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Rohm, H.; Eliskases‐Lechner, Frieda; Bräuer, Martina
doi: 10.1111/j.1365-2672.1992.tb01848.xpmid: N/A
H. ROHM, F. ELISKASES‐LECHNER AND M. BRÄUER. 1992. The biochemical properties of 1013 yeasts isolated from various milk products (yoghurt, kefir and cheese environment) were compared. The differences in percentage positive reactions described as variable in the standard descriptions indicate environmental selection mechanisms and the existence of yeast‐product associations. The effects of the results on three simplified identification methods are discussed.
doi: 10.1111/j.1365-2672.1992.tb01849.xpmid: N/A
S. YASSIN AND A. WHEALS. 1992. Neurospora species may occur as spoilage organisms in bakeries and bakery products. A survey of two bakeries over a 4 month period produced 315 individually isolated strains which were characterized with respect to six features: conidial colour, protoperitheciality, mating type and percentage dark‐coloured (fertile) ascospores in crosses with type specimens of Neurospora crassa, N. sitophila and N. intermedia. We concluded that (i) N: crassa of both mating types was by far the most abundant but N. sitophila and N. intermedia were also represented; (ii) conidial colour was not a good species criterion; (iii) the percentage of fertile ascospores produced in crosses with several type specimens provided a reliable and simple species indicator; (iv) identification of individuals based on these six characteristics suggested that a large number of genetically different organisms were present in the collection; and (v) bakery infection was not due to endemic contamination in the bakery or in raw materials but from repeated external infection, perhaps on contaminated returned goods.
Fernandez‐Astorga, Aurora; Aranguiz, Agueda Fernandez; Pocino, M.; Umaran, Adelaida; Cisterna, R.
doi: 10.1111/j.1365-2672.1992.tb01850.xpmid: 1618715
A. FERNANDEZ‐ASTORGA, A. FERNANDEZ DE ARANGUIZ, M. POCINO, A. UMARAN AND R. CISTERNA. 1992. The potential of the transfer of natural plasmids between sewage strains has been studied. In vitro transfer was conducted at 37°C in tryptone soya broth and sterile raw sewage as mating media. In situ transfer was carried out in sterile raw sewage within membrane diffusion chambers at 10.6°C. When the recipient was a laboratory strain of Escherichia coli K‐12, the in situ frequency values were significantly lower (P < 0.001) than those obtained in vitro for the same mating pair. When the laboratory recipient was replaced with recipients from the same sewage source, frequency values decreased progressively from the optimum conditions to the most adverse. However, in situ frequency values were higher than those for the same donors mated with a laboratory recipient.
Jaulhac, B.; Bes, M.; Bornsteint, N.; Plémont, Y.; Brun, Y.; Fleurette, J.
doi: 10.1111/j.1365-2672.1992.tb01851.xpmid: 1618716
B. JAULHAC, M. BES, N. BORNSTEIN, Y. PIÉMONTY. BRUN AND J. FLEURETTE. 1992. A dot blot hybridization technique with oligonucleotide probes was developed for the specific detection of the TSST‐1 gene and the staphylococcal enterotoxin (SE) genes A, B, C, D and E. For each toxin gene a probe sequence was chosen from the previously determined sequence. A total of 145 staphylococcal strains (133 Staphylococcus aureus and 12 coagulase‐negative staphylococci (CNS)) were studied by this genotypic method and by two phenotypic assays (gel immunodiffusion and ELISA). An excellent correlation (96%) was observed between the genotypic and phenotypic assays. DNA from two CNS strains hybridized with a probe without detection of the corresponding toxin (SEB for one strain and SEC for the other strain). One Staph. aureus strain was shown to be an SEC producer, but was not detected by the corresponding probe. Gene probe and immunological assays seem to be complementary methods for studies of staphylococcal strains producing (or potentially producing) TSST‐1 or enterotoxins.
Cano, R. J.; Torres, M.J.; Klem, R.E.; Palomares, J.C.; Casadesus, J.
doi: 10.1111/j.1365-2672.1992.tb01852.xpmid: 1618717
R. J. CANO, M.J. TORRES, R.E. KLEM, J.C. PALOMARES AND J. CASADESUS. 1992. This study evaluates a DNA hybridization assay for salmonella with AttoPhos™ (JBL Scientific, San Luis Obispo, CA), a fluorescent substrate for alkaline phosphatase. The probe used (50 ng/ml) was a biotinylated 600 bp fragment consisting of a tandem repeat of an insertion sequence (IS200) found in most Salmonella spp. evaluated. The hybridization was carried out at 65°C for 2 h without prior prehybridization and hybrids were detected by the addition of a streptavidin‐alkaline phosphatase conjugate. Circles (5 mm) were cut from the membrane and placed in a cuvette containing 1 ml of 1 mmol/1 AttoPhos™. The reaction was evaluated after 30 min at 37°C with a fluorometer with an excitation wavelength of 440 nm and an emission wavelength of 550 nm. The sensitivity of the probe was estimated to be 10 000 copies of target DNA or 5 times 10‐20 mol of DNA. All 74 salmonella strains tested reacted with the probe but none of the 98 heterologous species tested gave positive results. The results of this study indicate that our assay method, which employs a biotinylated tandem repeat of IS200 and AttoPhos™, is a specific and highly sensitive quantitative method for the detection of salmonellas.
