Rotational diffusion tensor of nucleic acids from 13C NMR relaxation

Rotational diffusion properties have been derived for the DNA dodecamer d(CGCGAATTCGCG)₂ from ¹³C R₁ and R₁ measurements on the C₁, C₃, and C₄ carbons in samples uniformly enriched in ¹³C. The narrow range of C-H bond vector orientations relative to the DNA axis make the analysis particularly sensitive to small structural deviations. As a result, the R₁/R₁ ratios are found to fit poorly to the crystal structures of this dodecamer, but well to a recent solution NMR structure, determined in liquid crystalline media, even though globally the structures are quite similar. A fit of the R₁/R₁ ratios to the solution structure is optimal for an axially symmetric rotational diffusion model, with a diffusion anisotropy, D_||/D, of 2.1±0.4, and an overall rotational correlation time, (2D_||+4D)^–1, of 3.35 ns at 35 °C in D₂O, in excellent agreement with values obtained from hydrodynamic modeling.     

On the formation of rho - petites in yeast. III. Effects of temperature on transmission and recombination of mitochondrial markers and on rho - cell formation in temperature sensitive mutants of Saccharomyces cerevisiae.

Summary The -factor stability is shown to be affected by four conditional mutations, tsm-8 (mitochondrial), tsp-20, tsp-25 and tsp-30 (nuclear). Growth of mutant cells at high temperature (35°C) results in the rapid production of ^– cells and concomittantly in the decrease of the ability to transmit mitochondrial genetic information to the ⁺ progeny of crosses. Kinetics of ^– cell formation during growth at 35°C have been compared with variations in transmission and recombination of mitochondrial markers in crosses. In all cases the transmission of mitochondrial markers of the ts-parent decreases as the number of cell generations increases. The frequencies of recombinants between mitochondrial markers either increase or decrease depending on the markers considered and the alleles of the -locus involved in the crosses.The results of all crosses performed have been compared with the predictions of the model for recombination and segregation of mitochondrial genes proposed by Dujon et al. (1974). This comparison indicates that the main result of high temperature treatment is a diminution of the input of mitochondrial information from the ts-parent into zygotes. Consequences of the induced variations of input follow the predictions of the model. The correlation found in ts-strains between the reduction of input in crosses and the formation of ^– cells is discussed in terms of molecular events occurring in mitDNA molecules during high temperature induction of ⁺ to ^– mutation.This paper is dedicated to Professor Dr. A. Butenandt on the occasion of his 75th birthday     

Detection of specific DNA sequences in yeast by colony hybridization

Summary A procedure is described for the detection of specific DNA sequences in Saccharomyces cerevisiae. This method allows a rapid screening of a large number of yeast colonies. The yeast cells of each colony, grown on nitrocellulose filters, are converted, in situ, to protoplasts by snail enzyme, and are then lysed and their DNAs are denatured and fixed on the filter. The presence of the specific DNA sequence is detected directly on the filter by hybridization with a radioactive cRNA.We have used successfully this technique to detect the presence or the absence of specific mt DNA sequences, in ⁺, ^- and ⁰ strains, and to detect the presence or the absence of the 2 m DNA sequences in different strains.     

On the density of intracellular water

The density of individualArtemia cysts has been determined by sedimentation velocity measurements at unit gravity. Dried cyst (< 0.02 g H₂O/g dry weight) densities, _s were obtained by successive sedimentation in two nonpenetrating organic solvents. This removes geometric terms from the equation relating density to sedimentation velocity. Hydrated cysts ( 1.68 g H₂O/g dry weight) were sedimented in 0.0750 m NaCl to obtain their density ( _c). Values of _s, _c, and their ratios were found to be independent of cyst volume; therefore, the weight fraction of water in hydrated cysts is very nearly the same in cysts of greatly different size. It can be concluded that measurement of the water content of large populations of these cysts accurately reflects the water content of individual cysts, a point which has been assumed in previous work on this system. If _s does not change appreciably when dried cysts are fully hydrated then the density of their water, _w, can be calculated to be 1.022 g/cm³ (±0.0011 ). That value is significantly higher than the density of pure water and is very close to estimates of _w in skeletal muscle and amphibian oocytes obtained by others. However, the assumption that _s is independent of hydration is open to serious criticism, for all these studies. Consequently, conclusions and interpretations derived from such measurements must be considered to be tentative and uncertain.     

