Extraction and PCR amplification of DNA from minute ectoparasitic fungi

New insights into the DNA extraction and PCR amplification of minute ascomycetes in the genus Laboulbenia (Pezizomycotina, Laboulbeniales)

Molecular studies of fungi within the order Laboulbeniales (Ascomycota, Pezizomycotina) have been hampered for years because of their minute size, inability to grow in axenic culture, and lack of reliable and cost-efficient DNA extraction protocols. In particular, the genus Laboulbenia is notorious for low success with DNA extraction and polymerase chain reaction (PCR) amplification. This is attributed to the presence of melanin, a molecule known to inhibit PCR, in the cells. We evaluated the efficacy of a standard single cell-based DNA extraction protocol by halving the recommended amount of reagents to reduce the cost per extraction and adding bovine serum albumin (BSA) during the multiple displacement amplification step to reverse the effect of melanin. A total of 196 extractions were made, 111 of which were successful. We found that halving the reagents used in the single cell-based extraction kit did not significantly affect the probability of successful DNA extraction. Using the halved protocol reduces cost and resource consumption. Moreover, there was no significant difference in the probability of successfully extracting DNA based on whether BSA was added or not, suggesting that the amount of melanin present in cells of the thallus has no major inhibitory effect on PCR. We generated 277 sequences from five loci, but amplification of the internal transcribed spacer region, the mitochondrial small subunit rDNA, and protein-coding genes remains challenging. The probability of successfully extracting DNA from Laboulbeniales was also impacted by specimen storage methods, with material preserved in > 95% ethanol yielding higher success rates compared to material stored in 70% ethanol and dried material. We emphasize the importance of proper preservation of material and propose the design of Laboulbeniales-specific primers to overcome the problems of primer mismatches and contaminants. Our new insights apply not only to the genus Laboulbenia; Laboulbeniales generally are understudied, and the vast majority of species remain unsequenced. New and approachable molecular developments will benefit the study of Laboulbeniales, helping to elucidate the true diversity and evolutionary relationships of these peculiar microfungi.

Five new species of Gloeandromyces (Fungi, Laboulbeniales) from tropical American bat flies (Diptera, Streblidae), revealed by morphology and phylogenetic reconstruction

This paper describes and illustrates five new species of Gloeandromyces (Ascomycota, Laboulbeniales) associated with tropical American bat flies (Diptera, Streblidae). These are Gloeandromyces cusucoensis sp. nov. from Trichobius uniformis in Costa Rica and Honduras, G. diversiformis sp. nov. from Strebla wiedemanni in Costa Rica, G. plesiosaurus sp. nov. from Trichobius yunkeri in Panama, G. pseudodickii sp. nov. from Trichobius longipes in Ecuador and Panama, and G. verbekeniae sp. nov. from Strebla galindoi in Ecuador and Panama. The description of these five species doubles the number of known species in the genus. Morphological characteristics, host association, and a three-locus (18S nuc rDNA, 28S nuc rDNA, TEF1) phylogenetic reconstruction support placement of these taxa in the genus Gloeandromyces. Three of the new species are polymorphic; they have multiple morphotypes that grow in specific positions on the host integument: G. diversiformis f. diversiformis, f. musiformis, and f. vanillicarpiformis; G. plesiosaurus f. asymmetricus and f. plesiosaurus; and G. verbekeniae f. verbekeniae and f. inflexus. Finally, a dichotomous key to all species and morphotypes is presented.

