Ca2+-calmodulin promotes survival of pheromone-induced growth arrest by activation of calcineurin and Ca2+-calmodulin-dependent protein kinase.

The cmd1-6 allele contains three mutations that block Ca2+ binding to calmodulin from Saccharomyces cerevisiae. We find that strains containing cmd1-6 lose viability during cell cycle arrest induced by the mating pheromone alpha-factor. The 50% lethal dose (LD50) of alpha-factor for the calmodulin mutant is almost fivefold below the LD50 for a wild-type strain. The calmodulin mutants are not more sensitive to alpha-factor, as measured by activation of a pheromone-responsive reporter gene. Two observations indicate that activation of the Ca2+-calmodulin-dependent protein phosphatase calcineurin contributes to survival of pheromone-induced arrest. First, deletion of the gene encoding the calcineurin regulatory B subunit, CNB1, from a wild-type strain decreases the LD50 of alpha-factor but has no further effect on a cmd1-6 strain. Second, a dominant constitutive calcineurin mutant partially restores the ability of the cmd1-6 strain to survive exposure to alpha-factor. Activation of the Ca2+-calmodulin-dependent protein kinase (CaMK) also contributes to survival, thus revealing a new function for this enzyme. Deletion of the CMK1 and CMK2 genes, which encode CaMK, decreases the LD50 of pheromone compared with that for a wild-type strain but again has no effect in a cmd1-6 strain. Furthermore, the LD50 of alpha-factor for a mutant in which the calcineurin and CaMK genes have been deleted is the same as that for the calmodulin mutant. Finally, the CaMK and calcineurin pathways appear to be independent since the ability of constitutive calcineurin to rescue a cmd1-6 strain is not blocked by deletion of the CaMK genes.     

Prion protein (PrP) with amino-proximal deletions restoring susceptibility of PrP knockout mice to scrapie.

The 'protein only' hypothesis postulates that the prion, the agent causing transmissible spongiform encephalopathies, is PrP(Sc), an isoform of the host protein PrP(C). Protease treatment of prion preparations cleaves off approximately 60 N-terminal residues of PrP(Sc) but does not abrogate infectivity. Disruption of the PrP gene in the mouse abolishes susceptibility to scrapie and prion replication. We have introduced into PrP knockout mice transgenes encoding wild-type PrP or PrP lacking 26 or 49 amino-proximal amino acids which are protease susceptible in PrP(Sc). Inoculation with prions led to fatal disease, prion propagation and accumulation of PrP(Sc) in mice expressing both wild-type and truncated PrPs. Within the framework of the 'protein only' hypothesis, this means that the amino-proximal segment of PrP(C) is not required either for its susceptibility to conversion into the pathogenic, infectious form of PrP or for the generation of PrP(Sc).     

Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves

A puzzling population-genetic phenomenon widely reported in allozyme surveys of marine bivalves is the occurrence of heterozygote deficits relative to Hardy-Weinberg expectations. Possible explanations for this pattern are categorized with respect to whether the effects should be confined to protein-level assays or are genomically pervasive and expected to be registered in both protein- and DNA-level assays. Anonymous nuclear DNA markers from the American oyster were employed to reexamine the phenomenon. In assays based on the polymerase chain reaction (PCR), two DNA-level processes were encountered that can lead to artifactual genotypic scorings: (a) differential amplification of alleles at a target locus and (b) amplification from multiple paralogous loci. We describe symptoms of these complications and prescribe methods that should generally help to ameliorate them. When artifactual scorings at two anonymous DNA loci in the American oyster were corrected, Hardy-Weinberg deviations registered in preliminary population assays decreased to nonsignificant values. Implications of these findings for the heterozygote-deficit phenomenon in marine bivalves, and for the general development and use of PCR-based assays, are discussed.      

Simulation of the effect of mixing,scale-up and pH-value regulation during glutamic acid fermentation

A mixing model is coupled with fermentation kinetics in order to simulate a fermentation as a function of mixing conditions and scale-up. The mixing model for a batch stirred tank with three stirrers consists of three regions, each of them characterized by an ideally mixed compartment around the stirrer and two macromixers, i.e. cascades of tank-in-series, describing the recirculation flow. The model contains four parameters — radial and axial circulation time, volume of the ideally mixed stirrer compartment and the number of tanks in each cascade. These values, determined by Mayr et al. in function of the operational conditions and scale-up, were choosen to simulate the fermentation of glutamic acid to show the pH-fluctuation at different control and scale conditions. By choosing optimal regulation properties, such as input flow rate and/or concentration of the base, regulation span, position of the pH-electrode and base input location, etc., fluctuations of the pH-value in the bio-reactor can be minimized. However, the negative effect of insufficient mixing conditions can be reduced only by an increasing number of the base input places. In large scale fermentors, the axial circulation time is rather high, about 5–10 times larger than the radial one. This might result in a large amplitude of the pH-fluctuation. As it is shown, using an input place for base in each stirrer region, the negative impact of the insufficient axial mixing on the fermentation can be diminished perfectly. In this case ammonia should be fed into the reactor as an aqueous solution.     

