Kinetic analysis of the synthesis and assembly of type 1 fimbriae of Escherichia coli

The adhesive organelles (type 1 fimbriae) of K-12 and other isolates of Escherichia coli are composed of identical 17,000-dalton subunits. We examined the assembly of these subunits into fimbrial organelles. After synthesis, the nascent subunits were first processed and then assembled into the organelles; the assembly step took almost 3 min in log-phase cultures at 37 degrees C. Even during blockage of protein synthesis, the free subunits continued to assemble until the pool was depleted. This pool was small in comparison with the amount of total fimbrial protein already assembled into surface organelles and was not sufficient to regenerate new detectable organelles after the removal of preexistent ones by blending. Assembly appeared to slow when the metabolic rate of the bacterial cells slowed, since subunits took longer to appear in the organelles at lower than optimal temperatures or as a culture entered the stationary phase. The synthetic rate of subunits slowed sooner than that of total cellular proteins as a culture approached the stationary phase and ceased completely as the culture entered the stationary phase. The amount of fimbrial antigen expressed on the surface of the cells remained relatively constant during growth of a culture.

Legionella pneumophila surface antigens cloned and expressed in Escherichia coli are translocated to the host cell surface and interact with specific anti-Legionella antibodies

Escherichia coli clones that express Legionella pneumophila antigens were isolated from a plasmid genomic library, and their antigens were characterized by immunoblotting with rabbit anti-L. pneumophila sera. Because previous studies of L. pneumophila antigens by whole-cell radioimmunoprecipitation suggested that comigrating native antigens were surface localized, we conducted experiments to determine if the cloned antigens were surface expressed in E. coli. Aliquots of antisera were absorbed by intact cells of three representative antigen-producing E. coli clones, and surface-bound antibodies were acid eluted from the intact cells. Immunoblots made with selectively absorbed antisera and eluted antibodies confirmed that reactivity to the homologous cloned antigens could be specifically absorbed from the antisera and then eluted from the cells, demonstrating a surface (antibody-accessible) localization in the cloned state. Antibodies eluted from the surface of an E. coli clone that expressed a 19-kilodalton antigen reacted with the surface of L. pneumophila in a liquid-phase, whole-cell enzyme-linked immunosorbent assay. In addition, intact cells of this clone were used in an enzyme-linked immunosorbent assay to detect serum antibody. E. coli cells that express foreign antigens on their surfaces can be used to develop antigen-specific immunoassays and to affinity purify monospecific antibodies.

Dependence of secretion and assembly of type 1 fimbrial subunits of Escherichia coli on normal protein export

The export of fimbrial subunits was found to be diminished at the restrictive temperature in a strain bearing a secA(Ts) mutation. Likewise, export was inhibited in a strain harboring a malE-lacZ protein fusion upon induction of hybrid protein synthesis. Both conditions resulted in the accumulation of a precursor protein ca. 2,000 daltons larger than the mature fimbrial subunit.

Cloning and expression of Legionella pneumophila antigens in Escherichia coli

To isolate and characterize Legionella pneumophila antigens, we constructed a genomic library of L. pneumophila serogroup 1 (strain 130b). L, pneumophila DNA fragments (2.5 to 7.5 megadaltons) obtained by partial digestion with Sau 3A endonuclease and size fractionation on a sucrose density gradient were inserted into the dephosphorylated BamHI site of vector pBR322; CaCl2-treated Escherichia coli cells of strain HB101 were transformed with hybrid plasmids. To detect expression of antigens, 2,559 ampicillin-resistant transformants were transferred to nitrocellulose paper, lysed in situ, and screened by enzyme immunoassay (EIA) with E. coli-absorbed rabbit anti-L. pneumophila sera. A total of 77 (3%) of the colonies were reactive by EIA; 31 (1.2%) were strongly reactive, and 6 were strongly reactive by EIA without colony lysis. Analysis of 29 stable, strongly reactive clones by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotting showed antigenic bands in 18 clones by EIA with E. coli-absorbed antisera. Absorption of antisera with heat- and Formalin-killed L. pneumophila antigen eliminated or diminished the reactivity of the antigenic bands in representative clones. These studies confirm that several L. pneumophila antigens can be cloned and expressed in E. coli.

