Effects of temperature on microbial ethanol production. III. The influence of the temperature on the relation existing between the specific ethanol formation rate of the yeast Saccharomyces cerevisiae Sc 5 and the ethanol concentration in the culture medium

The ethanol-inhibitory behaviour of the yeast Saccharomyces cerevisiae Sc 5 was found to be characterized by a continual-linear relation between the specific ethanol formation rate and the ethanol concentration. Therefore the simple equation could be applied for it. It is shown that this model is correct only then, if all of the process parameters are in their optimum. Out of the optimum temperature range the characteristics of the function ν = f(P) change in such a way that in regard to the ethanol concentration P twc linear relations exist for each suboptimum temperature: and a non-linear equation is current for each superoptimum temperature: where b_T is also a function of the temperature and always less than 1. Taking as a basis these equations the specific ethanol formation rate of the used strain can be calculated for the whole biokinetic P/T-sphere of ethanol production.     

The parabolic pattern of animal growth: determination of equation parameters and their temperature dependencies

1. Parabolic (power) growth is characteristic of many aquatic poikilothermic animals for certain stages of their development. The parabolic pattern describing growth in weight (or length) under constant ambient conditions can be expressed in the following general form: where Y is growth rate (or specific growth rate), X is animal size, and Ω and τ are coefficients. The constancy of ambient conditions is of cardinal importance in determining τ. The problem of maintaining a constant level of nutrition can be reliably solved only by the presence of food in excess of demand. Data satisfying these requirements have demonstrated that τ does not depend on factors such as temperature, and can be assumed to be independent of ambient conditions. In the growth rate-weight equation, τ ranges between 0.5 and 0.85 for animals representing a variety of taxonomic groups. 2. The coefficient Ω. is affected by ambient conditions (e. g. temperature, amount of food). Its value reflects the ‘level’ of the growth rate-size relationship under given conditions. For a specific time period, Ω can be computed from the following formula: where X₁ and X₂ are the animal sizes (weights, lengths) at time t₁ and t₂, the beginning and end of the time period. The calculated value of Ω corresponds to the average intensity of the ambient factor (F) affecting the growth during the period between the two observations. If the values of the Ω are calculated for wide range of the factor, the relationship between the Ω. and F, Ω=f(F), can be determined. The function can be then incorporated into the parabolic equation of growth, as 3. Dependence of the development rate (1/D, where D is time interval needed to complete a given stage) on temperature (T), and dependence of Ω on T, are both described by sigmoid-shape curves. The broad intermediate part of these curves, a range to which animals are adapted in nature, can be approximated by straight line functions. For two groups, pan-size sockeye salmon (Oncorhynchus nerka) and different species of chironomid larvae, it was shown that an equation combining parabolic growth and linear temperature patterns describes accurately the variability observed in growth rates under experimental and natural conditions.     

Inhibition-threshold substrate concentrations

A proposed substrate inhibition model (M. C. Tseng and M. Wayman, Can. J. Microbiol., 21 , 994 (1975)), ((1)) ((2)) derived from yeast growth rates has been applied to data for bacterial growth: Pseudomonas methanica grown on methanol and Arthrobacter AK19 grown on n-butanol. The model represents the experimental data very well.     

CULTURE STUDIES ON THURETELLOPSIS PEGGIANA KYLIN1

Information on the life history and development of Thuretellopsis peggiana Kylin (Cryptonemiales) has been obtained additional to that first given by Kylin in 1925. Culture studies showed the life history to consist of morphologically dissimilar gametangial and tetrasporangial phases. Examination of plants from, field material indicated carposporophyte development similar to that described by Kylin. Spermatangia were found in field-collected material also bearing carpogonial branches. Monosporangia were observed on field and cultural material of gametangial plants and on tetrasporangial plants in culture. A crustose tetrasporangial phase arose in culture from germinating carpospores under a photoperiod of 16– hr and formed tetrasporangia under a photoperiod of 9– hr. Germination of tetraspores yielded plants similar in morphology to gametangial plants collected in the field. The present study of the life history of T. peggiana and its crust, which has some similarity to Erythrodermis allenii, complements previous observations on the relationship between Halarachnion ligulatum and Cruoria rosea (Gigartinales). Observations on the arrangement of carpogonial and. auxiliary cell branches suggest the need for very close scrutiny of characters in cultured material.     

