Aquatic fungi of twelve Augustów Lakes with reference to the chemistry of the environment

Seventy five species of fungi were found in tbe Augustów Lakes. The following fungi unknown from Poland were rocorded: <i>Rhizophydium pollinis-pini, Chytriomyces cosmarii, C. poculatus, Lageaidium humanum, Aphanomyces astaci, Leptolegeniella piligena, Achlya klebsiana, Cladolegnia unispora, Zoophagus pectosporus, Rhodosporidium toruloides</i> and <i>Vargamyces aguaticus</i>.

Aquatic fungi and straminipilous organisms in lakes of the Augustowska Primeval Forest, Poland

We analyzed species composition of aquatic fungi and straminipilous organisms in six lakes located within the Augustowska Primeval Forest, Poland. Mycological observations conducted in the spring and autumn seasons together with hydrochemical analysis in the 2010–2012 revealed the presence of 44 species (10 aquatic fungi and 34 straminipilous organisms). Among the taxa detected, there were some potential pathogens of economically valuable fish species and spawn, including Achlya americana, Ac. polyandra, Saprolegnia ferax and S. parasitica. Some of the species were crustacean pathogens, such as Lagenidium giganteum, Myzocytium microsporum and M. zoophthorum. There were also some common human pathogens Aspergillus niger and Candida tropicalis. Some species, such as Achlya klebsiana, Ac. prolifera, Nowakowskiella elegans, N. macrospora, Pythium debaryanum, Py. inflatum, Rhizophlyctis rosea and Saprolegnia litoralis were common phytosaprobionts.The largest number of species of fungi and straminipilous organisms was identified in Lake Sajenek (22), the fewest in Lake Białe (12).The quantitative composition and qualitative differentiation of mycobiota were influenced by the content of biogenic compounds and the amount of organic substance. The elevated levels of these parameters (Lake Sajenek) stimulated the growth of fungi and straminipilous organisms, whereas very low concentrations of biogenic compounds and a small amount of organic matter (Lake Białe) had an inhibitory effect.Statistical analysis of the results was conducted to determine the correlations between the number of fungal and straminipilous species and the hydrochemical parameters, i.e. water temperature, the level of nitrogen compounds (nitrate nitrogen, ammonium nitrogen), calcium carbohydrate, magnesium carbohydrate, water oxidizability and the content of dry residue, dissolved substances and suspension.

Evolutionary stability of mitochondrial DNA organization in Achlya

A physical map of the mtDNA (mitochondrial DNA) of Achlya klebsiana has been constructed. The molecule is circular and has a size of 50.7 ± 1.3 kilobases (kb). A large portion of genome exists in the form of an inverted repeat region, each copy being from 9.74 to 10.92 kb in length. Part of the repeat region is homologous to the yeast mitochondrial 21S rRNA gene. Two isomers of the molecule are present owing to a flip–flop rearrangement of the unique regions. Since no restriction-site differences have been detected between the two repeat regions, it is likely that the inverted repeat condition promotes continual sequence conversion, thus preserving the evolutionary advantages of gene duplication. The physical map of A. klebsiana mtDNA was compared with that of Achlya ambisexualis E-87 and it was found that the inverted repeat regions, as well as a 7-kb unique region adjacent to one of the repeat regions, were highly conserved with respect to restriction-site spacing.

Meiosis and mitosis in Saprolegniaceae

The nuclei in hyphae, oospores, and gametangia of Achlya klebsiana and Saprolegnia ferax were examined by light microscopy after stain fixation with acetoorcein. It was found that the vegetative phase is diploid and that meiosis is not zygotic but is gametic in these organisms. The nuclear divisions in hyphae and germinating oospores were similar and were classically mitotic.