摘要:

The pattern of cell wall synthesis as measured by the incorporation of tritiated alanine into the cell wall ofBacillus cereus, and the number of synthesizing sites in the cell wall were studied by the direct and the reverse autoradiographic labelling methods.In the absence of chloramphenicol, the new cell wall was initiated at two or three segments, and later increased to four or five segments which continued to elongate but not to increase in number until the bacilli had made preparation for cell division. Shortly before the centripetal growth of the cell wall and constriction to separate daughter cells, two to three more new wall-segments were added to those already present. The second and third generation cells retained some old wall-segments from the first-generation mother, which remained as discrete clusters of grains, and could easily be distinguished from the new segments.In the presence of chloramphenicol, the new wall was initiated at 8 to 10 sites. Further incubation resulted in the uniform incorporation of labels at multiple sites along the entire cell length.The patterns of new wall replication as studied by the two methods were compared. To account for the difference in synthesizing sites when chloramphenicol is present, it is suggested that the cells have either used the maximum number of sites or have completely bypassed all the sites and allowed the tritiated alanine to diffuse into the wall to become incorporated.

ISSN:0008-4166    

DOI:10.1139/m67-046

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Stilbella thermophilaFergus was grown on a chemically denned medium ofD-glucose, KNO3, MgSO4, KH2PO4, agar, and microelements to determine the effect of environment and nutrition on growth and synnemata production. An exogenous supply of thiamine stimulated growth markedly on pyridine-purified agar, but both thiamine and biotin were required for synnemata to form. Pyrimidine was the effective moiety, not thiazole.S.thermophilagrew on a large number of carbon and nitrogen compounds substituted singly into the basal medium, but synnemata formed on less than half of such media. Sucrose did not inhibit synnemata formation with glucose present, but no synnemata formed with sucrose in the medium even with a number of different nitrogen sources. Synnemata production followed chance mold contamination on a few of the media that normally did not allow their production. The carbon–nitrogen ratio significantly affected synnemata formation. So did pH, concentration of phosphate buffer, and temperature. At suboptimal temperatures, reduced synnemata, or only loose bundles of conidiophores, formed. Light was not required for synnemata initiation nor for maturation. Synnemata formation occurred over a narrower range of temperature, pH, vitamin concentration, nutrient concentration, and nutrient spectrum (carbon and nitrogen sources) than did mycelial growth.

ISSN:0008-4166    

DOI:10.1139/m67-047

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The influence of amino acids on the stimulatory activity of cholesterol on the production of oogonia by a species ofPythiumis reported. None of the sterols tested was metabolized by the fungus, but the sterols which do affect oogonia production were adsorbed, unchanged by the organism, and probably incorporated in the cell membrane. The organism survived higher temperature when grown on a medium containing cholesterol than when grown on a medium without cholesterol.

ISSN:0008-4166    

DOI:10.1139/m67-048

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The mode of action of highly punned beta hemolysin derived from the R-1 strain ofStaphylococcus aureushas been investigated. Sphingomyelin was absent from lipid extracts of sheep erythrocytes treated with beta hemolysin when compared to normal cells. A correlation was also established between the sphingomyelin content of other erythrocyte species and their sensitivity to beta hemolysin. Further investigations revealed that sphingomyelin is hydrolyzed to yield phosphorylcholine and N-acyl sphingosine. Thus, the mode of action of the beta hemolysin is like that of phospholipase C. Various phosphate compounds other than sphingomyelin, including RNA, glycerophosphate, phenyl-phosphate, phosphatidylethanolamine, and phosphatidylcholine were tested as substrates, but virtually no hydrolysis was observed. In contrast with the results of other workers, R-1 beta hemolysin did not release detectable amounts of carbohydrate from staphylococcal cell walls.

ISSN:0008-4166    

DOI:10.1139/m67-049

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

When starved cells of thymine-requiringEscherichia coliB were placed in a complete induction medium there was an initial lag of 10 minutes before measurable amounts of the enzyme were detected. Cells exposed for 15 minutes to one inducer and then given an alternative inducer continued to manufacture the enzyme for 60 minutes at a rate characteristic of the initial inducer. After this period, enzyme manufacture assumed the characteristics of the second inducer. Glucose or mitomycin was found to inhibit enzyme synthesis only when they were added during the first 10 minutes or 45- to 60-minute periods of induction. Chloramphenicol stopped enzyme synthesis at any stage of induction. The synthesis of DNA was found to occur in two stages and enzyme synthesis was prevented by glucose or mitomycin only if they were added to the cells during a 10-minute period which immediately preceded DNA replication. It is concluded that a gene can express itself only once, and change in expression requires the synthesis of new DNA.

