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We compared growth rates and efficiencies of pelagic bacteria from an extremely acidic mining lake (pH 2.6, mean depth 4.6m) supplied with different sources of carbon: (1) excreted by phytoplankton, (2) derived from benthic algae, (3) entering the lake via ground water, and (4) leached from leaf litter. Bacteria exhibited high growth rate and efficiency on exudates of pelagic and benthic algae. In contrast, they showed a lower growth rate and efficiency with organic carbon from ground water, and grew at a very high rate but a very low efficiency on leaf leachate. Results from stable isotope analyses indicate a greater importance of benthic exudates and leaf leachate for bacteria in the epilimnion, and a higher impact of ground water sources in the hypolimnion. Given the magnitude of differential source inputs into the lake, we suggest that benthic primary production was the most important carbon source for pelagic bacteria. The benthic-pelagic coupling seems to be more relevant in this shallow acidic lake with low pelagic carbon dioxide concentrations than in neutral lakes
Terrestrial-derived dissolved organic carbon (DOC) contributes significantly to the energetic basis of many aquatic food webs. Although heterotrophic bacteria are generally considered to be the sole consumers of DOC, algae and cyanobacteria of various taxonomic groups are also capable of exploiting this resource. We tested the hypothesis that algae can utilise DOC in the presence of bacteria if organic resources are supplied in intervals by photolysis of recalcitrant DOC. In short-term uptake experiments, we changed irradiation in the range of minutes. As model substrates, polymers of radiolabelled coumaric acid (PCA) were used, which during photolysis are known to release aromatic compounds comparable to terrestrial-derived and refractory DOC. Three cultured freshwater algae readily assimilated PCA photoproducts equivalent to a biomass-specific uptake of 5-60% of the bacterial competitors present. Algal substrate acquisition did not depend on whether PCA was photolysed continuously or in intervals. However, the data show that photoproducts of terrestrial DOC can be a significant resource for osmotrophic algae. In long-term growth experiments, interval light was applied one hour per day. We allowed cultured Chlamydomonas to compete for ambient DOC of low concentration. We found higher abundances of Chlamydomonas when cultures were irradiated intermittently rather than continuously. These data suggest that photolysis of DOC supports algal heterotrophy, and potentially facilitates growth, when light fluctuations are large, as during the diurnal light cycle. We concluded that osmotrophic algae can efficiently convert terrestrial carbon into the biomass of larger organisms of aquatic food webs.
The activity of vacuolar H+-ATPase (V-ATPase) in the apical membrane of blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT). 5-HT induces, via protein kinase A, the phosphorylation of V-ATPase subunit C and the assembly of V-ATPase holoenzymes. The protein phosphatase responsible for the dephosphorylation of subunit C and V-ATPase inactivation is not as yet known. We show here that inhibitors of protein phosphatases PP1 and PP2A (tautomycin, ocadaic acid) and PP2B (cyclosporin A, FK-506) do not prevent V-ATPase deactivation and dephosphorylation of subunit C. A decrease in the intracellular Mg2+ level caused by loading secretory cells with EDTA-AM leads to the activation of proton pumping in the absence of 5-HT, prolongs the 5-HT-induced response in proton pumping, and inhibits the dephosphorylation of subunit C. Thus, the deactivation of V-ATPase is most probably mediated by a protein phosphatase that is insensitive to okadaic acid and that requires Mg2+, namely, a member of the PP2C protein family. By molecular biological techniques, we demonstrate the expression of at least two PP2C protein family members in blowfly salivary glands. © 2009 Wiley Periodicals, Inc.
