Purification of the bacteriocin bavaricin MN and characterization of its mode of action against Listeria monocytogenes Scott A cells and lipid vesicles.

Bavaricin MN was purified from Lactobacillus sake culture supernatant 135-fold with a final yield of 11%. Sequence analysis revealed bavaricin MN to be a 42-amino-acid peptide having a molecular weight of 4,769 and a calculated pI of 10.0. Computer analysis indicated that the C-terminal region may form an alpha-helical structure with an amphipathic nature deemed important in the interaction of bacteriocins with biological membranes. Bavaricin MN rapidly depleted the membrane potential (delta p) of energized Listeria monocytogenes cells in a concentration-dependent fashion. At a bavaricin MN concentration of 9.0 micrograms/ml, the delta p decreased by 85%. Both the electrical potential (delta psi) and Z delta pH components of the delta p were depleted, and this depletion was not dependent on a threshold level of proton motive force. In addition to studying the effect of bavaricin MN on the delta p of vegetative cells, bavaricin MN-induced carboxyfluorescein (CF) efflux from L. monocytogenes-derived lipid vesicles was also characterized. Bavaricin MN-induced CF leakage was also concentration dependent with an optimum of pH 6.0. The rate of CF efflux was 63% greater in lipid vesicles in which a delta psi was generated compared with that in lipid vesicles in the absence of a delta psi.     

The differential genetic and environmental canalization of fitness components in Drosophila melanogaster

Canalization describes the process by which phenotypic variation is reduced by developmental mechanisms. A trait can be canalized against environmental or genetic perturbations. Stabilizing selelction should favor improved canalization, and the degree of a trait's canalization should be positively correlated with its impact on fitness. Here we report, for Drosophila melanogaster, measurements of environmental canalization for five fitness components. We compare them with measurements of genetic canalization, and we discuss the impact of inbreeding on both. In three experiments we measured the variation of fitness components within lines nested within temperature, treatment, and experiment. Lines differed in the position of a P element insert or in genetic background. Within lines flies were genetically nearly identical. We designated trait variation within lines as environmental canalization. The canalization of the traits increased with their impact on fitness, and the pattern was similar to that found for the canalization of fitness components against genetic differences, measured as the variation among lines nested within temperature, treatment, and experiment. This suggests that developmental mechanisms buffer the phenotype against both genetic and environmental disturbance. The results also suggest, less strongly, that inbreeding weakens canalization.     

Biologie und Verhalten zentralasiatischer Schneefinken (Montifringilla) und Erdsperlinge (Pyrgilauda)

Snow Finches and Mountain-steppe Sparrows differ in habitat selection, feeding, social and vocal behaviour. For these reasons, separation of the genusMontifringilla intoMontifringilla andPyrgilauda is recommended.     

Flight manoeuvers used by a parasitic wasp to locate host-infested plant

Cotesia rubecula Marshall (Hymenoptera: Braconidae) is a specialist larval parasitoid of the butterfly Pieris rapae L. which itself feeds almost exclusively upon cruciferous plants. Female wasps are attracted to the odour of host-infested plant (plant-host complex: PHC) and the probability of flights in a wind tunnel depends on females' prior oviposition experience with the PHC and on the concentration of the PHC odour. This study considers the effect of both factors on characteristics of oriented flight upwind towards the PHC. The flight track parameters that we measured and calculated were not significantly affected by these factors. C. rubecula females exhibited high average flight velocity and relatively straight flight tracks. There was a considerable variability between individuals, however, in their odour-modulated upwind flight tracks. Some females generated a zigzagging upwind flight track similar to those commonly observed from male moths responding to female sex pheromone. Other females flew along a straight track directly upwind. The flight tracks of most female wasps were intermediate between these extremes. The full range of these flight performances was observed to all experimental treatments.     

Changes in Metabotropic Glutamate Receptor mRNA Levels Following Global Ischemia: Increase of a Putative Presynaptic Subtype (mGluR4) in Highly Vulnerable Rat Brain Areas

Abstract: Metabotropic glutamate receptors mediate their intracellular response by coupling to G proteins and may be divided into three subfamilies: mGluR1 and mGluR5, which stimulate phosphatidylinositol hydrolysis; mGluR2 and mGluR3, which are negatively coupled to cyclic AMP formation; and mGluR4 and mGluR6, which also inhibit forskolin-stimulated cyclic AMP formation. The mGluR4 subtypes may represent l -2-amino-4-phosphonobutyrate-sensitive presynaptic autoreceptors, and two alternatively spliced variants of the mGluR4 coding for two receptors with different C termini have been identified. Using in situ hybridization, we measured the levels of mGluR1–mGluR5 mRNA in regions of the rat brain 24 h after transient global ischemia, a time point when no neuronal damage can yet be observed morphologically. In the hippocampus, the mRNA levels for mGluR1, mGluR2, and mGluR5 were decreased, mGluR3 mRNA levels were unchanged, and the mGluR4 mRNA levels were strongly increased. The strongest increase appeared to be in the mRNA encoding mGluR4b. The mGluR4 mRNA was also increased in the parietal cortex, whereas the ventral posteromedial thalamic nucleus showed a small decrease in its mRNA content. These results suggest that vulnerable neurons react to an increased extracellular glutamate concentration by differential regulation of the mRNA for pre- and postsynaptically located metabotropic glutamate receptors.     