ISSN:0008-4166    

DOI:10.1139/m67-050

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Exposure of cells of several strains ofStaphylococcus aureusto 50 or 100 μg of N-methyl-N′-nitro-N-nitrosoguanidine for 30 to 60 minutes induced large numbers of mutants with pigment content different from that of the parent. By determination of the amount of pigment as related to the optical density of the cells, four to seven classes of pigmentation mutants could be defined. Mutants with pigment content differing from that of the parent could readily be mutated to other pigmentation states and are thus probable point mutations. In contrast, completely white mutants could not be induced by the mutagen to any degree of pigmentation and possibly represent minor deletions or cumulative single-site mutations in the chromosome. Growth of parent strains in media containing acridine dyes occasionally produced a low frequency (0.01%) of white mutants. Mutants differing in pigment content from that of the parent were unable to produce coagulase during growth, although the parent cultures elaborated considerable coagulase under identical conditions.

ISSN:0008-4166    

DOI:10.1139/m67-051

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Selective inhibitors of iron and sulfide oxidation, sodium azide and N-ethylmaleimide respectively, were used to demonstrate that washed cell suspensions ofThiobacillus ferrooxidansattacked both insoluble ferrous iron and sulfide during the oxidation of chalcopyrite (CuFeS2) and pyrite (FeS2). The oxidation of the two substrates occurred simultaneously and independently but the relative rates depended on how the cells were grown. When chalcopyrite-grown cells were used to oxidize chalcopyrite, 68–74% of the oxygen uptake was the result of sulfide oxidation and 25–30% the result of iron oxidation. With pyrite, all the oxygen uptake was due to sulfide oxidation. When iron-grown cells were used to oxidize chalcopyrite, two rates resulted. During the initial rapid rate, 80–90% of the oxygen uptake was due to iron oxidation, but, during the second slower rate, the result duplicated those found with chalcopyrite-grown cells. Iron-grown cells oxidized pyrite at a constant and more rapid rate than chalcopyrite-grown cells. The faster rate was due to iron oxidation; since only 20–30% of the total oxygen uptake was due to sulfide oxidation.

ISSN:0008-4166    

DOI:10.1139/m67-052

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A fluorescent pseudomonad producing a powerful extracellular proteinase and closely resembling but not identical withPseudomonas fluorescenswas isolated from skin lesions of rainbow trout. Subcutaneous injection of the live organism into healthy frogs caused a condition typical of redleg disease, followed by death, and its subcutaneous injection into healthy rainbow trout caused the formation of large, necrotic, swollen areas filled with fluid. The organism was re-isolated from the deliberately infected animals and histological examinations showed a high degree of destruction of the muscular tissue in the affected areas. The pathogenic effect observed was apparently due to the extracellular bacterial proteinase. Growth of the pseudomonad was insignificant at 3 °C and 37 °C, was slight at 8 °C, and optimal between 15 and 25 °C, and the culture filtrates possessed strong proteolytic activity against casein, hemoglobin, and rainbow trout muscle albumin. The production of this proteinase was dependent on the growth of the organism and the composition of the growth medium.

ISSN:0008-4166    

DOI:10.1139/m67-053

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The incubation ofBacillus subtilisW23 orBacillus cereuson a vancomycin-containing medium resulted in a rapid contraction or shrinkage of the cells which was followed by lysis. The ejection of protoplasm from the cell during lysis was very forceful. The "burst" of protoplasmic material was observed at the ends of the cell and at one or two sites on the lateral cell wall. The results are consistent with the hypothesis that vancomycin inhibits cell wall synthesis and ultimately destroys the normal structure and integrity of the wall.

ISSN:0008-4166    

DOI:10.1139/m67-054

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

not available

ISSN:0008-4166    

DOI:10.1139/m67-055

出版商:NRC Research Press    

年代:1967

数据来源: NRC