- Volume 17, Issue 2, 1957
Volume 17, Issue 2, 1957
- Article
-
-
-
Studies on Lysogeny in Staphylococci
More LessSUMMARY: A staphylococcus typing phage (NCTC 8426) was found to form lysogenic systems with three strains of staphylococci. In the case of two of these strains, staphylococci lysogenically infected with the typing phage were now lysed by the temperate phages they had previously carried. This loss of immunity was due to the replacement of the originally carried prophage by the prophage of phage 8426. This process could be reversed. With the third strain of staphylococcus the lysogenic offspring were not lysed by their original temperate phage, which they continued to carry. The NCTC phage 8426 appeared to undergo a modification when grown on the three strains described here, following which a few particles (c. 1 in 5 × 104) were able to lyse cells lysogenically infected with phage 8426. These virulent phage particles were maintained by propagation on lysogenic host cells but they reverted to the normal 8426 phage when grown on the non-lysogenic indicator. Finally phage 8426 showed another modification of its host range when grown on one of the three strains, this change was reversed when the modified phage was propagated on its normal host Staphylococcus aureus NCTC 8354.
-
-
-
The Maintenance of Eremothecium ashbyi
More LessSUMMARY: Different methods of maintenance of highly flavinogenic strains of Eremothecium ashbyi have been studied.
Storage for 6 months at room temperature or 4° on agar slants either untreated, layered with liquid paraffin or sealed with paraffin wax resulted in considerable loss of flavinogenic capacity. Similar losses also occurred when various strains were transferred regularly at 2-week intervals.
Complete maintenance of flavinogenic activity over 8 months was obtained by freeze-drying cultures, previously frozen at − 68°, in maltose or glucose solutions in either water or serum.
-
-
-
Nuclear Fusion in Spirillum spp
More LessSUMMARY: Cellular fusion of entwined fresh-water spirilla, Spirillum sinuosum and S. anulus, is followed by nuclear fusion. Evidence of nuclear fusion was obtained from impression smears (fixed in acetic-alcohol, hydrolysed in n-HC1 and stained with Giemsa) made at regular time intervals during the growth of cultures of these organisms. Following cellular fusion and nuclear fusion of opposing granules into rings of six granules, with the coalescence of the rings into a single, elongate body, the fusion cells enlarge into ‘giant’ organisms. The chromatinic bodies of these giants divide or separate into numerous rod-like chromatin structures around the vacuoles found in the later stages. The giant organisms either give off or fragment into small rod-like bodies, containing, at first, a triangular-shaped chromatinic structure. This triangular chromatinic structure condenses into a single spherical body as the small rod-like organisms are more clearly formed. The fate of these small rod-like organisms is unknown, but similar rod-like bodies which develop into the normal spirillum have been observed in young cultures of both S. sinuosum and S. anulus. Nothing resembling classical mitosis or meiosis was observed in any of the stained preparations of either organism.
-
-
-
Some Factors Affecting the Growth of Bordetella pertussis
More LessSUMMARY: Bordetella pertussis incubated in liquid media is prevented from multiplying by autoclaved cysteine and is rapidly killed by another substance, possibly a peroxide. The inhibition by autoclaved cysteine is overcome by serum albumin and the inhibition by ‘peroxide’ is overcome by red blood corpuscles, haemin, or ferrous sulphate sterilized by filtration. In a medium containing casein hydrolysate and yeast extract, logarithmic growth may continue for 40–50 hr. at one rate and then may change to a slower rate which continues for a further 20–30 hr. before growth stops. The initial growth rate can be maintained throughout by adding high concentrations of whole blood. The yield of organisms is proportional to the concentration of glutamic acid up to 0·3 % (w/v). It is possible that growth at greater concentrations is stopped by the high pH value caused by the oxidation of glutamate. Omission of casein hydrolysate decreases the yield of bacteria. A larger yield is obtained by the use of a large inoculum of bacteria with adherent blood.
