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Encapsulated and non-encapsulated variants of one strain of gonococcus were compared for their capacity to produce infection in chambers implanted subcutaneously in mice, for their reactions with specific antibody and for their precipitation with wheat germ agglutinin. Only the encapsulated variant could infect implanted chambers. Specific rabbit antiserum raised against the non-encapsulated variant killed both variants. Saline extracts and lipopolysaccharide preparations of the encapsulated variant differed from those of the non-encapsulated one in their reactions with wheat germ agglutinin and antibody in diffusion and electrophoresis tests. Preparations from infective encapsulated gonococci reacted with wheat germ agglutinin while those from the non-encapsulated variant did not. Immunodiffusion tests showed that lipopolysaccharides from both variants share a common antigenic determinant, but saline extracts and lipopolysaccharides from encapsulated gonococci possess an additional determinant. The significance of these findings is discussed.

Freeze-etching was applied to preparations, with and without glycerol, of Acinetobacter sp. strain MJT/F5/199A, consisting of intact cells after normal growth or after incubation with chloramphenicol, spheroplasts, and isolated cell walls and outer membranes. Etched preparations show that a regular array of subunits forms the surface of normal cells. Near the zones of constriction in dividing cells, blebs and irregularities are seen, and some blebs, consisting of both surface subunits and outer membrane, are released from the cells. The cross-fractured cell envelope shows four layers which are related to the structures seen in section as follows: cw1, which is not visible in section, contains the surface subunits; cw2 consists of all or part of the outer membrane; cw3 includes the intermediate and dense, peptidoglycan-containing layers; within these cell wall layers is the plasma membrane. Internal fracture of the plasma membrane occurs under all conditions tested, but the fracture plane in the cell wall is only revealed in chloramphenicol-treated cells or normal cells freeze-fractured with glycerol present; the characteristic fracture faces are not seen in spheroplasts or isolated outer membranes. The concave fracture face cw2 consists of densely packed granules, while the convex face cw3 is fibrillar. The probable location of this fracture plane is discussed. After incubation with chloramphenicol, the outer surface of the cells is obscured by extracellular material, the dense peptidoglycan-containing layer is increased in thickness, and the cytoplasm contains rounded bodies bounded by one or more unit membranes.

The chlamydial genus-specific antigen was extracted with phenol/chloroform/petroleum ether (PCP) from preparations of Chlamydia trachomatis and C. psittaci, and quantities measured using an assay for lipopolysaccharide (LPS). The LPS from C. trachomatis contained 2.2% (w/w) of ketodeoxyoctanoic acid. Five IgG monoclonal antibodies reacted in an ELISA with LPS from both species, the antigen being periodate-sensitive and heat-resistant, confirming that all antibodies were against the genus-specific antigen. All the antibodies bound to the PCP extract of C. trachomatis on an immunoblot, at a position corresponding to the periodate-Schiff-stained bands of both C. trachomatis extract and Salmonella Re-LPS. When linked to trypsin-treated sheep erthrocytes and used in reverse passive haemagglutination tests, all antibodies gave indicator cells capable of detecting chlamydial LPS or crude preparations of chlamydiae grown in McCoy cells, the sensitivity varying with the antibody used. The antibodies varied in IgG subclass (either IgG2a or IgG3), and in ability to precipitate in immunodiffusion tests. Two antibodies cross-reacted with one strain of Acinetobacter in ELISA and with Salmonella Re-LPS in both ELISA and immunodiffusion tests. The other three did not react in ELISA with Acinetobacter strains or Salmonella Re-LPS, and none of the five reacted with LPS of E. coli or Pseudomonas morsprunorum.

