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Uropathogenic Escherichia coli 536 (06:K15:H31) carries two unstable DNA regions, which were shown to be responsible for virulence. These regions, on which the genes for hemolysin production (hly) and P-related fimbriae (prj) are located, are termed pathogenicity islands (PAI) I and II, and were mapped to positions 82 and 97, respectively, on the E. coli K-12 linkage map. Sequence analysis of the PAI region junction sites revealed sequences of the leuX and selC loci specific for leucine and selenocysteine tRNAs. The tRNA loci function as the targets for excision events. Northern (RNA) blot analysis revealed that the sites of excision are transcriptionally active in the wild-type strain and that no tRNA-specific transcripts were found in the deletion mutant. The analysis of deletion mutants revealed that the excision of these regions is specific and involves direct repeats of 16 and 18 nucleotides, respectively, on both sides of the deletions. By using DNA long-range mapping techniques, the size of PAI I, located at position 82, was calculated to be 70 kb, while PA II, mapped at position 97, comprises 190 kb. The excision events described here reflect the dynamics of the E. cohi chromosome.

Fimbrial adhesins enable bacteria to attach to eucaryotic cells. The genetic determinants for S fimbrial adhesins (sfa) and for FlC ("pseudotype I") fimbriae (foc) were compared. Sfa and FlC represent functionally distinct adhesins in their receptor specificities. Nevertheless, a high degree of homology between both determinants was found on the basis of DNA-DNA hybridizations. Characteristic differences in the restriction maps of the corresponding gene clusters, however, were visible in regions coding for the fimbrial subunits and for the S-specific adhesin. While a plasmid carrying the genetic determinant for FlC fimbriae was able to complement transposon-induced sfa mutants, a plasmid carrying the genetic determinant for a third adhesin type, termed P fimbriae, was unable to do so. Proximal sfa-specific sequences carrying the S fimbrial structural gene were fused to sequences representing the distal part of thefoc gene cluster to form a hybrid cluster, and the foc proximal region coding for the structural protein was ligated to sfa distal sequences to form a second hybrid. Both hybrid clones produced intact fimbriae. Anti-FlC monoclonal antibodies (MAbs) only recognized clones which produced FlC fimbriae, and an anti-S adhesin MAb marked clones which expressed the S adhesin. However, one of four other anti-S fimbriae-speciflic MAbs reacted with both fimbrial structures, S and F1C, indicating a common epitope on both antigens. The results presented here support the view that sfa and foc determinants code for fimbriae that are similar in several aspects, while the P fimbriae are members of a more distantly related group.Fimbriae or pili are bacterial cell wall appendages which consist of about 1,000 identical protein subunits. A single fimbria is 7 nm in diameter and up to 1 ,um in length (9, 17). Very often fimbriae are associated with adhesins which enable the bacteria to attach to eucaryotic cells, including erythrocytes (RBC) (28, 31). Adherence of bacteria to eucaryotic cells is a prerequisite for many infectious diseases (27,30,41).Extraintestinal Escherichia coli isolates cause infections of the urinary tract and the blood (sepsis) and are also the causative agents of newborn meningitis (32). Such E. coli isolates may carry different types of fimbrial adhesins. P fimbriae recognize an ot-D-galactosyl-(1-4)-f3-D-galactose receptor. They are strongly associated with uropathogenic E. coli strains and can be further subdivided into nine serologically distinct groups (F71 through F13) (16,31,41). The P fimbrial gene clusters of different serogroups are functionally related. This was shown by the construction of hybrid clones consisting of DNA sequences derived from different P determinants (cis-complementation) and also by the fact that P-specific gene products were able to produce a wild-type phenotype of P insertion mutants (trans-complementation) (24,36,43,45). Another group of E. coli gene clusters, coding for type I fimbrial adhesins which interact with ct-D-mannose-containing receptors, are also complem...

The gene flaA, encoding the flagellum subunit protein of Legionella pneumophila serogroup 1, has been isolated from an expression library of L. pneumophila isolate Corby in Escherichia coli K-12 by using an antiflagellin specific polyclonal antiserum. DNA sequence analysis of the flaA gene revealed the presence of a 1,428-bp open reading frame encoding a protein of 475 amino acids with an apparent molecular mass of 48 kDa that is expressed independently of an E. coli vector promoter. Peptide sequencing of the N terminus of the isolated flagellum subunit protein confirmed that this open reading frame encodes the flagellin. By comparing the FlaA amino acid sequence with those of flagellins of various other bacteria, high degrees of homology in the N-terminal and C-terminal amino acids could be observed. The flaA-specific mRNA was determined to be 1.6 kb in size, the expected size of a monocistronic mRNA. Temperature-dependent expression of flagellin was found to be regulated at the transcriptional level. Sequence analysis and primer extension experiments indicated that the transcription of the gene flaA is directed by a 28-like RpoF-FliA factor. By using fliA and fliA ؉ E. coli K-12 mutants, it was shown that flaA expression in E. coli required the 28 factor. A flaA-specific DNA probe hybridizes with genomic DNA isolated from L. pneumophila and with most of the genomic DNAs from non-L. pneumophila Legionella strains. Two L. pneumophila strains and isolates of Legionella bozemanii and Legionella feeleii (serogroup 1) carry flaA-specific sequences but were not able to produce flagella.

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