Determination of taxonomic resolution capacity of conventional one-dimensional SDS-polyacrylamide gel electrophoresis of whole-cell proteins using Enterobacteriaceae

The capacity of one-dimensional SDS-PAGE of whole bacterial cells to both separate and cluster taxonomic units is studied using members of Enterobacteriaceae as test material. The results show that intraspecies variation can be detected and on the other hand the degree of taxonomic divergence which still can be grouped together is determined. In addition the system has high tolerance to changes in cell culture conditions making the usage of SDS-PAGE suitable for applications where rapid and reliable bacterial identification is needed.     

Ecology of bacteriophages infecting activated sludge bacteria.

Little is known about the endemic bacteriophages of activated sludge. In this investigation 49 virus-host systems were studied by isolating co-occurring bacteria and bacteriophages from the aeration basin of a sewage treatment plant during 5 successive weeks. The phage titers were high and fluctuated during the time period. The occurrence of phage-sensitive and -resistant hosts did not depend on the presence or absence of phages. Several phage-host systems expressed variable plating efficiencies. In addition, phages with broad host ranges were observed. These results show that phages are an active part of this ecosystem and that they may exert selection pressure for phage resistance on their bacterial host populations.     

Chloroplast DNA variation inAnemone s. lato (Ranunculaceae)

Chloroplast DNA of seven species belonging toAnemone (sectt.Omalocarpus, Anemonidium, andAnemonanthea),Hepatica, andPulsatilla have been analyzed by restriction enzymes. According to the dendrogram constructed, the sections ofAnemone and the generaHepatica andPulsatilla seem to be evolutionary approximately equidistant to each others. This supports the concept that these groups should be treated on a similar taxonomic level, either as genera or subgenera.     

Diversity of endophytic fungi of single Norway spruce needles and their role as pioneer decomposers

The diversity of endophytic fungi within single symptomless Norway spruce needles is described and their possible role as pioneer decomposers after needle detachment is investigated. The majority (90%) of all 182 isolates from green intact needles were identified as Lophodermium piceae. Up to 34 isolates were obtained from single needles. Generally, all isolates within single needles had distinct randomly amplified microsatellite (RAMS) patterns. Single trees may thus contain a higher number of L. piceae individuals than the number of their needles. To investigate the ability of needle endophytes to act as pioneer decomposers, surface-sterilized needles were incubated on sterile sand inoculated with autoclaved or live spruce forest humus layer. The dry weight loss of 13-17% found in needles after a 20-week incubation did not significantly differ between the sterilized and live treatments. Hence, fungi surviving the surface sterilization of needles can act as pioneer decomposers. A considerable portion of the needles remained green during the incubation. Brown and black needles, in which the weight loss had presumably taken place, were invaded throughout by single haplotypes different from L. piceae. Instead, Tiarasporella parca, a less common needle endophyte, occurred among these invaders of brown needles. Needle endophytes of Norway spruce seem thus to have different abilities to decompose host tissues after needle cast. L. piceae is obviously not an important pioneer decomposer of Norway spruce needles. The diversity of fungal individuals drops sharply when needles start to decompose. Thus, in single needles the decomposing mycota is considerably less diverse than the endophytic mycota.     

RNA reveals a succession of active fungi during the decay of Norway spruce logs

Current knowledge of the succession of fungi in decaying wood is mostly based on fruit bodies and in vitro culture. Here, we investigated the changing community of metabolically active fungi during the decomposition of fallen Picea abies logs by directly extracting and barcode sequencing precursor rRNA. We also compared rRNA-derived amplicons of the 18S and ITS regions in 21 isolates and discuss the use of RNA as a marker of metabolically active fungi. The richness of active fungi, revealed as separated bands in DGGE, peaked in logs at an advanced stage of decay. Soft-rot fungi were common in the early stages but white- and brown-rot fungi became dominant as decay progressed. Ectomycorrhizal fungi were detected at an early stage, and they became the most abundant group in the late stages of succession. A comparison of rRNA-derived amplicons revealed that although ITS was detected in the form of precursor rRNA, introns within 18S rDNA were already spliced. As such, rRNA- and rDNA-derived amplicons would yield different profiles of active and total communities if profiling method is affected by amplicon length.     

The susceptibility of European tree species to invasive Asian pathogens: a literature based analysis

Alien invasive pathogens have caused numerous disastrous epidemics around the globe during the last two centuries. The frequency of these catastrophes has increased in parallel with the increase of international plant trade. Effective control of the risks requires understanding of factors governing vulnerability of indigenous plants. We tested whether the threat caused by alien pathogens of Asian origin is random among various tree species in Europe or whether it relates to their distribution range. A database including distribution ranges of 75 European tree species and literature-derived information on their susceptibility to invasive forest pathogens (IFPs) of Asian origin was compiled. Analysis on this database indicated that the susceptibility to Asian pathogens is significantly more common among tree species that occur only within Europe than among species with distributional ranges from Europe to Siberia (disease susceptibility percentage, DSP, 52 and 19 %, respectively). Notably, all severely attacked tree species are strictly European while tree species with distribution ranges extending from Europe to Siberia show at most only mild or moderate symptoms of Asian IFPs. Furthermore, the proportion of European broadleaf tree species susceptible to Asian IFPs is significantly higher than that of conifer species. Our results suggest that in Europe, Asian pathogens cause a higher risk to temperate and Mediterranean forests, largely composed of broadleaved species with distributional ranges restricted to Europe, than to boreal forests dominated by conifers distributed to Siberia.     

Dependence of flocculation on aggregate formation and buoyant density in Flavobacterium sp.

The protease-sensitive self-flocculation of Flavobacterium sp. strain 304 was studied by analysing genetically or biochemically obtained flocculation-deficient cells. The flocculation of this species was dependent on three separable characteristics: (a) a sufficiently high buoyant density, (b) the capability for initial aggregate formation and (c) aggregate stabilization.     

Rapid classification of bacterial strains by SDS-polyacrylamide gel electrophoresis: population dynamics of the dominant dispersed phase bacteria of activated sludge

Summary Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of total cellular proteins has been used to classify bacterial strains of the dispersed phase of activated sludge. The dominant bacterial populations are shown to be in dynamic change at species level while higher order taxons are more stable.