Serum IgE levels can be measured by reverse passive antiglobulin haemagglutination (RPAH) of trypsin-treated human or sheep red cells coupled to sheep IgG anti-human IgE by chromic chloride. The results show a high correlation with those obtained by the radioactive single radial immunodiffusion method. Interfering anti-sheep IgG factors can be easily removed by absorption with small amounts of whole sheep or bovine serum cross-linked with glutaraldehyde. Standardisation with the British standard for IgE shows that the detection limit of the RPAH method is 0.5 IU/ml (1.2 ng/ml). The system is therefore comparable in sensitivity to the paper radio-immunosorbent test, and has the advantages of being simple, rapid and cheap. The RPAH method can be used to measure any class of immunoglobulin. For IgA the detection limit is found to be 10(-4) IU/ml (1.4 ng/ml).

Several substances in urine were found to inhibit the radioimmunoassay of added gonococcal antigens. The supernatants of two-thirds of urine samples from male patients with either gonorrhoea or non-specific urethritis (NSU) were inhibitory. The inhibition caused by many, but not all, samples was reduced or completely abolished by the addition of soybean trypsin inhibitor (STI); STI-sensitive inhibition is thought to be due to proteolytic enzymes, probably from pus cells. Their inhibitory effect was shown to be due to their action on gonoccocal antigens and not on antibodies in the assay system. Some supernatants contained other inhibitors unaffected by STI; some of these were dialysable and others were not. Sediments from the urine of patients with NSU or gonorrhoea were often strongly inhibitory, but treatment with STI annulled all but very slight inhibition. STI-treated sediments could, therefore, be used in an assay designed to detect gonococcal antigens.

The cell wall of the gram-negative bacterium Acinetobacter species strain MJT/F5/5 shows in thin section an external "additional" layer, an outer membrane, an intermediate layer, and a dense layer. Negatively stained preparations showed that the additional layer is composed of hexagonally arranged subunits. In glycerol-treated preparations, freeze-etching revealed that the cell walls consist of four layers, with the main plane of fracture between layers cw 2 and cw 3. The surface of [Formula: see text] 2 consisted of densely packed particles, whereas [Formula: see text] 3 appeared to be fibrillar. In cell envelopes treated with lysozyme by various methods, the removal of the dense layer has detached the outer membrane and additional layer from the underlying layers, as shown in thin sections. When freeze-etched in the absence of glycerol, these detached outer membranes with additional layers fractured to reveal both the faces [Formula: see text] 2 and [Formula: see text] 3 with their characteristic surface structures, and, in addition, both the external and internal etched surfaces were revealed. This experiment provided conclusive evidence that the main fracture plane in the cell wall lies within the interior of the outer membrane. This and other evidence showed that the corresponding layers in thin sections and freeze-etched preparations are: the additional layer, cw 1; the outer membrane, cw (2 + 3); and the intermediate and dense layers together from cw 4. Because of similarities in structure between this Acinetobacter and other gram-negative bacteria, it seemed probable that the interior of the outer membrane is the plane most liable to fracture in the cell walls of most gram-negative bacteria.

Chemical analysis of fractions of the cell envelope of Acinetobacter sp. strain MJT/F5/199A, prepared by breakage in the French press and removal of plasma membranes, followed by sequential treatment with lysozyme and with papain, confirmed the existence of layers previously identified by electron microscopy. Outside the plasma membrane and periplasmic space, the envelope is composed of (i) a peptidoglycan-containing dense layer, (ii) an intermediate layer, (iii) a lipopolysaccharide-containing outer membrane, and (iv) an ordered array of protein subunits. A small amount of carbohydrate (3%) is found associated with protein in the fraction containing both the surface subunits and the intermediate layer. The papain-treated outer membranes contain 67% protein, 24% lipid, together with 11% lipopolysaccharide, and about 6% of non-lipopolysaccharide hexosamine. Lipid is located only in the papain-treated outer-membrane and is mainly phospholipid: 29% phosphatidyl glycerol, 30% phosphatidyl ethanolamine, and 40% cardiolipin. The principal fatty acid is C(18:1). Significant amounts of alcohols(16:1) and alcohols(18:1), which are found in Acinetobacter waxes, were recovered from the outer membrane.

