Growth and phage production of B. megatherium. I. Growth of cells after infection with C phage. II. Rate of growth,phage yield,and RNA content of cells. III. Effect of various substances on growth rate and phage production

I. Lysogenic B. megatherium 899a (de Jong, 1931) produces two types of phage (Gratia, 1936 c) T and C. The T phage forms cloudy plaques and gives rise to fresh lysogenic strains (Gratia, 1936 b) when added to the sensitive strain of megatherium. It may or may not cause lysis, depending on the media (Northrop, 1951). The C phage occurs very rarely) forms clear plaques, does not give rise to lysogenic strains, and causes complete lysis of the sensitive strain under all conditions tested, provided infection occurs. If C phage is added to the sensitive strain, and the mixture allowed to stand, or made into a hanging drop preparation, the infected cells stop growing and lyse completely after 60 to 80 minutes with the liberation of from 50 to 200 phage particles per cell. If, however, C phage is added to a rapidly growing culture of B. megatherium and the suspension shaken at 34°, the cells continue to grow and divide for 50 to 60 minutes, after infection has occurred. They then lyse, with the liberation of from 1000 to 2500 phage particles per cell. II. The following determinations have been made on megatherium sensitive cells growing in 5 per cent peptone at different stages of growth. (1) Growth rate of infected and uninfected cells; (2) RNA, DNA, and protein content; (3) volume of the cell; (4) phage yield per cell by plaque count; (5) phage yield per cell by cell and plaque count; (6) lysis time. The growth rate decreases as the cell concentration increases. The lysis time and the protein N per cell are nearly independent of the growth rate; all the other values increase as the growth rate increases. The ratio See PDF for Equation is nearly constant. RNA and DNA per cell increase less rapidly than the volume, so that NA per unit volume is not constant, but decreases as the size of the cell increases. The phage yield measured under conditions in which the infected cells do not grow (by plaque count) is very nearly proportional to the size of the cell. The phage yield per cell, under conditions in which the infected cells do grow, increases more rapidly than the size of the cells. The phage yield per cell under these conditions may be calculated by the equation See PDF for Equation The determining factor for the variation in phage yield is the growth rate of the cells. This, in turn, is determined by the composition of the medium. III. The growth and phage production of megatherium 899a have been determined in the presence of the following substances: aureomycin, bacitracin, chloromycetin, gramicidin, Merck AB631, Merck AB191, Merck AB624, penicillin, streptomycin, terramycin, tyrothricin, usnic acid, acetone, chloroform, ethyl alcohol, formaldehyde, gentian violet, glycerin, maleic hydrazide, methyl alcohol, phenyl mercuric acetate, sodium fluoride, sulfanilamide, toluene, and urethane. In every case, the lowest concentration of the substance which completely inhibits growth, is also the lowest concentration which completely inhibits phage production. One antibiotic, Merck AB81, causes increased phage production in concentrations which partially inhibit growth, and low phage production in concentrations which completely inhibit growth (as determined by turbidity). Short exposure to ultraviolet light also decreases the growth rate, with increase in phage production. Longer exposure, which completely inhibits growth (as determined by turbidity) results in lysis and phage liberation.     

Effect of preincubation temperature on in vitro light saturated photosystem I activity in thylakoids isolated from cold hardened and nonhardened rye

Thylakoids isolated from winter rye (Secale cereale L. cv Muskateer) grown at 5°C or 20°C were compared with respect to their capacity to exhibit an increase in light saturated rates of photosystem I (PSI) electron transport (ascorbate/dichlorophenolindophenol → methylviologen) after dark preincubation at temperatures between 0 and 60°C. Thylakoids isolated in the presence or absence of Na⁺/Mg²⁺ from 20°C grown rye exhibited transient, 40 to 60% increases in light saturated rates of PSI activity at all preincubation temperatures between 5 and 60°C. This increase in PSI activity appeared to occur independently of the electron donor employed. The capacity to exhibit this in vitro induced increase in PSI activity was examined during biogenesis of rye thylakoids under intermittent light conditions at 20°C. Only after exposure to 48 cycles (1 cycle = 118 minutes dark + 2 min light) of intermittent light did rye thylakoids exhibit an increase in light saturated rates of PSI activity even though PSI activity could be detected after 24 cycles. In contrast to thylakoids from 20°C grown rye, thylakoids isolated from 5°C grown rye in the presence of Na⁺/Mg²⁺ exhibited no increase in light saturated PSI activity after preincubation at any temperature between 0 and 60°C. This was not due to damage to PSI electron transport in thylakoids isolated from 5°C grown plants since light saturated PSI activity was 60% higher in 5°C thylakoids than 20°C thylakoids prior to in vitro dark preincubation. However, a two-fold increase in light saturated PSI activity of 5°C thylakoids could be observed after dark preincubation only when 5°C thylakoids were initially isolated in the absence of Na⁺/Mg²⁺. We suggest that 5°C rye thylakoids, isolated in the presence of these cations, exhibit light saturated PSI electron transport which may be closer to the maximum rate attainable in vitro than 20°C thylakoids and hence cannot be increased further by dark preincubation.     

