Abstract
BackgroundWallemia ichthyophaga is a highly specialized basidiomycetous fungus. It is one of the most halophilic fungi ever described, only able to grow at low water activity. This specialization is thought to explain why it is only rarely isolated from nature.ResultsGenomes of 21 W. ichthyophaga strains were sequenced with PE150 reads on BGISEQ500 platform. The genomes shared high similarity with the reference genome of the species, they were all smaller than 10 Mbp and had a low number of predicted genes. Groups of strains isolated in the same location encompassed clones as well as very divergent strains. There was little concordance between phylogenies of predicted genes. Linkage disequilibrium of pairs of polymorphic loci decayed relatively quickly as a function of distance between the loci (LD decay distance 1270 bp). For the first time a putative mating-type locus was identified in the genomes of W. ichthyophaga.ConclusionBased on the comparison of W. ichthyophaga genomes it appears that some phylogenetic lineages of the species can persist in the same location over at least several years. Apart from this, the differences between the strains do not reflect the isolation habitat or geographic location. Together with results supporting the existence of (sexual) recombination in W. ichthyophaga, the presented results indicate that strains of W. ichthyophaga can form a single recombining population even between different habitats and over large geographical distances.
Highlights
Microbiological research of hypersaline environments has traditionally focused on prokaryotes and the alga Dunaliella salina (Zajc et al, 2017)
Most of the currently known strains of W. ichthyophaga were sequenced (Table 1), including isolates from sea-water-related hypersaline environments
When the genome of W. ichthyophaga was first sequenced, it was found to differ from other basidiomycetes in several ways, confirming the isolated phylogenetic position of the subphylum Wallemiomycotina
Summary
Microbiological research of hypersaline environments has traditionally focused on prokaryotes and the alga Dunaliella salina (Zajc et al, 2017). In the last two decades it has become clear that certain fungal species form an integral part of microbial communities in different hypersaline environments around the world (Zajc et al, 2017) Even though these species grow at salinities exceeding 2.9M NaCl, most of them grow in normal microbiological media with no Wallemia ichthyophaga Population Genomics added salt (i.e., they are halotolerant and not halophilic), unlike many prokaryotes from hypersaline environments, which are typically halophilic (Gostincar et al, 2015). Wallemia ichthyophaga is a highly specialized basidiomycetous fungus It is one of the most halophilic fungi ever described, only able to grow at low water activity. This specialization is thought to explain why it is only rarely isolated from nature
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