-
-
-
Some Characteristics of Vesicular Stomatitis Virus Growth-Curves in Tissue Culture
More LessSUMMARY: Vesicular stomatitis virus was released exponentially and fairly reproducibly after infecting chick embryo cell monolayers. This system appeared suitable for chemical studies, which are to be presented separately; the present paper is concerned with growth-curve methods and a discussion of the system. When the average multiplicity of adsorption was 6 plaque-forming units/cell the latent period was 1–2 hr., and growth appeared to follow a one-step cycle. At least 62–75 % of the cells were capable of releasing virus.
-
-
-
Paths of Phosphate Transfer in Normal Chick Embryo Cells and in Cells Infected with Vesicular Stomatitis Virus
More LessSUMMARY: The paths of phosphate transfer were compared in normal and vesicular stomatitis virus-infected chick embryo cell monolayers during one-step virus growth. Phosphate entered the normal cell via an inorganic pool in reversible equilibrium with external phosphate, and passed to large-molecule phosphate from this pool or from organic acid-soluble phosphate. During the latent and exponential release periods of virus infection there was no detectable slowing or stimulation of the rate of gain of 32P by acid-soluble inorganic and organic phosphates (AI and AO), lipid phosphate (LP), ribonucleic acid (RNA) and other phosphate fractions until uptake ceased in nearly all fractions about half-way through exponential release. Negligible P or 32P entered or left deoxyribonucleic acid (DNA) in normal or infected cells in this system. Before and during exponential release there was no detectable lysis of nuclei, mitochondria or microsomes (examined after isolation), and no detectable loss of 32P from AI, AO, LP, RNA or DNA, except for a late 30–50 % decrease in the 32P of the sucrose-soluble RNA of disrupted cells. This could be a secondary effect (i.e. onset of cell death) rather than an essential stage of virus growth. Gross lysis was evident in all fractions 20 hr. after infection, with the exception of the acid-soluble inorganic fraction not in reversible equilibrium with the medium.
-
-
-
An Osmotic Barrier for Inorganic Phosphate in Chick Embryo Cells and its Stability during the Latent and Release Periods of Infection by Vesicular Stomatitis Virus
More LessSUMMARY: An osmotic barrier for phosphate very near the visible surface of the chick-embryo cell appears to regulate the reciprocal exchange of inorganic orthophosphate between the medium and a component of the acid-soluble inorganic phosphate of cells kept in monolayer culture. Some non-reciprocal transfer of inorganic phosphate occurs, which may or may not be due to cell damage, and the apparent phosphate-impermeable volume decreases by half after 3 hr. contact with phosphate at 0°. At 2° the exchange is at least 97 % inhibited. The phosphate- impermeable volume after cell rupture is less than 10 % of the intact-cell value, when internal phosphate is released in a form shown by mild separation to be mostly inorganic orthophosphate. Cells lose internal phosphate more slowly in absence of external phosphate, and the addition of external phosphate increases the loss rate to a maximum at physiological concentrations and higher.
Such a barrier provides information on the nature of the cell surface, and shows that adsorption, penetration and release of vesicular stomatitis virus occurs without any detectable damage to the surface controlling the phosphate-exchange rate.
-
-
-
Yeasts Isolated from the Mammalian Alimentary Tract
More LessSUMMARY: A survey of the yeasts found in the alimentary canal of 169 animals has been carried out. Representatives of 17 species and 6 genera were isolated but of these only 4 species, Torulopsis pintolopesii, Saccharomycopsis guttulata, Candida albicans, and T. glabrata were considered to be true intestinal types. C. parapsilosis and C. krusei were classed as intermediates and the remainder as transients. The validity of the species T. pintolopesii is considered doubtful.
-
-
-
Labyrinthula minuta sp.nov
More LessSUMMARY: A new marine species of Labyrinthula is described for which the name L. minuta is proposed because of its diminutive proportions. This species has been isolated repeatedly from Viva lactuca and other algae collected from the Atlantic Ocean in the region of Woods Hole, Massachusetts. The vegetative stage, as in other species of Labyrinthula, consists of independent cells interconnected by threads of slime which form a net-like structure called the net-plasmodium. L. minuta differs from all previously described species of this genus in the size, shape, and movement of its cells, in its method of cell division, its colonial morphology and by the formation in aged cultures of multinucleate bodies which resemble miniature plasmodia. No fructification has yet been observed. This species has been grown in pure reproducible laboratory culture on a serum + sea water medium for a period of five years.
