Obituary

Water, Air, &; Soil Pollution: Focus -     

Pseudomonas lemoignei has five poly(hydroxyalkanoic acid) (PHA) depolymerase genes: A comparative study of bacterial and eukaryotic PHA depolymerases

Four polyhydroxyalkanoate (PHA) depolymerases were purified from the culture fluid ofPseudomonas lemoignei: poly(3-hydroxybutyrate) (PHB), depolymerase A (M _r , 55,000), and PHB depolymerase B (M _r , 67,000) were specific for PHB and copolymers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) as substrates. The third depolymerase additionally hydrolyzed poly(3-hydroxyvalerate) (PHV) at high rates (PHV depolymerase;M _r , 54,000). The N-terminal amino acid sequences of the three purified proteins, of a fourth partially purified depolymerase (PHB depolymerase C), and of the PHB depolymerases ofComamonas sp. were determined. Four PHA depolymerase genes ofP. lemoignei (phaZ1,phaZ2,phaZ3, andphaZ4) have been cloned inEscherichia coli, and the nucleotide sequence ofphaZ1 has been determined recently (D. Jendrossek, B. Müller, and H. G. Schlegel,Eur. J. Biochem. 218, 701–710, 1993). In this study the nucleotide sequences ofphaZ2 andphaZ3 were determined.PhaZ1,phaZ2, andphaZ4 were identified to encode PHB depolymerase C, PHB depolymerase B, and PHV depolymerase, respectively.PhaZ3 coded for a novel PHB depolymerase ofP. lemoignei, named PHB depolymerase D. None of the four genes harbored the PHB depolymerase A gene, which is predicted to be encoded by a fifth depolymerase gene ofP. lemoignei (phaZ5) and which has not been cloned yet. The deduced amino acid sequences ofphaZ1–phaZ3 revealed high homologies to each other (68–72%) and medium homologies to the PHB depolymerase gene ofAlcaligenes faecalis T₁ (25–34%). Typical leader peptide amino acid sequences, lipase consensus sequences (Gly-Xaa-Ser-Xaa-Gly), and unusually high proportions of threonine near the C terminus were found in PhaZ1, PhaZ2, and PhaZ3. Considering the biochemical data of the purified proteins and the amino acid sequences, PHA depolymerases ofP. lemoignei are most probably serine hydrolases containing a catalytical triad of Asp, His, and Ser similar to that of lipases. A comparison of biochemical and genetic data of various eubacterial and one eukaryotic PHA depolymerases is provided also.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.     

Root-surface phosphatase activity in shrublands across a European gradient: effects of warming

Root-surface phosphatase activities were measured in natural and semi-natural shrublands across an European climatic gradient of temperature and rainfall including Wales (WL), Denmark (DK), Netherlands (NL), Hungary (HU), Italy (IT) and Spain (SP). In each site a warming experiment was conducted since 1999 or 2001 by means of passive night-time warming using reflective curtains that covered the vegetation at night. The treatments increased yearly average soil temperatures around 0. 8 degrees C in most of sites. Root-surface phosphatase activity values ranged between 56 mg PNP g(-1) h(-1) in IT and 3.5 mg PNP g(-1) h(-1) in HU. Warming had no effect on root-surface phosphatase activity across the sites and only in Hungary a slight increase was detected. Plants at Mediterranean sites (IT, SP) showed a higher root-surface phosphatase activity than plants at temperate sites (WL, NL, DK). We suggest it might be an adaptation of plant species evolved under Mediterranean climate that allows them a) to compensate in wet period for the decrease in phosphatase activity, and thus P uptake, during drought periods, and/or b) to benefit from soluble organic P flushes following the frequent drying-rewetting episodes experienced by soils in Mediterranean ecosystems.     

