摘要:

The phialides ofPenicillium claviformewere examined with the light microscope, and as thin sections, with the electron microscope. Nuclear and spore wall arrangements during conidium production are described. The nuclear configurations are unlike those of normal mitosis. Spore wall formation and nuclear division are associated with the presence of membranous organelles resembling the mesosomes of gram-positive bacteria. The findings are discussed.

ISSN:0008-4166    

DOI:10.1139/m67-033

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

When cells ofEscherichia coliB were grown in a glucose – amino acid medium and then transferred to a minimal medium containing lactose or isopropyl-β-D-thiogalactopyranoside as a sole source of carbon, no induction of β-galactosidase occurred unless one or several amino acids were supplied. Of the amino acids tested, aspartic acid was the most effective and its ability to initiate the synthesis of the enzyme was increased by the addition of arginine. In the presence of these two, or all of the amino acids, there was a lag period of 10 min before enzyme synthesis occurred. The duration of the lag period was unaffected by the addition of nucleic acid bases or succinate to the induction medium. Succinate or glutamate partially inhibited the synthesis of the enzyme, whereas glucose, inositol, or chloramphenicol completely suppressed it. With the exception of that produced by chloramphenicol, inhibition was dependent on the time at which the inhibitor was added. If inhibitors were added after the 10-min lag period, they had no apparent effect until 45 min had elapsed. Cells transferred after 15 min from one induction medium to another displayed for 30 min the induction characteristics of the first medium. It appears that a process occurring during the early 15-min period determines the rate at which enzymes will be synthesized for the next 30 min and that the action of inhibitors is to prevent this process. The process seems to require intact DNA and amino acids and it is suggested that it determines the specificity and quantity of mRNA manufactured.

ISSN:0008-4166    

DOI:10.1139/m67-034

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Enteric bacteria recovered from the Cache la Poudre River and refrigerated for approximately 3 months were observed to form sectored colonies on MacConkey agar subculture. Organisms taken from each sector of the colonies were compared and a wide range of biochemical and serological variation was observed. Selected variant characteristics observed in the pure culture isolates from the sectored colonies were shown to be reproducible with membrane filter U tubes. Further investigation revealed that the agent responsible for the observed variations was submicrobial, survived chloroform and heat (56 C for 30 minutes) treatments, and produced occasional lysis in the non-lactose-fermenting strains. Additional cultures resembling the original variant organisms were recovered from the river but attempts to produce the sectoring phenomenon with these organisms were without success, although numerous sectoring isolates having similar variant characteristics were recovered from the stream.

ISSN:0008-4166    

DOI:10.1139/m67-035

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Spores ofBacillus popilliaeare enclosed within a large sporangium. In an effort to characterize the spores precisely, a method was developed to free them from their sporangia by sonic vibration. Separation of the free spores from sporangial debris was made by lysozyme treatment, centrifugation, and the Sacks and Alderton aqueous polymer two-phase system. The intact spores are fully refractile; they accept and retain malachite green applied by a modified Wirtz spore-staining technique. The free spores are elongated with rounded ends and measure 1.30–2.25 μ × 0.90–1.40 μ. Outgrowth of intact germinated spores is lowest when heat-activated at 80 °C and highest when heat-activated at 50 °C. Free spores are more heat sensitive than are intact spores, possibly because of damage by the sonic treatment.L-Alanine, adenosine, and glucose separately and in combination do not influence germination of either intact or free spores. Although potassium phosphate somewhat increased germination of intact spores, other salts were ineffective, but almost all salts increased germination of free spores.

ISSN:0008-4166    

DOI:10.1139/m67-036

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Spores ofClostridium botulinum33A in two suspending media, phosphate buffer and pork pea broth, were gamma irradiated at radiation temperatures from +20 °C to −196 °C. The liquid–solid transition around 0 °C introduced a one-step plateaulike change in radiation sensitivity of spores. The spores were considerably more resistant in the solidly frozen medium than in the liquid medium. The solid state reduced indirect effects of radiation by physical blocking of secondary radicals. The one-step transition was much smaller in pork pea broth than in buffer. This indicated that scavenging of secondary radicals by pork pea broth caused a considerable reduction of indirect effects of radiation, but did not completely eliminate them.Freezing alone did not eliminate all indirect effects. This was evident from the gradual reduction in radiation sensitivity of spores in the solidly frozen phosphate buffer betweeen −25 °C and −196 °C. Furthermore, even at −196 °C indirect effects of radiation remained active since (a) spore survival did not level off with respect to temperature and (b) the lethal efficiency of radiation was still appreciably greater in phosphate buffer than in pork pea broth at −196 °C.In frozen pork pea broth at −25 °C to −196 °C temperature had no effect on radiation sensitivity of spores. This indicated that spores were killed by direct hits; apparently physical blocking by the solidly frozen medium, plus radical scavenging by pork pea broth eliminated all indirect effects of radiation.

