An Escherichia coli mutant conditionally altered in respiratory chain components

Nitrosoguanidine mutagenesis was employed to isolate an Escherichia coli mutant conditionally altered in respiratory chain components. Mutant R25 was able to grow on glucose, fructose, and glycerol but failed to grow on succinate and acetate (suc-). Also, R25 exhibited leaky growth on DL-lactate, fumarate, and malate (lct*). The lct* mutation pleiotropically affected a number of respiratory chain components and its expression was conditional with the growth substrate. Glucose-grown R25 resting cell suspensions oxidized DL-lactate and formate; however, these two substrates were not oxidized by fructose- or glycerol-grown cell suspensions. The same conditional pattern was observed for the concentration of cytochrome components, the membrane-associated oxidation of NADH and formate, and formate phenazine methosulfate (PMS) reductase activity; succinate oxidase and PMS reductase activities were not exhibited by membranes under any growth condition due to the suc- mutation. R25 membrane-associated H(+)-translocating ATPase activity was not conditional with the growth substrate. R25PC, a spontaneous lct+ suc- partial revertant of R25, did not exhibit the conditional pattern of R25. The lct* mutation was found to map in the 27-30-min region and the suc- mutation in the 15-17-min region of the E. coli genome. Two distinct classes of R25 P1kc transductants were isolated that differed in both their growth response on succinate and DL-lactate and their oxidase activities.

Expression of foreign DNA in Chlamydomonas reinhardtii

A chimeric octopine synthase-neomycin phosphotransferase (ocs-nptII) gene was used to transform Chlamydomonas reinhardiii to kanamycin resistance. Southern hybridization using DNA isolated from one transformant, T6.1, indicated that the entire ocs-nptII gene and at least part of the plasmid were integrated into nuclear DNA. Neomycin phosphotransferase II activity has been detected in T6.1 cell extracts. Northern hybridizations, employing a radiolabeled ocs-nptII sequence, revealed a T6.1 transcript of approximately the same size as a homologous transcript isolated from E. coli carrying the nptII gene. Although T6.1 is an extremely rare example of a stable C. reinhardtii transformant, its occurrence nevertheless indicates that bacterial genes can be expressed in the nucleus of the alga.

Escherichia coli formate dehydrogenase mutants with altered selenopolymer profiles

Four classes of Escherichia coli mutants deficient in either or both of their anaerobic selenium-containing formate dehydrogenases (FDH) were isolated. A class I mutant devoid of FDHH activity specifically linked to benzyl viologen (BV) produced a small amount of the FDHH 80,000 dalton selenopeptide. Three class II mutants were deficient in FDHN activity specifically linked to phenazine methosulfate (PMS) and exhibited a selenopeptide "doublet" rather than the FDHN 110,000 dalton selenosubunit. Three class III mutants were selenium incorporation deficient and did not exhibit either FDH activity or 75Se-labeled selenopolymers. A class IV mutant was devoid of PMS-linked FDHN activity; neither its FDHN 110,000 dalton selenosubunit nor its BV-linked FDHH activity was fully regulated by nitrate.

An enzyme immunoassay for isotyping mouse monoclonal antibodies

A rapid, simply performed and relatively inexpensive enzyme immunoassay for isotyping mouse monoclonal antibodies is described, based on the urease/urea system. Because of the high sensitivity (less than 0.1 microgram/ml of immunoglobulin can be detected in cell culture medium) no treatment of the hybridoma supernatant sample is required prior to assay, and the isotype of a mouse immunoglobulin can be determined in about thirty minutes.

Immunogenicity of specific Bordetella pertussis surface antigens in diphtheria-tetanus-pertussis (DTP) vaccines

The predominant causative organism of whooping cough in Australia is of a serotype which has normally been associated overseas with unvaccinated communities. Australian DTP vaccines pass the statutory mouse test for Bordetella pertussis potency but this test is now believed to be relatively insensitive to certain factors, especially the major type-specific agglutinogens, which are presumably also important in the human host-parasite relationship. Because endemic B. bronchiseptica infections make some laboratory animals unsatisfactory for testing B. pertussis agglutinin responses, we have developed a test in which young farm sheep were immunized with vaccines. Type-specific agglutinins in their sera were assayed after absorption of non-specific agglutinins by suspensions of selected bordetella strains. Three well-reputed European DTP vaccines and two recent batches of Australian DTP vaccine were tested and compared thus. All evoked significant agglutinin responses to the main agglutinogens.