Membrane fluidity in glutamic acid-producing bacteria Brevibacterium sp. ATCC 13869

The bacterial secretion of glutamate was studied through plasma membrane fluidity, measured by anisotropy using the fluorophore TMA-DPH incorporated in the lipid part of the cell membrane. Cells of Brevibacterium sp. ATCC 13869 (wild type) were switched from the biotin-limited, producing state to the biotin-supplemented, non-producing state, and back. The following conclusions could be drawn: 1. It was not possible to detect any change in anisotropy by switching the cells from biotin-limited biotin-supplemented, as well as from biotin-supplemented, to biotin-limited, media. 2. The anisotropy value in the glutamic acid fermentation remains constant during the lag, exponential, growth, production and stationary phases. 3. The treatment of cells with a neutral synthetic polyester of ethylene-and propyleneoxide with soya oil-fatty acids increased the anisotropy values, indicating incorporation of the surfactant. 4. Glutamate secretion is not coupled with membrane fluidity, so a leak providing a general fluidization of the membrane could not be detected.     

Niche breadth explains the range size of European-centred butterflies,but dispersal ability does not

Aim

The breadth of ecological niches and dispersal abilities have long been discussed as important determinants of species' range sizes. However, studies directly comparing the relative effects of both factors are rare, taxonomically biased and revealed inconsistent results.

Location

Europe.

Time Period

Cenozoic.

Major Taxa

Butterflies, Lepidoptera.

Methods

We relate climate, diet and habitat niche breadth and two indicators of dispersal ability, wingspan and a dispersal tendency index, to the global range size of 369 European-centred butterfly species. The relative effects of these five predictors and their variation across the butterfly phylogeny were assessed by means of phylogenetic generalized least squares models and phylogenetically weighted regressions respectively.

Results

Climate niche breadth was the most important single predictor, followed by habitat and diet niche breadth, while dispersal tendency and wingspan showed no relation to species' range size. All predictors together explained 59% of the variation in butterfly range size. However, the effects of each predictor varied considerably across families and genera.

Main Conclusions

Range sizes of European-centred butterflies are strongly correlated with ecological niche breadth but apparently independent of dispersal ability. The magnitude of range size–niche breadth relationships is not stationary across the phylogeny and is often negatively correlated across the different dimensions of the ecological niche. This variation limits the generalizability of range size–trait relationships across broad taxonomic groups.     

Human appropriation of net primary production as driver of change in landscape-scale vertebrate richness

Aim

Land use is the most pervasive driver of biodiversity loss. Predicting its impact on species richness (SR) is often based on indicators of habitat loss. However, the degradation of habitats, especially through land-use intensification, also affects species. Here, we evaluate whether an integrative metric of land-use intensity, the human appropriation of net primary production, is correlated with the decline of SR in used landscapes across the globe.

Location

Global.

Time period

Present.

Major taxa studied

Birds, mammals and amphibians.

Methods

Based on species range maps (spatial resolution: 20 km × 20 km) and an area-of-habitat approach, we calibrated a “species–energy model” by correlating the SR of three groups of vertebrates with net primary production and biogeographical covariables in “wilderness” areas (i.e., those where available energy is assumed to be still at pristine levels). We used this model to project the difference between pristine SR and the SR corresponding to the energy remaining in used landscapes (i.e., SR loss expected owing to human energy extraction outside wilderness areas). We validated the projected species loss by comparison with the realized and impending loss reconstructed from habitat conversion and documented by national Red Lists.

Results

Species–energy models largely explained landscape-scale variation of mapped SR in wilderness areas (adjusted R²-values: 0.79–0.93). Model-based projections of SR loss were lower, on average, than reconstructed and documented ones, but the spatial patterns were correlated significantly, with stronger correlation in mammals (Pearson's r = 0.68) than in amphibians (r = 0.60) and birds (r = 0.57).

Main conclusions

Our results suggest that the human appropriation of net primary production is a useful indicator of heterotrophic species loss in used landscapes, hence we recommend its inclusion in models based on species–area relationships to improve predictions of land-use-driven biodiversity loss.     

Evaluation of laboratory indexes of absorption of soil phosphorus by plants: II

Summary A comparison was made of several laboratory methods for estimating the yield of phosphorus in plants grown in greenhouse cultures on samples of 22 soils from different parts of the United States. The methods investigated and their rank in order of increasing precision of the estimates of the yield of phosphorus were as follows: extraction with lactic acid, calcium lactate buffer solution extraction with 2 per cent citric acid solution < extraction with 0.03N NH₄F, 0.025N HCl solution < percentage phosphorus saturation (found as follows: 100 × labile phosphorus by isotopic dilution/ phosphorus adsorption capacity according to Langmuir adsorption equation) labile phosphorus by isotopic dilution phosphorus extracted by water.Journal Paper No. J-3747 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1183. Contribution from the Department of Agronomy.     

Routine metabolism of juvenile spot, Leiostomus xanthums (Lacépède), as a function of temperature, salinity and weight

Routine oxygen consumption rates of juvenile spot, Leiostomus xanthums , were measured over a range of temperatures, salinities and fish weights. As predicted, Q O₂ increased with temperature and decreased with body weight. However, Q O₂ decreased with decreasing salinity and did not show the expected minimum at isosmotic concentrations. The data are best described by the relationship: log₁₀ Q O₂ (mg O₂ g⁻¹ h⁻¹) = 0.129 log_lo salinity (%0) + 1.604 log₁₀ temperature (°C)-0.1401og₁₀(g)-2.767.