Assortative mating and the genetic correlation

Summary The effect of assortative mating on the genetic correlation between traits X and Y is considered. Assortation on trait X changes the magnitude of the genetic correlation but not its sign. There are two situations depending on the signs of the correlation between mates () and of the random mating genetic correlation (): 1) if sign () = sign (), then >, where is the genetic correlation at equilibrium after continued assortation, and 2) if sign () = sign (), then < . However, negative assortative mating is virtually powerless to alter the magnitude of the genetic correlation. The consequences of a mixed assortation model, e.g., high milk production females mated to fast growing males and lesser productive females mated to slower growing sires, were also studied. Mixed positive assortation always increases the genetic correlation, but negative assortation decreases it. The implications of assortative mating on correlated responses to selection and on the equilibrium covariances between relatives for pairs of traits are discussed.     

Effects of tumor promoters and diacylglycerol on the transdifferentiation of striated muscle cells of the medusa Podocoryne carnea to RF-amide positive nerve cells

Artemia sp (Tuticorin strain) was cultured at a density of 250 individuals 1^–1 at 35, 45, 60, 75 salinity using five combinations of groundnut oil cake, decayed cabbage leaves, single superphosphate and Baker's yeast as feed. Effects on survival, growth, and fecundity were noted.     

Assembly-dependent expression of antigenic epitopes by β2-microglobulinb

In this report we provide evidence for the expression of antigenic epitopes on mouse (₂-microglobulin^b _2m ^b) that result from assembly with cognate H-2 class I heavy chains. For the cell line 69.9.15 (₂m^a × ₂m^b), which expresses a mutant cytosolic form of H-2K^b and wild-type H-2D^b, flow cytometry with rabbit antiserum against mouse ₂m displayed ₂m expression by cells grown in the presence or absence of fetal calf serum. By contrast, the epitopes identified by the ₂m^b-specific monoclonal antibody (mAb) S19.8 and clone 23 were not expressed by 69.9.15 cells grown in serum-containing conditions, and although S19.8 reactivity was weakly recovered by culture in the absence of serum, no such reacitivity was observed with clone 23. Strong expression of these epitopes was achieved following transfection of 69.9.15 cells with the wild-type H-2K ^b gene, indicating that the ₂m^b epitopes defined by mAb S19.8 and clone 23 were expressed when ₂m^b was assembled with an appropriate heavy chain. In support of this conclusion, we observed the recovery of the S19.8 and clone 23 epitopes by in vitro assembly of H-2K^b heavy chains with ₂m^b in the presence of the VSV N protein p52–59; however, such epitopes were expressed neither by ₂m^b prior to heterodimer assembly nor by non-conformed ₂m^b present in tissue culture supernatants recovered from H-2 class I surface positive cells. Taken together, these data indicate that in addition to the property of ₂m to modify the antigenicity of the MHC class I heavy chains, ₂m epitopes are induced in a reciprocal manner by assembly with MHC class I heavy chain molecules. Correspondence to: R. A. Zeff.     