doi: 10.1111/j.1365-2672.1992.tb01853.xpmid: 1618718
T.M. MADELIN AND H.E. JOHNSON. 1992. An aerodynamic particle sizer (APS) that uses laser Doppler velocimetry was used to determine aerodynamic diameters of spores of fungal and thermophilic actinomycete species common in mouldy hay, acrosolized at different humidities and temperatures. Results were compared with those obtained from inertial impaction in a cascade impactor. The APS gave slightly smaller measurements than the cascade impactor. Both methods gave aerodynamic diameters generally slightly smaller than the average spore dimensions observed on cascade impactor slides with a microscope. The latter measurements were less than axial dimensions given in the literature. Brief passage of spores through air at 95% relative humidity (RH) and 38°C, compared with 40% RH and 20°C, caused an immediate increase in their aerodynamic diameter and the breaking of chains of spores. Cultures maintained at 75% RH and aerosolized at 98% RH similarly produced larger spore particles than those passed through dry air. These findings have implications for mould‐induced asthma and allergic alveolitis since they relate to physical behaviour of airborne spores and particle deposition sites in the lung.
doi: 10.1111/j.1365-2672.1992.tb01854.xpmid: N/A
A.S. KAPRELYANTS AND D.B. KELL. 1992. The fluorescent dye rhodamine 123 (Rh 123) is concentrated by microbial cells in an uncoupler‐sensitive fashion. Steady‐state fluorescence measurements with Micrococcus luteus indicated that provided the added dye concentration is below approximately 1 mmol/1, uptake is fully uncoupler‐sensitive and is not accompanied by significant self‐quenching of the fluorescence of accumulated dye molecules. ‘Viable’ and ‘non‐viable’ cells are easily and quantitatively distinguished in a flow cytometer by the extent to which they accumulate the dye. The viability of a very slowly growing chemostat culture of Mic. luteus is apparently only about40–50%, as judged by plate counts, but most of the ‘non‐viable’ cells can be resuscitated by incubation of the culture in nutrient medium before plating. The extent to which individual cells accumulate rhodamine 123 can be rapidly assessed by flow cytometry, and reflects the three distinguishable physiological states exhibited by the culture (‘non‐viable’, ‘viable’ and ‘non‐viable‐but‐resuscitable’). Gram‐negative bacteria do not accumulate rhodamine 123 significantly because their outer membrane is not permeable to it; a simple treatment overcomes this. Flow cytometry using rhodamine 123 should prove of general utility for the rapid assessment of microbial viability and vitality.
Monteiro, G.A.; Fialho, A.M.; Ripley, S.J.; Sá‐Correia, I.
doi: 10.1111/j.1365-2672.1992.tb01855.xpmid: N/A
G.A. MONTEIRO, A.M. FIALHO, S.J. RIPLEY AND I.SÁ ‐CORREIA. 1992. The electrotransformation of gellan‐gum producing or non‐producing strains of Pseudomonas elodea (Gel+ or Gel‐) was optimized with respect to growth stage, cell and DNA concentrations and pulse parameters. This technique proved to be a valuable alternative to conjugal mating to search for complementation of gellan mutations for cloning the gellan genes. The electrotransformation efficiency of Gel+ or Gel‐ strains was similar. The transformation of smaller plasmids was more efficient than that of larger plasmids, and recombinant plasmids with sizes larger than 35 kb, when extracted from Escherichia coli DH1, were not transformable at detectable frequency. This was partially related to the modification/restriction system active in the recipient cells.
Holland, K.T.; Marshall, J.; Taylor, D.
doi: 10.1111/j.1365-2672.1992.tb01856.xpmid: 1618719
K.T. HOLLAND, J. MARSHALL AND D. TAYLOR. 1992. Micrococcus sedentarius, an organism associated with pitted keratolysis, produced two proteinases in culture supernatant fluids, as shown by non‐denaturing PAGE with overlaying with a casein substrate. A mixture had optimal activity at pH 10 with azocasein substrate. At pH 7.1 and 8.1 in continuous culture with varying dilution rates high proteinase production occurred at relative specific growth rates (μrels) 0.39 and 0.77 and biomass concentrations decreased with increasing dilution rate. One proteinase was constitutive and varied little in production with different growth rates. The other proteinase was under control with high production at low growth rates and no production at high growth rates. With varying pH at μrels, 0.39 and 0.77 maximum biomass concentration and proteinase production occurred between pH 8.0 and 9.0 as did the highest specific growth rate. These results support the hypothesis that Mic. sedentarus produces pitting in the stratum corneum when the skin is hydrated and the pH rises above neutrality.
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