|
|
|
|
|
|
Development of Surface Adhesion in Caulobacter crescentus. Diane Bodenmiller, 2004.Caulobacter crescentus has a dimorphic life cycle composed of a motile stage and a sessile stage . In the sessile stage, C. crescentus is often found tightly attached to a surface through its adhesive holdfast . In this study, we examined the contributionof growth and external structures to the attachment of C . crescentus to abiotic surfaces . We show that the holdfast is essentialbut not sufficient for optimal attachment . Rather, adhesionin C . crescentus is a complex developmental process . We foundthat the attachment of C . crescentus to surfaces is cell cycle regulated and that growth or energy or both are essential forthis process . The initial stage of attachment occurs in swarmercells and is facilitated by flagellar motility and pili . Ourresults suggest that strong attachment is mediated by the synthesisof a holdfast as the swarmer cell differentiates into a stalkedcell. Pilot Randomized Double-Blind Trial of Treatment of Mycobacterium ulcerans Disease (Buruli Ulcer) with Topical Nitrogen Oxides. R. Phillips, 2004.Mycobacterium ulcerans disease (Buruli ulcer) is a serious ulcerating skin disease which is common in many tropical countries . Standard treatment, by extensive excision and skin grafting, is not available in rural communities where the disease is common . We evaluated the efficacy and safety of treatment with topical nitrogen oxides . Thirty-seven patients with a clinical diagnosis of Buruli ulcer caused by M . ulcerans disease were randomly assigned to one of two groups . In one group, two creams containing sodium nitrite (6%, wt/wt) or citric acid monohydrate (9%, wt/wt) were applied daily for 6 weeks, while the other group received a placebo . In the second 6 weeks, both groups received the nitrogen oxide-generating combination of creams . Treatment was continued for another 4 weeks for patients whose ulcers were not healed after 12 weeks . The ulcer surface area was monitored by weekly tracings made by assessors blinded to the treatment . In the first 6 weeks, patients on sodium nitrite and citric acid monohydrate (group I, active treatment) showed a rapid decrease in ulcer size from 28.6 ± 5.6 cm2 (mean ± standard error) to 12.6 ± 3.2 cm2, a decrease significantly greater than that in group II (from 15.3 ± 3.1 to 11.7 ± 3.7 cm2; P = 0.03) . Five ulcers in the placebo group enlarged during this period, compared with one in the active group . In the second 6 weeks (both groups on active treatment), the rates of healing were similar for the two groups and there was a significant reduction in ulcer size in group II (previously on placebo) compared to the first 6 weeks . Yellow pigmentation of the skin, which disappeared 3 days after treatment was stopped, was the only side effect to date . We conclude that creams releasing nitrogen oxides increase the healing rate of ulcers caused by M . ulcerans infection with minimal adverse events . This is the first controlled trial of any form of therapy which demonstrates efficacy in treating this disease . Diverse Tetracycline Resistance Genotypes of Megasphaera elsdenii Strains Selectively Cultured from Swine Feces. Thaddeus B. Stanton, 2004.A total of 30 Megasphaera elsdenii strains, selectively isolated from the feces of organically raised swine by using Me109 M medium, and one bovine strain were analyzed for tetracycline resistance genotypic and phenotypic traits . Tetracycline-resistant strains carried tet(O), tet(W), or a tet gene mosaic of tet(O) and tet(W) . M . elsdenii strains carrying tet(OWO) genes exhibited the highest tetracycline MICs (128 to >256 µg/ml), suggesting that tet(O)-tet(W) mosaic genes provide the selective advantage of greater tetracycline resistance for this species . Seven tet genotypes are now known for M . elsdenii, an archetype commensal anaerobe and model for tet gene evolution in the mammalian intestinal tract . Nucleotide Sequence of the Integration Site of the Temperate Bacteriophage 6220, Which Carries the Shiga Toxin Gene stx1ox3. Claudia Koch, 2003.The integration site, attR, of the Shiga toxin-encoding phage 6220 (stx1ox3) has been determined . The phage integrates into the chromosome of its Escherichia coli host strain, CB6220, within a gene that is homologous to gene Z2577 and encodes an oxidoreductase . This new integration site was found in different Stx1ox3-producing enterohemorrhagic E . coli strains, which were analyzed by PCR . Temperature Sensitivity Caused by Mutant Release Factor 1 Is Suppressed by Mutations That Affect 16S rRNA Maturation. Magdalena Kaczanowska, 2004.To study the effect of slow termination on the protein synthesizing machinery, we isolated suppressors to a temperature-sensitive release factor 1 (RF1) . Of 26 independent clones, five complementation groups have been identified, two of which are presented here . The first mutation disrupts a base pair in the transcription terminator stem for the rplM-rpsI operon, which encodes ribosomal proteins L13 and S9 . We have found that this leads to readthrough of the terminator and that lower levels of transcript (compared to the results seen with the wild type) are found in the cell . This probably leads to decreased expression of the two proteins . The second mutation is a small deletion of the yrdC open reading frame start site, and it is not likely that the protein is expressed . Both mutant strains show an increased accumulation of 17S rRNA (immature 16S rRNA) . Maturation of 16S rRNA is dependent on proper assembly of the ribosomal proteins, a process that is disturbed when proteins are missing . The function of the YrdC protein is not known, but it is able to bind to double-stranded RNA; therefore, we suggest that it is an assembly factor important for 30S subunit biogenesis . On the basis of our findings, we propose that lesser amounts of S9 or a lack of YrdC causes the maturation defect . We have shown that as a consequence of the maturation defect, fewer 70S ribosomes and polysomes are formed . This and other results suggest that it is the lowered concentration of functional ribosomes that suppresses the temperature sensitivity caused by the mutant RF1 . Nitrilotriacetate Stimulation of Anaerobic Fe(III) Respiration by Mobilization of Humic Materials in Soil. Y. Luu, 2003.An enrichment culture capable of naphthalene mineralization reduced Fe(III) oxides without direct contact in anaerobic soil microcosms when the Fe(III) was placed in dialysis membranes or entrapped within alginate beads . Both techniques demonstrated that a component in soil, possibly humic materials, facilitated Fe(III) reduction when direct contact between cells and Fe(III) was not possible . The addition of the synthetic Fe(III) chelator, nitrilotriacetic acid (NTA), to soil enhanced Fe(III) reduction across the dialysis membrane and alginate beads, with the medium changing from clear to a dark brown color . An NTA-soil extract was more effective in Fe(III) reduction than the extracted soil itself . Characteristics of the NTA extract were consistent with that of humic substances . The results indicate that NTA improved Fe(III) reduction not by Fe(III) solubilization but by extraction of humic substances from soil into the aqueous medium . This is the first study in which stimulation of Fe(III) reduction through the addition of chemical chelators is shown to be due to the extraction of electron-shuttling compounds from the soil and not to solubilization of the Fe(III) and indicates that mobilization of humic materials could be an important component of anaerobic biostimulation .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
