ISSN:0008-4166    

DOI:10.1139/m81-001

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A single medium, containing standard basal salts and three common carbon sources (sucrose, mannitol, and sodium lactate) is proposed to replace nitrogen-free media in common use for isolating dinitrogen-fixing bacteria. Eight commonly isolated genera of dinitrogen-fixing bacteria exhibited growth on this combined carbon medium that equalled or bettered growth on other carbon-containing media. Combined carbon medium also yielded the highest counts of putative dinitrogen-fixing bacteria from three southern Alberta soils. A survey of the bacteria isolated aerobically from the Burdett soil on combined carbon agar indicated that, at higher dilutions, 75% of the isolates exhibited acetylene reduction. These bacteria were identified asAzospirillumspp.,Bacillus polymyxa,B.macerans,Klebsiella pneumoniae,Erwinia herbicola, andEnterobacter cloacae. The inclusion of yeast extract in combined carbon medium is considered essential to supply organic growth factors and may supply "starter" nitrogen that promotes growth without inhibiting acetylene reduction.

ISSN:0008-4166    

DOI:10.1139/m81-002

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The growth inhibitory effect of 50 kPa (0.5 atm) CO2was tested forPseudomonas fragiin the temperature range 5–35 °C and of 101 kPa (1 atm) CO2onBacillus cereusin the range 18–46 °C. The maximum specific growth rate (μmax) ofP.fragiin air (pH 6.7) was 0.44 h−1at 35C, 0.66 h−1at 30 °C, and 0.078 h−1at 5 °C. In 50 kPa of CO2in air the relative inhibition of the growth rate was about 30% at 35 °C, 50% at 30 °C, and 90% at 5 °C. Thus, the inhibitory effect of CO2successively increased with decreasing temperature, an effect which was explained by the increasing solubility of CO2with decreasing temperature. The anaerobic growth ofB.cereus(101 kPa N2) was optimal at 40 °C and stopped at temperatures below 18 °C and above 46 °C. The relative inhibitory effect of 101 kPa CO2at the optimum growth temperature was about 40%; this increased to 100% near the maximum and minimum growth temperatures. The growth inhibitory effect of reduced temperature (below optimum) and CO2onB.cereuswas larger than that expected from the increased solubility of CO2at lower temperatures.

ISSN:0008-4166    

DOI:10.1139/m81-003

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A species ofArthrobacterwas recovered during culture of the causal organism of pitch canker of southern pines,Fusarium moniliformevar.subglutinans(FMS).Arthrobacteris a relatively common soil bacterium and is lytic to several fungal pathogens in the soil. Soil samples from two seed orchards with pitch canker and one from a healthy pine plantation all yieldedArthrobacter. These isolates were evaluated for their ability to inhibit the growth of FMS isolates from pitch canker tissue and from soil in areas with high pitch canker disease incidence, and to several other species ofFusariumisolated from the same soil samples whereArthrobacterwas recovered. Generally the pitch canker isolates were more sensitive toArthrobacterthan the soil fusaria. There was variation in the ability of theArthrobacterisolates to inhibit the growth of the fusaria recovered from the soil at the three different test sites. Light and scanning electron microscope observations revealed that hyphae of FMS growing near an isolate ofArthrobacterwere enlarged, producing many vesicularlike structures. The surface of these hyphae was warped and wrinkled in comparison with normal hyphae.

ISSN:0008-4166    

DOI:10.1139/m81-004

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

In vivophosphorylation of proteins that are associated with polysomes of poliovirus-infected VERO (African green monkey kidney) and HeLa (Henrietta Lacks) cells differed from phosphorylations observed with uninfected cells that were fed fresh medium. With both types of cells infection stimulated phosphorylation of proteins with molecular weights of 40 000 – 41 000, 39 000, 34 000, 32 000, and 24 000. Similarities of phosphorylations in VERO and HeLa cells suggest that they are a specific consequence of infection and might serve a regulatory function during protein synthesis.

ISSN:0008-4166    

DOI:10.1139/m81-005

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Light and electron microscopy was used to establish the structural organisation of the developing nodule of alfalfa. In these nodules three distinct regions were noted: (1) the base region, site of original infection where the nodule is attached to the root and now composed of degenerating nodule tissue, (2) the central region, or active region composed of nodule cells containing tightly packed bacteroids surrounding a central vacuole, and (3) the meristematic region, a site of new growth, behind which newly formed cells are continually invaded. The ongoing infection process accompanying continued nodule development provided the opportunity to study the release ofRhizobiumcells from the infection threads.In the nodules of alfalfa it would appear that theRhizobiumcells are released from infection thread into the nodule tissue in two different ways: (i) release with infection thread membrane and (ii) release in thin-walled vesicular structures. Thus it is concluded thatRhizobiumcells are surrounded by the infection thread membrane when they are released from the infection thread into nodule tissue.

