ISSN:0008-4166    

DOI:10.1139/m80-230

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Homoserine dehydrogenase in dialyzed cell extracts ofBacillus subtilis168 was studied, particularly with regard to inhibition, repression, and level of activity as a function of stage of development (growth and sporulation). It was assayed in the "forward direction" usingL-aspartic semialdehyde and NADPH as substrates. Of the potential inhibitors tested, only cysteine and NADP were found to be effective. BothL- andD-cysteine were equally effective. Therefore, the physiological significance of cysteine as an inhibitor is somewhat questionable. Amino acids involved in repression of homoserine dehydrogenase included methionine, isoleucine, possibly threonine, and one or more unidentified components of Casamino acids. The specific activity of homoserine dehydrogenase was highest during the exponential phase of growth and declined steadily during the stationary phase of growth. The low specific activity during late sporulation may favor preferential funneling ofL-aspartic semialdehyde into the lysine pathway, where it is needed for synthesis of large amounts of dipicolinic acid and diaminopimelic acid.

ISSN:0008-4166    

DOI:10.1139/m80-231

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Crossed immunoelectrophoresis and other related quantitative immunoelectrophoretic techniques have been used to elucidate the antigenic complexity of a reference preparation of capsular extract, potassium thiocyanate extract, lipopolysaccharide, heat-stable antigens, and free endotoxin fromPasteurella multocidaserotype 1. The reactions of these cellular fractions, in crossed immunoelectrophoresis, with reference anti-whole cell immunoglobulins disclosed five antigens in the capsular extract, seven in the potassium thiocyanate extract, one to three in the lipopolysaccharide, three in the heat-stable antigens, and five in the free endoxin. Comparison of these reference antigen–antibody systems, in crossed immunoelectrophoresis, with intermediate gel containing either a reference anti-cell envelope or anticytoplasmic immunoglobulins not only revealed the presence of additional antigens but also gave insight into the probable cellular origins (i.e., cell surface, cell envelope, or cytoplasm) of various antigens unveiled by reference anti-whole cell immunoglobulins. Using the principle of tandem crossed immunoelectrophoresis and crossed-line immunoelectrophoresis the immunochemical relationships between the antigenic components of these reference antigen–antibody systems were established.

ISSN:0008-4166    

DOI:10.1139/m80-232

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The study was prompted by our inability to concentrate phages by a membrane adsorption method effective for polioviruses. Consequently two coliphages, WPK and T4, and F116 ofPseudomonas aeruginosawere tested for their resistance to acid (pH 5.2–3.2) and alkaline (pH 10–11.5) exposures. Only T4 proved acid resistant, allowing for acid adsorption, and only WPK was sufficiently alkaline resistant to allow for alkaline elution. Thus, the differential susceptibility of various phages precludes the use of the acid membrane adsorption–alkaline elution method as a general method for the concentration of phages from large volumes of water.

ISSN:0008-4166    

DOI:10.1139/m80-233

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The polar lipids ofMicrococcus radioduransstrain Sark appear to be unique in that common bacterial phospholipids such as phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, and phosphatidylinositol are absent. Of the 13 polar lipids detected, 5 contain phosphorus and carbohydrate, 4 contain carbohydrate and no phosphorus, and 1 contains phosphorus as well as sulfur. None of the polar lipids contain free choline or amino groups and none are sensitive to phospholipases C or D. Of eight selected polar lipids tested, all were found to be labile to mild alkali, suggesting the presence of ester linkages. It is suggested that the unusual lipid profile ofM.radioduransstrain Sark may be useful in taxonomic considerations.

ISSN:0008-4166    

DOI:10.1139/m80-234

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Anad-9 strain ofNeurospora crassawas mutagenized with ethylmethane sulfonate (5%) and selected for guanine auxotrophy. The resultant double adenine plus guanine mutant was backcrossed with wild type and a single guanine auxotroph was isolated from the progeny.In vitroassays indicated that the mutant had GMP synthetase activity comparable with wild type, but was completely lacking in IMP dehydrogenase activity. The guanine requirement can therefore be explained by the mutant's inability to convert IMP to XMP. Another guanosine auxotroph was able to adapt and grow on minimal medium after 3 days. This mutant had GMP synthetase activity comparable with wild type but had only 10% of the IMP dehydrogenase activity of wild type, which may possibly explain its ability to grow on minimal medium after 3 days. It was confirmed that the two isolates are not allelic by crossing the two and recovering 25% wild-type progeny. Our isolate must therefore be designatedgua-2.