Photoinduced Seed Germination of Oenothera biennis L: I. General Characteristics

General characteristics of light-induced germination of Oenothera biennis L. seeds were investigated at 24°C. During dark imbibition, seeds reached maximal respiration in 7 hours and maximal water content and photosensitivity in 24 hours. After dark imbibition of 24 hours, seeds required a long exposure (>36 hours) to red or white light for maximal germination. Two photoperiods (12 and 2 hours) separated by a period of darkness of 10 to 16 hours gave near maximal germination. For the two photoperiod regime, the first light potentiates a reversible phytochrome response by the second light. A 35°C treatment for 2 to 3 hours in the dark immediately prior or subsequent to 8 hours of light caused a higher percentage of germination. A 2 hour treatment at 35°C also potentiates a reversible phytochrome response. Halved seeds germinated at 100% in light or darkness indicating that the light requirement of the seeds is lost in the halving procedure. After-ripened seeds required less light and germinated more rapidly and at higher percentages than seeds tested shortly after maturation.     

The accelerating action of illumination in recovery of Arbacia eggs from exposure to ultraviolet radiation

Light of wave lengths 0.30µ to 0.50µ, accelerates return of the cleavage rate of Arbacia eggs to normal, after delay by exposure to ultraviolet radiation (wave lengths 0.238µ to 0.31µ). Recovery is apparently complete. Wave lengths 0.30µ to 0.50µ have no effect on the cleavage rate of normal eggs, nor does such illumination previous to dosage with ultraviolet radiation influence subsequent recovery. Acceleration of recovery of the egg occurs before fertilization as well as after. The effects of ultraviolet radiation and recovery therefrom are essentially the same in nucleated "white halves" as in the intact eggs. This phenomenon in the Arbacia egg seems basically comparable to photoreactivation of bacteria and fungi.     

CARBON DIOXIDE PRODUCTION AND DURATION OF LIFE OF DROSOPHILA CULTURES

The total CO₂ produced by aseptic Drosophila cultures during the entire duration of life has been determined at 15°, 26°, and 30°C. in the dark and at 22–26°C. in the light. The total amount of CO₂ produced is not constant but is greater at 15° than at 26° or 30°, and is much greater in the light than in the dark. The total duration of life, therefore, is not determined by the time required to produce a limiting amount of CO₂.     

Action of Phytochrome During Prechilling of Amaranthus retroflexus L. Seeds

Dark germination of Amaranthus retroflexus L. seeds at 35° increased after several days of prechilling at 20° or lower. Irradiation with far-red light for short periods during the early hours of a prechilling period at 10° inhibited subsequent dark germination at 35°. The inhibition was completely reversible with red light. Far-red irradiation in the latter part of the prechilling period was less effective. Increased dark germination of A. retroflexus seeds following a prechilling period at 20° or less is attributed to action of preexistent P_FR, the far-red absorbing form of phytochrome, within the seeds. Inactivation of P_FR was found to proceed ca. 4 times more rapidly at 25° than at 20°. Failure of imbibition temperatures above 20° to increase dark germination of A. retroflexus seeds is attributed to the rapid thermal reversion of pre-existent P_FR. We suggest that the action of prechilling (layering) on many other seed kinds arises in a similar way.     

Studies on the origin of bacterial viruses. V. The effect of temperature on the terramycin-resistant and phage-producing cells of Bacillus megatherium cultures

The growth rates, the mutation frequency rate constants of the terramycin-resistant cells, the burst size of the phage-producing cells, and the ratio of phage to cells all have a temperature coefficient of about 2 from 20 to 35° (µ = 9 x 10³ calories), with a maximum at 40°. The mutation frequency rate constant (or time rate constant) of the phage-producing cells increases from 20 to 45° with a temperature coefficient of about 3 (µ = 2 to 3 x 10⁴ cal.). The change in the values for the growth rate, mutation rate, and cell volume occurs in less than 1 hour, after the temperature is changed. The value for the burst size of phage-producing cells changes for 3 to 4 hours. Prolonged growth of megatherium 899 at 48 to 50° results in the production of C + S phage, in place of T. Returning the culture to 25° results in the production of small T phage.     

