摘要:

Enterobacter cloacae, like most enteric bacteria, can grow in the presence of 10% sodium dodecyl sulfate (SDS). The bacteria tolerate the detergent and do not metabolize it. In a defined glucose–salts medium the growth rate remained unchanged (G = 55 min) as the detergent concentration was increased from 0 to 10% SDS. However, growth in SDS exhibited a two-part energy dependence. In part 1, the SDS-grown cells underwent rapid lysis when they ran out of energy. Cells that had entered stationary phase owing to carbon limitation lysed, while those that had entered owing to nitrogen or phosphorus limitation did not. We attribute part 1 of the energy dependence to SDS as a detergent. In part 2, the cells grown in 5 or 10% SDS exhibited longer lag periods, potassium accumulation, decreased cell yields, and higher oxygen consumption. The higher oxygen consumption occurred during both exponential phase and nitrogen-limited stationary phase. However, the decreased cell yield and higher oxygen consumption of SDS-grown cells were mimicked by cells grown in equivalent concentrations of sucrose or polyethylene glycol. We attribute part 2 of the energy dependence to SDS as a solute. Finally, with regard to the as yet unidentified bacterial osmotic stress detector, we used the micelle-forming nature of SDS to conclude that the detector was responding to turgor pressure – water activity rather than to osmolarity itself.Key words: sodium dodecyl sulfate, bacterial detergent resistance, osmotic stress, oxygen consumption, energy-dependent cell lysis.

ISSN:0008-4166    

DOI:10.1139/m93-080

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Several strains of a new haploid, heterothallic species ofMetschnikowiahave been isolated fromAgave tequilanavar.azulin two agave-growing localities of Jalisco, Mexico. The new yeast species forms two aciculate ascospores per ascus after conjugation of enlarged and elongated compatible cells. Named after its host,Metschnikowia agaveaeresembles superficiallyMetschnikowia hawaiiensis, but differs from the latter by some physiological and morphological characteristics. These two species exhibited no signs of sexual cross-reactivity. Strain UWO(PS)92-207.1 (h+, CBS 7744, ATCC 90148) is the type culture, and strain UWO(PS)92-210.1 (h−, CBS 7745, ATCC 90147) has been designated as isotype.Key words: agave, yeast,Metschnikowia, new species.

ISSN:0008-4166    

DOI:10.1139/m93-081

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Soil and root samples collected from fields cropped to spring wheat (Triticum aestivumL. cv. Katepwa) and lentil (Lens esculentaL. cv. Eston) at 11 sites across four soil zones of Saskatchewan were analyzed for spore numbers, level of vesicular–arbuscular mycorrhizal (VAM) colonization, and VAM species. The number of VAM spores detected in field soils ranged from 78 to 272 per 100 g soil. Vesicular–arbuscular mycorrhizae colonized wheat and lentil at all the field study sites, but levels of colonization in the two crops varied from site to site and the differences were more pronounced in wheat than in lentil. Generally, lentil both exhibited a higher percentage of VAM colonized roots and contained more arbuscules and vesicles than wheat roots. However, wheat appeared to be colonized by different types of VAM depending on the field sites. Differences in VAM colonization were not related to the moisture and temperature gradient of the four soil zones or soil properties. Seven VAM species were isolated by enriching indigenous VAM mixtures (collected from wheat field soils of six field sites) on maize. The VAM isolated most closely resembledAcaulospora denticulata,Gigaspora decipiens,Glomus clarum,Glomus etunicatum,Glomus fasciculatum,Glomus mosseae, andGlomus versiforme. The species composition of the VAM community varied at the different field sites.Key words: VAM,Acaulospora,Gigaspora,Glomus.