Das Gesetz der absoluten Geschwindigkeiten biologischer Prozesse

The dependency of the velocity of biological processes from the temperature is described by the “Law of absolute velocity of biological processes”, which has only the individual parameters energy of activation ΔE, and the universal constant C. The law holds for all biological processes and is expressed by the equation: where C is: .     

Assessing the Semelparity Hypothesis: Egg-guarding and Fecundity in the Malaysian Treehopper Pyrgauchenia tristaniopsis

According to the semelparity hypothesis, iteroparous insects should provide either no maternal care or less care than related semelparous species. We present field data on reproductive output and maternal care in the Southeast Asian treehopper Pyrgauchenia tristaniopsis (Mt. Kinabalu, Borneo) relevant to a preliminary assessment of the hypothesis. In a mark‐recapture experiment, more females than expected under semelparity were found to have oviposited a second clutch (37%). Female longevity was a of 75 d. Both these estimates were highly conservative. Oviposition was successive resulting in a of 46 eggs per clutch. Females provided care for eggs only, occasionally scraping their legs along the sides of the clutch apparently attempting to deter Brachygrammatella sp. egg parasitoids (Trichogrammatidae). Females straddled their clutch for a of 27 d, i.e. until 8 d after the beginning of first instar hatching. First instars hatched successively over a period of 11 d. When a female deserted her clutch, it contained about 37% yet unhatched eggs. Egg‐guarding effectively reduced egg mortality: the earlier a female was experimentally removed from her clutch the higher the egg mortality. Displacement experiments demonstrated that egg‐guarding is a behaviour actively maintained despite disturbances and specifically directed towards the egg clutch but not to the feeding site. We interpret our findings as being in accordance with the weaker claim of the semelparity hypothesis, i.e. the iteroparous P. tristaniopsis provided less maternal care than semelparous membracid species. Continued female feeding is discussed as a mechanism to display some level of care despite iteroparity.     

Functional importance vs keystoneness: Reformulating some questions in theoretical biocenology

Abstract Two concepts relating to the influence of individual species on the biocenoses in which they occur are reviewed. The first, the general functional importance of a species, is denned as the sum, over all species, of the changes (sign ignored) in productivity which would occur on removal of the particular species from the biocenosis. General functional importance is calculated as: where P_j is the productivity of the jth species before (t= 0) and after (t= 1) removal of the particular (ith) species being evaluated. Though I_i values cannot be determined empirically, this concept raises provocative questions for theoretical biocenology. The second concept reviewed is that of the keystone species. Never having been precisely or operationally defined,‘keystone’ has come to mean little more than ‘important for something.’ Moreover, there is no empirical or theoretical foundation for the idea that there exists in any biocenosis a natural dichotomy corresponding to the verbal one of keystone and non-keystone species. Some investigators have implied that such a dichotomy is suggested by the frequency distributions of experimentally determined values of interaction strength. The patterns they refer to are, however, artifacts resulting from small sample sizes and the plotting of frequency distributions on arithmetic rather than logarithmic scales. As a casual metaphor ‘keystone species’ was appealing and harmless; but the pretence that it is a well-defined concept or phenomenon has had a stultifying effect on ecological thought and argument.     

Seasonal changes of osmotic pressure, symplasmic water content and tissue elasticity in the blades of dune grasses growing in situ along the coast of Oregon

Abstract Midday water potentials of blades of the dune grasses Ammophila arenaria (L.) Link and Elymus mollis Trin. ex Spreng. growing in situ declined over the summer growing period, indicating a trend of increasing water stress. An analysis of the water relations characteristics of these blades using pressure-volume techniques demonstrated that both species increased bulk osmotic pressure at full hydration () and, therefore, bulk turgor as an acclimation response. In A. arenaria, however, the increase of osmotic pressure (+ 0.35 MPa) was entirely the result of decreasing symplasmic water content. The increase of osmotic pressure (+ 0.54 MPa) observed in E. mollis blades was due to solute accumulation (72% of Δ) and to a lesser degree, decreased symplasmic water content (28% of Δ). Osmotic adjustment in E. mollis blades was accompanied by a significant decrease in tissue elasticity (_max went from 12 to 19 MPa). The elastic properties of A. arenaria blades remained constant over the same period and had a maximum modulus (10 MPa) that was always less than that of E. mollis, As estimated from Höfler plots, these seasonal adjustments of osmotic pressure and differences in tissue elasticity enabled plants in situ to maintain turgor pressure in the range of 0.5–0.6 MPa at the lowest water potentials of mid-August. Laboratorygrown plants exhibited the species-specific differences in osmotic pressure, turgor pressure, and tissue elasticity observed in field plants. Although certain alterations of leaf structure were expected to coincide with the observed changes and species-specific differences in symplasmic water content and tissue elasticity, these could not be detected by measurements of specific leaf weight or the ratio of dry matter to saturated water content.     