Genetic mapping and transcriptional orientation of the fimD gene

Expression of type 1 fimbriae in Escherichia coli exhibits phase variation whereby individual cells can alternate between states of organelle expression and nonexpression. Strains carrying fim-lac operon fusions in which lac operon expression is under the control of a fim promoter undergo Lac+ in equilibrium Lac- phase variation. We have determined the genetic map location and direction of transcription of a fim-lac operon fusion which was obtained by insertion of lac into a locus we have named fimD. We found the gene order to be as follows: valS fimD uxuA serB. The direction of transcription of fimD was found to be clockwise on the E. coli chromosome.

Isolation and characterization of a monoclonal antibody directed against type 1 fimbriae organelles from Escherichia coli

We have isolated a mouse immunoglobulin M (IgM) monoclonal antibody directed against type 1 fimbriae from the Escherichia coli K-12-derived strain CSH50. Antibody specificity was demonstrated by (i) the ability of fimbriate but not nonfimbriate bacteria to compete with solid-phase purified fimbriae for antibody binding in an enzyme-linked immunosorbent assay, (ii) the visualized binding of antibody to fimbriae alone by electron microscopy, and (iii) the appearance in a radioimmunoprecipitation assay of a single electrophoretic band comigrating with pure type 1 fimbriae. The monoclonal antibody was further characterized by immunoblot analysis and compared with previously prepared rabbit anti-fimbrial antisera. Whereas the monospecific but polyvalent antisera recognized both fimbrial monomeric subunits and non-disaggregated fimbriae organelles, the monoclonal antibody recognized only the intact organelles even when the samples were prepared under nondenaturing conditions. The monoclonal antibody, therefore, might be directed against an epitope spanning two (or more) adjacent fimbrial subunits.

Antigenic quantitation of type 1 fimbriae on the surface of Escherichia coli cells by an enzyme-linked immunosorbent inhibition assay

Type 1 fimbriae from two strains of Escherichia coli, K-12-derived CSH50 and a clinical isolate VL-2, were purified by a simplified procedure, which should be applicable to a variety of bacterial strains. After mechanical removal from the cells, the fimbriae were sedimented in the ultracentrifuge and resuspended in 5 M urea to disaggregate cell membranes and flagella, leaving the urea-resistant fimbriae intact. After several hours at 37 degrees C, this crude fimbrial suspension was diluted to 1 M urea, and the intact fimbriae were sedimented through a 1 M urea-1 M sucrose cushion. The pellet was found to be pure fimbriae by sodium docecyl sulfate-polyacrylamide gel electrophoresis, with apparent subunit molecular weights of 17,000 for the fimbriae from K-12 strain CSH50 and 19,000 for those from the clinical isolate VL-2. High-titer rabbit antiserum raised against CSH50 fimbriae was specific for fimbriae by indirect ferritin labeling and immunoprecipitation and was used to develop an enzyme-linked immunosorbent assay. Competitive inhibition of antifimbrial antiserum in the enzyme-linked immunosorbent assay by a known amount of either purified fimbriae or fimbriae-bearing bacteria permitted precise quantitation of fimbrial antigen in cultures of strain CSH50, thereby providing a simple means of determining the effects of environmental conditions on the synthesis of type 1 fimbriae.

Pseudocatabolite repression of type 1 fimbriae of Escherichia coli

Previous work on the control of fimbriation in bacteria has demonstrated the importance of environmental factors such as static versus shaking broth and the absence versus the presence of glucose on the degree of fimbriation. When the Pil+ K-12 strain of Escherichia coli CSH50 was grown in static broth, the bacteria grown with glucose were less fimbriate (as determined by electron microscopy) than those grown without glucose. In contrast, a derivative, the pil-lac operon fusion strain VL361, gave off similar proportions of Lac+ and Lac- colonies when grown with or without glucose. Introduction of delta cya into either CSH50 or VL361 did not affect synthesis of either fimbriae or beta-galactosidase, respectively. When total synthesis of fimbriae by strain CSH50 was assayed, using an enzyme-linked immunosorbent inhibition test, glucose-grown bacteria made less antigen when they were grown in static broth but not when they were grown in shaking broth. When results are taken together, we interpret them as showing that glucose does not suppress fimbrial synthesis by classic catabolite repression but rather merely prevents the outgrowth or fimbriate bacteria in static broth.

Operon fusion of the phase variation switch. A virulence factor in Escherichia coli

A derivative strain of a K-12 isolate of Escherichia coli was selected utilizing the operon fusion technique of Casadaban. This derivative strain (VL 361) was characterized by its ability to synthesize the enzyme beta-galactosidase - the gene product of the inserted lacZ gene - as if it were type 1 fimbriae. Enzyme production was found to behave according to the properties of phase variation, thus mimicking the phase variation seen with type 1 fimbriae. The oscillation between the on-and-off synthesis of enzyme was found to be random, and was not influenced by such environmental factors as temperature, glucose or cyclic AMP. Thus the selection in various media of either fimbriate or non-fimbriate states is probably not genetic in nature, but rather the outgrowth of one type of phase over another.