Distribution and abundance of littoral benthic fauna in Canadian prairie saline lakes

The littoral benthos of 18 lakes in Alberta and Saskatchewan ranging in salinity from 3 to 126 (g1^–1 TDS) were investigated twice, in the spring and in the summer of 1986. Multiple Ekman dredge samples were taken at water depths of about 0.5, 1.0 and 2 metres in each transect. Two to three transects were used in each lake according to its estimated limnological diversity for a total of 114 stations. A total of 76 species was present varying from 29–31 species in the three lakes of lowest salinity (means of 3.1–5.55) to only 2 species in lakes exceeding 100. Species richness decreased rapidly in salinities greater than 15.Biomass maximum mean of 10.91 g m^–2 dry weight (maximum 63.0 g m^–2) occurred in culturally eutrophic Humboldt Lake (3.1) but one third as great in other low salinity lakes. However, biomass again increased to about 4.5 gm^–2 in two lakes of 15 As the salinity increased still further biomass declined steadily until a minimum of 0.0212 g m^–2 was recorded in most saline Aroma Lake (mean 119). Summer biomass (11 lakes) was greater than spring biomass (4 lakes) because some groups such as amphipods, corixids and ostracods became more abundant in summer. Wet weight biomass averaged 15.8 of dry weight biomass.Seasonality (spring or summer), sediment texture and organic matter content, water depth, pH, salinity (TDS) and the presence of aquatic plants ( plant cover) were considered in the matrix involving species dry weight biomass at each of 117 stations. TWINSPAN classification of the samples yielded a dendrogram with 18 indicator species. Successive dichotomies divided these indicator species into four main lake groups based on salinity, i.e., Group I: 3–10 (Gammarus, Glyptotendipes I, Chironomus cf. plumosus), Group II: 10–38%. (Hyalella, Enallagma,Bezzia), Group III: 38–63 (Hygrotus salinarius, Cricotopus ornatus), Group IV: >63 (Dolichopodidae, Ephydra hians). Each of these main groups was subdivided into smaller groups of lakes based on factors such as pH, seasonality (spring or summer species dominance), organic matter and plant cover. Depth of samples played no apparent role.     

Die Aktivit?tsperiodik bei V?geln mit und ohne dunklem Schlafkasten

Zusammenfassung In 2 Versuchsserien wurden Kohlmeisen(Parus major) und japanische Möwchen(Lonchura striata var.domestica) einzeln und schallisoliert gehalten. In der ersten Versuchsserie, in der alle Vögel einen dunklen Schlafkasten hatten, wurde der Einfluß der Beleuchtungsstärke auf die Periode () der Hüpfaktivität und auf das Verhältnis von Aktivitätszeit zu Ruhezeit ( : -Verhältnis) untersucht. Sowhol Kohlmeisen als auch japanische Möwchen folgen der Regel, daß mit wachsender Beleuchtungsstärke die Periode kürzer und das : -Verhältnis größer wird.In der 2. Serie wurde der Einfluß Ruhe im dunklen Schlafkasten auf die Periodenlänge und auf das : -Verhältnis untersucht. Es wurden die Messungen aus Bedingung 1 (der Vogel hat einen dunklen Schlafkasten zur Verfügung) mit den Messungen aus Bedingung 2 (der Vogel hat keinen oder einen hellen Schlafkasten zur Verfügung) verglichen. Das Ergebnis bei Kohlmeisen entspricht den Befunden bei konstantem Licht verschiedener Intensität. Unter Bedingung 1 ist länger und das : -Verhältnis kleiner als in Bedingung 2. Das Ausmaß der Änderung von nach Fortnahme des dunklen Kastens ist unabhängig von der Periodenlänge in Bedingung 1. Das Ausmaß der änderung von : ist unabhängig von a : in Bedingung 1, jedoch schwach negativ korreliert mit der Periodenlänge in Bedingung 1.Bei japanischen Möwchen entsprechen die Ergebnisse dieser Versuchsserie nicht der Regel für tagaktive Vögel. Mit Benützen des dunklen Schlafkastens ist kürzer als ohne den Schlafkasten. Ohne den Schlafkasten ist etwa 24 Std. Das : -Verhältnis ist in Bedingung 1 unter bestimmten Voraussetzungen kleiner als in Bedingung 2. Das Ausmaß der Änderung von nach Fortnahme des Kastens ist mit der dazugehörigen Periode in Bedingung 1 hochsignifikant korreliert (Regressionskoeffizient b=-1.01, Korrelationskoeffizient r=0.89). Ebenfalls ist das Ausmaß der Änderung von : nach Fortnahme des Kastens mit : aus Bedingung 1 korreliert; es scheint, als würde ein bevorzugtes : -Verhältnis von etwa 2.0 eingeregelt.Die Ergebnisse werden im Hinblick auf 4 Punkte diskutiert: 1) Das circadiane System arbeitet innerhalb eines engen Bereiches von - und : -Werten optimal. 2) Der Optimalbereich wird bevorzugt unter ungünstigen Bedingungen angestrebt. 3) Der Entzug des dunklen Schlafkastens belastet japanische Möwchen mehr als Kohlmeisen. 4) Bei japanischen Möwchen wird in Bedingung 1 durch fortplfanzungsphysiologischen Einfluß verkürzt.

