The fungus that came in from the cold: dry rot's pre-adapted ability to invade buildings.

Many organisms benefit from being pre-adapted to niches shaped by human activity, and have successfully invaded man-made habitats. One such species is the dry rot fungus Serpula lacrymans, which has a wide distribution in buildings in temperate and boreal regions, where it decomposes coniferous construction wood. Comparative genomic analyses and growth experiments using this species and its wild relatives revealed that S. lacrymans evolved a very effective brown rot decay compared to its wild relatives, enabling an extremely rapid decay in buildings under suitable conditions. Adaptations in intracellular transport machineries promoting hyphal growth, and nutrient and water transport may explain why it is has become a successful invader of timber in houses. Further, we demonstrate that S. lacrymans has poor combative ability in our experimental setup, compared to other brown rot fungi. In sheltered indoor conditions, the dry rot fungus may have limited encounters with other wood decay fungi compared to its wild relatives. Overall, our analyses indicate that the dry rot fungus is an ecological specialist with poor combative ability against other fungi.

Phenotypic variation within a clonal lineage of Phytophthora infestans infecting both tomato and potato in Nicaragua.

Late blight caused by Phytophthora infestans (Mont.) de Bary is a constraint to both potato and tomato crops in Nicaragua. The hypothesis that the Nicaraguan population of P. infestans is genotypically and phenotypically diverse and potentially subdivided based on host association was tested. A collection of isolates was analyzed using genotypic markers (microsatellites and mitochondrial DNA haplotype) and phenotypic markers (mating type, virulence, and fungicide sensitivity). The genotypic analysis revealed no polymorphism in 121 of 132 isolates of P. infestans tested. Only the Ia haplotype and the A2 mating type were detected. Most of the tested isolates were resistant to metalaxyl. The virulence testing showed variation among isolates of P. infestans. No evidence was found of population differentiation among potato and tomato isolates of P. infestans based on the genotypic and phenotypic analysis. We conclude that the Nicaraguan population of P. infestans consists of a single clonal lineage (NI-1) which belongs to the A2 mating type and the Ia mitochondrial DNA haplotype. Moreover, based on the markers used, this population of P. infestans does not resemble the population in countries from which potato seed is imported to Nicaragua or the population in neighboring countries. The data presented here indicate that the NI-1 clonal lineage is the primary pathogen on both potato and tomato, and its success on both host species is unique in a South American context.

Microsatellite markers for the ectomycorrhizal basidiomycete Lactarius mammosus.

We report the characterization of polymorphic microsatellite markers in the ectomycorrhizal fungus Lactarius mammosus Fr. Two enrichment protocols were used to isolate microsatellite loci and polymorphism was explored within 31 sporocarps originating from a forest site in northern Sweden. We found nine variable microsatellite loci with the number of alleles per locus varying between 2 and 5, and expected heterozygosities ranging from 0 to 0.84. These loci are available for the analysis of genetic structure and gene flow in L. mammosus populations.

Population structure of the wood decay fungus Fomitopsis pinicola.

Three populations of the wood decay fungus Fomitopsis pinicola, one from each of three countries (Sweden, Russia and Lithuania), were studied by means of arbitrary primed PCR. The genetic structure of the populations was assessed by inferring the genotype of the genets by studying the haplotypes of several single-spore isolates from one sporocarp for each individual. Heterozygotes could therefore be detected with a dominant genetic marker. The amplified band and the null allele of all loci segregated in a way that was in agreement with a 50:50 ratio. Genetic analysis showed that the total population as well as the subpopulations had heterozygote frequencies in agreement with Hardy-Weinberg expectations. No population differentiation was detected in spite of large geographical distances among the populations studied. We also compared the methods of somatic incompatibility and AP-PCR in terms of their value in detecting fungal genets. This was tested for a sample of dikaryotic mycelia from Switzerland. For the tested material the two methods gave congruent results.

Genetic differentiation in Fomitopsis pinicola (Schwarts: Fr.) Karst studied by means of arbitrary primed-PCR.

Genetic variation within and among one Finnish and three Swedish populations of Fomitopsis pinicola (Schwarts: Fr.) Karst. were studied by amplifying DNA from haploid isolates originating from single spore cultures using two arbitrary primers. Analysis offspring from single fruit bodies revealed only three pairs of codominant alleles among 42 variable genetic markers, the remaining 38 segregated independently. Genetic similarity was measured in terms of Euclidean distance. Individuals in the Finnish population tended to form a distinct cluster in the principal component analysis. Variation within and among populations/regions was partitioned by Analysis of Molecular Variance-AMOVA. Within population variation accounted for 91.6% of the total genetic variation. The remaining 7.68% was accounted for by variation between the Finnish population and each of the three Swedish ones. Variation among the Swedish populations accounted for only 0.72% of the total variation. Wright's Fst was 0.17 for all four populations and 0.13 for the three Swedish populations. These relatively low values indicate that there is gene flow among all populations or that they are derived from a common ancestral population. The observed pattern of genetic variation is probably the result of effective spore dispersal and the continuous distribution of this common early successional species.

Diagnosis and treatment of acute gastrointestinal haemorrhage in a small district hospital.

Ninety-eight consecutive patients admitted to a small district hospital because of acute gastrointestinal haemorrhage have been studied. Patients with haematemesis and/or melaena were treated with antacids and tranexamic acid from the very beginning and were examined with early panendscopy. All patients were closely observed in an ordinary medical ward by a staff especially trained to handle acute gastrointestinal bleeding. Seven patients required acute surgery. The overall mortality was 4.1%. It is concluded that acute gastrointestinal haemorrhage can be successfully handled with modern diagnosis and treatment in a small hospital.