The linear mitochondrial genome of the quarantine chytrid Synchytrium endobioticum; insights into the evolution and recent history of an obligate biotrophic plant pathogen
Vossenberg, Bart van de; Brankovics, Balázs ; Nguyen, Hai D.T. ; Gent-Pelzer, Marga van; Smith, Donna S. ; Dadej, K. ; Przetakiewicz, J. ; Kreuze, Jan ; Boerma, M. ; Leeuwen, Gerard C.M. van; Lévesque, C.A. ; Lee, Theo van der - \ 2018
Wageningen University and Research
Mitochondrial haplotypes - Pest introduction - Population dynamics - Fungal communities - Pathotype formulation - Chytridiomycota
Chytridiomycota species (chytrids) belong to a basal lineage in the fungal kingdom. Inhabiting terrestrial and aquatic environments, most are free-living saprophytes but several species cause important diseases: e.g. Batrachochytrium dendrobatidis, responsible for worldwide amphibian decline; and Synchytrium endobioticum, causing potato wart disease. S. endobioticum has an obligate biotrophic lifestyle and isolates can be further characterized as pathotypes based on their virulence on a differential set of potato cultivars. Quarantine measures have been implemented globally to control the disease and prevent its spread. We used a comparative approach using chytrid mitogenomes to determine taxonomical relationships and to gain insights into the evolution and recent history of introductions of this plant pathogen. Results We assembled and annotated the complete mitochondrial genome of 30 S. endobioticum isolates and generated mitochondrial genomes for five additional chytrid species. The mitochondrial genome of S. endobioticum is linear with terminal inverted repeats which was validated by tailing and PCR amplifying the telomeric ends. Surprisingly, no conservation in organisation and orientation of mitochondrial genes was observed among the Chytridiomycota except for S. endobioticum and its sister species Synchytrium microbalum. However, the mitochondrial genome of S. microbalum is circular and comprises only a third of the 72.9 Kbp found for S. endobioticum suggesting recent linearization and expansion. Four mitochondrial lineages were identified in the S. endobioticum mitochondrial genomes. Several pathotypes occur in different lineages, suggesting that these have emerged independently. In addition, variations for polymorphic sites in the mitochondrial genome of individual isolates were observed demonstrating that S. endobioticum isolates represent a community of different genotypes. Such communities were shown to be complex and stable over time, but we also demonstrate that the use of semi-resistant potato cultivars triggers a rapid shift in the mitochondrial haplotype associated with increased virulence. Conclusions Mitochondrial genomic variation shows that S. endobioticum has been introduced into Europe multiple times, that several pathotypes emerged multiple times, and that isolates represent communities of different genotypes. Our study represents the most comprehensive dataset of chytrid mitogenomes, which provides new insights into the extraordinary dynamics and evolution of mitochondrial genomes involving linearization, expansion and reshuffling.
Influence of salinity on fungal communities in a submerged fixed bed bioreactor for wastewater treatment
Cortés-Lorenzo, C. ; González-Martínez, A. ; Smidt, H. ; González-López, J. ; Rodelas, B. - \ 2016
Chemical Engineering Journal 285 (2016). - ISSN 1385-8947 - p. 562 - 572.
Fungal communities - Pyrosequencing - Saline wastewater - Submerged fixed bed bioreactor - Wastewater treatment
Salinity is known to influence the performance of biological wastewater treatment plants. While its impact on bacterial communities has been thoroughly studied, its influence on fungal communities has been largely overlooked. To address this knowledge gap, we assessed the effect of saline influents (0, 3.7, 24.1 and 44.1. g. NaCl/L) on the community structure and diversity of fungi in a submerged fixed bed bioreactor (SFBBR). For this purpose, denaturing gradient gel electrophoresis (DGGE) and 454-pyrosequencing of PCR-amplified fungal 18S rRNA gene fragments and ITS regions, respectively, were used. Significant differences in the fungal community structure were found in relation to the NaCl concentration. Fungal diversity increased as salinity increased to a concentration up to 24.1. g. NaCl/L, but was significantly reduced at 44.1. g. NaCl/L. Basidiomycota dominated the fungal community in the absence of NaCl but decreased in relative abundance with increasing salinity, being replaced progressively by Ascomycota.