-
-
-
Sodium Chloride and the Growth of Desulphovibrio desulphuricans
More LessSUMMARY: The effect of sodium chloride on the multiplication of four freshwater and three salt-water strains of sulphate-reducing bacteria was examined by determining the numbers of organisms in a known population which were viable in media of unfamiliar NaCl concentrations. The salt-water strains all produced variants viable at high NaCl concentrations; a population able to multiply in 1 %–10 % NaCl was obtained by ‘training’ one salt-water strain. They differed, however, in the frequency with which non-exacting variants appeared, ranging from a strain in which the whole population grew with 0·25 % NaCl to one which would not grow with less than 0· % NaCl even after repeated attempts at acclimatization. Replacement experiments indicated that the exigent strain required chloride ion; a less- exacting strain required sodium ion. The fresh-water strains produced few variants viable at NaCl concentrations above 3 %, but one strain produced variants of the salt-water type after ‘training’ to grow with 4% NaCl; sodium ion was mainly responsible for the inhibition of this strain by high NaCl concentrations. We conclude that the differences among the salt- and fresh-water strains of Desulphovibrio do not at present justify their separation into the two species aestaurii and desulphuricans.
-
-
-
Hippurate Hydrolysis in Klebsiella-Cloaca Classification
More LessSUMMARY: 169 strains of Klebsiella pneumoniae and 68 strains of Cloaca cloacae were used in an examination of Hajna & Damon’s hippurate test and various modifications of it. The addition of a pH indicator (phenol red) to the medium enabled hydrolysis to be detected by a change of colour. Clear-cut distinction between K. pneumoniae and C. cloacae was not obtained with any method, but the indicator medium gave the best results and was simplest.
-
-
-
Gelatin Liquefaction: a Microtest
More LessSUMMARY: A slide microtest for gelatin liquefaction is described. Members of the genera Cloaca, Bacillus and Clostridium were tested with varying results. A limitation of the method is its ability to detect only ready-formed enzyme. The main advantage is that small amounts of culture are needed and the organisms may be grown under any selected conditions.
-
-
-
Quantitative Analysis of the Gram Reaction
More LessSUMMARY: The crystal violet and iodine uptake by suspensions of Staphylococcus aureus and Escherichia coli was determined. It was found that equal amounts of intracellular dye-iodine complex were formed in these micro-organisms. The molar ratio dye to iodine was 1:2. The extractability of this complex with methanol and ethanol was compared with the relative solubility of dye-iodine precipitates. Results with E. coli suggest that the solvents pass freely into the cells and decolorize them after dissociation of the dye-iodine complex. Gram-positive micro-organisms may be arranged in a number of groups according to their extractability pattern with regard to the complex. These patterns suggest the presence of interaction between the cells and ethanol. This interaction may be located at the cell wall.
-
-
-
The Development and Testing of a Method of Counting Rumen Ciliate Protozoa
More LessSUMMARY: The limitations of methods previously used for counting rumen ciliates, and the value of developing a method of known accuracy, are discussed. Two counting-chambers, one based on the Sedgwick-Rafter cell, the other on the MacMaster eelworm-counting cell, were constructed and tested. A MacMaster-type cell was adopted. The preparations of suitable suspensions for counting organisms from washed suspensions and from rumen contents are described. The counting technique adopted was found to be reliable; its accuracy depends upon the number of organisms counted. In one sheep on a constant diet, day-to-day differences in rumen ciliate population were far greater than the differences found throughout the rumen at any one time, or the variations due to technique.
-
-
-
The Occurrence of Rare Motile Bacteria in some Non-motile Salmonella Strains
More LessSUMMARY: The presence of rare motile bacteria in 22 of 48 non-motile Salmonella strains tested has been inferred from the production of satellite micro-colonies in semi-solid medium. Such rare motile bacteria have been isolated by micromanipulation ; they are not motile mutants, since their progeny are nearly all non-motile. They transmitted motility to only a few of their descendants, as if their motility were due to the presence of non-multiplying motility-conferring particles which were transmitted to their progeny at cell division. It is inferred that small numbers of such particles arise during an intracellular ‘event’; this event probably consists of a transient ability to synthesize new flagella. The frequency of events in one Salmonella O strain was found to be c. 4 × 10−5/bacterium/generation.