Hospital renovation projects: phased construction requires planning at its best

Building a new hospital facility is a difficult task, but adding onto and renovating an existing structure while normal activity continues is even more difficult. Project planners, designers, contractors, and hospital managers must carefully program the joint effort of construction and hospital operation. Several factors in the construction process and potential problems for hospital operations are described to help hospital managers better anticipate difficulties before plans are finalized and construction commences.

Storage of pathogenic leptospires in liquid nitrogen

The virulence and viability of various serovars of Leptospira interrogans were successfully preserved by storage in liquid nitrogen. Dimethyl sulphoxide at a final concentration of 2.5% (v/v) was added as cryoprotectant to a culture of leptospires grown in Ellinghausen-McCullough-Johnson-Harris medium. Ampoules were cooled at a controlled rate of 1 degree-3 degrees C/min to -70 degrees C, then transferred to the liquid phase of a liquid nitrogen storage unit. Glycerol was discounted as a cryoprotectant as it was found to be approximately 10 times more toxic than dimethyl sulphoxide to four of five serovars used in this study. The viability of nine strains has so far been observed over a period of 8-22 months storage in liquid nitrogen and full viability of all strains has been preserved over this period. Virulence of strains of serovars pomona and hardjo was well preserved, as demonstrated by challenge tests in guinea pigs and domestic pigs.

Inactivation of poliovirus with beta-propiolactone

The recovery of poliovirus D-antigen after virus inactivation was studied for two inactivating agents (beta-propiolactone and formalin) using the three poliovirus types (Sabin types 1, 2 and 3). With beta-propiolactone (BPL), D-antigen recoveries were high (88, 88 and 60%, respectively) but were significantly less when formalin was used (22, 15 and 25%). beta-Propiolactone inactivated virus was purified, combined with Freund's adjuvant and used to hyperimmunize rabbits. High titres (50 000-200 000) of specific neutralizing antibody were obtained.

The infectivity of Encephalitozoon cuniculi in vivo and in vitro

The infectivity of Encephalitozoon cuniculi grown in cell cultures was determined in cultured cells and in wild and domestic rabbits. The ratio of the total to tissue culture viable count was 1,300 (median of seven determinations). The mean ratio of intact spore count to total count, as determined by electron microscopy was 0.12. Although variation between infectivity experiments was large, the median animal infective dose contained 51 FFU (cell culture focus-forming units) for wild rabbits (Oryctolagus cuniculus) and 40 FFU for domestic rabbits. These two infectivities were not statistically different.

An evaluation of the use of a pH indicator for the detection of beta-lactamase in enzyme immunoassay

The use of a mixed pH indicator containing bromocresol purple and bromothymol blue was evaluated for the detection of beta-lactamase activity in enzyme immunoassays (EIA) based on this enzyme. The EIA was found to correlate well with a bioassay for antibodies to tetanus toxoid in sheep sera. Results could be read spectrophotometrically at 450 nm or visually as a colour change from dark blue to yellow. The mixed pH indicator was found to have a number of desirable features including good stability, ease of preparation and a sharp colour change which makes the system suitable for visual determination of titration end points.

Immune response and reactions to various dose regimens for raising hyperimmune antisera in sheep

To determine the optimum procedure for raising hyperimmune sera to tetanus toxin, three adjuvants, four antigen preparations and two routes of administration in various combinations were investigated in sheep. Oil-in-water adjuvants alone or in combination with aluminum gels were superior to aluminium gels on their own. This disadvantage of aluminium gels was partially but not completely abrogated when the frequency of doses was increased to three per week. Intensity of local reaction was strongly correlated with immune response; the more immunogenic a dose, the more reactive. Reactivity of oily adjuvants could be lessened by use of a more suitable route of administration, thus oily adjuvants appeared suitable for use when administered by the intraperitoneal route even though moderate to severe reactions resulted from subcutaneous injections. Of other variables investigated, toxin did not confer any advantage over toxoid as an immunogen, purified toxoid was a significantly better immunogen than unpurified toxoid and two large bleeds (30% of total blood volume each) every six weeks rather than 20 ml test bleeds did not affect the titre of the hyperimmune serum produced.

Enzyme immunoassay for antibodies to membrane associated antigen of varicella zoster virus

An in situ enzyme immunoassay to viral membrane antigen was developed to enable the specific estimation of antibodies to varicella zoster (VZ) virus. The technique was compared with a modified fluorescent antibody to membrane antigen (FAMA) procedure and with the complement fixation (CF) test by parallel assay of 352 plasma samples. The enzyme immunoassay (EIA) procedure showed very good correlation with the modified FAMA procedure, and both were far more specific than the CF test. This specificity was achieved by the use, in the EIA, of VZ virus-infected cells grown and fixed in situ with glutaraldehyde. Thus the only virus antigens accessible to antibody were the VZ-specific antigens expressed at the cell membrane, cross-reactions with herpes simplex virus antibodies thereby being avoided.

