Ecological selection of siderophore‐producing microbial taxa in response to heavy metal contamination

Some microbial public goods can provide both individual and community‐wide benefits, and are open to exploitation by non‐producing species. One such example is the production of metal‐detoxifying siderophores. Here, we investigate whether conflicting selection pressures on siderophore production by heavy metals – a detoxifying effect of siderophores, and exploitation of this detoxifying effect – result in a net increase or decrease. We show that the proportion of siderophore‐producing taxa increases along a natural heavy metal gradient. A causal link between metal contamination and siderophore production was subsequently demonstrated in a microcosm experiment in compost, in which we observed changes in community composition towards taxa that produce relatively more siderophores following copper contamination. We confirmed the selective benefit of siderophores by showing that taxa producing large amounts of siderophore suffered less growth inhibition in toxic copper. Our results suggest that ecological selection will favour siderophore‐mediated decontamination, with important consequences for potential remediation strategies.     

Homozygous ablation of fibroblast growth factor-23 results in hyperphosphatemia and impaired skeletogenesis, and reverses hypophosphatemia in Phex-deficient mice.

Fibroblast growth factor-23 (FGF-23), a recently identified molecule that is mutated in patients with autosomal dominant hypophosphatemic rickets (ADHR), appears to be involved in the regulation of phosphate homeostasis. Although increased levels of circulating FGF-23 were detected in patients with different phosphate-wasting disorders such as oncogenic osteomalacia (OOM) and X-linked hypophosphatemia (XLH), it is not yet clear whether FGF-23 is directly responsible for the abnormal regulation of mineral ion homeostasis and consequently bone development. To address some of these unresolved questions, we generated a mouse model, in which the entire Fgf-23 gene was replaced with the lacZ gene. Fgf-23 null (Fgf-23-/-) mice showed signs of growth retardation by day 17, developed severe hyperphosphatemia with elevated serum 1,25(OH)2D3 levels, and died by 13 weeks of age. Hyperphosphatemia in Fgf-23-/- mice was accompanied by skeletal abnormalities, as demonstrated by histological, molecular, and various other morphometric analyses. Fgf-23-/-) mice had increased total-body bone mineral content (BMC) but decreased bone mineral density (BMD) of the limbs. Overall, Fgf-23-/- mice exhibited increased mineralization, but also accumulation of unmineralized osteoid leading to marked limb deformities. Moreover, Fgf-23-/- mice showed excessive mineralization in soft tissues, including heart and kidney. To further expand our understanding regarding the role of Fgf-23 in phosphate homeostasis and skeletal mineralization, we crossed Fgf-23-/- animals with Hyp mice, the murine equivalent of XLH. Interestingly, Hyp males lacking both Fgf-23 alleles were indistinguishable from Fgf-23/-/ mice, both in terms of serum phosphate levels and skeletal changes, suggesting that Fgf-23 is upstream of the phosphate regulating gene with homologies to endopeptidases on the X chromosome (Phex) and that the increased plasma Fgf-23 levels in Hyp mice (and in XLH patients) may be at least partially responsible for the phosphate imbalance in this disorder.     

Physiological Concentration of Exogenous Lactate Reduces Antimycin A Triggered Oxidative Stress in Intestinal Epithelial Cell Line IPEC-1 and IPEC-J2 In Vitro

Weaning triggers an adaptation of the gut function including luminal lactate generation by lactobacilli, depending on gastrointestinal site. We hypothesized that both lactobacilli and lactate influence porcine intestinal epithelial cells. In vivo experiments showed that concentration of lactate was significantly higher in gastric, duodenal and jejunal chyme of suckling piglets compared to their weaned counterparts. In an in vitro study we investigated the impact of physiological lactate concentration as derived from the in vivo study on the porcine intestinal epithelial cells IPEC-1 and IPEC-J2. We detected direct adherence of lactobacilli on the apical epithelial surface and a modulated F-actin structure. Application of lactobacilli culture supernatant alone or lactate (25 mM) at low pH (pH 4) changed the F-actin structure in a similar manner. Treatment of IPEC cultures with lactate at near neutral pH resulted in a significantly reduced superoxide-generation in Antimycin A-challenged cells. This protective effect was nearly completely reversed by inhibition of cellular lactate uptake via monocarboxylate transporter. Lactate treatment enhanced NADH autofluorescence ratio (F_cytosol/F_nucleus) in non-challenged cells, indicating an increased availability of reduced nucleotides, but did not change the overall ATP content of the cells. Lactobacilli-derived physiological lactate concentration in intestine is relevant for alleviation of redox stress in intestinal epithelial cells.     

