摘要:

Protoplasts were released from mycelium and the cylindrical type of arthroconidia fromGeotrichum candidumby a lytic enzyme (Novozym 234). This enzyme was unable to release protoplasts from the ellipsoidal type of arthroconidia, which reflects a difference in the cell walls of the two types of conidia. The conditions necessary to obtain stable protoplasts were determined. Magnesium sulphate (0.8 M) was the best osmotic stabilizer for the formation of protoplasts, whereas both mannitol and magnesium sulphate could be used for regeneration. The regeneration was faster with mannitol than with magnesium sulphate.

ISSN:0008-4166    

DOI:10.1139/m85-019

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A Gram-negative rod which grew with an unusual colonial "water-drop" form was isolated from periodontal pocket samples from 12 patients. Six strains were characterized by biochemical tests, cell wall analyses, malate dehydrogenase mobilities, protein profiles, and serology. By these criteria, the organisms formed a group of similar strains which were anaerobic, nonmotile, nonsporing, Gram-negative rods resemblingBacteroides. Comparison of the isolates to American Type Culture Collection strains ofBacteroidesshowed that they represented a closely related group, distinct from the described species of oralBacteroides. Initial results on the DNA of the isolates suggested a base ratio of 54–57% G + C. Despite the DNA G + C base ratios currently accepted for theBacteroides(28–61 mol% G + C), many species fall into a narrower range of 40–52 mol% G + C. This range would exclude the organisms described here and suggests that placing them into the genusBacteroidesmay be inappropriate.

ISSN:0008-4166    

DOI:10.1139/m85-020

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The invasive sector modification ofNectria haematococca, associated with a cytoplasmic factor σ, is characterized by an alteration of growth and an hyperproduction of pigments. To obtain insight into the molecular nature of this factor, we devised a curing protocol for cells which carry it. We tested the effect of elevated temperatures and drugs on the maintenance or the replication of the σ factor as estimated by the frequency of cultures which have lost the modified character. Modified cultures were converted into normal cultures when grown at 34 °C or in the presence of ethidium bromide, but not in the presence of cycloheximide or 5-fluorouracil. These results are discussed in connection with the possible involvement of a DNA plasmid in the control of sector modifications.

ISSN:0008-4166    

DOI:10.1139/m85-021

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Asynchronous populations of the budding yeastSaccharomyces cerevisiaestrain AG1-7 were examined by freeze-fracture electron microscopy for ultrastructural changes occurring in response to changes in the environment, specifically the following: temperature (23 or 37 °C); cell density (exponential, early stationary, and stationary phases); various periods of nitrogen starvation at low cell density, and return of nitrogen-starved cells to nitrogen-replete medium. This information has been gathered in preparation for ultrastructural examination of comparable responses of temperature-sensitive cell-cycle mutants. The plasma membrane was found to be particularly responsive to changes in environment. A high proportion (75%) of cells in exponential phase populations at 37 °C displayed paracrystalline arrays of plasma membrane particles, whereas this proportion was much lower (20%) at 23 °C in the same medium; plasma membrane grooves were longer at 37 than at 23 °C. In budded cells, the mother cell displayed paracrystalline arrays more frequently than the bud. Entry of cells into stationary phase, either through permitting population growth or by limiting nitrogen supply, resulted in increases in numbers of paracrystalline arrays and grooves. Groove depth also increased. The paracrystalline-array and groove-density responses were independent, both during entry into stationary phase and during the subsequent lag phase. Unusual groove forms appeared during stationary phase in high cell density populations, but not in low cell density nitrogen-starved populations. "Aggregate" and "geometric" tonoplast forms, previously described in strain A364A when grown under some of the conditions used here, were not found in AG1-7 under any of the conditions used here. It was demonstrated that particle-free patches can arise rapidly on the tonoplast of AG1-7 in response to temperature change from 37 to 23 °C. During stationary phase, spherosomes (lipid droplets) increased in size, particularly in response to nitrogen depletion. After 72 h of nitrogen starvation, about 10% of cell volume consisted of spherosomes. Changes in vacuolar content and mitochondrial form were also noted during entry into stationary phase.

ISSN:0008-4166    

DOI:10.1139/m85-022

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Cultures ofStreptomyces venezuelaepresented with a mixture of ammonium and an amino acid as nitrogen sources used both compounds together. Absence of ammonium repression of alternative nitrogen assimilation pathways was also observed when ammonium was added to cultures already growing on proline. The presence of ammonium in the mediumab initiodepressed the yield of chloramphenicol. However, its addition to a culture growing on proline caused only a temporary inhibition of antibiotic synthesis, even when sufficient ammonium was added to create an excess. Continuous cultures supplied with ammonium as the growth-limiting nutrient showed no significant change in specific antibiotic production at different specific growth rates. The overall results indicate that inS.venezuelaeneither nitrogen utilization pathways nor chloramphenicol biosynthesis is controlled by nitrogen repression.

