摘要:

During a 2-year study, samples of various types of soils were collected from 115 fields that had not previously been treated withBacillus thuringiensisand which were remote from any large-scale aggregations of lepidopterous insects in rearing or grain-storage areas. An average of about 400 isolates were examined from each soil, and, of 46 373 isolates examined, only 250 (0.5%) were identified asB.thuringiensis. While it was almost impossible to insure that a field had never been treated withB.thuringiensisor that drift from some nearby application had not reached the field, it is noteworthy that of the 250 isolates, 156 (62.4%) were not var.kurstaki, the only variety that has been used commercially in the United States in about 10 years. This is a strong indication that theB.thuringiensisisolates observed were present naturally. To verify the procedures used, samples were taken from two adjacent experimental plots which had been treated about 12 months previously with formulations of var.kurstakiand var.galleriae, respectively. With practically no exception, the variety recovered from each plot was the variety applied, indicating that the varietal status ofB.thuringiensisis stable in the soil.

ISSN:0008-4166    

DOI:10.1139/m81-137

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Seven strains ofAzospirillum brasilensewere compared for their effect on the growth ofZea maysgrown under temperate conditions in sand–vermiculite pot cultures. Inoculation with all seven strains tested, including Fix−mutant strains, increased dry weight and total nitrogen content of shoots, but nitrogen concentrations were unaffected. Low and variable rates of acetylene reduction activity were observed from excised roots of inoculated plants without preincubation. Estimates of N2-fixingA.brasilenseassociated with inoculated roots showed differences between strains in establishing themselves in the rhizosphere and endorhizosphere. In some strains enrichment in the endorhizosphere of roots occurred following inoculation, but the relative numbers and location of the strains did not appear to affect the yield response.

ISSN:0008-4166    

DOI:10.1139/m81-138

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Acetylene inhibition and13N methods were used to assay digested sludge for its potential to denitrify and to reduce nitrate to ammonium. At nitrate concentrations below 10 μM, the reduction of N2O to N2was not inhibited by acetylene concentrations as high as 80 kPa, though at higher nitrate concentrations acetylene was an effective inhibitor. NO, N2O, and N2were produces immediately after addition of nitrate or nitrite, indicating that denitrifying enzymes were present. NO was maintained at a concentration of 2–5 nM, while nitrate or nitrite were being reduced, but this gas was depleted once the ionic N oxide substrates were exhausted. Acetylene had little effect on appearance and disappearance of NO. It was also noted that NO was readily consumed by chemical reactions in the anaerobic sludge. Added N2O was reduced without a lag, but pasteurized samples did not consume N2O although they produced it. Fresh digested sludge reduced 60–70% of the added13NO3−to13NH4+with the rest of the NO3−-N presumably lost to denitrification. This agrees well with the nitrate partitioning observed by the acetylene inhibition method in which 30–40% of the NO3−-N was recovered as N2O. Denitrification capacity persisted in both digested sludge and methanogenic enrichment culture which had been grown in a chemostat for 2.5 years with acetate and ammonium as the solid carbon and nitrogen source. This suggests that denitrifiers with capacities for alternative anaerobic energy metabolism may be more common than now known.

ISSN:0008-4166    

DOI:10.1139/m81-139

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Sclerotia ofSclerotinia minorwere parasitized byTeratosperma oligocladum, a recently described dematiaceous hyphomycete. The mycoparasite was cultured on living sclerotia placed on water agar and on sclerotia in moist sand. It grew poorly on several common laboratory media but growthin vitrowas enhanced by supplements of soil extract and, especially, by aqueous extracts of sclerotia. Sclerotia ofS.minor,S.sclerotiorum,S.trifoliorum,Sclerotium cepivorum, andBotrytis cinereawere parasitizedin vitro, but sclerotia ofSclerotium rolfsiiandMacrophomina phaseolinawere not. Macroconidia ofT.oligocladumgerminated on membrane filters placed on soil containing sclerotia ofS.minorbut not on soil without sclerotia. Sclerotia of threeSclerotiniaspp. were infected within 2 weeks in soil infested with the mycoparasite.Teratosperma oligocladumparasitized and destroyed all of the sclerotia ofS.minorburied in a natural soil by 10 weeks. Parasitism was equally good at 20 and 25 °C, but occurred more slowly at 15 °C. No parasitic activity occurred at 30 °C. The morphology, cultural characteristics, and mycoparasitic habit ofT.oligocladumindicated that it was similar in many respects to the mycoparasite,Sporidesmium sclerotivorum, and that it is a potentially useful agent for the biological control of sclerotial plant pathogens.

ISSN:0008-4166    

DOI:10.1139/m81-140

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The response to dinitrofluorobenzene (DNFB), bovine serum albumin (BSA), and sheep red blood cells (SRBC) was studied in CBA mice infected withTrypanosoma musculiat days ranging from 3 to 63 days of infection. DNFB contact sensitivity was normal. In 3-, 10-, and 15-day infected mice, anti-BSA hemagglutinating antibody titers were lower than in noninfected controls when determined after 21 days of BSA challenge, and were normal in sera collected after 10 and 14 days. In 14 day infected mice, anti-SRBC indirect plaque-forming cells (PFC) (per million of nucleated spleen cells and per total spleen) were strongly diminished, but anti-SRBC direct PFC were diminished only per million of nucleated spleen cells. InT.musculirecovered mice, the response to DNFB, BSA, and SRBC was normal.

