Taxonomy and phylogeny of theFusarium dimerumspecies group

Abstract

The morphospecies Fusarium dimerum, known only from its anamorph, comprises at least 12 phylogenetically distinct species. Analyses of the large subunit ribosomal DNA (LSU rDNA) show they are taxa of the Nectriaceae (Hypocreales), related to F. domesticum and form a phylogenetically distinct clade within Fusarium. Fusarium dimerum, for which no herbarium material could be located, is characterized by macroconidia with a single, median septum, according to the original description and illustration. Fusarium lunatum (= F. dimerum var. violaceum) forms similar but longer macroconidia and purple, catenate or clustered chlamydospores. Fusarium delphinoides sp. nov., F. biseptatum sp. nov., F. penzigii sp. nov., F. nectrioides comb. nov. (= F. dimerum var. nectrioides) and two unnamed Fusarium spp. produce macroconidia with mostly two or rarely three septa. The name F. dimerum, which originally was applied to a fungus from a citron, is used for a taxon including isolates causing infections in immunocompetent and immunocompromised patients. Fusarium nectrioides, F. delphinoides, F. penzigii and F. biseptatum are known from soil and dead plant substrata or rarely as agents of trauma-related eye infections of humans. Fusarium lunatum is an inhabitant of the cladodes of species within the cactus genera Opuntia and Gymnocalycium. Its unnamed closest sister taxon, which also forms 1-septate macroconidia and purple, clustered chlamydospores, was isolated from a human sinus. Fusarium delphinoides is a pathogen of the cactus-like African species Hoodia gordonii (Apocynaceae). Phylogenetic analyses based on combined sequences of the internal transcribed spacer region, LSU rDNA and partial sequences of the elongation factor 1-alpha and beta-tubulin genes identified a clade of several species producing predominately 2-septate macroconidia as the reciprocally monophyletic sister of F. dimerum. The basal sister group of the two aforementioned clades includes Fusarium lunatum and two undescribed species, all of which form 1-septate macroconidia.

Emergence of fusarioses in a university hospital in Turkey during a 20-year period

“…Tentative identification of species (complexes) was by nuclear ribosomal internal transcribed spacer (ITS) sequencing with primers ITS1 and ITS4 [21] and a part of the translation elongation factor 1-alpha (tef-1α) gene with primers EF1 and EF2 [22]. To determine the exact haplotypes within species, partial sequences of the rpb2 gene [5], the intergenic spacer region IGS [3], the large ribosomal subunit LSU, and the beta-tubulin gene [23] were obtained as needed. For sequence typing of members of the FSSC, LSU and rpb2 [2] were used in addition to ITS and tef-1α, for members of the FDSC and the FFSC, rpb2 and β-tubulin [23], and for the FOSC, IGS and rpb2 [3].…”

“…To determine the exact haplotypes within species, partial sequences of the rpb2 gene [5], the intergenic spacer region IGS [3], the large ribosomal subunit LSU, and the beta-tubulin gene [23] were obtained as needed. For sequence typing of members of the FSSC, LSU and rpb2 [2] were used in addition to ITS and tef-1α, for members of the FDSC and the FFSC, rpb2 and β-tubulin [23], and for the FOSC, IGS and rpb2 [3]. All strains could, thus, unambiguously be assigned to the species or haplotype level.…”

Widespread Occurrence of Diverse Human Pathogenic Types of the Fungus Fusarium Detected in Plumbing Drains

“…ST nomenclature for the FDSC has not been developed.) To compare the diversity of drain fusaria with the diversity of clinical fusaria, the frequencies of human pathogenic STs belonging to different Fusarium species complexes were compiled from published phylogenetic analyses (8,41,42,44,49,58) using MLST data.…”

“…All six STs have been recovered from hospital environments, including plumbing systems (2,8,38,41,43,49,58). This connection has led to the hypothesis that indoor plumbing-associated biofilms may act as hidden source of infection in hospitals and the community.…”

Accurate and Practical Identification of 20 Fusarium Species by Seven-Locus Sequence Analysis and Reverse Line Blot Hybridization, and an In Vitro Antifungal Susceptibility Study

“…As such, nomenclature systems based on multilocus sequence typing (MLST) schemes incorporating sequence analysis of 2 to 5 genetic loci have been developed to classify a number of Fusarium species complexes according to genotype or haplotype (7,9,12,15,23,24,27). This approach has further revealed the necessity of developing species and sequence type (ST) nomenclatures to designate cryptic speciation within the FSSC (2,9,20,24,27,42), F. oxysporum species complex (FOSC) (22,26,27), Gibberella (Fusarium) fujikuroi species complex (GFSC) (21,27), F. dimerum species complex (FDSC) (23,27,33), F. chlamydosporum species complex (FCSC) and F. incarnatum-F. equiseti species complex (FIESC) (25,27), F. sambucinum species complex (FSAMSC), and F. tricinctum species complex (FTSC) (27). Recently, O'Donnell et al evaluated a new 3-locus MLST scheme incorporating the partial translation elongation factor 1 alpha gene (EF-1␣), the largest subunit of the RNA polymerase gene (RPB1), and the second largest subunit of the RNA polymerase gene (RPB2) loci to identify with good discriminatory capacity 69 Fusarium species within the FCSC, FDSC, FIESC, FOSC, FSAMSC, FSSC, and GFSC (27).…”