Serum IgE levels can be measured by reverse passive antiglobulin haemagglutination (RPAH) using trypsin-treated human red cells coupled to anti-human IgE by chronic chloride. The results are read after only 90 min incubation. RPAH and double antibody radioimmunoassay have been used to measure IgE levels in 100 sera, with levels ranging from 5 to 43,000 international units (i.u.)/ml. Correlation between the two assays was high over the whole range, provided that affinity-purified anti-IgE was used in the RPAH test. When two non-affinity-purified anti-IgE reagents were used in the RPAH, correlation was poor for sera with levels below 1000 i.u./ml. It is concluded that RPAH tests for IgE are of comparable sensitivity and specificity to radioimmunoassay procedures, and provide a useful simple, yet more rapid alternative.

An assay for the detection of Brucella abortus is described. IgG from rabbit antisera against live brucellae or brucella extracts was chemically linked to cellulose to form a solid phase reagent capable of binding brucella antigens present in buffer solutions or serum. After washing away any unbound material the presence of bound antigen was revealed by incubation with radioactively-labelled anti-brucella antibodies. The assay was capable of detecting less than 100 pg brucella antigen in a 20 microliter sample. Experiments in which IgG of non-related specificity was used in place of anti-brucella IgG showed that the test was specific. Normal human serum had only a slight inhibitory effect but anti-brucella antibodies were strongly inhibitory if present in the test sample. The extent of this effect and its relationship to antibody titre was investigated in 12 sera from brucellosis patients.

Acinetobacter 199A carries on the outer surface of its outer membrane a layer of regularly arranged protein subunits. The isolated surface protein assembles into the same regular array even in the absence of the underlying outer membrane. Cl- minus is required for this self-assembly. Evidence is presented that the interaction of the surface protein with the outer membrane involves the linking of a carboxyl group in the surface protein to a negatively charged group in the outer membrane protein, via a divalent cation. The surface protein could be detached from the outer membrane by the protein perturbant urea, by the chelating agent EDTA and by replacing Mg-2+ with Na+. It could not be detached by treatment with phospholipases A anc D or the detergents Tween 80 and sodium deoxycholate. The conditions favourable for reattachment of surface protein to the cell wall were the presence of divalent cations and a pH of 3-5. Conversion of carboxyl groups in the surface protein to amine with carbodiimide and ethylene diamine interfered with reattachment. The surface protein did not attach to isolated cell wall lipid or lipopolysaccharide.

A study by light microscopy, using Leishman's stain alone or Leishman's stain followed by nigrosin, showed the presence of capsules on gonococci of two strains subcultured from subcutaneous chambers in guinea pigs. With the Alcian blue method of preparation for electron microscopy, gonococci of both strains recently grown in vivo showed densely stained capsules on some cells, while others in the same preparation showed only irregular masses of dense material on their surfaces with strands connecting adjacent bacteria. Treatment with antiserum, complement and conglutinin revealed irregular masses and strands of extracellular material with fixatives that did not contain Alcian blue.

A reverse passive haemagglutination test (RPH) has previously been developed to detect the genus-specific antigen of Chlamydia. Clinical samples were obtained from various sites of different animal species. The RPH test detected chlamydial antigen from clinical cases of conjunctivitis in cats, abortion in sheep and psittacosis in birds. Although not as sensitive as cell culture isolation, this test has the advantages of rapidity and of detecting antigen from dead chlamydiae.

High-resolution two-dimensional polyacrylamide gel electrophoresis was used to analyse the soluble proteins from seven strains of Neisseria gonorrhoeae, six strains of Neisseria meningitidis and one or two strains of twelve other species. Approximately 200 individual polypeptides could be visualized as Coomassie Blue stained spots on an electrophoretogram of N. gonorrhoeae and similar numbers were found for the other bacteria. Each species of bacterium had a distinctly different pattern of spots which could be recognized. Quantitative comparisons of 48 selected spots derived from one strain of N. gonorrhoeae with those of five other strains of gonococcus, three strains of N. meningitidis and one of Branhamella catarrhalis, showed relationships in agreement with their current taxonomic classification but with a higher level of discrimination than that of previously used methods. It was also possible to distinguish the individual gonococcal strains. It is suggested that the method could be useful for bacterial classification and identification.

