摘要:

A temperate phage was induced from exponential phase cells ofErwinia herbicolaY46 by treatment with mitomycin C. The phage was purified by single plaque isolation, and produced in bulk by successive cultivation in young cultures ofE.herbicolaY178. Phages were concentrated from culture filtrates by rate zonal centrifugation and resuspension in 0.02 M Tris buffer, pH 7.2, twice, yielding suspensions of about 5 × 1011 PFU/ml. Purification was achieved by centrifugation in buffered sucrose solutions. The band at the 30/40% sucrose interface yielded intact particles having regular hexagonal heads and long contractile tails, with base plates. Fibers were not seen. The mean dimensions were head, 51 nm; neck length, 11 nm; overall tail length, extended, 98 nm and contracted, 75 nm; diameter of tail sheath, 24 nm. The phage was stable from pH 4.0 to 11.0, but unstable at pH 3.0, the response being independent of the suspending medium used. At pH 3.0, a survival curve having a biphasic appearance was observed, which was not due to a mixed population of phages. Stability to heat was good up to 45 °C, above which a logarithmic decline with temperature increase occurred. The average inactivation rate constant at 50 °C and pH 6.8 was 0.15 min−1. Adsorption toE.herbicolaY178 cells exhibited first-order kinetics, the adsorption rate constant being 2.5 × 10−10 ml/min. One-step growth-curve experiments indicated a burst size of 35–40, and a minimum latent period of 80 min. Probit analysis gave a mean latent period of 140 min (SD 25). The phage caused lysis of onlyE.herbicolastrains Y178 and Y186.

ISSN:0008-4166    

DOI:10.1139/m75-138

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The internalization of virulentChlamydia psittaci6BC particles by wandering mononuclear phagocytes in the peritoneal cavity of intraperitoneally inoculated mice occurred asynchronously, i.e., fragile reticulate bodies (RB) appeared to be more readily phagocytized than the rigid elementary bodies (EB). Early damage of mononuclear phagocytes occurred after internalization of chlamydiae. This was followed by a decreased uptake of particles, and may explain the relatively long persistence (up to 6 h after inoculation) of free, extracellular, "swollen," and RB-like particles. Internalized particles within phagolysosomes showed varying degrees of disintegration. The subsequent influx of polymorphonuclear phagocytes and monocytes into the inflammed peritoneal cavity may explain the rapid disappearance of chlamydiae and their antigens from the peritoneal fluid. The alteration in ultrastructure of peritoneal cells and chlamydial parasites during the inflammatory process are discussed.

ISSN:0008-4166    

DOI:10.1139/m75-139

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A survey (1964–1973) was conducted on naturally occurring western equine encephalomyelitis (WEE) virus infections of Richardson's ground squirrels (RGS) in agricultural areas of Saskatchewan. The survey included both serology and virus isolation attempts on live-trapped wild squirrels. Throughout the study, seropositive squirrels were found in the known enzootic regions of the province each summer. The infection rate was high (11.6% of 250) in the epidemic year of 1965 and low (less than 2% of 681) in the subsequent non-epidemic years. The maximal seasonal prevalence of seropositive RGS coincided with the time when the squirrel population and aedine mosquito abundance reached their seasonal peaks. Five virus isolations were obtained from the blood and brains of naturally infected squirrels. All isolations were from squirrels collected in June. The early seasonal infections in squirrels could provide a source of virus forCulex tarsalis, the epidemic vector. In view of their abundance in the enzootic agricultural areas and the high annual population turnover, the RGS may play an important role in the natural history of WEE virus in the Canadian prairies.

ISSN:0008-4166    

DOI:10.1139/m75-140

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A simple procedure has been developed for freezing of vegetative amoebae of various cellular slime mold species. This procedure can be used to store stocks of both developmentally competent and developmentally defective strains of cellular slime molds for periods up to at least 1 year.

ISSN:0008-4166    

DOI:10.1139/m75-141

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The aerial, thick-walled spores ofDiheterospora chlamydosporiaarose as terminal swellings on erect hyphae. Repeated septation of the continuously swelling spore resulted in a multicellular structure. Immediately after the onset of septation secondary wall material was laid down between the two-layered primary wall and the plasmalemma. The presence of secondary wall material indicates that the multicellular spore is a dictyochlamydospore and not an aleuriospore. The relationship between chlamydospores and aleuriospores in other fungi is discussed.

ISSN:0008-4166    

DOI:10.1139/m75-142

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A series of bacterial species was examined for their sensitivity to ochratoxin A. Only gram-positive bacteria could be inhibited, generally at a pH lower than 7.0.Bacillus subtilisdid not show any reduction of growth rates in presence of ochratoxin A, but had a prolonged lag phase. WithStaphylococcus pyogenesvar.aureusandStreptococcus faecalis, a prolonged lag phase and a reduction of the growth rates was observed. Most sensitive wasStreptococcus faecalisin the exponential-growth phase. The inhibition could be diminished by changing the pH to neutral, or by addition of yeast extract, tetrahydrofolate, or MgSO4. With MgSO4a complete abolition of the inhibitory effect was achieved, but not with CaCl2. During growth inhibition, protein and RNA synthesis were reduced simultaneously, but not DNA synthesis. Even with the very high concentration of 1 mg/ml, no lethal effect was observed.

ISSN:0008-4166    

DOI:10.1139/m75-143

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The dinitrogen fixing enzyme nitrogenase (nitrogen:(acceptor) oxidoreductase) (EC 1.7.99.2) is monitored by its ability to reduce acetylene to ethylene. Low, non-inhibitory concentrations of acetylene (~10−7 mol/litre) are mixed with the gas flow aerating microbial cultures, and acetylene and ethylene in the effluent gas are determined by gas chromatography. The procedure is safe, simple and is carried outin situwithout disturbing the growing culture. Transient changes in nitrogenase activity are easily detected. The technique may be automated.

ISSN:0008-4166    

DOI:10.1139/m75-144

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Azotobacter vinelandiiOP was synchronized by the continuous phased culture technique. The nitrogenase (nitrogen:(acceptor) oxidoreductase) (EC 1.7.99.2) activity of the culture was determined continuously within the fermentor by acetylene reduction. Addition of NH4+in excess of 5 × 10−3 M to the culture lowered nitrogenase activity immediately. Other sources of fixed nitrogen had no immediate effect on nitrogenase activity, but nitrogenase synthesis decreased in the cell cycle following the one in which the fixed nitrogen was added.

ISSN:0008-4166    

DOI:10.1139/m75-145

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Vesicular-arbuscular mycorrhizae of yellow poplar (Liriodendron tulipiferaL.) were examined by scanning electron microscopy. The morphology and spatial distribution of endophytic structures are illustrated. The use of stereoscopic techniques in conjunction with removal of host cytoplasm permits detection of subtle morphological alterations and progressive deterioration of the fungal component.

ISSN:0008-4166    

DOI:10.1139/m75-146

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

TwoCandidaspecies and aSaccharomyceswere grown on ethyl alcohol, acetic acid, ethyl acetate, and 1-butanol, and their growth rates at a series of concentrations of each substrate are reported. Substrate concentrations higher than a characteristic threshold substrate concentrationS0inhibited growth in accordance with a new relationship:whereiis an inhibition constant and the other symbols have their usual meanings. Complete inhibition, that is, no growth, takes place whenS = Si, the total inhibition concentration. Values ofS0,Si, andiwere calculated for the examples studied. Also discussed are the observed lag periods and also the lowered yields at high substrate concentrations.

ISSN:0008-4166    

DOI:10.1139/m75-147

出版商:NRC Research Press    

年代:1975

数据来源: NRC