Vacuole integrity maintained by DUF300 proteins is required for brassinosteroid signaling regulation
(2018)
Brassinosteroid (BR) hormone signaling controls multiple processes during plant growth and development and is initiated at the plasma membrane through the receptor kinase BRASSINOSTEROID INSENSITIVE1 (BRI1) together with co-receptors such as BRI1-ASSOCIATED RECEPTOR KINASE1 (BAK1). BRI1 abundance is regulated by endosomal recycling and vacuolar targeting, but the role of vacuole-related proteins in BR receptor dynamics and BR responses remains elusive. Here, we show that the absence of two DUF300 domain-containing tonoplast proteins, LAZARUS1 (LAZ1) and LAZ1 HOMOLOG1 (LAZ1H1), causes vacuole morphology defects, growth inhibition, and constitutive activation of BR signaling. Intriguingly, tonoplast accumulation of BAK1 was substantially increased and appeared causally linked to enhanced BRI1 trafficking and degradation in laz1 laz1h1 plants. Since unrelated vacuole mutants exhibited normal BR responses, our findings indicate that DUF300 proteins play distinct roles in the regulation of BR signaling by maintaining vacuole integrity required to balance subcellular BAK1 pools and BR receptor distribution.
Puumala virus (PUUV) causes many human infections in large parts of Europe and can lead to mild to moderate disease. The bank vole (Myodes glareolus) is the only reservoir of PUUV in Central Europe. A commercial PUUV rapid field test for rodents was validated for bank-vole blood samples collected in two PUUV-endemic regions in Germany (North Rhine-Westphalia and Baden-Wurttemberg). A comparison of the results of the rapid field test and standard ELISAs indicated a test efficacy of 93-95%, largely independent of the origin of the antigens used in the ELISA. In ELISAs, reactivity for the German PUUV strain was higher compared to the Swedish strain but not compared to the Finnish strain, which was used for the rapid field test. In conclusion, the use of the rapid field test can facilitate short-term estimation of PUUV seroprevalence in bank-vole populations in Germany and can aid in assessing human PUUV infection risk.
Standing stocks are typically easier to measure than process rates such as production. Hence, stocks are often used as indicators of ecosystem functions although the latter are generally more strongly related to rates than to stocks. The regulation of stocks and rates and thus their variability over time may differ, as stocks constitute the net result of production and losses. Based on long-term high frequency measurements in a large, deep lake we explore the variability patterns in primary and bacterial production and relate them to those of the corresponding standing stocks, i.e. chlorophyll concentration, phytoplankton and bacterial biomass. We employ different methods (coefficient of variation, spline fitting and spectral analysis) which complement each other for assessing the variability present in the plankton data, at different temporal scales. In phytoplankton, we found that the overall variability of primary production is dominated by fluctuations at low frequencies, such as the annual, whereas in stocks and chlorophyll in particular, higher frequencies contribute substantially to the overall variance. This suggests that using standing stocks instead of rate measures leads to an under- or overestimation of food shortage for consumers during distinct periods of the year. The range of annual variation in bacterial production is 8 times greater than biomass, showing that the variability of bacterial activity (e.g. oxygen consumption, remineralisation) would be underestimated if biomass is used. The P/B ratios were variable and although clear trends are present in both bacteria and phytoplankton, no systematic relationship between stock and rate measures were found for the two groups. Hence, standing stock and process rate measures exhibit different variability patterns and care is needed when interpreting the mechanisms and implications of the variability encountered.
The human face shows individual features and features that are characteristic for sex and age (the loss of childlike characteristics during maturation). The analysis of facial dimensions is essential for identifying individual features also for forensic issues.
The analysis of facial proportions was performed on photogrammetric data from front views of 125 children. The data were pooled from 2 different studies. The children's data were obtained from a longitudinal study and reduced by random generator to ensure the data of adults from a separate cross-sectional study.
We applied principal component analysis on photogrammetric facial proportions of 169 individuals: 125 children (63 boys and 62 girls) aged 2-7 years and 44 adults (18 men and 26 women) aged 18-65 years.
Facial proportions depend on age and sex. Three components described age: (1) proportions of facial height to head height, (2) proportions that involve endocanthal breadth, and (3) bigonial to bizygonial proportions. Proportions that associate with sex are connected with nasal distances and nasal to bizygonial distances.
Twenty-three percent of the variance, particularly variance that are connected with proportions of lower and middle face heights to head height, do neither depend on sex nor on age and thus appear useful for screening purposes, eg, for dysmorphic genetic syndromes.