A method of detecting gonococcal antigens by solid-phase radioimmunoassay with radioactively labelled antibody is described. A specificity test has been developed that enables this method to be used to detect gonococcal antigens in urine sediments. When sediments from samples of urine from male patients with gonorrhoea were tested, 31 (74%) of 42 gave positive results, clearly distinguishing them from sediments from urine samples from men with non-specific urethritis, none of which was positive. Ten of 14 urine sediments from urine samples from women with gonorrhoea gave positive results, as did 3 of 18 sediments from urine samples from women patients without gonorrhoea. These experiments demonstrate that gonococcal antigens can be detected in urine by radioimmunoassay; the method could be useful in diagnosis if, after refinement, its sensitivity and specificity were to be increased.

Acinetobacter sp. strain MJT/F5/199A carries an array of tetragonally arranged subunits on its outer surface. The subunits can be detached from isolated cell walls by incubation with 1 M urea or by washing with water after treatment with 10 mM ethylenediaminetetraacetic acid or ethyleneglycol-bis(beta-aminoethylether)N,N'-tetraacetic acid. After removal of the urea, they reaggregate into the same ordered array at air-water interfaces in the presence of MgCl(2). The detached subunits were characterized as an acidic protein of molecular weight 65,000. They represent one-fifth of the total cell wall protein.

The report described the development of a mixed reverse (solid-phase) passive antiglobulin haemadsorption (MRsPAH) test for specific IgE antibody to castor bean allergen. The allergen is immobilised by formalin fixation in the wells of polyvinyl chloride microtitre plates. After allowing allergen-specific antibodies in the test serum to bind to the allergen, plates are washed thoroughly, and red cells coupled by chromic chloride to sheep IgG anti-human IgE are used to detect specifically bound IgE. This system was compared with a solid-phase radioimmunoassay in which 125I-labelled anti-IgE was substituted for the antiglobulin-linked red cells of the MRsPAH test; the earlier stages of both tests being the same. 12 sera, 10 from patients with allergic asthma to castor bean allergen and two from non-allergic controls, were tested for castor-bean-specific serum IgE by both methods and the results showed high correlation. The MRsPAH tst for allergen-specific serum IgE provides a useful alternative to the RAST system, being free of the disadvantages inherent in the use of radio-labelled materials.

A method has been developed for the isolation of outer membranes from Acinetobacter sp. strain MJT/F5/199A. Washed cells were broken in a French press and, after deoxyribonuclease and ribonuclease treatment, removal of intact cells, and four washes in 20 mosmol phosphate buffer, pH 7.4, with centrifugation at 25,000 x g for 10 min, preparations of cell wall fragments from which almost all pieces of plasma membrane had been removed resulted. Treatment of the cell walls with lysozyme and further washing, in the presence of 20 mM MgCl(2), yielded preparations of outer membranes. Electron microscopy of freeze-etched preparations shows that a regular pattern of subunits is present on the outer surfaces of intact cells. After negative staining, these subunits are visible on isolated walls and outer membranes; they can be removed by brief treatment with papain. In section, the cell wall structure is that typical of gram-negative bacteria, but the subunits are not detectable on the surface of the outer membrane. The outer membrane retains the appearance of a "unit membrane" in the cell wall, isolated outer membrane, and papain-treated outer membrane fractions. Both cell walls and outer membranes contain a high percentage of protein (76 and 84%, respectively) and not more than 5% carbohydrate, of which glucose and galactose are constitutents. The outer membranes of this Acinetobacter thus differ in structure and composition from those of bacteria in the Enterobacteriaceae.