ISSN:0008-4166    

DOI:10.1139/m81-141

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The ranges of the major ion composition of near neutral hypersaline lakes have been described in terms of the charge concentration and the mole fraction of monovalent cations. An ion interactive method was used to establish the thermodynamic activity of the chemical species in these model brines, which were then used in culture media forHalobacterium halobium,H.salinarium, andH.volcanii. The bacteria grew rapidly at water activities of 0.78, 0.79, and 0.925, respectively. The growth areas for these organisms were not easily defined in terms of the Na+or Cl−activity. The morphology ofH.halobiumandH.salinariumchanges from rod shaped to spherical when the Mg2+activity drops below 0.15 mol∙kg−1. Niches described by the chemical parameters reflect the marine origin of the environments ofH.halobiumandH.salinarium, and the more heterogeneous environments ofH.volcani

ISSN:0008-4166    

DOI:10.1139/m81-142

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Fouling biofilm development was monitored in a completely mixed tubular recycle reactor. A unique sampling system allowed direct (brightfield, epifluorescence, and scanning electron photomicroscopy) and indirect (increased fluid frictional resistance) observations of biofilms. Low fluid velocity (138.5 cm/s) experiments had shorter induction times and biofilm matrixes which included firmly adherent filamentous bacteria. High fluid velocity (265.4 cm/s) experiments had longer induction times with firmly adherent filamentous bacteria present only after the accumulation of extracellular materials. In both cases the fluid frictional resistance increased after filamentous bacteria became a permanent part of the biofilm.

ISSN:0008-4166    

DOI:10.1139/m81-143

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A bacteriocin, streptococcin sal-P, was isolated by freeze-thaw elution from cultures ofStreptococcus salivariusstrain P grown on tryptic soy agar plus 1 % neopeptone. The inhibitor could also be extracted with either 7 Murea or 1 MNaCl from cells grown on this medium, but little activity was recovered from cells grown in liquid media or from the supernatants of these cultures. Streptococcin sal-P was found to be a proteinaceous substance of molecular weight approximately 8000. It was remarkably stable at extremes of pH or temperature and appeared to adsorb nonspecifically to both sensitive and resistant bacterial cells and also to cellulose membranes. The range of its inhibitory activity was almost entirely against Gram-positive bacteria, particularly streptococci, including strains ofS.pyogenesandS.sanguis, but notS.mutansor group D streptococci. Streptococcin sal-P was bactericidal for actively metabolizing susceptible strains.

ISSN:0008-4166    

DOI:10.1139/m81-144

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

When amoebae ofPolysphondylium pallidumWS320 are placed in nonnutrient buffer in roller tube culture they form spherical or ellipsoidal aggregates. At first the aggregates demonstrate a "loose" morphology but by 12 h, with the formation of a cellulose-containing, peripheral sheath, they become "tight" aggregates. At this time stalk differentiation begins. Using various methods for the resolution of prespore (ultrastructure, spore antigen immunofluorescence, periodic acid – Schiff staining) and prestalk (ultrastructure, alkaline phosphatase histochemistry, neutral red staining, Calcofluor fluorescence) cell localization, the pattern of cell differentiation in submerged aggregates was shown to be essentially identical to that of normal pseudoplasmodia. Furthermore, using a cAMP bioassay it was revealed that the submerged aggregates, while devoid of a morphological tip, do possess a biochemical tip which is correlated with sites of neutral red staining and stalk cell differentiation. As a result of these studies, an earlier argument that the tip of the pseudoplasmodium is not essential for the establishment of pattern or in the "organization" of cellular differentiation during slime mould development is contradicted.

ISSN:0008-4166    

DOI:10.1139/m81-145

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

An abbreviated procedure for the biochemical identification ofYersinia enterocoliticaisolated from food enrichments on CIN (cefsulodin–irgasan–novobiocin) agar was investigated. A total of 170 colonies resemblingY.enterocoliticain colonial morphology and appearance on CIN agar were selected for identification using API strips. Ninety-three of these isolates were examined with the PathoTec ornithine decarboxylase, Voges–Proskauer, and urease test strips. The PathoTec urease strip alone was adequate for identification of all isolates ofY.enterocolitica. Christensen's urea agar was applied to the remaining 77 isolates and found less specific in that 1 isolate ofEnterobacter agglomeronswas urease positive along with 10 isolates ofY.enterocolitica. CIN agar is a highly specific medium for isolation ofY.enterocolitica, requiring only Kligler iron agar and urea slants for confirmation of presumptive colonies.

ISSN:0008-4166    

DOI:10.1139/m81-146

出版商:NRC Research Press    

年代:1981

数据来源: NRC