ISSN:0008-4166    

DOI:10.1139/m93-082

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The biodegradation of both ann-alkane and several carboxylated cycloalkanes was examined within tailings produced by the extraction of bitumen from the Athabasca oil sands. The carboxylated cycloalkanes examined were structurally similar to naphthenic acids that have been associated with the acute toxicity of oil sand tailings. The biodegradation potential of naphthenic acids was estimated by determining the biodegradation of both the carboxylated cycloalkanes and hexadecane in oil sand tailings. Carboxylated cycloalkanes were biodegraded within oil sand tailings, although compounds with methyl substitutions on the cycloalkane ring were more resistant to microbial degradation. Microbial activity against hexadecane and certain carboxylated cycloalkanes was found to be nitrogen and phosphorus limited.Key words: biodegradation, carboxylated cycloalkanes, oil sand tailings.

ISSN:0008-4166    

DOI:10.1139/m93-083

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

HI plasmids are distinguished by their thermosensitive mode of conjugation (transfer efficiency is optimal at 22–30 °C) and their capacity to encode multiple antibiotic resistance. These traits have implicated HI plasmids as potential vectors in the dissemination of antibiotic resistance among pathogenic and indigenous bacterial species in water and soil environments. We compared the transfer efficiency of HI plasmids with that of plasmids from 13 other incompatibility groups at 37, 24, and 14 °C in intragenic conjugations between laboratory strains ofEscherichia coliK-12 underin vitroconditions. Only the HI plasmids and a representative plasmid from incompatibility groups M, N, Pα, T, and W were observed to be transmissible at 14 °C. These plasmids, along with HI plasmids and the related HII representative, were tested for their host range and transfer proficiency toEnterobacteriaspecies and some other Gram-negative organisms of environmental significance at 24 and 14 °C. Notable differences in the host range of HI plasmids compared with plasmid representatives from the other enterobacterial groups were not evident at 24 °C. At 14 °C, R478 (HI2) displayed the broadest host range and transfer proficiency among the test plasmids. The ability of several plasmid groups, including HI, to transfer at 14–24 °C toVibrio choleraenon 01,Salmonella typhi, and the fish pathogensAeromonas salmonicida,Vibrio anguillarum, andYersinia ruckerineeds to be corroborated byin situstudies.Key words: conjugation, plasmids, thermosensitive transfer, host range.

ISSN:0008-4166    

DOI:10.1139/m93-084

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A mass fermentation medium for growth and morphogenesis of the entomopathogenic fungusEntomophaga aulicaewas developed. This fungus is a major pathogen of larval eastern hemlock looper and spruce budworm. The medium consists of a basal medium plus 0.8% tryptic soy broth and 0.4% calcium caseinate. This medium is a major breakthrough in that (i) theE.aulicaedevelopmental sequence from protoplast inoculum to hyphal bodies competent to form conidia can be carried out in a single medium without adjustment, (ii) by examining the fermentation product it can be determined if conidia can be produced prior to engaging in costly field spraying, (iii) this medium supports the growth ofE.aulicaeisolates from different geographical areas, (iv) the medium is relatively inexpensive, (v) the hyphal bodies are easily separated from the spent growth medium, and (vi) the hyphal body yield is high.Key words:Entomophaga aulicae, mass fermentation medium, hyphal bodies, conidia, insect biocontrol.

ISSN:0008-4166    

DOI:10.1139/m93-085

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Pseudomonas testosteroniB-356 was able to degrade approximately 50% of the Aroclor 1242 mixture in shaken culture. The aims of the present study were to evaluate the capabilities of this bacterial strain to degrade PCBs in soil microcosms and to identify some of the factors likely to favor the degradative performance of the implanted bacteria. The presence of biphenyl as cosubstrate was the most important factor affecting PCB degradation in soil. However, because biphenyl was rapidly depleted in soil microcosms, repeated addition of small amounts of biphenyl to maintain a constant level of the cosubstrate allowed the achievement of a higher degree of degradation of the tetrachlorinated components of Aroclor 1242 than was achieved with a single addition at the time of inoculation. Degradation of di- and tri-chlorinated PCB congeners was less affected by repeated addition of biphenyl because these congeners were degraded very fast and complete degradation was achieved before biphenyl was depleted in the soil. Biodegradation was also related to bioavailability of the substrate. We observed that the proportion of each congener degraded was higher in the microcosms receiving both the producer of the surface-active agent,Alcaligenes faecalisB-556, and strain B-356. Under the best conditions (presence of a constant level of biphenyl and of strain B-556)P.testosteroniB-356 was able to degrade approximately 30% of the Aroclor 1242 added to soil microcosms; some other factors reducing the PCB degradation capabilities of the implanted bacteria are also discussed.Key words: Aroclor 1242, biodegradation, bioremediation,Pseudomonas, soil.

