ABSTRACT
Type 1 and F1C fimbriae are surface organelles of Escherichia coli which mediate receptor-specific binding to different host surfaces. Such fimbriae are found, among others, on strains associated with urinary tract infections. Biosynthesis of type 1 and F1C fimbrial organelles requires individual, specialized two-component assembly systems. The organization of the fim and foc gene clusters encoding these fimbriae, as well as the structure of the organelles, is very similar; however, the actual sequence homology of the structural elements is not remarkable (34 to 60%). Both gene clusters encode a periplasmically located chaperone and an usher protein, located in the outer membrane, required for organelle biogenesis. Deletion of either element causes abolishment of fimbriation. The present report addresses the question of promiscuity in fimbrial biogenesis. Our data indicate that the two-component export systems of the two organelle systems are reciprocally interchangeable; however, they seem to function only in parental pairs.
Subject(s)
Bacterial Proteins , Escherichia coli Proteins , Fimbriae Proteins , Fimbriae, Bacterial/physiology , Amino Acid Sequence , Animals , Bacterial Outer Membrane Proteins/genetics , Cell Line , Genes, Bacterial , Guinea Pigs , Humans , Molecular Chaperones/physiology , Molecular Sequence DataABSTRACT
The genes responsible for the expression of type 1 fimbriae, produced by the majority of E. coli strains, have been cloned from an E. coli K12 strain. The "passenger" DNA from an initial cosmid clone was reduced in size and subcloned in pACYC184 and pBR322 vectors. A DNA fragment of around 8 kbp was found to be required for the biosynthesis of type 1 fimbriae. This was further studied by transposon-mediated insertional inactivation and by BAL31-mediated deletions. Four genes, designated fimA, B, C, and D were found to be involved in the synthesis of the fimbriae. They encoded proteins that in their processed form appeared with apparent molecular weights of 16.5 kd, 23 kd, 26 kd, and 89 kd, the 16.6 kd polypeptide being the fimbrial subunit. The order to the genes was found to be: fimB, fimA, fimC, and fimD, organized in three transcriptional units.
Subject(s)
Bacterial Outer Membrane Proteins/genetics , Cloning, Molecular , Escherichia coli/genetics , Fimbriae, Bacterial/physiology , Genes, Bacterial , Animals , Base Sequence , DNA Restriction Enzymes , Escherichia coli/ultrastructure , Fimbriae Proteins , Genetic Complementation Test , Guinea Pigs , Hemagglutination , Molecular Weight , PlasmidsABSTRACT
In 12 patients with cirrhosis of the liver, determination of the liver volume by ultrasonic scanning and of the galactose elimination capacity (GE) were made before and after portal decompression surgery. The liver volume decreased significantly, with a median decrease of 402 ml (psmaller than 0.01). Also the GE decreased, but relatively less than the liver volume, so that the calculated GE per unit liver volume increased, with a median increase of 5 mg per minute times 100 ml liver volume (psmaller than 0.005). The decrease in liver volume following portal decompression is assumed to be due in part to reduction of liver blood volume, in part to loss of tissue water and fat, and probably to some loss of parenchyma, accounting for a reduction of the GE.