Phase variation of type 1 fimbriae in Escherichia coli is under transcriptional control

An operon fusion of the lac genes to those required for synthesis of type 1 fimbriae (pili) has been achieved in a K12 strain of Escherichia coli lysogenized by the bacteriophage mu d (Ap4, lac). Synthesis of beta-galactosidase, therefore, reflected pil gene transcription and was used as a probe of fimbrial regulation. Expression of the operon fusion was found to oscillate, demonstrating that phase variation between fimbriate and nonfimbriate states is under transcriptional control. The transition rates from fimbriate to nonfimbriate were 1.05 X 10(-3) per bacterium per generation and from nonfimbriate to fimbriate, 3.12 X 10(-3) per bacterium per generation.

Disseminated gonococcal infection (DGI) and gonococcal arthritis (GCA): II. Clinical manifestations, diagnosis, complications, treatment, and prevention

This is the second part of an integrated review of disseminated gonococcal infection (DGI) and gonococcal arthritis (GCA). It covers clinical manifestations, spectrum of GCA, diagnosis and treatment. These disorders are important since DGI may be the most frequent form of acute arthritis in sexually active younger females, and other selected groups. Although the spectrum of disease is varied, it may be classified into stages and clinical subgroups. N. gonorrhoeae strains causing DGI in the U.S. have been highly sensitive to penicillin. Such findings require revision in beliefs that high-dose intravenous penicillin is needed for effective initial therapy of GCA. Recommended treatment protocols for localized gonorrhea and DGI are reviewed as well as the occurrence and implications for treatment of penicillinase-producing N. gonorrhoeae (PPNG) infection in the U.S.

Loss of lectin-like activity in aberrant type 1 fimbriae of Escherichia coli

Growth of a streptomycin-resistant strain of Escherichia coli (VL-2) in the presence of 30 microgram of streptomycin per ml resulted in the production by these bacteria of structurally altered, nonfunctional type 1 fimbriae. This strain, when grown in this subinhibitory concentration of streptomycin, became incapable of producing mannose-sensitive hemagglutination (<1% of that of the control). Adhering ability to epithelial cells and human leukocytes was also diminished (42 and 7% of that of the control, respectively). Although these streptomycin-treated bacteria were as heavily fimbriated as untreated bacteria, their fimbriae were significantly longer. Furthermore, in contrast to the fimbriae of the untreated bacteria, those isolated from the drug-treated bacteria were found to lack mannose binding activity as measured by hemagglutination. It appears, therefore, that streptomycin can cause even resistant bacteria to produce an aberrant fimbrial protein, possibly by causing misreading of messenger RNA. These studies indicate that the use of sublethal doses of certain antibiotics whose mode of action is well known may shed light on the genetic and chemical modulation of bacterial factors involved in mucosal colonization.

Divergent effects of cyclic adenosine 3',5'-monophosphate on formation of type 1 fimbriae in different K-12 strains of Escherichia coli

Exogenous cyclic adenosine 3',5'-monophosphate either increased or decreased the expression of type 1 fimbriae in different cya strains of Escherichia coli, demonstrating the complexity of regulation of this surface protein.

Influence of sublethal concentrations of antibiotics on the expression of the mannose-specific ligand of Escherichia coli

The ability of streptomycin, in subinhibitory concentrations, to differentially suppress the acquisition of the mannose-binding activity of Escherichia coli was demonstrated in several strains, but not one with a ribosomal mutation to high-level streptomycin resistance, rpsL. We also determined that the growth of bacteria in other antibiotics, notably those that interfere with protein synthesis, resulted in diminished mannose-binding activity (as measured by yeast cell agglutination), degree of piliation (as measured by electron microscopy), and adherence to human oral epithelial cells. The aminoglycoside antibiotics streptomycin, gentamicin, and neomycin had the most marked effects relative to their minimum inhibitory concentrations, followed by tetracycline. Both spectinomycin and chloramphenicol had more effect on adherence than on piliation, although spectinomycin had a more pronounced effect on mannose-binding activity than did chloramphenicol. We conclude that antibiotics, at concentrations below their minimum inhibitory concentration, may have profound effects on surface properties of bacteria that may be pertinent for their ability to colonize and infect human mucosal surfaces. The mechanism(s) may vary from one drug to another, but appear to depend on the classic actions of the antibiotics on inhibiting protein synthesis.

