TRANSFER-RNA GENES AND PATHOGENICITY ISLANDS - INFLUENCE ON VIRULENCEAND METABOLIC PROPERTIES OF UROPATHOGENIC ESCHERICHIA-COLI

The uropathogenic Escherichia coli strain 536 (O6:K15:H31) carries two unstable DNA regions on its chromosome which were termed pathogenicit y islands (Pais). Both pathogenicity islands, Pai I and Pai II, are in corporated into tRNA specific loci: Pai I is located in the tRNA gene for selenocysteine (selC), and Pai II is integrated in the leucine-spe cific tRNA locus leuX. Mutant strain 536-21 has lost the two pathogeni city islands together with the intact tRNA genes. While 536 is a virul ent strain, 536-21 has lost a number of properties, including in vivo virulence. In previous publications we reported that the genes coding for two haemolysins (hlyI, hlyII) and P-related fimbria (prf) are loca ted on the Pais. In this paper, we demonstrate that the expression of other gene products influencing metabolic properties in addition to in vivo virulence are strongly dependent on the intact tRNA loci selC an d leuX. In order to determine the influence of the two tRNAs on the ex pression of these properties, the genes selC and leuX were cloned from the genome of strain 536 and then introduced into the mutant 536-21. Our results clearly show that the selenocysteine-specific tRNA (tRNA(S ec)) directly influences the ability of the bacteria to grow under ana erobic conditions, because selenocysteine is part of the enzyme format e dehydrogenase (FDH) which is involved in mixed acid fermentation. Th e rare leucine-specific tRNA(5)(Leu), encoded by leuX, influences a nu mber of properties including type 1 fimbria production, flagellation a nd motility, production of enterobactin and serum resistance, and is a lso necessary for full in vivo virulence. While the tRNA(Sec) is direc tly involved in the production of FDHs, the leuX specific tRNA(5)(Leu) appears to influence the expression of various factors through specif ic transcriptional or translational control mechanisms.