Turgor and osmotic relations of the desert shrub Larrea tridentata

Abstract Leaf water relations characteristics of creosote bush, Larrea tridentata, were studied in view of previous reports that its leaves commonly experience zero or negative turgor under dry conditions. Leaf turgor loss point () was determined by a pressure-volume method for samples subjected to a hydration procedure and for untreated samples. Hydration caused to increase by as much as 3 M Pa. Hydration of samples also caused changes in other leaf water relations characteristics such as symplastic solute content, tissue elasticity and symplasmic water fraction, but total leaf solute content was unchanged. Comparison of our field plant water potential data with values of obtained by the two methods resulted in predictions of turgor loss during part or all of a diurnal cycle based on hydrated samples, and turgor maintenance (at least 0.3 MPa) based on untreated samples. Pooled data for obtained from both partially hydrated and untreated samples showed that L. tridentata maintains fairly constant levels of turgor over a wide range of leaf water potential. Dilution of cell contents by apoplastic water introduced significant errors in psychrometric determinations of osmotic potential in both frozen and thawed leaf tissue and expressed cell sap. Use of these values of osmotic potential resulted in predictions of zero turgor at all plant water potentials measured in the field.     

A kinetic study of the alcoholic fermentation of grape juice

The alcoholic fermentation of grape juice by a wine yeast was studied batchwise at pH 3.6 and 4.05 to develop kinetic equations relating cell concentration, N, to product concentration, P. In the exponential growth phase where A, B, and C are constants, and μ is the specific growth rate. In the stationary phase, where the cell population is constant, was found to apply. This equation, which incorporates a stoichiometric constant, P_m, predicted correctly the operation of a continuous fermentor at pH 3.6 and at 4.05. To study more fully the effect of alcohol concentration on yeast growth, a continuous fermentor was used in which the grape juice feed was supplemented with pure alcohol. At pH 3.6 the specific growth rate varied as, There was no growth inhibition below an alcohol concentration of 2.6 g./100 cc., but inhibition was complete above 6.85 g./100 cc. This is a modified form of the relation suggested by Hinshelwood.¹ The data suggest that growth in batch culture was limited not only by alcohol but also by some other factor, probably a nutritional deficiency.     

Apparent Survival Estimates for Five Species of Tropical Birds in an Endangered Forest Habitat in Western Ecuador1

Estimates of annual survival are essential for addressing topics in evolutionary and conservation ecology. However, most demographic studies of land birds are based on north temperate species, and few robust estimates of survival based on mark–recapture statistics are available for continental South American birds. We used time‐since‐marking models to estimate apparent survival of adult birds from 7 yr of mist netting data in the Colonche Hills. This site is one of few remaining large tracts of premontane forest in southwestern Ecuador, and an area of high priority for avian conservation. Species with sufficient data for analysis included three hummingbirds (Adelomyia melanogenys, Heliodoxa jacula, Phaethornis baroni), a cotinga (Schiffornis turdinus), and a wren (Henicorhina leucophrys). Our parameter estimates had reduced precision because the number of recaptures was small. Probability of recapture was low in three species , and moderate in two others . Adelomyia and Phaethornis had moderate apparent survival (; probability that a bird neither died nor emigrated from our survey area in a given year). Adults of Adelomyia moved seasonally, and it is possible that permanent emigration from our survey area contributed to low estimates of apparent survival. The other three species had relatively high estimates of adult apparent survival ranging from in Heliodoxa and Schiffornis to a high of in Henicorhina.     

