Projects / Programmes
Molekularno-biološke raziskave mikroorganizmov (Slovene)
January 1, 1999
- December 31, 2003
| Code |
Science |
Field |
Subfield |
| 1.05.00 |
Natural sciences and mathematics |
Biochemistry and molecular biology |
|
| 3.01.00 |
Medical sciences |
Microbiology and immunology |
|
| Code |
Science |
Field |
| B220 |
Biomedical sciences |
Genetics, cytogenetics |
| B230 |
Biomedical sciences |
Microbiology, bacteriology, virology, mycology |
| P320 |
Natural sciences and mathematics |
Nucleic acids, protein synthesis |
| P340 |
Natural sciences and mathematics |
Lipids, steroids, membranes |
Researchers (15)
Organisations (1)
Abstract
Plasmids of the IncFI incompatibility group are large conjugative plasmids which frequently encode antibiotic resistances and virulence determinants important in pathogenesis. It has been presumed that their host range is narrow.
80 isolates belonging to eight bacterial species of the family Enterobacteriacea were analyzed for plasmid content. For this purpose DNA of all isolates was isolated and examined with agarose gel electrophoresis. Further, PCR with primers specific for the three IncFI replication regions (RepFIA, RepFIB and RepFC), as well as the traJ gene encoding the central positive regulator of conjugation, was performed on whole cell lysates. Nucleotide sequences corresponding to the RepFIA and RepFIB regions were determined in 16 and 29%, respectively, while the RepFIC replicon was found in only one strain. RepFIA sequences were determined in 35 % of the examined animal strains. All five examined Klebsiella isolates and all three Erwinia isolates harbored RepFIA sequences. On the other hand, in the human isolates, sequences characteristic of IncFI plasmids were found only in E. coli.
Further, RepFIB sequences were determined only in E. coli strains. On the basis of our results we conclude that of the three IncFI replicons, RepFIA has the widest host range. Our results also corroborate the significance of plasmid replication for host range.
The high percentage of strains with IncFI plasmids also indicates that they successfully avoid mechanisms which prevent maintenance of horizontally transferred DNA, for example restriction-modification systems.
Clostridium difficile is an important pathogen causing intestinal infections. The main virulence factors are two large toxins, toxin A (TcdA) and toxin B (TcdB). Recently, a group of strains was described, where only TcdB is detected. TcdA can not be detected with commercial immunological kits, but the gene tcdA is present. As such A-B+ strains can still cause disease the question arrose, whether they are real nonproducers or immunologicaly changed TcdA is produced. We have characterised representative A-B+ strains and showed that the immunodominant part of the toxin A, when expressed in E. coli, can be detected with specific antibodies. However, a nonsense mutation was found at the beginning of the tcdA gene, which explains the lack of TcdA production.
The bacitracin resistance of Bacillus licheniformis, a producer of bacitracin, is mediated by an ABC transporter Bcr. B. subtilis cells carrying bcr genes on high-copy number plasmids developed collateral detergent sensitivity, as did human cells with overexpressed multidrug resistance P-glycoprotein. Resistance against bacitracin and sensitivity of resistant cells to detergents were shown to be unseparable phenomena associated with the membrane part of the Bcr transporter, namely protein BcrC. A fused protein, consisting of the ATP-binding protein BcrA and membrane component BcrC was contructed. It resembled a half molecule of P-glycoprotein and was capable of providing a significant degree of antibiotic resistance and detergent sensitivity (Podlesek et al. 2000. The role of the bacitracin ABC transporter in bacitracin resistance and collateral detergent sensitivity. FEMS Microbiol. Lett., 188:103-106.)
Most important scientific results
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Most important socioeconomically and culturally relevant results
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