A rapid semi quantitative capillary enzyme immunoassay for digoxin

A rapid and sensitive enzyme immunoassay (EIA) which does not require highly trained personnel or specialised instrumentation is described for the estimation of digoxin in serum, plasma or whole blood samples. The method is based on the ability of digoxin in a clinical sample to inhibit the binding of urease-conjugated sheep-antidigoxin immunoglobulin to a glass capillary tube coated internally with a human serum albumin-digoxin conjugate. The bound enzyme activity can then be measured using a substrate solution containing urea and a pH indicator, most suitably bromocresol purple. The enzymic hydrolysis of urea produces ammonia which causes a vivid yellow to purple colour change in the pH indicator. Plasma samples from 92 patients receiving digoxin were screened in parallel with reference plasma containing 1.3 or 3.8 nmol/l digoxin. The results were available within a total test time of 30 min, and showed excellent correlation with those obtained by radioimmunoassay.

A comparison of enzyme immunoassay and bioassay for the quantitative determination of antibodies to tetanus toxin

Antibodies to tetanus toxin were induced in sheep by hyperimmunization over 24 weeks. Bleeds taken at weeks 4, 8, 20 and 30 were assayed for antibody titre by both an enzyme immunoassay (EIA) using a newly-described urease enzyme/substrate system and by bioassay in mice. There was a very good correlation between the two assay systems and, with the exception of the week 4 Bleeds, the relationship was the same at all stages of hyperimmunization regardless of titre, adjuvant, or whether toxin or toxoid was used as immunogen or for coating the plates. The results establish that the EIA can replace the bioassay for the determination of tetanus antitoxin in ovine sera.

An investigation of the use of urease-antibody conjugates in enzyme immunoassays

The development of urease (E.C.3.5.1.5) as a label for enzyme immunoassay (EIA) procedures is described and the use of such conjugates illustrated with examples. Urease catalyzes the hydrolysis of urea to carbon dioxide and ammonia. The production of ammonia may be detected readily by a pH shift which we have found best indicated by the vivid colour change (yellow to purple) of bromocresol purple incorporated in the substrate solution. This enzyme-substrate system offers a number of important advantages. The substrate in aqueous solution is stable, titration end points are sharp and readily visible and the enzyme is not inhibited by sodium azide. Thus, test reagents may be prepared with this preservative and stored ready to use. Urease of high specific activity is commercially available and because it does not occur in mammalian tissues, it is suitable for use in EIA tests to detect cell-associated antigens and their antibodies. Finally, the enzyme reaction may be stopped by the addition of organomercurial preservatives, thus allowing storage of developed tests for later examination.

Photopigments in Rhodopseudomonas capsulata cells grown anaerobically in darkness

The phototrophic bacterium Rhodopseudomonas capsulata can obtain energy for dark anaerobic growth from sugar fermentations dependent on accessory oxidants such as trimethylamine-N-oxide or dimethyl sulfoxide. Cells grown for one to two subcultures in this fashion, with fructose as the energy source, showed approximately a twofold increase in bacteriochlorophyll content (per milligram of cell protein) and developed extensive intracytoplasmic membranes in comparison with cells grown photosynthetically at saturating light intensity. Cells harvested from successive anaerobic dark subcultures, however, showed progressively lower pigment contents. After ca. 20 transfers, bacteriochlorophyll and carotenoids were barely detectable, and the amount of intracytoplasmic membrane diminished considerably. Spontaneous mutants incapable of producing normal levels of photosynthetic pigments arose during prolonged anaerobic dark growth. Certain mutants of this kind appear to have a selective advantage over wild-type cells under fermentative growth conditions. Of four pigment mutants characterized (two being completely unable to produce bacteriochlorophyll), only one retained the capacity to grow photosynthetically.

Toxoplasmosis and the wild rabbit Oryctolagus cuniculus in Victoria, Australia with suggested mechanisms for dissemination of oocysts

Sera or serum eluates from 1697 wild rabbits [Oryctolagus cuniculus (L)], collected over the past 10 years from 24 sites in 5 geographic regions of Victoria, were examined for antibodies to Toxoplasma gondii. Sera generally were classified into three broad groups, negative (titre less than 10), weakly reactive (titre 10 to 100) and strongly positive (titre greater than 1000). Strongly positive sera came from rabbits collected in a small number of localized areas, most significantly the Melbourne and Metropolitan Board of Works (MMBW) Sewerage Farm at Werribee and Mud Island in Port Phillip Bay.