ISSN:0008-4166    

DOI:10.1139/m67-037

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

In an initial attempt to develop a technique for the enumeration of bacteria on littoral algae, the authors observed that homogenization of the algal samples in the Waring Blendor resulted in the death of the marine bacteria contained in the samples. Further work on this lethal effect of blending showed that two detrimental factors, heat and mechanical injury of the cells, were implicated. These factors were due to the increase in temperature during homogenization and the high speed of rotation of the knife-blade assembly of the Waring Blendor. From these findings, a satisfactory technique was formulated for obtaining homogenates of marine materials for the total count of bacteria. This involved homogenization at speeds of about 5000 r.p.m. (using a Servall Omni-Mixer homogenizer) and a temperature of homogenization not exceeding 30 °C.

ISSN:0008-4166    

DOI:10.1139/m67-038

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Lysogenic cells ofEscherichia coliK12 (λ+) andEscherichia coliM3 (λ59) were held in atmospheres having relative humidities (R.H.) from 30% to 80% and irradiated with 2537 Å ultraviolet light (uv.). The colony-forming ability of both types of cell was destroyed more rapidly at 55% R.H. than at any other level of R.H. WithE.coliK12 (λ+) the percentage of cells in which prophage induction occurred increased as the dose of ultraviolet light increased and the maximum number of inductions occurred at 55% R.H. Inositol prevented (λ+) prophage induction but was less effective in doing so at 55% R.H. Desiccation alone induced the (λ59) prophage and subsequent uv. irradiation resulted in the destruction of the prophage. The maximum rate of destruction was found at 55% R.H. Inositol prevented the uv. inactivation of the (λ59) prophage, resulting in an increase in inductions with uv. dose at 30% R.H. The free phages were found to have the same sensitivity to ultraviolet light as the induced prophages but were less protected by inositol.It is proposed that water molecules hold the prophage to or in the host DNA and that ultraviolet light induces the prophage and destroys its integrity by reorientating these water molecules.

ISSN:0008-4166    

DOI:10.1139/m67-039

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A simple, rapid and reproducible micro tissue culture assay in the BS-C-1 (Cercopithecusmonkey kidney) cell line was developed for the titration and neutralization of measles virus. Serial dilutions of virus (or serum) were made with spiral loops in disposable microplates and 8 × 103BS-C-1 cells suspended in 0.05 ml of medium 199 with 2% fetal bovine serum were added to each dilution. After the addition of 0.1 ml of sterile mineral oil to each microculture, the plates were covered with a plexiglass sheet and placed in a humidified incubator (37 °C) under a constant pressure of 5% CO2for S days. Micro tissue cultures were examined with the aid of an inverted microscope for viral cytopathic changes on the fourth and fifth day.The micro assay was applied to the virus titration of various live, attenuated measles vaccines, as well as to the antibody titration of human and animal sera following vaccination with either live or inactivated measles vaccines.

ISSN:0008-4166    

DOI:10.1139/m67-040

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

During growth ofStaphylococcus aureuscells, sublethal concentrations of nafcillin induce changes in the cell wall resulting in a pronounced increase in susceptibility to lysis by lysozyme and proteolytic enzymes. Data presented demonstrate that this property of nafcillin is dose dependent, and the relatively low concentration needed to influence lysis significantly, approximately 1/80th the minimum inhibiting concentration, suggests that we are dealing with a specific and primary action on cell wall synthesis. The enhancement in lytic response observed during the logarithmic phase of growth is consistent with the hypothesis that an impairment of cross-linking in mucopeptide synthesis occurs following exposure to nafcillin. Since heat treatment (60 °C, 20 min) of nafcillin-treated cells considerably reduces lysis, the rate and extent must depend in part on the activity of one or more autolytic factors. Enzymic lysis is also enhanced by addition of sodium bicarbonate to control and nafcillin-treated suspensions, a phenomenon interpreted as a reversible bicarbonate-induced effect on cell permeability.

ISSN:0008-4166    

DOI:10.1139/m67-041

出版商:NRC Research Press    

年代:1967

数据来源: NRC

ISSN:0008-4166    

DOI:10.1139/m67-042

出版商:NRC Research Press    

年代:1967

数据来源: NRC