A posteriori Investigation of Spatial Arrangements in Gnathostomulida and Copepoda

Copepods at MHTL and gnathostomulids from MHTL to sublittoral sands were studied in 162 samples from Tucker's Town Cove beach, Bermuda. Species were analyzed for mean density (X̄), mean crowding ( ), and patchiness ( /X) using Lloyd's a posteriori statistic for mean crowding. Diversity was computed using the Shannon-Wiener Index (H′). Copepoda were found to be nearly three times more abundant than Gnathostomulida at the MHSL site. 74% of the copepods were found in the surface cm of sediment while 87% of the gnathostomulids were located between 1–4 cm deep and within the RPD layer. Similar gnathostomulid distributions were found at MSL and sublittorally. Mean density and mean crowding were highly variable for the numerically dominant species in each group, whereas patchiness was relatively constant with values ranging between /X̄ = 1.50 to 2.73 for P = 0.05. Such consistency in patchiness between two diverse taxa having distinctly different vertical distributions may suggest that there exists an optimum degree of patchiness for interstitial fauna and that the optimum values may lie within a range similar to that of the numerically dominant Copepoda and Gnathostomulida. Overall patchiness was slightly higher in the gnathostomulids and in the rarer species as predicted by Lloyd's statistic. Diversity was higher in the Copepoda, attributable primarily to species richness.     

Cover Image,Volume 92, Issue 5

Front Cover: The cover image is based on the Research Article Transmembrane proteins—Different anchoring systems by Irena Roterman et al., https://doi.org/10.1002/prot.26646

     

Issue Information

Cover Image Evening sun bathing flowers of Cymbidium dayanum. Photographed by Naoto Sugiura, Minami-Osumi, Kagoshima, Japan.

     

Conformational aspects of polypeptides. XVII. Synthesis of oligomers and co-oligomers derived from L-alanine and L-glutamic acid

A series of oligomers was synthesized of the form: Where Z is the benzyloxycarbonyl group and n = 2, 3, 5, 10. We encountered difficulty in dissolving the decamer in any solvent except strong organic acids. We therefore prepared co-oligomers of the type: where (a) w = x = y = 1; (b) w = 0, x = y = 3; and (c) w = x = y = 3. A series of model compounds composed of glycine L -alamine and γ-methyl-L -glutamate were also prepared. We converted manyof the benzyloxycarbonyl oligopeptides into their corresponding acetyl derivatives. Some of these peptides were synthesized by mixed anhydride and active ester techniques while others were prepared via azide coupling techniques using the tert-butoxycarbonylhydrazide blocking group. All reactions proceeded with retention of configuration.     

Buoyant densities of natural and synthetic DNA's in CsCl and Cs2SO4 considered as sequence-dependent properties

The buoyant densities of natural and synthetic DNA's can be accurately interrelated if second-neighbor influences are taken into account. We derive the following expressions, based partly on the buoyant densities of six synthetic DNA's, for the buoyant densities ρ (g/cm³) of DNA's having random sequences. In CsCl, and in Cs₂SO₄, . In these equations, H_G is the mole fraction of G : C base pairs in the DNA and the buoyant densities are calculated relative to densities for E. coli DNA of 1.703 and 1.426 (g/cm³) in CsCl and Cs₂SO₄, respectively.     

Effects of moderate ammonium enrichment on three submersed macrophytes under contrasting light availability

1. Increased ammonium concentrations and decreased light availability in a water column have been reported to adversely affect submersed vegetation in eutrophic waters worldwide. 2. We studied the chronic effects of moderate enrichment (NH₄–N: 0.16–0.25 mg L^?1) on the growth and carbon and nitrogen metabolism of three macrophytes (Ceratophyllum demersum, Myriophyllum spicatum and Vallisneria natans) under contrasting light availability in a 2‐month experiment. 3. The enrichment greatly increased the contents of free amino acids and nitrogen in the shoot / leaf of the macrophytes. This indicates that was the dominant N source for the macrophytes. 4. Soluble carbohydrate contents remained relatively stable in the shoot / leaf of the macrophytes irrespective of the treatments. Under ambient light, the starch contents in the shoot / leaf of C. demersum and M. spicatum increased with enrichment, whereas V. natans did not exhibit any change. The starch contents decreased in C. demersum, increased in M. spicatum and remained unchanged in V. natans after the combined treatment of enrichment and reduced light. 5. The enrichment did not affect the growth of the three macrophytes under the ambient light. However, it did suppress the growth of C. demersum and M. spicatum under the reduced light. The results indicate that a moderate enrichment was not directly toxic to the macrophytes although it might change their viability in eutrophic lakes in terms of the carbon and nitrogen metabolism.     