Zeaxanthin Synthesis, Energy Dissipation, and Photoprotection of Photosystem II at Chilling Temperatures

When leaves of a mangrove, Rhizophora mangle, were exposed to an excess of light at chilling temperatures, synthesis of zeaxanthin through violaxanthin de-epoxidation as well as nonphotochemical fluorescence quenching were markedly reduced. The results suggest a protective role of energy dissipation against the adverse effects of high light and chilling temperatures: leaves of R. mangle that had been preilluminated in 2% O₂, 0% CO₂ at low photon flux density and showed a high level of zeaxanthin, and leaves that had been kept in the dark and contained no zeaxanthin, were both exposed to high light and chilling temperatures (5°C leaf temperature) in air and then held under control conditions in low light in air at 25°C. Measurements of chlorophyll a fluorescence at room temperature showed that the photochemical efficiency of PSII and the yield of maximum fluorescence of the preilluminated leaf recovered completely within 1 to 3 hours under the control conditions. In contrast, the fluorescence responses of the predarkened leaf in high light at 5°C did not recover at all. During a dark/light transient in 2% O₂, 0% CO₂ in low light at 5°C, nonphotochemical fluorescence quenching increased linearly with an increase in the zeaxanthin content in leaves of R. mangle. In soybean (Glycine max) leaves, which contained a background level of zeaxanthin in the dark, a similar treatment with excess light induced a level of nonphotochemical fluorescence quenching that was not paralleled by an increase in the zeaxanthin content.     

Chilling sensitivity of cucumber cotyledon protoplasts and seedlings

Cucumber (Cucumis sativus L.) seedlings are more sensitive to chilling stress when transferred to low temperature from the night cycle than from the day cycle. However, greater damage occurs when chilling is carried out in light than in dark. Freshly isolated protoplasts are extremely sensitive to damage when chilled at 4°C in light, but suffer significantly less injury when chilled in dark. If freshly isolated protoplasts are pre-chill conditioned at 27°C in either light or dark for a few hours prior to exposure to various chilling stresses, subsequent chilling damage is markedly reduced. Damage to chilled protoplasts also is reduced if cultures are placed in dark instead of light immediately following removal from low temperature. Experiments utilizing the cell wall synthesis inhibitor, dichlorobenzonitrile, showed that cell wall regeneration during the pre-chill conditioning period at 27°C does not appear to be associated with the enhanced chilling tolerance observed in these cultures. The results obtained in this investigation suggest that the physiological properties of cucumber cotyledon protoplasts accurately reflect those of intact seedlings, and hence provide a good system for studies into the mechanism of chilling damage in plants.     

THE EFFECT OF LOW TEMPERATURE ON THE DEVELOPMENT OF THE LAMELLAR SYSTEM IN CHLOROPLASTS

The influence of low temperature (3°C.) on development of submicroscopic structure in plastids of Zea m. leaves was studied. Leaves from 8-day old etiolated plants, with plastids showing the prolamellar body and few lamellae, were floated for 1 day on tap water both in the dark and in the light, at 26°C and at 3°C. The structures remain unchanged in the dark, independent of temperature. Whereas in the light at 26°C., normal development of parallel compound lamellae and formation of grana occurs, in light at 3°C. ring structures are formed. Under the latter conditions protochlorophyll is converted to chlorophyll, although the in situ absorption maximum is different from the one for chlorophyll in plants grown in light at 26°C. When leaves were transferred from light at 3°C. to light at 26°C., ring structures in the plastids disappeared and normal development occurred. The possibility is discussed that development of parallel-arranged compound lamellae is due both to photochemical and synthetic processes, involving not only accumulation of chlorophyll, but also synthesis of other compounds.     

Plant growth environment effects on rapeseed microspore development and culture : a flow cytometric study

The influence of donor plant growth conditions on microspore embryogenesis in rapeseed (Brassica napus) was studied for plants grown at 23/18°C (16/8 hours) under continuous light, 23/18°C (16/8 hours) with a light/dark (16/8 hours) cycle, 15/12°C (16/8 hours) under continuous light and 15/12°C (16/8 hours) with a light/dark (16/8 hours) cycle. Significantly higher embryo yields were obtained from microspore cultures initiated from donor plants grown at 15/12°C instead of 23/18°C. Flow cytometric measurements of the microspores isolated from 2.5- to 5.0-millimeter buds showed that the microspores isolated from low-temperature-grown plants had significantly lower log 90-degree light scatter to forward angle light scatter and log 90-degree light scatter to time of flight ratios than those isolated from high-temperature-grown plants, suggesting that the former are more translucent than the latter. Thus, the effect of donor plant growth temperature on microspore embryogenesis may be mediated by a change in the physiology of the microspore cell, which results in the reduction of its cytoplasmic granularity and/or exine density.     