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Circadian activity rhythms of birds with and without a dark nest box

Summary Perch-hopping activity of Great tits(Parus major) and Bengales finches(Lonchura striata domestica), housed individually in soundproof boxes, was studied in two series of experiments. In the first series all birds had access to a dark nest box, in which they retired during their subjective night. In this experiment the effect of light intensity on the freerunning circadian activity rhythm was investigated. Both Great tits and Bengalese finches obey the circadian rule by responding to an increase in light intensity with shortening the circadian period () and with an increase of the ratio of activity time and rest time ( : ).In the second series of experiments the influence of sleeping in the dark nest box on both circadian period and : -ratio was studied. The results of two experimental conditions — without and with access to a dark nest box — were compared. In the Great tits, the results are in agreement with the effect of light intensity: when a dark nestbox is available, is longer and the : -ratio is smaller than in the absence of a nest box. The magnitude of the change in free-running period after removal of the nest box is independent of the original value of ; the amount of change : -ratio is likewise independent of the original : -ratio, but is weakly correlated to the original .InLonchura striata var. domestica, removal of the dark nest box leads to a lenghtening of the free-running period to about 24 hours; the : -ratio is smaller in the presence of a dark nestbox, if certain other conditions are fulfilled. The magnitude of the change in after removal of the nest box is highly correlated to the original free-running period (r=-0.89) in such a way that, without nest box, the period approaches a value of 24 hours. Also, the amount of change in : -ratio due to nest box removal is negatively correlated to the original : -ratio. A probably preferred : -ratio of 2.0 is adopted.These results are discussed in the view of 4 points: 1) The circadian system operates at its optimum within a narrow range of - and : -values. 2) This optimal range is especially adopted when conditions become adverse. 3) Removal of the dark nest box results in a more stressful situation for Bengalese finches than for Great tits. 4) In the Bengalese finches, is shortened in the presence of a nest box due to effects on reproductive physiology.

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Herrn Prof. Dr. JürgenAschoff zum 60. Geburtstag gewidemt.     

Modelling of predator–prey trophic interactions. Part I: two trophic levels

A class of lumped parameter models to describe the local dynamics in a controlled environment of a two-trophic chain is considered. The class is characterized by a trophic function (functional response of predator to the abundance of prey) depending on the ratio of prey biomass x and a linear function of predator biomass y: f(qx/[(1-)k+y]), where q is the efficiency of the predation process, k is a reference biomass, and (01) specifies the predation model. The trophic function is defined only by some properties determining its shape. A stability analysis of the models has been performed by taking the parameters q and as bifurcation parameters: the regions in the (,q) plane of existence and stability of nonnegative equilibrium states and limit cycles are determined. This analysis shows that the behaviour of the models is qualitatively similar for 0<1 (in particular the null state is always a saddle point), while the value =1 gives rise to some kind of structural instability of the system (in particular the null state becomes an attractor for sufficiently high predation efficiency).     