Resolution of distinct selenium-containing formate dehydrogenases from Escherichia coli

Formate dehydrogenase, a component activity of two alternative electron transport pathways in anaerobic Escherichia coli, has been resolved as two distinguishable enzymes. One, which was induced with nitrate reductase as a component of the formate-nitrate reductase pathway, utilized phenazine methosulfate (PMS) in preference to benzyl viologen (BV) as an artificial electron acceptor and appeared to be exclusively membrane-bound. A second formate dehydrogenase, which was induced as a component of the formate hydrogenlyase pathway, appeared to exist both as a membrane-bound form and as a cytoplasmic enzyme; the cytoplasmic activity was resolved completely from the PMS-linked activity on a sucrose gradient. When E. coli was grown in the presence of 75Se-selenite, a 110,000-dalton selenopeptide, previously shown to be a component of the PMS-linked enzyme, was induced and repressed with this activity. In contrast, an 80,000-dalton selenopeptide was induced and repressed with the BV-linked activity and exhibited a distribution similar to the BV-linked formate dehydrogenase in cell fractions and in sucrose gradients. The results indicate that the two formate dehydrogenases are distinguishable on the basis of their artificial electron acceptor specificity, their cellular localization, and the size of their respective selenoprotein components.

Simple diagnostic test for antibodies to Encephalitozoon cuniculi based on enzyme immunoassay

Rabbit antibodies against Encephalitozoon cuniculi were detected in an enzyme immunoassay procedure in which antigen was grown and used in situ. The test appeared to be more sensitive than the indirect immunofluorescence test with which it was compared, but gave essentially the same results for the 64 sera evaluated. This procedure will allow any laboratory with cell-culture facilities to produce a diagnostic antigen without the need for antigen processing. It is simple and reliable, and does not require specialized equipment or microscopic assessment.

An immunofluorescence study of influenza virus filament formation

A study is described in which filamentous forms of influenza virus were observed budding from host cell surfaces. Cell cultures infected with influenza virus were stained by indirect immunofluorescence using an antiserum to purified haemagglutinin. Filaments greater than 100 micrometers in length, with several branch points along their length were observed; the number and length of filaments varied according to the virus strain and the time after infection. Examination of infected cells by electron microscopy confirmed the presence of branched structures with an ultrastructure typical of filamentous forms of influenza virus. The immunofluorescence technique was quicker than thin section electron microscopy and was a more sensitive procedure for the detection of filamentous forms of influenza virus than electron microscopy using negative stain. It also enabled the antigenic composition of the filaments to be observed.

Physiology of dark fermentative growth of Rhodopseudomonas capsulata

The photosynthetic bacterium Rhodopseudomonas capsulata can grow under anaerobic conditions with light as the energy source or, alternatively, in darkness with D-fructose or certain other sugars as the sole source of carbon and energy. Growth in the latter mode requires an "accessory oxidant" such as trimethylamine-N-oxide, and the resulting cells contain the photosynthetic pigments characteristic of R. capsulata (associated with intracytoplasmic membranes) and substantial deposits of poly-beta-hydroxybutyrate. In dark anaerobic batch cultures in fructose plus trimethylamine-N-oxide medium, trimethylamine formation parallels growth, and typical fermentation products accumulate, namely, CO2 and formic, acetic, and lactic acids. These products are also found in dark anaerobic continuous cultures of R. capsulata; acetic acid and CO2 predominate when fructose is limiting, whereas formic and lactic acids are observed at elevated concentrations when trimethylamine-N-oxide is the limiting nutrient. Evidence is presented to support the conclusions that ATP generation during anaerobic dark growth of R. capsulata on fructose plus trimethylamine-N-oxide occurs by substrate level phosphorylations associated with classical glycolysis and pyruvate dissimilation, and that the required accessory oxidant functions as an electron sink to permit the management of fermentative redox balance, rather than as a terminal electron acceptor necessary for electron transport-driven phosphorylation.

A serological survey of Encephalitozoon cuniculi infection in the wild rabbit in England and Scotland

Sera from 175 wild rabbits trapped in England or Scotland over the past two years were tested for antibodies to Encephalitozoon cuniculi. No sera were positive, suggesting that this common laboratory rabbit pathogen is rare in wild rabbits in these areas.