Fast Cytoplasmic pH Regulation in Acid-Stressed Leaves

Induction of photosynthesis in leaves was prolonged, and steadystate photosynthesis was inhibited by very high CO₂ concentrationswhich cause cytoplasmic acidification. Prolonged exposure tohigh CO₂ relieved initially observed inhibition of photosynthesisat least partially. The sensitivity of carbon assimilation tohigh CO₂ was different in different plant species. Acidificationby CO₂ (or subsequent alkalization) was detected by measuringrapid CO₂-release from the tissue and by monitoring fluorescenceof pH-indicating dyes which had been fed to the leaves throughthe petiole. The results indicate that two different mechanismsoperate in leaves to achieve and maintain pH homeostasis. Rapidand efficient pH-adjustment is provided by proton/cation exchangeacross the tonoplast. Slower and less efficient regulation occursby formation or consumption of base. In the presence of highCO₂ concentrations, protons are pumped from the cytosol intoalready acidic vacuoles. In turn, vacuolar cations replace exportedprotons in the cytosol permitting bicarbonate accumulation andincreasing the pH of the acidified cytosol. Similarly effectiveand fast proton/cation exchange relieves acid-stress in thechloroplast stroma and permits photosynthesis to proceed withhigh quantum efficiency or high light-saturated rates in thepresence of CO₂ concentrations which would, in the absence offast cytoplasmic pH regulation, inhibit photosynthesis. By inference,proton/cation exchange must also occur across the mitochondrialboundary. After cytoplasmic pH adjustment in the presence ofhigh CO₂, removal of CO₂ results in transient cytoplasmic alkalizationand, subsequently, in the return of cytoplasmic pH values tolevels observed prior to acid-stress. In addition to fast pHregulation by rapid proton/cation exchange across biomembranes,slow base production (e.g. NH₃-formation) also contributes torelieving acid stress. Base produced in the presence of highCO₂ is rapidly consumed after removal of CO₂. Implications of the findings in regard to forest damage by potentiallyacidic air pollutants such as SO₂ are briefly discussed. (Received November 8, 1993; Accepted February 3, 1994)     

Microbial transformation of ethylpyridines

Pyridine and its derivatives have been found as pollutants in the environment. Although alkylpyridines constitute the largest class of pyridines contaminating the environment, little information is available concerning the fate and transformation of these compounds. In this investigation ethylpyridines have been used as model compounds for investigating the biodegradability of alkylpyridines. A mixed culture of ethylpyridine-degrading microorganisms was obtained from a soil that had been exposed to a variety of pyridine derivatives for several decades. The enrichment culture was able to degrade 2-, 3-, and 4-ethylpyridine (100 mg/L) at 28° C and pH 7 within two weeks under aerobic conditions. The degradation rate was greatest for 2-ethylpyridine and least for 3-ethylpyridine. Transformation of ethylpyridines was dependent on substrate concentration, pH, and incubation temperature. Studies on the metabolic pathway of 4-ethylpyridine revealed two products; these chemicals were identified by MS and NMR analyses as 4-ethyl-2(1H)-pyridone and 4-ethyl-2-piperidone. 6-Ethyl-2(1H)-pyridone was determined to be a product of 2-ethylpyridine degradation. These results indicate that the transformation mechanism of ethylpyridines involves hydroxylation and reduction of the aromatic ring before ring cleavage.     

Proteomic fingerprinting enables quantitative biodiversity assessments of species and ontogenetic stages in Calanus congeners (Copepoda,Crustacea) from the Arctic Ocean

Species identification is pivotal in biodiversity assessments and proteomic fingerprinting by MALDI-TOF mass spectrometry has already been shown to reliably identify calanoid copepods to species level. However, MALDI-TOF data may contain more information beyond mere species identification. In this study, we investigated different ontogenetic stages (copepodids C1–C6 females) of three co-occurring Calanus species from the Arctic Fram Strait, which cannot be identified to species level based on morphological characters alone. Differentiation of the three species based on mass spectrometry data was without any error. In addition, a clear stage-specific signal was detected in all species, supported by clustering approaches as well as machine learning using Random Forest. More complex mass spectra in later ontogenetic stages as well as relative intensities of certain mass peaks were found as the main drivers of stage distinction in these species. Through a dilution series, we were able to show that this did not result from the higher amount of biomass that was used in tissue processing of the larger stages. Finally, the data were tested in a simulation for application in a real biodiversity assessment by using Random Forest for stage classification of specimens absent from the training data. This resulted in a successful stage-identification rate of almost 90%, making proteomic fingerprinting a promising tool to investigate polewards shifts of Atlantic Calanus species and, in general, to assess stage compositions in biodiversity assessments of Calanoida, which can be notoriously difficult using conventional identification methods.