Off-resonance R1rho relaxation outside of the fast exchange limit: an experimental study of a cavity mutant of T4 lysozyme

An ¹⁵N off-resonance R ₁ spin relaxation study of an L99A point mutant of T4 lysozyme is presented. Previous CPMG-based relaxation dispersion studies of exchange in this protein have established that the molecule interconverts between a populated ground state and an excited state (3.4%) with an exchange rate constant of 1450 s^–1 at 25°C. It is shown that for the majority of residues in this protein the offset dependence of the R ₁ relaxation rates cannot be well fit using models which are only valid in the fast exchange regime. In contrast, a recently derived expression by Trott and Palmer (J. Magn. Reson., 154, 157–160, 2002) which is valid over a wider window of exchange than other relations, is shown to fit the data well. Values of (signed) chemical shift differences between exchanging sites have been extracted and are in reasonable agreement with shift differences measured using CPMG methods. A set of simulations is presented which help establish the exchange regimes that are best suited to analysis by off-resonance R ₁ techniques.     

The mitochondrially encoded "phantom ATPase" of S. cerevisiae. II. A heterogeneous mitochondrial ATPase population in situ.

Summary The mitochondrial ATPase from a PHO 1 mutant (OLI 2, PHO 1, OLI 4 region on mit DNA of S. cerevisiae) was further examined. A new purification method using Lysolecithin instead of Triton allowed us to solubilize and separate a heterogeneous ATPase population from PHO 1-mitochondria: the major abnormal fraction had extremely low oligomycin-sensitivity (but normal specific immunological reactivity), while a minor normal fraction (representing about 20% of the initial mitochondrial ATPase activity) had high sensitivity and affinity for oligomycin.Moderate urea treatment of PHO 1-mitochondria leads to partial loss of ATPase activity and a concomitant increase of oligomycin-sensitivity, suggesting that a heterogeneous ATPase population exists in situ in the mitochondrial membrane: part of the major abnormal ATPase fraction is selectively inactivated by urea, producing a concomitant enrichment in the initially minor normal ATPase fraction.If the minor normal ATPase fraction is the only one capable of in vivo ATP synthesis, the deficient but oligomycin-sensitive cell growth and oxidative phosphorylation in vitro are readily explained.Further structural studies are under way to ascertain whether the minor normal ATPase fraction is strictly identical to the wild type, in which case PHO 1 is a regulatory gene, or not, in which case PHO 1 is a structural gene.     

Optomotorische Untersuchung des visuellen systems einiger Augenmutanten der Fruchtfliege Drosophila

Summary The optical properties of the compound eye of Drosophila have been analysed using the optomotor reactions of flies with normal and mutant eye pigmentation. The stimulus was provided by cylindrical patterns with different periodic intensity distributions rotating at different speeds. The response consists of a torque about the vertical axis and was recorded under conditions of fixed flight. (Maximum reaction is about 0.04 dyn · cm). The transfer characteristics of the optical system are determined by the inter-ommatidial angle , influencing the resolving power and by the width of the visual field of single ommatidia , influencing the response at high spatial frequencies. The values = 4.6° and = 3.5° are obtained from stimulus-response experiments with Drosophila. They are independent of the presence of screening pigments. Differences in the response of flies with strong (+, se), weak (w ^a), and missing (w) pigmentation can be explained by the increased amount of scattered light in the pigment-deficient eyes. The overall intensities in the equally illuminated receptors are expected to be in the ratio 11825, respectively. The perception of motion depends only on the temporal, not on the spatial phase relations between periodic intensity variations in neighbouring ommatidia. Therefore the inhomogeneous distribution of the inter-ommatidial angle changes the resolving power in different parts of the eye without changing the response to motion. Different simultaneous stimuli of equal strength in different parts of the eye are averaged in the perceptive system of Drosophila according to the number of ommatidia in these parts.     