Biogeochemical consequences of rapid microbial turnover and seasonal succession in soil

Soil microbial communities have the metabolic and genetic capability to adapt to changing environmental conditions on very short time scales. In this paper we combine biogeochemical and molecular approaches to reveal this potential, showing that microbial biomass can turn over on time scales of days to months in soil, resulting in a succession of microbial communities over the course of a year. This new understanding of the year-round turnover and succession of microbial communities allows us for the first time to propose a temporally explicit N cycle that provides mechanistic hypotheses to explain both the loss and retention of dissolved organic N (DON) and inorganic N (DIN) throughout the year in terrestrial ecosystems. In addition, our results strongly support the hypothesis that turnover of the microbial community is the largest source of DON and DIN for plant uptake during the plant growing season. While this model of microbial biogeochemistry is derived from observed dynamics in the alpine, we present several examples from other ecosystems to indicate that the general ideas of biogeochemical fluxes being linked to turnover and succession of microbial communities are applicable to a wide range of terrestrial ecosystems.     

Klimawandel und zukünftig mögliche temperaturgesteuerte Malariatransmission in Deutschland

Background, aim and scope On behalf of the Centre of Excellence for Climate Effects and Adaption (KomPass) of the German Federal Environment Agency (UBA) an Expert Information System on Climate Change and Adaption (FISKA) was developed. FISKA shall provide the governmental institutions with basic information and models on climate change impacts for the development and accomplishment of adaption strategies. In this paper the impact model on potential temperature-dependent malaria transmissions is presented. It shows how, together with the REMO and WettReg climate models implemented in FISKA, areas at risk of malaria can be identified. Materials and methods FISKA was developed as an open and modular expert information system and allows the exchange of data and information with other institutions. Climate change impacts are implemented as calculation engines. The system allows for implementing additional data and impact models to improve existing impact models. For the calculation of the temperature-dependent potential secondary malaria infections the basic reproduction rate was used and the according algorithms were implemented in two calculation engines. One engine allows the calculation of the secondary infections and the other allows the calculation of the seasonal transmission gates. Measured air temperatures for the period 1961–2007 were provided by the German Meteorological Service (DWD), data on future air temperatures were extracted from the climate models REMO and WettReg for the climate reference periods 1991–2020, 2021–2050, and 2051–2080. The respective secondary infections and the resulting seasonal transmission gates for each period were regionalised on the basis of an ecological land classification to analyse significant ecoregional differences. Results Comparing the climate reference period 1961–1990 and the following period 1991–2007, the proportion of Germany featuring a potential seasonal malaria transmission gate of one or rather two months has been reduced in favour of a three months transmission gate. Accordingly, in the period 1991–2007 malaria transmissions during three months are possible on 70?% of the German territory instead of 26?% in 1961–1990. The percentage of a four months transmission gate has increased from 0.02?% to 0.76?%, and even a five months transmission is possible on 0.15?% of Germany. For future periods the number of potential secondary infections increases and further extensions of the seasonal transmission gates were revealed. In case of REMO A1B in 2051–2080, almost whole Germany features thermal conditions allowing malaria transmissions during four or rather five months. Discussion Rising air temperatures lead to changes in the spatial structure of the ecological elementary factor temperature, which can, under otherwise identical conditions, facilitate the reproduction of pathogens (here Plasmodium vivax) and vectors (here Anopheles atroparvus) as well as the spread of diseases. The basic reproduction rate serves the calculation of secondary malaria infections, which are the infections of host by a vector under the assumption that every member of the host population is susceptible for the pathogen. Improved thermal conditions alone do not necessarily imply the development of a malaria epidemic. Other factors like population density or medical care and the presence of vector habitats are of major importance, however, not considered by the calculation engines. The example of malaria is intended to be a model for a range of temperature-dependent vector-borne diseases. Conclusions The impact model on temperature-dependent malaria infections shows exemplarily the information content and functionality of FISKA. Data and functionality of FISKA serve as an expert information system for the detection of risks due to climate change. The results can be published as interactive maps via the FISKA internet interface. From a technical point of view, every impact model based on a calculation engine can be implemented and published via the web interface, provided that the impact models and the resulting risk maps rely on scientific reliable assumptions and are documented comprehensively. Recommendations and perspectives An improvement of FISKA considering the European scale is technically possible. It would require the development of GIS- and model applications on the basis of Europe-wide basic and specific data. For small-scale model runs a dynamic modelling of the water balance including soil hydrology as well as consideration of microclimate effects are required.