Quantifying photosynthetic capacity and its relationship to leaf nitrogen content for global-scale terrestrial biosphere models

Photosynthetic capacity and its relationship to leaf nitrogen content are two of the most sensitive parameters of terrestrial biosphere models (TBM) whose representation in global‐scale simulations has been severely hampered by a lack of systematic analyses using a sufficiently broad database. Here, we use data of qualitative traits, climate and soil to subdivide the terrestrial vegetation into functional types (PFT), and then assimilate observations of carboxylation capacity, V_max (723 data points), and maximum photosynthesis rates, A_max (776 data points), into the C₃ photosynthesis model proposed by Farquhar et al. to constrain the relationship of (V_max normalised to 25 °C) to leaf nitrogen content per unit leaf area for each PFT. In a second step, the resulting functions are used to predict per PFT from easily measurable values of leaf nitrogen content in natural vegetation (1966 data points). Mean values of thus obtained are implemented into a TBM (BETHY within the coupled climate–vegetation model ECHAM5/JSBACH) and modelled gross primary production (GPP) is compared with independent observations on stand scale. Apart from providing parameter ranges per PFT constrained from much more comprehensive data, the results of this analysis enable several major improvements on previous parameterisations. (1) The range of mean between PFTs is dominated by differences of photosynthetic nitrogen use efficiency (NUE, defined as divided by leaf nitrogen content), while within each PFT, the scatter of values is dominated by the high variability of leaf nitrogen content. (2) We find a systematic depression of NUE on certain tropical soils that are known to be deficient in phosphorous. (3) of tropical trees derived by this study is substantially lower than earlier estimates currently used in TBMs, with an obvious effect on modelled GPP and surface temperature. (4) The root‐mean‐squared difference between modelled and observed GPP is substantially reduced.     

Yield components in Hevea brasiliensis– theoretical considerations

Abstract A theoretical analysis of yield components of Hevea brasiliensis is attempted in this paper. The effect of the major yield components, i.e. initial flow rate per unit length of tapping cut, length of the cut, percentage rubber content and plugging index on rubber yield is represented by the formula Variation in yield within and between clones can be ascribed to variation to any one of the above components. The importance of high growth rate for maintaining high yield throughout the life cycle of the tree is theoretically elucidated. While the present contention of a theoretical maximum yield of 9.5 t ha^?1 with a stand of 350 trees is questioned, the theoretical possibility of attaining that yield by increasing the stand per ha to 600 is analysed.     

Modelling evolutionary processes in small populations: not as ideal as you think

Evolutionary processes are routinely modelled using ‘ideal’ Wright–Fisher populations of constant size N in which each individual has an equal expectation of reproductive success. In a hypothetical ideal population, variance in reproductive success (V_k) is binomial and effective population size (N_e) = N. However, in any actual implementation of the Wright–Fisher model (e.g., in a computer), V_k is a random variable and its realized value in any given replicate generation () only rarely equals the binomial variance. Realized effective size () thus also varies randomly in modelled ideal populations, and the consequences of this have not been adequately explored in the literature. Analytical and numerical results show that random variation in  and  can seriously distort analyses that evaluate precision or otherwise depend on the assumption that  is constant. We derive analytical expressions for Var(V_k) [4(2N – 1)(N – 1)/N³] and Var(N_e) [N(N – 1)/(2N – 1) ≈ N/2] in modelled ideal populations and show that, for a genetic metric G = f(N_e), Var(?) has two components: Var_Gene (due to variance across replicate samples of genes, given a specific ) and Var_Demo (due to variance in ). Var(?) is higher than it would be with constant N_e = N, as implicitly assumed by many standard models. We illustrate this with empirical examples based on F (standardized variance of allele frequency) and r² (a measure of linkage disequilibrium). Results demonstrate that in computer models that track multilocus genotypes, methods of replication and data analysis can strongly affect consequences of variation in . These effects are more important when sampling error is small (large numbers of individuals, loci and alleles) and with relatively small populations (frequently modelled by those interested in conservation).