Passive cable properties of hippocampal CA3 pyramidal neurons

The passive electrical cable properties of CA3 pyramidal neurons from guinea pig hippocampal slices were investigated by applying current steps and recording the voltage transients from 25 CA3 neurons, using a single intracellular microelectrode and a 3-kHz time-share system. Two independent methods were used for estimating the equivalent electrotonic length of the dendrites, L, and the dendritic to somatic conductance ratio, . The first method is similar to that used by Gorman and Mirolli (1972) and gave an average L of 0.96; the average was 2.44. The second method is derived here for the first time and assumes a finite-length cable with lumped soma. It is an exact solution for L and , using the slopes and intercepts of the first two peeled exponentials. The average L was 0.94; the average was 1.51. The results, using both methods, are in close agreement. The average membrane time constant for all 25 CA3 neurons was 23.6 ms, suggesting a large (23,600 cm²) average membrane resistivity. It is concluded that CA3 neurons are electronically short.This work was supported by Grants NS 11535 and NS 15772 from the National Institute of Neurological and Communicative Disorders and Stroke, National Institutes of Health, U.S. Public Health Service.     

Bacteriophage phi 1 as a gene-cloning vector in Bacillus subtilis

Summary We attempted to use Bacillus subtilis phage 1 as a gene-cloning vector since the 1 genome was found to have few cleavage sites upon digestion with several kinds of restriction endonucleases. A 1 stock supplied by J. Ito (University of Arizona, Tucson, USA) consisted of two phages, 1E1 and 1E2, having one and two EcoRI-cleavage sites in their genomes respectively. From the latter isolate a deletion mutant 1E21 was induced to increase the size range of DNA segments to be cloned. It was demonstrated, by in vitro recombination experiments with phage 11 DNA, that 1E21 can be used for cloning EcoRI fragments of various sizes. We analyzed the DNAs of ten 1 clones isolated from independent transfectants and found that six of them carried 11 DNA fragments inserted at either of the two EcoRI-cleavage sites. Some of the hybrid phage DNAs were found to be cleaved with BamHI and HaeIII endonucleases at the 11 DNA portion, whereas the parental 1E21 DNA was insensitive to any of these enzymes. These hybrid phages would therefore be useful vectors for cloning foreign DNA fragments generated by cleavage with BamHI or HaeIII endonucleases.     

Measurement of proton relaxation rates in proteins

Summary Five different types of experiment are described which make it possible to measure various relaxation rates of selected protons in crowded spectra of macromolecules such as proteins: longitudinal spin-lattice relaxation rates =1/T₁, transverse relaxation rates =1/T₂ measured under conditions of free precession, transverse relaxation rates ¹ _LOCK=1/T₁ measured under conditions of spin-locking, and transverse relaxation rates ^DQC=1/T₂ ^DQC and ^ZQC=1/T₂ ^ZQC of double- and zero-quantum coherences. The surprisingly large discrepancy between the transverse rates ^t and ^t is discussed in detail. To separate overlapping proton signals, the experimental schemes involve one or several magnetization transfer steps, using a doubly selective homonuclear Hartmann-Hahn method. Numerous variants of the basic ideas can be conceived, depending on the extent of signal overlap and on the topology of the networks of scalar couplings. Applications are shown to H and H of Tyr²³, to H, H and H of Cys³⁰, and to H and H of Ala²⁴ in bovine pancreatic trypsin inhibitor (BPTI).     