ISSN:0008-4166    

DOI:10.1139/m85-023

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

This study was aimed at assessing the role of water as a vehicle for rotavirus spread by determining how well these viruses survive in the water environment. A cell culture adapted strain of human rotavirus subgroup 2, grown in MA-104 cells, was used as a model. Virus survival was tested in the following types of water samples, derived from the Ottawa River, at two different times of the year: (i) raw water (RW), (ii) municipally treated tap water (TW), and (iii) raw water that had been filtered (FW) through a membrane (0.22 μm). The water samples, with approximately 5.0 × 104plaque-forming units (PFU) of the virus, were held at either 4 or 20 °C and tested for infectious virus over a period of 64 days. The TW samples had a total and free chlorine content of 0.05 and <0.05 mg/L, respectively. The chlorine in these samples was not neutralized before virus contamination. Irrespective of the holding temperature, the virus titre in FW remained essentially unaltered throughout the test period. In TW held at 4 °C, there was no significant drop in the virus titre even after 64 days, whereas at 20 °C the titre in TW was reduced by about 2 log10over the same period. Even though the loss of virus infectivity was most rapid in RW held at 20 °C, it took about 10 days for a 99.0% reduction in the plaque titre of the virus. These findings, therefore, indicate that rotaviruses can survive for several days in raw and treated river water thus making recreational and potable waters potential vehicles for the transmission of rotavirus infections.

ISSN:0008-4166    

DOI:10.1139/m85-024

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Long-chain fatty aldehydes are reported for the first time as fungal products. They were isolated from potato dextrose agar cultures ofCercospora arachidicolaas mixtures that were found by analytical procedures to consist predominantly of penta-and heptadecanal and heptadec-8-enal. Small to trace amounts of tetra-, hexa-, and nonadecanal, tetra- and pentadec-2-, and pentadec-6-enal, and heptadec-8,11 -dienal were also present, together with a mono- and a di-unsaturated C16aldehyde. Brassicasterol was also isolated.

ISSN:0008-4166    

DOI:10.1139/m85-025

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Collagenolytic activity of 12 species of oral bacteria was assessed using two methods of detection. Except for two species, all bacterial strains tested were capable of degrading at least one general protein substrate. Results of collagenolytic activity in a growth assay indicate thatBacteroides gingivalisis the only bacterium capable of degrading collagen when the substrate is sterilized using ethylene oxide. However, if the substrate is sterilized by autoclaving, in the presence or absence of the growth medium, other bacterial species could be shown to be collagenolytic. Collagenolytic activity was also demonstrated when whole or broken cells were used in a [14C]collagen assay. Results from this assay and from inhibition studies indicate that collagenolytic activity can either be the result of the combined activities of both a specific collagenase and nonspecific proteases (B.gingivalis) or nonspecific proteases only (other strains in this study), although in the latter case, the time taken to hydrolyze collagen can be 10 times longer than with a specific collagenase.

ISSN:0008-4166    

DOI:10.1139/m85-026

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Conditions for the production of nitrite and nitrous oxide by an obligate methanotroph,Methylosinus trichosporium(OB 3b), were studied. The rate of nitrite productionwas correlated with the concentration of ammonia up to 20 mMin the presence of sufficient amounts of oxygen and inversely correlated with the amounts of methane in the system. The rate of nitrous oxide (N2O) productionwas correlated positively withand the amount of nitrite produced and inversely with the oxygen concentration in the system. Nitrite started to disappear when either oxygen or methane or both were depleted, but only a part of the loss could be accounted for by an increase in N2O. Maximum rates of nitrite and N2O production byMs.trichosporiumwere 6.9 ×5 1016and 2.2 × 10−17 mol∙cell−1∙day−1, respectively. These values are about 0.2 and 1.6% of the values forNitrosomonas europaea. Therefore, production of nitrite and N2O by methanotrophs in aquatic environments may not be as significant as that ofNitrosomo

ISSN:0008-4166    

DOI:10.1139/m85-027

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Cellulase activity inTrichocladium achrasporumwas demonstrated by its ability to produce cell-associated and extracellular cellulolytic enzymes when grown on a crystalline cellulose substrate. In addition, azure dye was solubilized from dyed crystalline cellulose, appearing in the growth medium during the phase of cell lysis. Exoglucanase activity was highest in the culture filtrate, with slight activity in the cell fractions, while endoglucanase was associated only with the mycelium. No desorbable exoglucanase nor endoglucanase activity could be released by sonication of residual cellulose particles removed from actively growing cultures. β-Glucosidase activity was located only in the cell-associated fractions during active growth. All enzymes had optimal activity at 50 °C; in the particulate fraction β-glucosidase exhibited a second optimum at 30 °C. In the filtrate, soluble intracellular and particulate fractions optimal exoglucanase activity occurred at pH 6.4, 7.0, and 5.8, respectively. Endoglucanase activity was optimal at pH 5.8 in the soluble cell fraction, and at pH 5.4 in the particulate fraction.

ISSN:0008-4166    

DOI:10.1139/m85-028

出版商:NRC Research Press    

年代:1985

数据来源: NRC