ISSN:0008-4166    

DOI:10.1139/m93-086

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Great variations in tolerance to osmotic dehydration during batch growth of the salt-tolerant yeastDebaryomyces hanseniihave been demonstrated. The variations in osmotolerance were dependent on the cultivation conditions. The cells developed osmosensitivity at the beginning of the growth period. In medium in which the nitrogen source of the cells was changed from ammonium to urea during the growth cycle, the resulting transition state induced a marked increase in the osmotolerance of the cells. However, when the pH was kept constant at 6.0, the osmosensitive period disappeared almost completely. Various possible osmotolerance factors, such as the intracellular polyol and ion concentrations, the "G3P shuttle," and the cells' total activity measured by means of microcalorimetry, have been studied. Only small variations in the intracellular pools of polyols and ions were observed during different cultivation conditions and phases of growth. No single factor seems to be the determinant for osmotolerance and the overlap between osmoregulatory and osmotolerance factors is limited.Key words: osmotolerance, stress tolerance, calorimetry, heat production,Debaryomyces hansenii.

ISSN:0008-4166    

DOI:10.1139/m93-087

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

In a 50-L pot experiment withMedicago sativagrown under nonsterile conditions, a combined treatment ofAzospirillumandRhizobiumwas measured against soil inoculated withRhizobiumorAzospirillumalone or a control with a low background level of autochthonous rhizobia. The combined treatment significantly increased the shoot length and weight at 6 weeks and the regrowth shoot weight at 14 weeks when compared with the treatment withRhizobiumalone. In 1.5-L pots in which gnotobiotic conditions were maintained, the combined treatment led to more nodules on the main root at intermediateRhizobiumconcentrations, and a greater root surface area at intermediate and highRhizobiumconcentrations after 2 weeks but not after 4 weeks. In pouch-grown seedlings, plants were inoculated with eitherRhizobiumalone or in combination withAzospirillumor applied together with a flavonoid, luteolin (a nodulation gene inducer), or with a cytokinin, benzyl adenine. Luteolin had similar effects to those ofAzospirillumin increasing the main root nodule number and the total nodule number. With Fahraeus slides, a significant increase was observed in the number of root hairs and the root diameter in the presence ofAzospirillumas compared with the control andRhizobiumalone. There was no increase in the total number of infection threads; however, the combined treatment caused a significant decrease in the percentage of infected root hairs.Key words:Rhizobium,Azospirillum,Medicago, flavonoid, inoculation.

ISSN:0008-4166    

DOI:10.1139/m93-088

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The incorporation of 5-fluorouracil (FUra) into RNA ofMycobacterium aviumcomplex strain LM1 was evaluated. Cells were labeled with either [14C]FUra or [3H]uracil and the ribonucleosides were analyzed by high-performance liquid chromatography. The identification of the ribonucleosides was facilitated by the use of an isocratic system that provided unambiguous identification of the RNA pyrimidine components. Uracil was incorporated into RNA as uridine, but an equal amount was converted to cytidine. [14C]FUra was incorporated directly into RNA as 5-fluorouridine and there was no evidence of its conversion to other pyrimidines. The ratio of 5-fluorouridine:uridine was 2.8-fold greater for cells grown in 100 μg FUra/mL than for cells grown in 20 μg FUra/mL. Analysis of the RNA nucleotides was performed and deoxyribonucleotides were present; DNA contamination was estimated to range from about 2 to 8% of the RNA preparations.Key words: 5-fluorouracil, RNA,Mycobacterium aviumcomplex, HPLC, ribonucleoside.

ISSN:0008-4166    

DOI:10.1139/m93-089

出版商:NRC Research Press    

年代:1993

数据来源: NRC