摘要:

Fourteen species and six strains of fungi were tested for viability after their spores had been stored on silica gel crystals in test tubes at −20 °C. Some of the fungi were maintained up to 3 years without measurable loss of viability by this method, but others could not be stored or only for a few weeks. Three insect pathogenic species,Beauveria bassiana,Metarrhizium anisopliae, andSpicaria rileyi, retained pathogenicity after 3 years storage when laboratory bioassays were conducted against host insects.

ISSN:0008-4166    

DOI:10.1139/m74-098

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Temperature-induced, non-pigmented, auxotrophic derivatives ofErwinia herbicolaY46 show variation in their extracellular diffusible antigens, both among themselves, and with the parent strain. The pattern of variation did not correspond to those of other observed physiological differences. A variable, but minor, degree of cross-reaction withErwinia amylovora595 was observed. Ultrasonic disruption ofE.herbicolacells revealed a major antigen component in some variants. However, this method reduced the precipitation of some other components, and is recommended for use in antigen preparation in these organisms only under carefully specified conditions. None of theE.herbicolavariants tested were phytopathogenic to pear fruitlets.

ISSN:0008-4166    

DOI:10.1139/m74-099

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Characterization of an indirect, or enhanced, neutralization of T-even phage is reported. It is concluded that addition of anti-Fab, but not anti-Fcγ, converts a complex of phage and anti-phage from an infectious plaque former to a noninfectious, or neutralized, phage. It is also concluded that the antiphage involved in this indirect neutralization reacts with the T-even tail sheath, and not with the tail fibers as is the case with direct neutralization.

ISSN:0008-4166    

DOI:10.1139/m74-100

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Formalinized vaccines prepared from the Nine Mile, Phase I, strain ofC.burnetior purified preparations of the Phase I antigen initiate a state of delayed hypersensitivity in guinea pigs as determined by the in vitro migration inhibition system. This delayed hypersensitivity is directed against the protein as well as the carbohydrate component of the Phase I antigen. Guinea pigs that had recovered from Q-fever demonstrated a similar state of delayed hypersensitivity. Circulating antibody levels as determined by the microagglutination test were readily apparent in both infected and vaccinated animals.

ISSN:0008-4166    

DOI:10.1139/m74-101

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Twenty-one naturally contaminated high-moisture food samples were analyzed to compare the relative efficiency of using thirteen 25-g, three 108.3-g, one 325-g, and one 500-g subsamples in recovery of salmonellae. In addition, recovery by preenrichment in lactose broth was compared with direct selective enrichment in selenite cystine and tetrathionate brilliant green broths. Analysis of preenriched large lumped subsamples, prepared by combining multiple 25-g subsamples, detected positive samples as effectively as the analysis of individual 25-g subsamples. In the analysis of 25-g subsamples, direct enrichment detected as many positive "lots" as preenrichment, but in the analysis of lumped subsamples, direct enrichment gave dramatically reduced recovery. Nevertheless, directly enriched 25-g subsamples resulted in a significantly lower rate of recovery than preenriched subsamples. The results indicate that analysis of a single lumped 325-g preenriched subsample is as efficient in the recovery of salmonellae as the analysis of thirteen 25-g preenriched subsamples. Further, it is apparent that preenrichment of high-moisture foods, such as meat, poultry, and eggs is to be recommended over direct enrichment for the detection of salmonellae.

ISSN:0008-4166    

DOI:10.1139/m74-102

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The effect of cooling and warming rates on the cryosurvival of chemostat populations ofEscherichia coliwas investigated. Survival curves were obtained which were similar in shape to those obtained by others for other cell types, with saline always a more lethal environment than distilled water.For organisms frozen in either distilled water or saline, as the cooling rate was increased survival increased to a maximum at 6 C/min, decreased to a minimum at 100 C/min, and then continued to increase as the cooling rate was increased to ultrarapid rates (about 6000 C/min). At these ultrarapid rates of cooling but not at lower rates, increasing the rate of warming enhanced survival; slow warming rates were detrimental to survival and eliminated the increase in survival associated with these cooling rates. Solution of a theoretical equation predicted that supercooling of cell water, and thus the likelihood of internal freezing, should increase as the cooling rate was increased from 3.5 to 350 C/min. This increase in probability of internal freezing was paralleled by a decrease in viability of cells as the cooling rate was increased from 6 to 100 C/min.The effectiveness of three protectants was investigated over the whole cooling rate range. Glycerol or sucrose added to suspensions of cells in distilled water protected over the whole range; but at lower cooling rates (less than 6 C/min) they did so with an altered stoichiometry. Sucrose protected organisms frozen in saline and Tween 80, a non-ionic detergent, protected organisms frozen either in saline or distilled water from rapid or ultrarapid cooling only. The evidence supports a two-factor hypothesis to explain cryoinjury.

ISSN:0008-4166    

DOI:10.1139/m74-103

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The influence of nutritional status and growth rate on the cryosurvival ofEscherichia coliwas investigated. Organisms grown at rates between 0.1 and 0.6 h−1, under carbon- or nitrogen-limiting conditions all showed a basically similar cooling rate – survival profile; a peak of survival was noted in the lower cooling rate range (less than 100 C/min), a trough of minimum survival at 100 C/min, and increased survival as the cooling rate was increased to ultrarapid rates. Carbon-limited organisms showed a shift of the peak from 6 C/min for slowly grown organisms (D = 0.11) to 40 C/min at higher growth rates (D = 0.60 h−1); their survival at these peaks also showed a slightly upward trend. Nitrogen-limited organisms showed a similar trend of a shifting of the peak of survival. However, as the growth rate was increased, survival at this peak, and at other regions, decreased. For carbon-limited organisms, above 100 C/min, survival was growth rate independent, unlike nitrogen-limited organisms, which exhibited lower survivals as the cooling rate was increased in the ultrarapid range. The survival of both carbon-and nitrogen-limited organisms at the peak of survival showed a correlation with their carbohydrate and protein contents. The relevance of these findings is discussed.

ISSN:0008-4166    

DOI:10.1139/m74-104

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A bacterium which utilizes picolinic acid as a carbon and energy source is identified as a new member of the genusArthrobacter. The nameArthrobacter picolinophilusis proposed.

ISSN:0008-4166    

DOI:10.1139/m74-105

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Picolinic acid is oxidized by cells and extracts ofArthrobacter picolinophilusto 6-hydroxypicolinic acid. The enzyme involved is a particulate hydroxylase which appears to incorporate the hydroxyl group of water into the substrate. The enzyme was purified about 60-fold. The molecular weight as determined by gel filtration was 230 000 daltons. Activity of the purified enzyme was stimulated by ferrous ions and was inhibited by quinacrine. Flavin mononucleotide reversed the inhibition by quinacrine.

ISSN:0008-4166    

DOI:10.1139/m74-106

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Meringue powder naturally contaminated with salmonellae was sent to 14 laboratories for analysis by their current method. A total of 16 methods were used for the analysis and considerable variation was noted in the complexity of the methods, as well as their ability to isolateSalmonellafrom the specimens. The need for collaborative assays to define such methodology, particularly for foods moving in international commerce, is recognized.

ISSN:0008-4166    

DOI:10.1139/m74-107

出版商:NRC Research Press    

年代:1974

数据来源: NRC