-
-
-
The Cellular Polysaccharide of a Type II non-capsulated Pneumococcus
More LessSUMMARY: A purified cellular polysaccharide was obtained from a non-capsulated pneumococcus (Streptococcus pneumoniae, strain R19, derived from a Type II organism). The main purification steps were peptic, tryptic and ribonuclease digestions, removal of protein by the Sevag technique and ethanol precipitation of the polysaccharide. Ribonuclease digestion was an essential step in the purification procedure. The constituent sugars of the isolated polysaccharide were galactose, mannose and glucosamine. The acetyl content of the polysaccharide indicated that the glucosamine was fully acetylated on the N position and that some O-acetyl was also present. The phosphorus content was not entirely explicable in terms of the known ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) contamination. Residual amino acid was consistently present which may have been due to bound amino acids or to protein contamination.
-
-
-
A Comparative Study of Cellulose-Producing Cultures and Celluloseless Mutants of certain Acetobacter Spp
R. Steel and T. K. WalkerSUMMARY: Comparative studies have been conducted with two strains of Acetobacter acetigenum (NCIB 8132, NCIB 5346), one strain of A. xylinum var. africanum (NCIB 7029) and a total of 26 celluloseless mutants obtained from these three parent cultures. In addition to the loss of ability to produce a cellulose pellicle, other consistent differences were also observed between the parent and the mutant cultures. Whereas the parent cultures oxidized ethanol to acetic acid this reaction was not observed with mutant organisms. The mutants showed (1) optimum growth in alkaline media, (2) growth in glucose yeast-extract medium in the presence of 10–12% (v/v) ethanol, (3) proteolytic activity, (4) growth at 40°, and (5) growth in yeast-extract medium; these abilities were not shown by the wild-type cultures. Variations in colony form, nutritional requirements, the ability to produce acid from certain sugars and to oxidize glycerol appeared to occur at random among the mutant cultures.
-
-
-
Formation of the Veǵetative Pool by Induced Defective and Healthy Lysoǵenic Strains of Escherichia coli
More LessSUMMARY: Comparison of two defective λ prophages carried by strains of Escherichia coli, with respect to their physiological properties following induction, has revealed that one defective mutant (λ i 2) can multiply normally as vegetative phage but cannot mature into normal infectious phage, whereas the other defective phage (λ i1) can undergo only limited multiplication since it is unstable in the vegetative state. Consideration of the properties of λ i 1 has led to an hypothesis that radiation induction causes the prophage to produce a vegetative replica which becomes autonomous rather than conversion of the prophage into vegetative phage.
-
Volumes and issues
-
Volume 170 (2024)
-
Volume 169 (2023)
-
Volume 168 (2022)
-
Volume 167 (2021)
-
Volume 166 (2020)
-
Volume 165 (2019)
-
Volume 164 (2018)
-
Volume 163 (2017)
-
Volume 162 (2016)
-