Sodium balance after adrenal enucleation

To better define the relationship between adrenal enucleation (AE), sodium retention and adrenal regeneration hypertension (ARH), we measured daily sodium balance in rats after bilateral adrenal enucleation with (AEN) and without uninephrectomy (AE), and before and after development of ARH, along with the appropriate control groups. We found that both AE and AEN groups retained sodium during 7 days after surgery; AE 1.16 +/- 0.24 and AEN 1.32 +/- 0.33 meq/100 g body wt. Sham-operated, uninephrectomized rats and AE rats treated with spironolactone were in zero sodium balance. In the AEN rats after the development of ARH (BP greater than 150 Torr), zero sodium balance was also noted. Only AEN rats developed hypertension while sham-operated, uninephrectomized rats and AE rats with both kidneys remained normotensive for 28 wk. In summary, we have demonstrated that for 1 wk after AE, rats are in positive sodium balance and this is reversed by spironolactone but not by uninephrectomy.

Benign familial haematuria in children from the Jewish communities of Israel: clinical and genetic studies

Over 7 years, 130 children were referred for prolonged isolated haematuria of unknown cause. In 34 instances, haematuria was also found in one or more family members. In 23 of these families (18% of all referrals for isolated haematuria), investigation and follow-up, for periods of 5 to 10 years, of the index cases and of 56 haematuric relatives showed no evidence of renal disease and no other pathological findings. These subjects were diagnosed as having benign familial haematuria. The gene for benign familial haematuria is apparently transmitted as an autosomal dominant with reduced penetrance and variable expressivity. In Israel, the disorder seems to be more frequent among Jews of non-Ashkenazi descent than among those of European ancestry (Ashkenazim).

Suppression of bacterial adherence by subminimal inhibitory concentrations of beta-lactam and aminoglycoside antibiotics

Nonseptate filaments of Escherichia coli obtained by growth of a temperature-sensitive mutant of the organism at its restrictive temperature in the absence of antibiotics or at its permissive temperature in the presence of approximately one-half the MIC of penicillin (27 micrograms/ml; MIC of penicillin, 50 micrograms/ml) lacked the ability both to bind to mannose and to adhere to host tissues. Addition of low concentrations (0.5-10 micrograms/ml) of streptomycin to cultures of E. coli resulted in marked suppression of the mannose-binding and adhering ability of streptomycin-sensitive E. coli (MIC, 30 micrograms/ml). In contrast, up to 5,000 microgram of streptomycin/ml had no effect on an isogenic streptomycin-resistant mutant of E. coli (MIC, 20,000 micrograms/ml). No concentration of penicillin or streptomycin that was tested was able to suppress either the mannose-binding or the adhering ability of E. coli once those activities had been acquired by the organism. These results suggest that subminimal inhibitory concentrations of antibiotics suppress the ability of bacteria to adhere to cells.

Interference with the mannose binding and epithelial cell adherence of Escherichia coli by sublethal concentrations of streptomycin

When Escherichia coli was grown in sublethal concentrations of streptomycin, mannose binding activity and epithelial cell adherence of the E. coli cultures at stationary phase were significantly reduced in the drug-grown organisms. In a strain whose minimal inhibitory concentrations was 30 mug/ml, the percentage of reduction in mannose binding activity was dose related over a range of concentrations between 0.5 and 10 mug/ml streptomycin. Concomitant with the drug-induced suppression of mannose binding activity, antigenic and ultrastructural alterations on the surface of the drug-grown organisms were observed by agglutination tests and electron microscopy, respectively. The streptomycin effect was reversible, required actively growing organisms, and was most apparent in the early log-phase of growth. High doses of antibiotic were ineffective when added to cultures which had acquired mannose binding activity. An isogenic derivative with high-level resistance to streptomycin was obtained as a single-step mutation from the test E. coli strain. Whereas the isogenic mutant possessed mannose binding activity and adhering ability similar to the parent strain, it was resistant to the streptomycin-induced suppression of the two activities at enormous concentrations (up to 10,000 mug/ml) of streptomycin. Taken together the results suggest that the suppression of epithelial cell adherence and mannose binding activity of E. coli grown in sublethal concentrations of streptomycin is a result of classic mechanisms of drug action upon the bacterial ribosome. The results support the possibility that antibiotics may act through mechanisms other than inhibition of growth and bacterial killing to eradicate bacteria from mucosal surfaces.