On the influence of provenance to soil quality enhanced stress reaction of young beech trees to summer drought

Climate projections propose that drought stress will become challenging for establishing trees. The magnitude of stress is dependent on tree species, provenance, and most likely also highly influenced by soil quality. European Beech (Fagus sylvatica) is of major ecological and economical importance in Central European forests. The species has an especially wide physiological and ecological amplitude enabling growth under various soil conditions within its distribution area in Central Europe. We studied the effects of extreme drought on beech saplings (second year) of four climatically distinct provenances growing on different soils (sandy loam and loamy sand) in a full factorial pot experiment. Foliar δ¹³C, δ¹⁵N, C, and N as well as above‐ and belowground growth parameters served as measures for stress level and plant growth. Low‐quality soil enhanced the effect of drought compared with qualitatively better soil for the above‐ and belowground growth parameters, but foliar δ¹³C values revealed that plant stress was still remarkable in loamy soil. For beeches of one provenance, negative sandy soil effects were clearly smaller than for the others, whereas for another provenance drought effects in sandy soil were sometimes fatal. Foliar δ¹⁵N was correlated with plant size during the experiment. Plasticity of beech provenances in their reaction to drought versus control conditions varied clearly. Although a general trend of declining growth under control or drought conditions in sandy soil was found compared to loamy soil, the magnitude of the effect of soil quality was highly provenance specific. Provenances seemed to show adaptations not only to drought but also to soil quality. Accordingly, scientists should integrate information about climatic pre‐adaptation and soil quality within the home range of populations for species distribution modeling and foresters should evaluate soil quality and climatic parameters when choosing donor populations for reforestation projects.     

The sporoderm ultrastructure inPersea,Nectandra, Hernandia,Gomortega and some other Lauralean genera

The sporoderm ultrastructure of some genera in theLauraceae, Hernandiaceae andGomortegaceae (Laurales) was re-investigated. This and a comparison with some Zingiberalean genera (Canna, Heliconia, Strelitzia) leads to a re-interpretation of the peculiar pollen wall structure of the Lauralean families recently described in this journal (Kubitzki 1981). Their pollen is now interpreted as being nearly exine-less: The (sporopollenin-containing) exine consists only of a thin, skin-like, coherent layer ornamented with spines and globules. The (cellulosic) intine is composed of an unstratified inner and a thick, channelled outer layer. The striking similarity of the pollen ultrastructure between theLaurales studied and some members of theZingiberales can be interpreted as an example of convergent evolution in angiosperm pollen walls.     

Kern- und Chloroplastenteilung sowie Photosyntheseleistung synchron kultivierter Bumilleriopsis (Xanthophyceae)

1. Durch Licht-Schwachlicht-Temperatur-Wechsel (LS-T 33:15 h/15000: 3000 Lux/24: 19 C) wird Bumilleriopsis zu 96 bis 98% synchronisiert. 2. Die Kernzahl je Zelle wurde während der Zellentwicklung im LS-T verfolgt. Während des größten Teils des Zyklus sind die Zellen mehrkernig; Zellwandbildungen treten erst nach Abschluß der Kernteilungen auf. Der Anteil der Zellen mit zwei Kernen ist 12 bis 14 Stunden, derjenige mit vier Kernen 20 bis 21, derjenige mit acht Kernen 23 bis 27 Stunden nach Zyklusbeginn maximal. Es wurden keine Zellen mit drei, fünf, sechs oder sieben Kernen gefunden, so daß die Teilungen innerhalb einer Zelle sehr synchron zu sein scheinen. 3. Chloroplasten werden während der gesamten ersten Phase der synchronisierenden Bedingungen gebildet; ein Zusammenhang mit der Zellteilung besteht nicht. 4. Die Photosyntheserate nimmt gegen Ende der ersten Phase des LS-T stark ab und durchläuft etwa 35 bis 36 Stunden nach Zyklusbeginn (also während der Zellwandbildung) ein Minimum. Im anschließenden Bereich, in den die vollständige Zellteilung fällt, steigt die Rate auf den zwei- bis dreifachen Wert rasch an. Gleiche Verhältnisse liegen bei Temperaturwechseln in Dauerlicht (33: 15 h/15 000 Lux/24: 19 C) vor. Herrn Prof. Dr. P. Böger danke ich für sein stetes Interesse an diesen Untersuchungen, Herrn P. Bley für sorgfältige technische Assistenz. Die Arbeit wurde durch den Sonderforschungsbereich 138 unterstützt.     

T-cell prolymphocytic leukemia (T-PLL) with unique surface phenotype

Leukemic cells of a 19 year old patient with prolymphocytic leukemia of T-cell type (T-PLL) were characterized by surface markers and immunologic functions. Phenotypic analysis using a large panel of monoclonal antibodies corresponding to the clusters (CD) of differentiation antigens established on the Leukocyte Typing Workshops I and II revealed a unique T-cell phenotype not yet reported in the literature: CD1 (T6)-, CD2 (T11)+, CD3 (T3)+, CD4 (T4)-, CD5 (T1)-, CD6 (T411)+, CD7 (Leu9)+, CD8 (T811)-, CD10 (J5)-, CD11 (M22)+, CD12 (M67)-, CD13 (My7)-, CD14 (Mo2)-, CD16 (Vep13, 3G8, Leu11)+, CD18 (MHM23)+, CD19 (B4)-, CD20 (B1)-, CD25 (TAC)-, MHC-class II (HLA-DR, HLA-DQ)-, NKH1A+, Leu7-. Despite the expression of surface structures associated with natural killer (NK) function (CD16, CD18, NKH 1 A) the T-PLL cells were inactive in NK assays in vitro. Low in vitro ADCC activity was detectable. This unusual T-PLL phenotype might help to identify a new distinct T-cell differentiation stage.