.Myxobacteria build their species-specific fruiting bodies bycell movement and then differentiate spores in specific placeswithin that multicellular structure . New steps in the developmentalaggregation of Myxococcus xanthus were discovered through aframe-by-frame analysis of a motion picture . The formation andfate of 18 aggregates were captured in the time-lapse movie.Still photographs of 600 other aggregates were also analyzed.M . xanthus has two engines that propel the gliding of its rod-shapedcells: slime-secreting jets at the rear and retractile piliat the front . The earliest aggregates are stationary massesof cells that look like three-dimensional traffic jams . We proposea model in which both engines stall as the cells' forward progressis blocked by other cells in the traffic jam . We also proposethat these blockades are eventually circumvented by the cell'scapacity to turn, which is facilitated by the push of slimesecretion at the rear of each cell and by the flexibility of the myxobacterial cell wall . Turning by many cells would transform a traffic jam into an elliptical mound, in which the cells are streaming in closed orbits . Pairs of adjacent mounds are observedto coalesce into single larger mounds, probably reflecting thefusion of orbits in the adjacent mounds . Although fruiting bodiesare relatively large structures that contain 105 cells, no long-range interactions between cells were evident . For aggregation, M. xanthus appears to use local interactions between its cells. Antistaphylococcal Activity of CB-181963 (CAB-175), an Experimental Parenteral Cephalosporin. Dianne B. Hoellman, 2004.Among 265 methicillin-susceptible and -resistant staphylococci, CB-181963 (CAB-175) had a 50% minimum inhibitory concentration of 2 µg/ml and a 90% minimum inhibitory concentration of 4 µg/ml . All strains except two vancomycin-resistant S . aureus and 5 vancomycin-intermediate S . aureus strains were also susceptible to vancomycin and teicoplanin, and all were susceptible to linezolid, ranbezolid, tigecycline, and quinupristin-dalfopristin . Most methicillin-resistant strains were levofloxacin resistant . CB-181963 was bactericidal against all six methicillin-resistant strains at four times the MIC after 24 h . Arthrobacter aurescens TC1 Atrazine Catabolism Genes trzN, atzB, and atzC Are Linked on a 160-Kilobase Region and Are Functional in Escherichia coli. Kannika Sajjaphan, 2004. Group I Self-Splicing Intron in the recA Gene of Bacillus anthracis. Minsu Ko, 2002.Self-splicing introns are rarely found in bacteria and bacteriophages . They are classified into group I and II according to their structural features and splicing mechanisms . While the group I introns are occasionally found in protein-coding regions of phage genomes and in several tRNA genes of cyanobacteria and proteobacteria, they had not been found in protein-coding regions of bacterial genomes . Here we report a group I intron in the recA gene of Bacillus anthracis which was initially found by DNA sequencing as an intervening sequence (IVS) . By using reverse transcriptase PCR, the IVS was shown to be removable from the recA precursor mRNA for RecA that was being translated in E . coli . The splicing was visualized in vitro with labeled free GTP, indicating that it is a group I intron, which is also implied by its predicted secondary structure . The RecA protein of B . anthracis expressed in E . coli was functional in its ability to complement a recA defect . When recA-negative E . coli cells were irradiated with UV, the Bacillus RecA reduced the UV susceptibility of the recA mutant, regardless of the presence of intron . Low-Temperature-Induced Changes in Composition and Fluidity of Lipopolysaccharides in the Antarctic Psychrotrophic Bacterium Pseudomonas syringae. G. Seshu Kumar, 2002.The Antarctic psychrotrophic bacterium Pseudomonas syringae was more sensitive to polymyxin B at a lower (4°C) temperature of growth than at a higher (22°C) temperature . The amount of hydroxy fatty acids in the lipopolysaccharides (LPS) also increased at the lower temperature . These changes correlated with the increase in fluidity of the hydrophobic phase of lipopolysaccharide aggregates in vitro . Aerobic Denitrifying Bacteria That Produce Low Levels of Nitrous Oxide. Naoki Takaya, 2003.Most denitrifiers produce nitrous oxide (N2O) instead of dinitrogen (N2) under aerobic conditions . We isolated and characterized novel aerobic denitrifiers that produce low levels of N2O under aerobic conditions . We monitored the denitrification activities of two of the isolates, strains TR2 and K50, in batch and continuous cultures . Both strains reduced nitrate (NO3-) to N2 at rates of 0.9 and 0.03 µmol min-1 unit of optical density at 540 nm-1 at dissolved oxygen (O2) (DO) concentrations of 39 and 38 µmol liter-1, respectively . At the same DO level, the typical denitrifier Pseudomonas stutzeri and the previously described aerobic denitrifier Paracoccus denitrificans did not produce N2 but evolved more than 10-fold more N2O than strains TR2 and K50 evolved . The isolates denitrified NO3- with concomitant consumption of O2 . These results indicated that strains TR2 and K50 are aerobic denitrifiers . These two isolates were taxonomically placed in the ß subclass of the class Proteobacteria and were identified as P . stutzeri TR2 and Pseudomonas sp . strain K50 . These strains should be useful for future investigations of the mechanisms of denitrifying bacteria that regulate N2O emission, the single-stage process for nitrogen removal, and microbial N2O emission into the ecosystem .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