The core interthreshold zone during exposure to red and blue light

Background

This study tested the hypothesis that the core interthreshold zone (CIZ) changes during exposure to red or blue light via the non-visual pathway, because it is known that light intensity affects the central nervous system. We conducted a series of human experiments with 5 or 10 male subjects in each experiment.

Methods

The air temperature in the climatic chamber was maintained at 20 to 24°C. The subjects wore suits perfused with 25°C water at a rate of 600 cm³/min. They exercised on an ergometer at 50% of their maximum work rate for 10 to 15 minutes until sweating commenced, and then remained continuously seated without exercise until their oxygen uptake increased. The rectal temperature and skin temperatures at four sites were monitored using thermistors. The sweating rate was measured at the forehead with a sweat rate monitor. Oxygen uptake was monitored with a gas analyzer. The subjects were exposed to red or blue light at 500 lx and 1000 lx in both summer and winter.

Results

The mean CIZs at 500 lx were 0.23 ± 0.16°C under red light and 0.20 ± 0.10°C under blue light in the summer, and 0.19 ± 0.20°C under red light and 0.26 ± 0.24°C under blue light in the winter. The CIZs at 1000 lx were 0.18 ± 0.14°C under red light and 0.15 ± 0.20°C under blue light in the summer, and 0.52 ± 0.18°C under red light and 0.71 ± 0.28°C under blue light in the winter. A significant difference (P <0.05) was observed in the CIZs between red and blue light at 1000 lx in the winter, and significant seasonal differences under red light (P <0.05) and blue light (P <0.01) were also observed at 1000 lx.

Conclusions

The present study demonstrated that dynamic changes in the physiological effects of colors of light on autonomic functions via the non-visual pathway may be associated with the temperature regulation system.     

Effect of Dichlorodifluoromethane on the Appearance, Viability, and Integrity of Escherichia coli

Cultures of Escherichia coli H52 were treated with liquid dichlorodifluoromethane (fluorocarbon-12 [f-12]) for 2 h at 22 C and then examined microscopically. Treated cells tended to clump, and their cytoplasms were generally less dense and less uniform in appearance than those of control cells. E. coli ML30 was exposed to f-12 at a concentration of 1.25 × saturation for times up to 1,200 min at 22 C. Cells were examined for changes in viability (plate count), permeability (as measured by exit of α-[¹⁴C]methylglucoside or uptake of o-nitrophenyl-β-D-galactopyranoside), release of compounds absorbing at 260 nm, and lysis (changes in absorbance at 420 nm). Large losses of α-methylglucoside and of percentage of viability occurred after brief exposure to f-12. Release of compounds absorbing at 260 nm occurred more slowly than the aforementioned events, possibly because these molecules are larger than α-methylglucoside. During 1,200-min exposure to f-12, the number of survivors decreased from 10⁹ to 10⁴ organisms/ml, the loss of compounds absorbing at 260 nm amounted to 50% and 32% lysis occurred. Most of these changes occurred during the first 300 min of treatment. Loss of α-methylglucoside was almost complete after 1-min exposure to f-12. These results suggest that death of the cell involves several stages, with a change of permeability occurring first, followed by leakage of compounds of increasing size and, finally, lysis.     

Studies on a Maize Mutant Sensitive to Low Temperature II. Chloroplast Structure, Development, and Physiology

In the Zea mays L. mutant M11 grown in the dark at 15°, the ultrastructure of the etioplast is abnormal. The pigment content of the etioplasts is reduced but the in vivo absorption characteristics suggest that the normal protochlorophyll (ide)-holochrome is present. The lowered synthetic ability of the etioplasts is not primarily due to a reduced complement of plastid ribosomes. The plastids of mutant M11 grown in the light at 15° contain little pigment, are markedly deficient in ribosomes and their ultrastructure is abnormal. In mutant M11 grown at 15°, an extreme sensitivity of the plastid membranes to light was observed.     

