摘要:

As the second phase of an international comparative study for the enumeration ofClostridium perfringens, four methods were compared for "total" and spore counts ofC.perfringensin fecal specimens: the SFP (Shahidi-Ferguson perfringens) agar (A), TSC (tryptose–sulfite–cycloserine) agar (B), SC (sulfite–cycloserine) agar (C), and neomycin blood agar (D) methods. In both the total and spore count procedures, the confirmedC.perfringenscounts in method D were lower than in methods A, B, and C. Little differences among methods were found in the percentages of presumptive colonies confirmed asC.perfringens. The nonspecific counts in methods A and D were generally greater than in B and C, but nonspecific microorganisms did not interfere in the enumeration ofC.perfringensspores by any of the four methods. In overall performance, methods B and C were superior to A and D. The meanC.perfringensspore count was only 0.17 log lower than the mean total count. Spore counts alone are, therefore, adequate in investigations ofC.perfringensoutbreaks.

ISSN:0008-4166    

DOI:10.1139/m79-146

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A capillary assay was used to evaluate the chemotactic responses ofVibrio alginolyticusto three common algal extracellular products. Acrylate and glycolate attracted the motile marine bacterium. The peak response occurred with 10−2 Mof each chemical. Acrylic and glycolic acid also attractedV.alginolyticus, with the peak response occurring at 5 × 10−4 Mof each chemical. Higher concentrations of the organic acids resulted in a decreased response. The bacteria also displayed positive chemotaxis to dimethyl sulfide.

ISSN:0008-4166    

DOI:10.1139/m79-147

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The presence of a virulent bacteriophage in the root zone of clover growing in seedling agar under controlled environments (14–17 and 19–23 °C) produced changes in the persistence and symbiotic effectiveness of a susceptible strain ofRhizobium trifolii. The phage reduced the rhizoplane population of rhizobia and led to the appearance of variant substrains which were less susceptible to the bacteriophage and mostly ineffective in symbiotic nitrogen fixation. Some were also changed in colonial morphology and nutritional requirements. At the higher temperature, the frequency of bacterial variants increased and the number of nodules due to the parent strain decreased. A large initial population of bacteriophage was able to reduce, but generally did not completely suppress, nodulation.

ISSN:0008-4166    

DOI:10.1139/m79-148

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The effect of a virulent bacteriophage on the competitive behaviour of paired strains ofRhizobium trifoliiin the root zone of clover plants was examined. The presence of bacteriophage reduced the population density of susceptible strains on the root surface and, in nodulation, favoured resistant or even partially resistant strains which were otherwise less able to form nodules. These effects occurred with different growth temperatures, host species, and ratios of strains in the inoculum.

ISSN:0008-4166    

DOI:10.1139/m79-149

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Six strains ofRhizobium trifoliiwere exposed to specific bacteriophages and the properties of 10 surviving clones of each studied. Two temperate bacteriophages produced clones which were lysogenic but showed no changes in colony form, symbiotic properties, or somatic antigens. Of forty clones selected by exposure to four other bacteriophages, none were lysogenic although there was some indication of unusually long association of phage with bacteria in infected cultures. Seventeen of these clones were changed in symbiotic properties, 15 in colony morphology, and 13 in somatic cross-reaction with the parent. Unexpectedly, despite stringent selection conditions, 28 were still either partially or completely susceptible to the selecting phage.

ISSN:0008-4166    

DOI:10.1139/m79-150

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A new type of tube (the Lee tube) has been developed for use in the cultivation and enumeration of obligate anaerobes. The Lee tube is a double-walled, screw-capped tube which allows the formation of a thin cylinder of agar medium between the two walls. Anaerobiosis is achieved through deoxygenation of the deep cylinder of agar during sterilization, a minimum of head space, and use of a reducing agent to absorb oxygen introduced during the inoculation procedure. For several species ofClostridium,Bacteroides fragilis,Fusobacterium necrophorum,Veillonella alcalescens, andPectinatus cerevisiiphilus, colony counts of cultures in the Lee tubes were comparable with those obtained in pour plates incubated in a BBL GasPak system and in anaerobic roll tubes.

ISSN:0008-4166    

DOI:10.1139/m79-151

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Inhibition ofMycobacterium smegmatis,M.vaccae, andM.diernhoferiby Trimethoprim (Tmp) in both liquid and solid media is described. Other mycobacteria were not inhibited by the same concentrations. The selective inhibition of the above strains, particularlyM.smegmatis, by Tmp could be used for differentiation of these species from other fast-growing acid-fast bacteria.

ISSN:0008-4166    

DOI:10.1139/m79-152

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The mouse model of intraperitoneal enterobacterial sepsis was used to evaluate the anti-endotoxic effect of polymyxin B sulfate. Single or multiple therapeutic doses of polymyxin, administered either before or after lethal challenge withSerratia marcescens, produced statistically and clinically significant protective effects.

ISSN:0008-4166    

DOI:10.1139/m79-153

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Between May and December, the annual stratification period in Lake Kinneret, sulfide is formed and accumulates in the hypolimnion. In July–August a large population (up to 106 cells/mL) of green, photosynthetic, sulfur bacteria develops at the boundary of the oxidative and reductive zones of the water column lasting for 3–8 weeks. These bacteria were isolated from the lake and identified asChlorobium phaeobacteroides. Optimal growth conditions included 160 mg S=L−1and light intensities of 5–0 μEinstein (μE) m−2s−1. Glucose and acetate augmented growth when added to the mineral medium. The lowest light intensity which still supported growth was 0.3 μE m−2s−1when acetate was present and 1.0 μE m−2s−1when no organic substrate was present. Under complete darkness, either with or without organic substrate, the bacteria die. Photosynthetic activity was higher when no organic compound was added to the medium. Uptake of acetate was light-dependant.In the lake the photosynthetic activity of the bacteria is low because of the limited light intensity (0.3 μE m−2s−1) at the bloom layer. It is suggested that the appearance and the disappearance of the bloom are caused by the influence of the daily internal seiche.

ISSN:0008-4166    

DOI:10.1139/m79-154

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

In the absence of added Mg2+, alkylsulfatase induction in resting cells ofPseudomonas aeruginosawas inhibited 17% by exogenous 0.05 mMUTP. Under these conditions, the cells converted UTP to ATP and rapid degradation of these nucleotides did not occur. In the presence of 0.73 mMMg2+, 0.05 mMUTP repressed the synthesis of the enzyme by 71%. Under these conditions, the cells rapidly degraded both ATP derived from UTP as well as residual UTP. In the presence of Mg2+and 0.1 mMUTP, full repression of alkylsulfatase formation occurred whereas Mg2+-depleted cell suspensions were still capable of synthesizing 47% of the enzyme under these conditions compared with control levels. The inhibition of alkylsulfatase induction was highly specific for UTP. Some inhibition was observed with exogenous uracil, uridine, and pyrophosophate but only at concentrations > 1.0 mM. Exogenous UMP and UDP (2 mM) had no effect.

ISSN:0008-4166    

DOI:10.1139/m79-155

出版商:NRC Research Press    

年代:1979

数据来源: NRC