Identifying environmental factors affecting the microbial community composition on outdoor structural timber.

Timber wood is a building material with many positive properties. However, its susceptibility to microbial degradation is a major challenge for outdoor usage. Although many wood-degrading fungal species are known, knowledge on their prevalence and diversity causing damage to exterior structural timber is still limited. Here, we sampled 46 decaying pieces of wood from outdoor constructions in the area of Hamburg, Germany; extracted their DNA; and investigated their microbial community composition by PCR amplicon sequencing of the fungal ITS2 region and partial bacterial 16S rRNA genes. In order to establish a link between the microbial community structure and environmental factors, we analysed the influence of wood species, its C and N contents, the effect of wood-soil contact, and the importance of its immediate environment (city, forest, meadow, park, respectively). We found that fungal and bacterial community composition colonising exterior timber was similar to fungi commonly found in forest deadwood. Of all basidiomycetous sequences retrieved, some, indicative for Perenniporia meridionalis, Dacrymyces capitatus, and Dacrymyces stillatus, were more frequently associated with severe wood damage. Whilst the most important environmental factor shaping fungal and bacterial community composition was the wood species, the immediate environment was important for fungal species whilst, for the occurrence of bacterial taxa, soil contact had a high impact. No influence was tangible for variation of the C or N content. In conclusion, our study demonstrates that wood colonising fungal and bacterial communities are equally responsive in their composition to wood species, but respond differently to environmental factors. KEY POINTS: • Perenniporia meridionalis and Dacrymyces are frequently associated with wood damage • Fungal community composition on timber is affected by its surrounding environment • Bacterial community composition on structural timber is affected by soil contact.

Environmental enrichment during early rearing provokes epigenetic changes in the brain of a salmonid fish.

Environmental enrichment is used to increase structural complexity of captive rearing systems and has been shown to provoke a wide range of effects in the kept animals. Here we studied the effects of enrichment on DNA methylation patterns at the whole-genome level in the brain of rainbow trout reared in an aquaculture setting. We investigated the epigenetic effects between different types of enrichment (natural substrate vs. artificial substrate vs. barren) in three developmental stages (egg vs. alevin vs. fry) and as enrichment was discontinued at the fingerling stage by means of the Methylation-Sensitive Amplified Polymorphism (MSAP) technique. While enrichment did not affect growth in body size, we found enrichment to affected global DNA methylation in the brain at the egg and alevin stage, i.e., the period during development where the animals are in close physical contact with the substrate. At these stages, trout reared on the two substrates differed more from the control than the substrates differed from each other. Only minor differences between rearing environments were detected following emergence at the fry stage. When enrichment was discontinued during the rearing of fingerlings, no differences in DNA methylation patterns were observed between the rearing environments. Our results provide further evidence on the effects of enrichment in the captive rearing of fish and show that enrichment can even modulate epigenetic patterns. The effect on the epigenome may be causal for the previously reported effects of enrichment on gene expression, behaviour and brain development.

Metamorphosis and transition between developmental stages in European eel (Anguilla anguilla, L.) involve epigenetic changes in DNA methylation patterns.

The life history of the European eel (Anguilla anguilla, L.) is characterized by a series of metamorphoses and transitions that provoke drastic morphological changes. Most of these changes go along with the catadromous life cycle in eels, involving extensive physiologically adaptations. In this study it was investigated whether these drastic changes have an epigenetic basis by analyzing global methylation patterns in liver, gill and brain tissue from glass eels caught at the British coast as well as yellow and silver eels from River Rhine using methylation-sensitive amplified polymorphisms (MSAP). Analysis of molecular variance (AMOVA) on MSAP data derived from liver tissue revealed only minor differences in methylation patterns between glass, yellow and silver eels, reflecting uniform functioning of the liver throughout the investigated lifespan. In brain and gill tissue, however, marked differences in methylation patterns were found. Principal coordinates analysis (PCoA) revealed yellow eels being partially clustered with silver eels and a more distinct cluster of glass eels based on the methylation patterns in the brain. According to results found in the gills, glass eels were more similar to silver eels whereas yellow eels were found to be clustered separately. From these results it can be concluded that epigenetic changes in gill tissue most likely reflect and are linked with adaptation towards salt- and freshwater conditions. The observed differences in brain methylation patterns, however, might be linked to morphological and physiological changes during metamorphosis and transitions within the life history of European eels potentially affecting subsequent differential gene expression patterns required for such changes.