TROSY experiment for refinement of backbone psi and phi by simultaneous measurements of cross-correlated relaxation rates and 3,4J(H alpha HN) coupling constants

The TROSY principle has been introduced into a HNCA experiment, which is designed for measurements of the intraresidual and sequential H-C/H^N-N dipole/dipole and H-C/N dipole/CSA cross-correlated relaxation rates. In addition, the new experiment provides values of the ^3,4 J _{H HN} coupling constants measured in an E.COSY manner. The conformational restraints for the and angles are obtained through the use of the cross-correlated relaxation rates together with the Karplus-type dependencies of the coupling constants. Improved signal-to-noise is achieved through preservation of all coherence transfer pathways and application of the TROSY principle. The application of the [¹⁵N,¹³C]-DQ/ZQ-[¹⁵N,¹H]-TROSY-E.COSY experiment to the 16 kDa apo-form of the E. coli Heme Chaperon protein CcmE is described. Overall good agreement is achieved between and angles measured with the new experiment and the average values determined from an ensemble of 20 NMR conformers.     

Isolation of pea nodule bacteroids utilizing silica sol (Percoll) density gradient centrifugation

Isolation of bacteroids from effective (Fix⁺) and ineffective (Fix^–) pea nodules, inoculated withRhizobium leguminosarum K, were performed by a density gradient centrifugation method using silica sol (Percoll). Only one zone (=1.064–1.072; n-zone) was recognized in the Fix⁺ nodule which contained typical Y-shaped bacteroids while two zones (n-zone and =1.125–1.145; n'-zone) were obtained from the Fix^– nodule. The cells in the n'-zone, which are long rods differed morphologically from free-living cells at any growth phase (=1.108–1.125; f-zone and =1.074–1.078; f'-zone), and differed from Y-shaped bacteroids by cell density. The esterase isozyme pattern of bacteroids in the n-and n'-zones also showed clear differences from that of f-and f'-zone of free-living cells.     

Synergistic effects of ethanol and temperature on yeast mitochondria

At temperatures lower than 37°C, the ethanol inhibition constant (Ki) for growth or fermentation inrho ⁺ cells of theSaccharomyces cerevisiae strain S288C was always higher (1.1M) than inrho ^– mutants (0.7M). At 37°C these differences disappeared, and both strains were equally inhibited by ethanol (Ki=0.7m). Mitochondrial activity can be inhibited by high ethanol concentration and temperature. In fact, the stronger inhibition by ethanol of therho ⁺ strain at 37°C was due to the fact that, under these conditions, this strain loses the advantage conferred by mitochondrial activity since the induction ofrho ^– cells in the population is very high. This does not result in an increase in the frequency ofrho ^– mutants because of the poor viability of these mutants in conditions of high temperature and ethanol. In consequence, S288C strain becomes as strongly inhibited by ethanol as therho ^– mutant strains. Differences in viability were not related to the fatty acids and ergosterol composition of the strain. In the presence of ethanol, bothrho ⁺ andrho ^– strains modified their lipids in the same way, but these changes did not improve their ethanol tolerance. They were not due to differences in adaptation to ethanol either, since after successive transfers in ethanol, growth () and fermentation () rates in therho ^– mutants were increasingly inhibited with time, whereas in the S288C strain inhibition of and by ethanol remained unaltered. Rather,rho ^– mutants are less viable thanrho ⁺ cells because of the inability of the former to respire. At 37°C the Ki increased to 0.9M ethanol either when mitochondrial from highly ethanol-tolerant wine yeasts were transferred torho ^– mutants of the strain S288C or when the mitochondria of strain S288C were preadapted by growing the strain in glycerol instead of glucose before it was cultivated in ethanol.     

The effect of monoterpenes on astaxanthin production by a mutant ofPhaffia rhodozyma

Summary The total pigment and astaxanthin content ofPhaffia rhodozyma increased with increasing concentrations -pinene up to 500 l -pinene/l. Above this concentration the total pigment and astaxanthin content as well as the biomass production decreased. The addition of 500 l -pinene/l increased the total pigment content from 1652 g/g to 2201 g/g and the astaxanthin content from 1554 g/g to 1883 g/g. A sharp decrease in maximum specific growth rate occurred above 150 l -pinene/l.