ISSN:0008-4166    

DOI:10.1139/m80-235

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In commercial vacuum-packed bologna, growth ofBrochothrix thermosphactawas limited at 5 °C during a 4-week storage period. Factors controlling the growth of this organism were associated in part with certain lactobacilli isolated from the meat. The lactic acid bacteria associated with the decline ofB.thermosphactaand overall spoilage of vacuum-packed bologna were isolated and identified. The principal organisms wereLactobacillus brevis,Lactobacillus buchneri,Lactobacillus plantarum,Lactobacillus viridescens,Leuconostoc mesenteroides, and certain streptococci. In associated growth experiments withB.thermosphactaat 5 and 15 °C,L.brevisandL.plantarumshowed the greatest antagonism towards theBrochothrixspecies. Studies with changes in incubation temperatures (5 or 15 °C) or nitrite levels (0–50 μg/mL) indicated that these two factors influence the antagonism but were minorcompared with the influence of the lactic acid bacteria.

ISSN:0008-4166    

DOI:10.1139/m80-236

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Bacteriophage 12P caused lysis ofPseudomonas phaseolicolabut not other plant pathogenic or saprophytic pseudomonads. Specificity of the bacteriophage may depend on recognition of some unique feature of theP.phaseolicolacell surface polysaccharides. Exopolysaccharide (EPS) and lipopolysaccharide (LPS) fromP.phaseolicolawere more efficient at inhibiting bacteriophage attachment than were identically prepared extracts from five other pseudomonad species. Mutants ofP.phaseolicolawith bacteriophage resistance produced EPS and LPS different in amount and composition from those of the parental strain. Thus, in some manner the EPS and LPS structures ofP.phaseolicolaare distinct from those of other plant pathogenic and saprophytic species. The difference may prevent recognition and initiation of resistance events whenP.phaseolicolachallenges its susceptible host plant, bean.

ISSN:0008-4166    

DOI:10.1139/m80-237

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The lipid composition of the fungusPullularia pullulanshas been investigated at different stages of the morphogenetic transition from yeast-like, through the so-called "large cells," to chlamydospores. The first 3 days of culture correspond to the period of exponential growth. There is a rapid consumption of glucose and ammonium, until the latter becomes exhausted, and a concomitant decrease of pH down to values of about 2. A decrease in fatty acid unsaturation takes place at this stage, together with an increase in the proportion of long-chain aldehydes. The period between days 3 and 6 is dominated by the large cells. They accumulate large amounts of triacylglycerols; phospholipids and free sterols are also synthesized in this period, suggestingde novosynthesis of membranes. Chlamydospores can be seen from the 6th day on. Simultaneously, a decrease in free sterols and phospholipids takes place, while saturated triacyglycerol production goes on. The lipid composition of chlamydospores suggests that these are resistance forms, induced by the hostile environmental conditions of the medium after the end of the exponential growth.

ISSN:0008-4166    

DOI:10.1139/m80-238

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Swiss-Webster mice were vaccinated by the intraperitoneal route (i.p.) withMycobacterium tuberculosisBCG and challenged i.p. 4–10 weeks later with 104virulentSalmonella typhimuriumin the presence or absence of purified protein derivative (PPD) of tuberculin. Normal control mice were similarly challenged. Such an infection was fatal to the normal mice within 12 days. BCG vaccination prolonged the survival time and protected about 36% of the salmonella-infected mice from death. In contrast, tuberculin sensitivity, elicited in the BCG-vaccinated mice, significantly increased the survival time and protected about 70% of the mice against an otherwise fatal challenge. When these experiments were repeated using an infective dose of 106organisms, the protective effect of the tuberculin reaction became substantially reduced, but there remained a statistically significant improvement in the survival distribution of the challenged mice as compared with that among the BCG-vaccinated mice. The examination of peritoneal washings obtained from BCG-vaccinated mice stimulated with PPD showed that the enhanced resistance to salmonella infection was directly associated with a quantitatively increased influx of phagocytic leukocytes accumulating at the site of infection as a result of the elicitation of tuberculin sensitivity.

ISSN:0008-4166    

DOI:10.1139/m80-239

出版商:NRC Research Press    

年代:1980

数据来源: NRC