Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

Declining foliar and litter δ¹⁵N diverge from soil, epiphyte and input δ¹⁵N along a 120,000 yr temperate rainforest chronosequence

Patterns in the natural abundance of nitrogen (N) isotopes (1?N and 1?N) can help in the understanding of ecosystem processes along environmental gradients, because some processes fractionate against the heavier isotope. We measured δ1?N in many components of the Franz Josef soil chronosequence in New Zealand to see how each component varied along the sequence and within sites, and to see what this variation can tell us about how ecosystem processes such as N losses change with soil age. We analyzed δ1?N in foliage from 18 woody species, abscised leaves from seven woody species, three soil horizons, bryophytes, lichens, bulk deposition, and nodules from the N-fixing tree Coriaria arborea (Coriariaceae). Foliar δ1?N varied significantly across plant species. Foliage and bulk litter became 1?N-depleted as soil age increased. Soil N from organic and mineral horizons was significantly more 1?N-enriched than bulk litter N at each site. Increasing precipitation also decreased foliar and soil δ1?N. Comparing input and whole ecosystem δ1?N revealed limited evidence for net fractionation during N losses. These trends are consistent with some combination of increasing fractionation during plant N uptake, mycorrhizal transfer, within-plant processing, and soil decomposition as soils age.     

Evaluating 50 years of time-series soil radiocarbon data: towards routine calculation of robust C residence times

In 1959, Athol Rafter began a substantial programme of monitoring the flow of ¹⁴C produced by atmospheric thermonuclear tests through New Zealand’s atmosphere, biosphere and soil. By building on the original measurements through ongoing sampling, a database of over 500 soil radiocarbon measurements spanning 50 years has now been compiled. The datasets, including an 11-point time series, allow strong focus on the robust quantification of residence times ranging from years to decades. We describe key aspects of the dataset, including the ability to identify critical assumptions inherent in calculating soil C residence times. The 3 most critical assumptions relate to: (1) the proportion of old C (“fraction passive”), (2) the lag time between photosynthesis and C entering the modeled pool, and (3) changes in the rates of C input (i.e., steady state). We demonstrate the ability to compare residence times in contrasting sites, such Andisols and non-Andisols, and the ability to calculate residence times across a range of soil depths. We use ¹⁴C in a two-box model to quantify soil carbon turnover parameters in deforested dairy pastures under similar climate in the Tokomaru silt loam (non-Andisol) versus the Egmont black loam (Andisol), originally sampled in 1962, 1965 and 1969, and resampled again in 2008. The ¹⁴C-based residence times of the main soil C pool in surface soil (~8 cm) are ~9 years in the Tokomaru soils compared to ~17 years for the Egmont soils. This difference represents nearly a doubling of soil C residence time, and roughly explains the doubling of the soil C stock. Passive soil C comprises 15% of the soil C pool in Tokomaru soils versus 27% in Egmont soils. A similar difference in residence times is found in a second surface soil comparison between the Bruntwood soil (Andisol) and the Te Kowhai soil (non-Andisol) with residence times of 18 and 27 years, respectively. The comparisons support evidence that C dynamics do differ in Andisols versus non-Andisols, as a result of both the mineral allophane and Al complexation. Expanding our calculations beyond surface soil, we show that thickening the calculation depth by combining horizons allows robust residence times to be calculated at a range of depths. Overall, the large and systematically collected dataset demonstrate that soil C residence times of the main soil C pool can be routinely calculated using ¹⁴C wherever samples collected 10 or more years apart in New Zealand grassland soils are available, and presumably under similar circumstances in other soils worldwide.