Oxidized and reduced nicotinamide adenine dinucleotide phosphate levels of plants hardened and unhardened against chilling injury

Pea plants (Pisum sativum L. var. Alaska) subjected to low temperature (5°) in the light acquired resistance against chilling injury.

Unhardened plants maintained high NADP and low NADPH levels during illumination at 25° but hardened plants had low NADP and high NADPH levels in the light. When the unhardened plants were transferred to the dark room at 25°, their NADPH levels decreased immediately. On the other hand, hardened plants maintained a high NADPH level for a few hours even in the dark.

     

Influence of light on the heat sensitivity of the photosynthetic apparatus in isolated spinach chloroplasts

The most heat-sensitive functions of chloroplasts in Spinacia oleracea L. including the stromal carboxylation reaction, the light-induced electrical field gradient across the thylakoid membrane, as well as the overall photosynthetic CO₂ fixation were less affected by heat if chloroplasts were heated in the light: 50% inactivation occurred around 35°C in the dark and around 40°C in the light. Relative low light intensities were sufficient to obtain optimal protection against heat. In contrast, the light-induced ΔpH across the thylakoid membrane, the photophosphorylation, and the photochemical activity of photosystem II which were less sensitive to heat in the dark (50% inactivation above 40°C) were not protected by light. Photosystem II even was destabilized somewhat by light.

The effect of light on the heat sensitivity of the water-splitting reaction was dependent on the pH in the medium. Protection by light only occurred at alkaline pH, in which case heat sensitivity was high (50% inactivation at 33°C in the dark and at 38°C in the light). Protection was prevented by uncouplers. At pH 6.8 when the heat sensitivity was low in any case (50% inactivation at 41°C in the dark), light had no further protecting effect.

Protection by light has been discussed in terms of light-induced transport of protons from the stroma to the thylakoid space and related ion fluxes.

     

The association of carbohydrate changes in the shoot tip of cauliflower with flowering

Changes in levels of sugars and starch in the shoot tip of cauliflower, Brassica oleracea L. var. botrytis D. C. cv. Main Crop were studied during periods of growth which were inductive or non-inductive to flowering. Flowering was induced by growing plants for 2 weeks under 16 hr of light at 5°. During this period of floral induction there was a significant increase in sugar and starch content compared to that in vegetative plants grown at 20 to 26°. Sugar and starch content did not increase and flowering was prevented when light and CO₂ were excluded during growth at 5°. A 3-day dark period at 20° or a high temperature treatment at 33° with light following growth at 5° reduced the carbohydrate level and prevented flowering.     

Phototropism and Local Adaptation in Phycomyces Sporangiophores

Phototropic responses to unilateral ultraviolet stimuli were studied to determine whether the response of one side of the cell is affected by the previous exposure of the opposite side to ultraviolet. It has been found that the direction of bending is not parallel to the stimulus direction, but is along a straight line rotated 17° clockwise from the stimulus direction. This deviation indicates that the photoreceptors may be in a state of continual clockwise rotation. If before the stimulus the cell is exposed briefly to ultraviolet and rotated through 90°, the response is not along the 17° line, but is deviated a greater or lesser amount, depending on whether the 90° rotation is clockwise or counterclockwise. This difference is evidence that the first ultraviolet exposure leaves a persistent patch of light-adapted receptors and the shaded part of the cell remains dark adapted. The phototropic stimulus straddles the edge between light- and dark-adapted regions, and the differing responses of the two regions affects the direction of phototropic bending. A phototropic mechanism is proposed which combines the features of local adaptation and photoreceptor rotation.     

Effect of Temperature Alterations on the Diurnal Expression Pattern of the Chlorophyll a/b Binding Proteins in Tomato Seedlings

In the leaves of plants that are grown in the natural environment, the accumulation of mRNAs encoding the chlorophyll a/b binding proteins (CAB) follow a circadian rhythm. It is generally accepted that the day/night (sunset, light/dark) or night/day (sunrise, dark/light) transitions play an important role in the synchronization of the rhythm and the determination of the accumulation amplitude. As the results of the experiments presented in this paper indicate, temperature alterations also support the setting and the arrangement of the rhythm. Apparently, simulating “day/night” temperature alternations influences the tomato (Lycopersicon esculentum) plants to express a typical circadian oscillation pattern of cab mRNAs. This rhythm was sustained in the plants after long-term exposure to an alternating temperature regime. In constant conditions, e.g. continuous illumination at either 18°C or 24°C or in continuous darkness at 24°C, this diurnal fluctuation pattern with a period of about 24 hours remained present for at least 2 days.