Bacterial role in the decomposition of marine-derived material (penguin guano) in the terrestrial maritime Antarctic

Bacterial decomposition of Adélie Penguin (Pygoscelis adeliae) guano was followed during 42 days exposure in a rookery in Admiralty Bay, King George Island, South Shetland Islands, Antarctica. Bacterial abundance, both total counts (TC) determined by epifluorescence microscopy, and colony forming units (CFU) determined on nutrient media, was enhanced by an air temperature of between 7 and 11 °C, while temperatures above and below this negatively affected abundance. Optimal temperatures for guano decomposition ranged from 3 to 11 °C. Increasing wind velocity positively influenced photoautotrophic bacteria (TAC: total autotrophic bacteria count); photoautotrophs were enumerated during epifluorescence microscopy by their autofluorescence. Guano dry weight attained the lowest value of 74% of initial dry weight after 20 days in situ exposure. Changes in guano resulted from decomposition of the component fats, proteins, chitin, nitrogen and carbon, as well as of mineral recycling (Ca, P, Mg, and others). All transformations accompanied bacterial growth, with TC and CFU both attaining 10¹¹ cells g⁻¹ d wt of guano. Total bacterial biomass (TBB) increased from 594 μg C g⁻¹ dry weight in fresh guano, to 9101 μg C g⁻¹ dry weight after 42 days exposure in situ. Mean cell volume (MCV) also increased from 0.236 to 0.343 μm³. Photoautotrophic bacteria were numerically the smallest TC fraction throughout the incubation, with TAC to TC ratio ranging from 0.01 to 0.22%. Culturable bacteria abundance in guano increased dramatically from 0.28% of TC (in fresh guano) to 26% (3-h day), and 90% (42nd day) of TC. Within the total CFU population, copiotrophic bacteria were ca. two orders of magnitude more abundant than oligotrophic bacteria. Chitinolytic bacteria in guano were detected only late in the incubation; by 42 days, >40% of the initial chitin content remained. This material may comprise a significant fraction of the soil in the penguin rookery. Bacteria cultivated from the penguin guano displayed high morphophysiological diversity.     

Detection of potato spindle tuber viroid by molecular hybridization and bioassay. A large-scale comparison

Summary To assess the reliability of dot-spot hybridization assay for the Potato Spindle Tuber Viroid, more than 1000 potato samples were cross-tested by biological and hybridization methods. Both methods gave similar results with a range of cultivars. The dot-spot hybridization test was reproducible with formaldehyde-denaturated cell-sap samples stored at room temperature for over 6 months. This finding means that samples can be transported from field stations to a diagnostic laboratory and allows for cross-checking of results between laboratories. The data suggest that dot-spot hybridization is suitable for breeding and quarantine purposes.     

Two fiber genes of nearly equal lengths are a common and distinctive feature of Fowl adenovirus C members

The complete genome or the genome region containing the two fiber genes of two reference strains and one field isolate representing both serotypes of Fowl adenovirus C were sequenced. Two fiber genes were revealed in the genomes of all three isolates. Fiber-1 and fiber-2 genes of several Fowl adenovirus C isolates were sequenced as well. Both serotypes 4 and 10 have two fiber genes. The genome region containing the fiber gene was also sequenced for the reference strain of Fowl adenovirus B. Just one fiber gene was revealed in this strain. Predicted amino acid sequences were compared to already published fiber sequences of different adenovirus isolates and one amino acid substitution within fiber-2 was detected in all of the Fowl adenovirus C isolates that were isolated from chickens with hepatitis-hydropericardium syndrome in comparison to apathogenic isolates. Phylogenetic analyses provided insights about the evolution of fiber genes in avian adenoviruses and their genetic relationships.     

Response of fungal and plant communities to management-induced overstorey changes in montane forests of the Western Carpathians

The effect of forest management on biodiversity is a crucial issue for sustainable forestry and nature conservation. However, the ways in which management affects macrofungal and plant communities and diversity of mountain temperate forests still remain poorly understood. We performed a random sampling stratified by stand age and stand type on the sites of temperate montane fir–beech forests. Diversity of macrofungi and the vascular plant understorey in beech- and spruce-dominated managed stands was investigated and compared to primeval forests located in the Po?ana Biosphere Reserve, Western Carpathians. Both the vascular plant and the macrofungal communities were altered by management, and the response of the macrofungal species (especially wood-inhabiting fungi) was more pronounced in terms of species composition change. Species turnover evaluation seems to be an important tool of forest natural status assessment, because alpha diversity did not change as much as species composition. Certain species of Carpathian primeval forests were confirmed as good indicators for natural forest change; others were proposed. Species pool and mean number of species per plot were the highest in unmanaged fir–beech forests, and species diversity significantly decreased in spruce plantations. The number of species decreased significantly due to the change of canopy tree species composition only in the macrofungal communities. As an outcome for forest management, we recommend keeping mixed forests involving all natural tree species and providing at least a minimal amount of dead wood necessary for wood-inhabiting organisms and leaving some area of unmanaged natural forests within complexes of managed stands.