摘要:

Three strains of group H streptococci have been found to produce competence factors (CF's) similar to that synthesized by the highly transformable strain Challis. All these factors efficiently converted to competency for DNA uptake the spontaneously nontransformable strain Wicky. Two of the three strains could be transformed to drug resistance with an extremely low efficiency and one strain was nontransformable. When the bacteria were exposed to tritium-labeled DNA, it was found that a viable unit of the three strains contained about 10 times less radioactivity than a viable unit of Challis and Wicky in the competent state. The probability that CF may not be the only factor required for DNA uptake is discussed.

ISSN:0008-4166    

DOI:10.1139/m71-201

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A large group of DBA/2 mice with established Friend virus leukemia was treated with a regimen of non-viral inducers of interferon. Treatment was begun 7 days postinoculation of Friend virus and continued at 7-day intervals through 28 days. Treated mice exhibited an increased mean survival of 19 days, decreased splenomegaly, and lower Friend virus titers in the spleen. Fewer viral particles and reticulum type cells were demonstrated in the spleens of the treated animals, as revealed by electron microscopy. Leukemic and normal mice produced comparable levels of interferon in response to the inducers used.

ISSN:0008-4166    

DOI:10.1139/m71-202

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The characterization of the genetic determinant(s) governing resistance to the antibioticD-cycloserine inStaphylococcus aureusU9W was described. Only single-step low-grade resistant mutants developed from the parent strain, which was originally sensitive to the antibiotic. After exposure of resistant mutants to acridine orange and (or) elevated temperature,D-cycloserine-sensitive segregants were recovered. No resistant recombinants were obtained from transduction experiments using variousD-cycloserine-sensitive "cured" mutants as donors. Buoyant density studies, however, did not reveal satellite DNA.

ISSN:0008-4166    

DOI:10.1139/m71-203

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

An enzyme obtained fromBacillus cereusT spores which catalyzes the reduction of the disulfide, 5, 5′-dithiobis (2-nitrobenzoic acid) (DTNB), has been partially purified and characterized. The enzyme required either reduced nicotinamide adenine dinucleotide phosphate (NADPH2) or reduced nicotinamide adenine dinucleotide (NADH2) as electron donor. It had a pH optimum of 8, was destroyed by heating at 70C for 5 min, and was stimulated by Ca2+and Mg2+. No other small molecular weight disulfides were found to be substrates for the enzyme.

ISSN:0008-4166    

DOI:10.1139/m71-204

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A method is described whereby enterovirus present in a 5-ml liquid sample may be efficiently recovered for plaque enumeration on a single 60 × 15 mm culture dish. Adsorption is accomplished by constant agitation of the sample with suspended cells followed by a stationary period to allow monolayer formation for plaque development. Comparative studies with the use of coxsackievirus B5 and poliovirus 1, on HEp-2 and Vero cells respectively, indicated that the conventional method of adsorption onto stationary monolayers would require 50 times as many dishes and cells for an equal efficiency. The new method might be useful for the recovery of small numbers of viruses from food or water samples providing they are nontoxic to cells and contain no bacteria.

ISSN:0008-4166    

DOI:10.1139/m71-205

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The envelope (wall plus plasma membrane) of a viomycin-resistant mutant ofRhizobium melilotiexhibited a higher calcium concentration than that of the viomycin-sensitive parent strain. However, the cation exchange capacity of the sensitive cells was almost twice that of the resistant cells, indicating that the excess calcium in the resistant cells is not available for exchange with external cations. Since externally supplied cations can block viomycin uptake by sensitive cells it is suggested that viomycin penetration in such cells involves an initial attraction of the basic antibiotic molecules to negatively charged sites in the envelope. Viomycin resistance in the mutant strain appears to be the result of (a) a decrease in the number of negatively charged sites and (b) the association with these sites, via calcium-bridging, of previously discovered envelope phospholipids capable of complexing with the drug.Chelators decreased viomycin resistance in the mutant strain, presumably by removal or destruction of the barrier in the cell envelope involved in decreased drug penetration. The decrease in viomycin resistance caused by cold shock was accompanied by a release of envelope phospholipid without a concurrent release of Ca2+.