Laboulbeniomycetes: Evolution, natural history, and Thaxter's final word

Historically, thallus-forming Laboulbeniomycetes, including the orders Laboulbeniales and Herpomycetales, were set apart because of their distinctive morphology and ecology. Although some biologists correctly interpreted these arthropod ectoparasites as fungi, even ascomycetes, others thought they were worms, red algae, or members of taxa described especially for them. Speculation on the evolution of the group involving red algae, the morphology-based Floridean Hypothesis, persisted deep into the 20th century, in part because valid alternatives were not presented. Although the distinctive features of Laboulbeniales clearly set them apart from other fungi, the difficulty was in the absence of characters grouping them among the fungi. Thaxter considered the Laboulbeniales to be ascomycetes, but he avoided phylogenetic discussions involved in the Floridean Hypothesis all of his life. Eventually, developmental studies of the life history of Pyxidiophora species, hyphal perithecial ascomycetes with 2-celled ascospores, revealed characters connecting Laboulbeniales to other ascomycetes. The distinctive morphological features of Laboulbeniales (absence of mycelium, a thallus developed from 2-celled ascospores by cell divisions in several planes, arthropod parasitism) can be best understood by comparison with Pyxidiophora. The development of a 3-dimensional thallus composed of true parenchyma occurs not only in Laboulbeniales, but also in Pyxidiophora species. The life history of arthropod ectoparasitism of Laboulbeniales as well as mycoparasitism and phoretic dispersal by arthropods of Pyxidiophora species can be explained by Tranzschel's Law, originally applied to rust fungi. Molecular analyses including other arthropod-associated fungi have contributed to a better understanding of an enlarged class, Laboulbeniomycetes, which now includes a clade comprising Chantransiopsis, Tetrameronycha, and Subbaromyces. A two-locus phylogenetic tree highlights evolutionary and life history questions with regard to the placement of Herpomycetales as the first diverging lineage of the Laboulbeniomycetes. The sister group for all the Laboulbeniomycetes remains to be discovered.

Draft Genome Sequence of the Globally Distributed Cockroach-Infecting Fungus Herpomyces periplanetae Strain D. Haelew. 1187d

Herpomyces periplanetae is an obligate biotroph of Periplaneta americana, the American cockroach. Its nearly cosmopolitan distribution is shaped by its globally invasive host and the international pet trade. Here, we report the draft genome sequence of H. periplanetae, based on a thallus from P. americana collected in Cambridge, Massachusetts.

Herpomyces periplanetae is an obligate biotroph of Periplaneta americana, the American cockroach. Its nearly cosmopolitan distribution is shaped by its globally invasive host and the international pet trade. Here, we report the draft genome sequence of H. periplanetae, based on a thallus from P. americana collected in Cambridge, Massachusetts.

Bats, Bat Flies, and Fungi: A Case of Hyperparasitism

Bats are parasitized by numerous lineages of arthropods, of which bat flies (Diptera, Nycteribiidae and Streblidae) are the most conspicuous. Bat flies themselves can be parasitized by Laboulbeniales, fungal biotrophs of arthropods. This is known as hyperparasitism, a severely understudied phenomenon. Three genera of Laboulbeniales occur on bat flies: Arthrorhynchus on Nycteribiidae, Gloeandromyces and Nycteromyces on Streblidae. In this review we introduce the parasitic partners in this tripartite system and discuss their diversity, ecology, and specificity patterns, alongside some important life history traits. Furthermore, we cover recent advances in the study of the associations between bat flies and Laboulbeniales, which were neglected for decades. Among the most immediate needs for further studies are detailed tripartite field surveys. The vermin only teaze and pinch Their foes superior by an inch So, naturalists observe, a flea Has smaller fleas that on him prey; And these have smaller still to bite 'em, And so proceed ad infinitum. Jonathan Swift (On Poetry: A Rhapsody, 1733).

Bringing Laboulbeniales into the 21st century: enhanced techniques for extraction and PCR amplification of DNA from minute ectoparasitic fungi

Laboulbeniales is one of the most peculiar orders of Ascomycota. These fungi are characterized by an ectoparasitic life-style on arthropods, determinate growth, lack of an asexual stage, high species richness, and intractability to culture. The order Laboulbeniales, sister to Pyxidiophorales, has only recently been assigned a separate class, the Laboulbeniomycetes, based on very few ribosomal DNA sequences. So far, DNA isolations and PCR amplifications have proven difficult. Here, we provide details of isolation techniques and the application of commercially available kits that enable efficient and reliable genetic analyses of these fungi. We provide 43 newly generated Laboulbeniales ribosomal DNA sequences, among which are the first published sequences for species in the genera Gloeandromyces, Herpomyces, Laboulbenia, Monoicomyces, and Polyandromyces. DNA extractions were possible using from 1 to 30 thalli from hosts preserved in ethanol (70–100 %). In two cases, we successfully isolated DNA from thalli on dried insect collections. Laboulbeniales molecular systematics could be substantially enhanced through these improved methods by allowing more complete sampling of both taxa and gene regions.