ISSN:0008-4166    

DOI:10.1139/m81-006

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The viability of resting suspensions ofEscherichia coliK12 Ymel exposed to air plus 300 psi (1 psi = 6.895 kPa) oxygen (hyperbaric oxygen) decreased as an apparent first-order process after an initial period of constant viability. Control suspensions exposed to air plus 300 psi nitrogen (hyperbaric nitrogen) did not lose viability over the 96 h of the experiment. It was observed that a decrease in the refractive index of the cells preceded the loss of viability in hyperbaric oxygen. This finding together with electron micrographs, which showed extensive loss of ribosomal particles in bacteria incubated in hyperbaric oxygen, led us to suspect that ribosome injury or disassociation might be important in hyperbaric oxygen toxicity. In support of this we found that cellular RNA, labeled with [5-3H]uridine, was much more rapidly and more completely degraded in hyperbaric oxygen than in hyperbaric nitrogen. Furthermore, a far greater proportion of RNA was degraded than was DNA or protein. A direct assay for ribosome particles by sucrose gradient centrifugation showed that only 34% of the 70S ribosome particles was lost during the first 24 h in hyperbaric nitrogen whereas in hyperbaric oxygen 99.6% of the 70S particles was degraded during the same period. In hyperbaric oxygen the rate of viability loss between 24 and 72 h was equal to the rate of 70S ribosome degradation during the first 24 h. If 70S ribosome disassociation in hyperbaric oxygen continues at the same rate after the first 24 h, then cumulative 70S ribosome disassociation or injury may lead to and provide an explanation for irreversible bacterial cell injury and the loss of viability.

ISSN:0008-4166    

DOI:10.1139/m81-007

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Turfs of 'Park' Kentucky bluegrass reestablished in the greenhouse and inoculated withKlebsiella pneumoniae(W6) showed significantly increased nitrogen fixation (acetylene reduction) compared with control turfs. Mean ethylene production rates per pot were 368 nmol h−1forK.pneumoniaetreated turfs, 55 nmol h−1for heat-killedK.pneumoniaetreated turfs, and 44 nmol h−1for untreated turfs. Calculated lag periods before activity was observed were generally very short (less than 1 h).When 'Park' Kentucky bluegrass was grown from seed on soil-less medium of Turface, a fired aggregate clay, inoculation withK.pneumoniae(W6) resulted in 9 of 11 turfs showing nitrogenase activity (mean ethylene producion rate per pot was 195 nmol h−1). Only 3 of 11 turfs treated with heat-killedK.pneumoniaeshowed any activity and their mean rate of ethylene production (40 nmol h−1per pot) was significantly lower than that for turfs treated withK.pneumoniae.Using the 'Park'–Turface soil-less model system it was shown that acetylene reducing activity was (i) root associated, (ii) generally highest at a depth of 1–4 cm below the surface, (iii) enhanced by washing excised roots, and (iv) inhibited by surface sterilization of excised roots.Klebsiella pneumoniaewas recovered from Turface and roots showing acetylene reducing activity.

ISSN:0008-4166    

DOI:10.1139/m81-008

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Bacillus brevisstrains contain a defective prophage. In strain ATCC 10068 this prophage is responsible for the production of particles resembling phage tails and the induction of events leading to cell lysis. There is a slow rate of spontaneous production of particles, which is greatly increased by treating growing cells with mitomycin C, ultraviolet light,N-methyl-N-nitroso-N′-nitroguanidine, and acridine orange or by changing the growth medium. There is no conversion of host DNA to a unique, phage-size DNA entity associated with induction. It was not possible to detect strains that did not produce particles on treatment with mitomycin C. The particles themselves had no recognised biological activity. The molecular weight of the major sheath protein was 49 000 and at least four other protein components were detected in partially purified preparations. DNA and RNA were not associated with the particles but a small amount of carbohydrate was detected.

ISSN:0008-4166    

DOI:10.1139/m81-009

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Cells ofStreptococcus faecalisthat survived heating for 21 min at 60 °C were killed when resuspended at an initial cell density of about 1 × 108viable units/mL and incubated at 33 °C for 24 h in a no-growth medium containing potassium phosphate buffer, pH 7.1, glucose, and casein hydrolysate. When such heated cells were resuspended at an initial cell density of about 1 × 107viable units/mL or lower, subsequent cell death was reduced at least 10 000-fold. Unheated cells incubated under similar conditions at about 1 × 108and 1 × 109viable units/mL did not die. Cell death was due to a toxic compound synthesized by the heated cells, and supernatants from incubations showing a bactericidal effect contained a component, absent in nonlethal supernatants, that reacted with 2,4-dinitrophenylhydrazine. Thin-layer chromatography, mass spectrometer analysis, and the visible spectrum of the 2,4-dinitrophenylhydrazine derivative of the unknown and authentic methylglyoxal, and the positive response shown by the free unknown compound when used as a substrate for glyoxalase I, suggested that methylglyoxal was the bactericidal compound. Solutions of authentic methylglyoxal were bactericidal at concentrations above 0.2 mMand lethal supernatants contained about 1 mMmethylglyoxal, whereas supernatants that were not lethal contained <0.02 mMmethylglyoxal.

ISSN:0008-4166    

DOI:10.1139/m81-010

出版商:NRC Research Press    

年代:1981

数据来源: NRC