ISSN:0008-4166    

DOI:10.1139/m71-206

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A cell-free enzyme preparation which catalyzed the hydrolysis of chloramphenicol was obtained fromStreptomycesspecies 3022a, a chloramphenicol-producing actinomycete. The enzyme was difficult to release from the mycelium and had low substrate affinity (Ks0.2 mM) and activity (Vmax2.86 nmoles/h) towards chloramphenicol. Activity was present in chloramphenicol-sensitive non-producing cultures not previously exposed to the antibiotic and did not increase during development of resistance. The results suggest that inactivation of chloramphenicol may be a subsidiary function of the enzyme.

ISSN:0008-4166    

DOI:10.1139/m71-207

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The effects of nutritional factors on the capacity ofMucor alternansto degrade14C-DDT in shake cultures were investigated. Fungal spores did not grow in media that contained DDT as the sole carbon source, but they remained viable over a 2-month period and developed into a mycelium, once glucose had been added. The degradation of DDT by the fungus was not related to the mycelial mass. The quantity of water-soluble metabolites produced from DDT was, to some extent, dependent on the insecticide concentration, but largely on the carbon and nitrogen sources in the culture media. Largest quantities of the metabolites were formed with glucose and ammonium nitrate. The concentration of glucose affected this metabolism quantitatively. With the exception of ribose, growth on other sugars resulted in a decrease in the production of DDT-metabolites, which was most noticeable when maltose was used. No qualitative differences in the metabolites were observed. When ammonium nitrate was replaced with other nitrogen sources, the production of water-soluble metabolites was substantially reduced (35 to 75%) and qualitative differences in the appearance of metabolites were also observed.

ISSN:0008-4166    

DOI:10.1139/m71-208

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A principal component (PC) analysis was used to examine binary descriptive data for 38 cultures ofArthrobacter, 16 ofAgrobacterium, and 27 ofRhizobium. The descriptions were based on the responses of the cultures to 65 tests concerned with the following: nutritional requirements; use of acetate, succinate, citrate, aldoses, adonitols, ketoses, disaccharides, trisaccharides, aromatic compounds, and amino acids; hydrolysis of starch and protein; and reduction of nitrate. No data for morphological, for symbiotic characteristics, or for pathogenicity were included. The PC analysis showed that the rhizobia, the agrobacteria, and the arthrobacters were separable in terms of the tests used, and that the rhizobia and agrobacteria groups were most alike. The PC analysis indicated important characteristics which distinguished these three groups from each other. Such characteristics included the following: use of arabinose, dulcitol, adonitol, sorbose, inulin, aromatic compounds, glycine, and phenylalanine as carbon and energy sources; use of glucose as carbon and energy source under anaerobic conditions; growth in the presence of 10% NaCl; growth in medium at pH 4.5 or 9.0; growth at 4C; and hydrolysis of starch. Bacteriological characteristics, DNA guanine–cytosine contents, and clustering of the arthrobacter cultures are discussed.

ISSN:0008-4166    

DOI:10.1139/m71-209

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A strain ofPseudomonas fluoresceinwhich synthesizes large quantities of an inducible extracellular pectate lyase proved to act as a virulent soft rot organism on potatoes, whereas a parent strain that synthesized no lyase showed little pathogenicity. The procedure for inducing lyase synthesis involves culture ofP.fluorescensfor at least five generations on a combined carbon source of pectin plus a factor extracted from acetone powders of potatoes. The extracted factor is dialyzable and heat-labile but can be sterilized by Millipore filtration. When soil was inoculated into the induction medium, microorganisms present synthesized pectate lyase.Less than half of the single colony isolates obtained by plating out induced cultures ofP.fluorescenssynthesized pectate lyase when reinoculated into induction medium. Serial reisolation and reinoculation of induced cultures failed to increase the proportion of induced cells. This failure suggests that inducibility is lost during growth of cells on induction medium and (or) on solid agar used for plating. Under similar conditions, cultures ofErwinia carotovoracontained induced cells only. The apparent loss of inducibility that occurs inP.fluorescensmay account for its generally saprophytic behavior in nature.

ISSN:0008-4166    

DOI:10.1139/m71-210

出版商:NRC Research Press    

年代:1971

数据来源: NRC