Volume 161 (2015)
-
Volume 160 (2014)
-
Volume 159 (2013)
-
Volume 158 (2012)
-
Volume 157 (2011)
-
Volume 156 (2010)
-
Volume 155 (2009)
-
Volume 154 (2008)
-
Volume 153 (2007)
-
Volume 152 (2006)
-
Volume 151 (2005)
-
Volume 150 (2004)
-
Volume 149 (2003)
-
Volume 148 (2002)
-
Volume 147 (2001)
-
Volume 146 (2000)
-
Volume 145 (1999)
-
Volume 144 (1998)
-
Volume 143 (1997)
-
Volume 142 (1996)
-
Volume 141 (1995)
-
Volume 140 (1994)
-
Volume 139 (1993)
-
Volume 138 (1992)
-
Volume 137 (1991)
-
Volume 136 (1990)
-
Volume 135 (1989)
-
Volume 134 (1988)
-
Volume 133 (1987)
-
Volume 132 (1986)
-
Volume 131 (1985)
-
Volume 130 (1984)
-
Volume 129 (1983)
-
Volume 128 (1982)
-
Volume 127 (1981)
-
Volume 126 (1981)
-
Volume 125 (1981)
-
Volume 124 (1981)
-
Volume 123 (1981)
-
Volume 122 (1981)
-
Volume 121 (1980)
-
Volume 120 (1980)
-
Volume 119 (1980)
-
Volume 118 (1980)
-
Volume 117 (1980)
-
Volume 116 (1980)
-
Volume 115 (1979)
-
Volume 114 (1979)
-
Volume 113 (1979)
-
Volume 112 (1979)
-
Volume 111 (1979)
-
Volume 110 (1979)
-
Volume 109 (1978)
-
Volume 108 (1978)
-
Volume 107 (1978)
-
Volume 106 (1978)
-
Volume 105 (1978)
-
Volume 104 (1978)
-
Volume 103 (1977)
-
Volume 102 (1977)
-
Volume 101 (1977)
-
Volume 100 (1977)
-
Volume 99 (1977)
-
Volume 98 (1977)
-
Volume 97 (1976)
-
Volume 96 (1976)
-
Volume 95 (1976)
-
Volume 94 (1976)
-
Volume 93 (1976)
-
Volume 92 (1976)
-
Volume 91 (1975)
-
Volume 90 (1975)
-
Volume 89 (1975)
-
Volume 88 (1975)
-
Volume 87 (1975)
-
Volume 86 (1975)
-
Volume 85 (1974)
-
Volume 84 (1974)
-
Volume 83 (1974)
-
Volume 82 (1974)
-
Volume 81 (1974)
-
Volume 80 (1974)
-
Volume 79 (1973)
-
Volume 78 (1973)
-
Volume 77 (1973)
-
Volume 76 (1973)
-
Volume 75 (1973)
-
Volume 74 (1973)
-
Volume 73 (1972)
-
Volume 72 (1972)
-
Volume 71 (1972)
-
Volume 70 (1972)
-
Volume 69 (1971)
-
Volume 68 (1971)
-
Volume 67 (1971)
-
Volume 66 (1971)
-
Volume 65 (1971)
-
Volume 64 (1970)
-
Volume 63 (1970)
-
Volume 62 (1970)
-
Volume 61 (1970)
-
Volume 60 (1970)
-
Volume 59 (1969)
-
Volume 58 (1969)
-
Volume 57 (1969)
-
Volume 56 (1969)
-
Volume 55 (1969)
-
Volume 54 (1968)
-
Volume 53 (1968)
-
Volume 52 (1968)
-
Volume 51 (1968)
-
Volume 50 (1968)
-
Volume 49 (1967)
-
Volume 48 (1967)
-
Volume 47 (1967)
-
Volume 46 (1967)
-
Volume 45 (1966)
-
Volume 44 (1966)
-
Volume 43 (1966)
-
Volume 42 (1966)
-
Volume 41 (1965)
-
Volume 40 (1965)
-
Volume 39 (1965)
-
Volume 38 (1965)
-
Volume 37 (1964)
-
Volume 36 (1964)
-
Volume 35 (1964)
-
Volume 34 (1964)
-
Volume 33 (1963)
-
Volume 32 (1963)
-
Volume 31 (1963)
-
Volume 30 (1963)
-
Volume 29 (1962)
-
Volume 28 (1962)
-
Volume 27 (1962)
-
Volume 26 (1961)
-
Volume 25 (1961)
-
Volume 24 (1961)
-
Volume 23 (1960)
-
Volume 22 (1960)
-
Volume 21 (1959)
-
Volume 20 (1959)
-
Volume 19 (1958)
-
Volume 18 (1958)
-
Volume 17 (1957)
-
Volume 16 (1957)
-
Volume 15 (1956)
-
Volume 14 (1956)
-
Volume 13 (1955)
-
Volume 12 (1955)
-
Volume 11 (1954)
-
Volume 10 (1954)
-
Volume 9 (1953)
-
Volume 8 (1953)
-
Volume 7 (1952)
-
Volume 6 (1952)
-
Volume 5 (1951)
-
Volume 4 (1950)
-
Volume 3 (1949)
-
Volume 2 (1948)
-
Volume 1 (1947)