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DNA hybridization experiments demonstrated that the gene clusters encoding the F8 fimbriae (fei) as well as the type I fimbriae (pi/) exist in a single copy on the chromosome of E. coli 018:K5 strain 2980. In conjugation experiments with appropriate donors, the chromosomal site of these gene clusters was determined. The pil genes were mapped close to the gene clusters thr and Jeu controlling the biosynthesis of threonine and leucine, respectively. The fei genes were found to be located close to the galactose operon (gal) between the position 17 and 21 of the E. coli chromosomallinkage map.
Ten Legionella pneumophUa strains isolated from dift'erent sources were analyzed according to their restriction fragment patterils obtained by cle~vage of gen.omic DNA With Notl and Sftl and separation by pulsed field electrophoresis. Three L. pneumophila isolate~ from a nosocomial outbreak in Lü~k (Germany) and three other L. prreumophilll stralns independently isolated from a water tap located in the care unit where tbe patients were bospitalized 'xhibited identical restricti9n fragment profiles. Therefore, we concluded that these environment81 spee~ens were the source of the Legionnatres dlsease. Anotber two isolates from patients and two strains from the environment, all unrelated to the outJlreak described, sbowed different cleavage patterns.
Legionella pneumophila, the causative agent of Legionnaires' disease is able to live and multiply within macrophages as weil as within protozoan organisms. Legionella strains inhibit phagosome-lysosome fusion and phagosome acidification. By using two different cell culture systems, one derived from human macrophages and the other from human.embryo lung fibro:blastic cells, it is demonstrated that Legionella strains lose their virulence following cultivation in the laboratory. In order to study the mechanisms involved in intracellular survival of Legionella a genomic library of strain Legionella pneumophila Philadelphia I was established in Escherichia coli K-12. By cosmid cloning technique we were able to clone five putative virulence factors, two of which exhibit hemolytic activities and three of which represent membrane-associated proteins of 19, 26 and 60 kilodalton. One of the hemolytic proteins, termed legiolysin, represents a new toxin which specifically lyses human erythrocytes. The other hemolysin exhibits proteolytic properties in addition and is cytolytic for Vero and CHO cells. Further sturlies will be necessary to determine the exact role of the cloned proteins in the pathogenesis of Legionella. Zusammenfassung: Intrazelluläres Überleben
The uropathogenic Escherichia coli wiJd..:type strain 536 produces S-fimbriae, P-related fimbriae and type I fimbriae. Using immuno-colony dot and ELISA techniques, variants were detected showing an increased degree of S-fimbrial production. It was demonstrated by itrtmunofluorescence microscopy that in noimal (wild-type) and hyperS- fimbriated E. coli populaiions non-fimbriated cells also · exist, and that the percentage of Sfinibrlated and non-fimbriated bacteria was roughly identica1 in either population. Hyper-Sfimbriated variants could be stably maintained. The transition from wild-type to hyper-S-fimbriation, which occurs spontaneously, is markedly higher than vice versa. Southern blot analysis of the S fimbrial adhesin (sfa) determinants of normal and hyper-fimbriated strains revealed no marked difference in the gene structure.
A total of 16 Escherichia coli 06 strains isolated from cases of extraintestinal infections were analysed for the genetic presence and phenotypic expression of fimbrial adhesins ( P, S/FIC, type I), aerobactin and hemolysin. ln addition restriction fragment length polymorphisms (RFLPs) of Xbal-cleaved genomic DNA of seven selected strains, separated by orthogonal field alternation gel electrophoresis {OFAGE) were determined and virulence-associated DNA probes were used for Southern hybridization studies of the Xbal-cleaved genomic DNAs. The virulence characteristics and hybridization patterns obtained differed between the various isolates. ln three isolates hemolysin genes and P fimbrial determinants were located on the same Xbal fragments. Furthermore, multiple copies of FIC determinants (foc) could be detected in two strains. Our data show that the new technique of pulse field electrophoresis tagether with Southern hybridization represents a powerful tool for the genetic analysis of pathogenic bacteria.
S fimbrial adhesins (Sfa) enable pathogenic Escherichia coli strains to bind to sialic acid-containing eucaryotic receptor molecules. In order to determine the inftuence of culture conditions on the expression of the sfa determinant in a wild-type strain, we fused the gene lacZ, coding for the enzyme ß-galactosidase, to the sfaA gene, responsible for the major protein subunit of S fimbriae. By using a plasmid which carries an R6K origin, the sfaA-Iac hybrid construct was site-specifically integrated into the chromosome of the uropathogenic E. coli strain S36WT. The expression of lacZ, which was under the control of the sfa wild-type promoters, was now equivalent to the sfa expression of strain S36WT. With the help of this particular wild-type construct, it was demonstrated that the sfa determinant is better expressed on solid media than in liquid broth. The growth rate bad a strong inftuence on Sfa expression under aerobic but not under anaerobic conditions. Production of Sfa was further regulated by catabolite repression, osmolarity, and temperature.
Genome analysis of Legionella spp. by orthogonal field alternation gel electrophoresis (OFAGE)
(1990)
Various Legionella isolates from different sources and origins were analysed by orthogonal field alternation gel electrophoresis of Not I cleaved genomic DNA. The genome of L pneumophila Philadelphia I, the original isolate of the epidemics in 1976, exhibits only five Not I fragments. Two virulent derivatives. derived from L pneumophila Philadelphia I. which were obtained by prolonged passage on artificial cuhure media, did not differ from their isogenic virulent strain according the Not I fragment pattern. By summing the lengths of the Notl fragments, the genome size of L. pneumophila Philadelphia I was calculated as approximately 3.9 Mb. Environmental L pneumophila strains exhibited different Not I pattems, as did Legionella strains not belongi'ng to the species pneumophila. The usefulness of DNA long range mapping of Legionella ssp. with Notl for epidemiology and evaluation of their evolutionary rela· tionships is discussed.
The S fimbrial adhesin (sfa) determinant of E. co/i comprises nine genes situated on a stretch of 7.9 kilobases (kb) DNA. Here the nucleotide sequence of the genes sfa B and sfaC situated proximal to the main structural gene sfaA is described. Sfa-LacZ fusions show that the two genes are transcribed in opposite directions. The isolation of mutants in the proximal region of the sfa gene cluster, the construction of sfa-phoA gene fusions and subsequent transcomplementation sturlies indicated that the genes sfaB and sfaC play a role in regulation of the sfa determinant. ln addition the nucleotide sequence of the genes sfa D, sfa E and sfa F situated between the genes sfaA and sfaG responsible for S subunit proteins, were determined. lt is suggested that these genes are involved in transport and assembly of fimbrial subunits. Thus the entire genetic organization of the sfa determinant is presented and compared with the gene clusters coding for P fimbriae (pap), F1 C fimbriae (foc) and type I fimbriae ( fim). The evolutionary relationship of fimbrial adhesin determinants is discussed.
The genetic determinant coding for the Pspecific F8 fimbriae was cloned from · the chromosome of the Escherichia coli wild-type strain 2980 (018: K5: H5: FlC, F8). The F8 determinant was further subcloned into the Pstl site of pBR322 and a restriction map was established. In a Southern hybridization experiment identity between the chromosomally encoded F8 determinant of 2980 and its cloned Counterpart was demonstrated. The cloned F8 fimbriäe and those of the wild type strain consist of a protein subunit of nearly 20 kDa. F8 fimbriated strains were agglutinated by an F8 polyclonal antiserum, caused mannose-resistant hemagglutination and attached to human uroepi thellal cells. The cloned F8 determinant was weil expressed in a variety of host strains.