Contrasting dynamics of ciliate communities in sandy and silty sediments of an estuarine intertidal flat

During a 1-year study of the ciliate faunas of a silty and a sandy site on an intertidal flat in the Westerschelde estuary, a total number of 107 taxa were recorded belonging to at least 52 genera and 15 orders. Our results suggest that physical properties of the sediment were more important in regulating ciliate abundance, diversity and community composition than food availability, predation, temperature or oxygen concentration. Ciliate abundance and diversity were positively related to sediment grain size and the ciliate community of silty sediments was found to be a subset of that of sandy sediments. At the sandy site, where the sediment composition was stable, seasonal changes in the ciliate community were related to changes in food availability and/or temperature. At both the sandy and silty sites, a clear vertical gradient in the ciliate community was observed that appeared to be linked to gradients in food availability and oxygen concentration. These vertical gradients in ciliate community composition, however, were less steep than the measured oxygen gradients, probably due to the presence of oxic microniches in the anoxic zone.     

Ecotones in vegetation ecology: methodologies and definitions revisited

In this review paper, we highlight some of the trends and issues that have dominated ecotone research over the decade of 1996–2006. The terms and definitions of ecotone research in vegetation ecology are reviewed. We summarize the most important techniques and highlight the discrepancies between the definitions and their scientific application in vegetation ecology. We see a need for semantic uniformity with regard to the term and the definition of “the ecotone”, as the variable and the non-exclusive use of terms and definitions can be a source of confusion when interpreting and comparing different studies. To avoid further confusion, a unique definition of the term “ecotone” should be agreed upon, based upon a set of general characteristics. We therefore adapted and extended the definition from Holland et al. (Ecotones: the role of landscape boundaries in the management and restoration of changing environments, 1991) to “A multi-dimensional environmentally stochastic interaction zone between ecological systems with characteristics defined in space and time, and by the strength of the interaction”. We also advocate that (1) a shift in focus from one-dimensional to two-dimensional techniques in ecotone characterization is desirable and (2) more research into novel techniques, including multi-dimensional data and time series, is needed in view of local and global ecotone changes.     

Comparative study of monomeric reconstituted and membrane microsomal monooxygenase systems of the rabbit liver. I. Properties of NADPH-cytochrome P450 reductase and cytochrome P450 LM2 (2B4) monomers.

Oligomers and monomers of NADPH-cytochrome P450 reductase and cytochrome P450 LM2 (2B4) isolated from the liver microsomes of phenobarbital-treated rabbits were examined for physicochemical properties and catalytic activities. As measured using laser correlation spectroscopy the particle sizes of NADPH-cytochrome P450 reductase and cytochrome P450 LM2 oligomers were 14.8 +/- 1.7 and 19.2 +/- 1.4 nm, respectively. Twenty-four-hour incubation with Emulgen 913 at 4 degrees C at a molar ratio of 1:100 led to the monomerization of NADPH-cytochrome P450 reductase and cytochrome P450 LM2 oligomers, the particle sizes diminishing to 6.1 +/- 1.3 and 5.2 +/- 0.4 nm, respectively. The thermal stability of NADPH-cytochrome P450 reductase monomers was the same as that of oligomers, whereas cytochrome P450 LM2 monomers were less thermostable than oligomers and cytochrome P450 in microsomes. Similar to cytochrome P450 LM2 oligomers and the microsomal hemoprotein, cytochrome P450 LM2 monomers formed complexes with type I and II substrates, but with Kd values higher than those of microsomes and cytochrome P450 LM2 oligomers. Kinetic parameters (Vmax and Km) of H2O2- and cumene hydroperoxide-dependent oxidation of benzphetamine and aniline in the presence of cytochrome P450 LM2 oligomers, monomers, and microsomes were determined. Peroxidase activities of the oligomers and monomers were the same, but were lower than those of microsomes. Thus the substitution of protein-protein interactions in cytochrome P450 LM2 oligomers with protein-detergent interactions in the monomers did not influence the catalytic properties of the hemoprotein.     

Two new species of freshwater Ostracoda of the genus Parastenocypris Hartmann, 1964 from Kerala,India

Parastenocypris goddeerisi n.sp. and P. achandii n.sp. are described from temporary habitats in Kerala, southern India. The morphology of both males and females is illustrated and the new species are compared to the known representatives of the genus. Stenocypris fernandoi Neale, described from Sri Lanka, is here referred to Parastenocypris.     

Inoculation history affects community composition in experimental freshwater bacterioplankton communities

Priority effects occur when the arrival order of species or genotypes has a lasting effect on community or population structure. For freshwater bacteria , priority effects have been shown experimentally among individual species, but no experiments have been performed using complex natural communities. We investigated experimentally whether a foreign bacterioplankton community influences the community assembly trajectory when inoculated prior to the local community, whether inoculation time lag affects priority effects, and how the individual OTUs responded to time lag. Two bacterioplankton communities from dissimilar ponds were inoculated into one of the natural media with a time lag of 0, 12, 36 or 60 h, giving advantage in time to the foreign community . All three time lags resulted in priority effects, as the final community composition of these treatments differed significantly from that of the treatment with no time lag, but compositional shifts were not linear to inoculation time lag. The responses of individual OTUs to time lag were highly diverse and not predictable based on their immigration history or relative abundance in the inocula or control. The observed impact and complexity of priority effects in multispecies systems emphasize the importance of this process in structuring both natural and industrial bacterial communities.     

Increased transgenerational epigenetic variation,but not predictable epigenetic variants,after environmental exposure in two apomictic dandelion lineages

DNA methylation is one of the mechanisms underlying epigenetic modifications. DNA methylations can be environmentally induced and such induced modifications can at times be transmitted to successive generations. However, it remains speculative how common such environmentally induced transgenerational DNA methylation changes are and if they persist for more than one offspring generation. We exposed multiple accessions of two different apomictic dandelion lineages of the Taraxacum officinale group (Taraxacum alatum and T. hemicyclum) to drought and salicylic acid (SA) treatment. Using methylation‐sensitive amplified fragment length polymorphism markers (MS‐AFLPs) we screened anonymous methylation changes at CCGG restriction sites throughout the genome after stress treatments and assessed the heritability of induced changes for two subsequent unexposed offspring generations. Irrespective of the initial stress treatment, a clear buildup of heritable DNA methylation variation was observed across three generations, indicating a considerable background rate of heritable epimutations. Less evidence was detected for environmental effects. Drought stress showed some evidence for accession‐specific methylation changes, but only in the exposed generation and not in their offspring. By contrast, SA treatment caused an increased rate of methylation change in offspring of treated plants. These changes were seemingly undirected resulting in increased transgenerational epigenetic variation between offspring individuals, but not in predictable epigenetic variants. While the functional consequences of these MS‐AFLP‐detected DNA methylation changes remain to be demonstrated, our study shows that (1) stress‐induced transgenerational DNA methylation modification in dandelions is genotype and context‐specific; and (2) inherited environmental DNA methylation effects are mostly undirected and not targeted to specific loci.