Are alkalitolerant fungi of the Emericellopsis lineage (Bionectriaceae) of marine origin?

Abstract

Surveying the fungi of alkaline soils in Siberia, Trans-Baikal regions (Russia), the Aral lake (Kazakhstan), and Eastern Mongolia, we report an abundance of alkalitolerant species representing the Emericellopsis-clade within the Acremonium cluster of fungi (order Hypocreales). On an alkaline medium (pH ca. 10), 34 acremonium-like fungal strains were obtained. One of these was able to develop a sexual morph and was shown to be a new member of the genus Emericellopsis, described here as E. alkalina sp. nov. Previous studies showed two distinct ecological clades within Emericellopsis, one consisting of terrestrial isolates and one predominantly marine. Remarkably, all the isolates from our study sites show high phylogenetic similarity based on six loci (LSU and SSU rDNA, RPB2, TEF1-α, β-tub and ITS region), regardless of their provenance within a broad geographical distribution. They group within the known marine-origin species, a finding that provides a possible link to the evolution of the alkaliphilic trait in the Emericellopsis lineage. We tested the capacities of all newly isolated strains, and the few available reference ex-type cultures, to grow over wide pH ranges. The growth performance varied among the tested isolates, which showed differences in growth rate as well as in pH preference. Whereas every newly isolated strain from soda soils was extremely alkalitolerant and displayed the ability to grow over a wide range of ambient pH (range 4-11.2), reference marine-borne and terrestrial strains showed moderate and no alkalitolerance, respectively. The growth pattern of the alkalitolerant Emericellopsis isolates was unlike that of the recently described and taxonomically unrelated alkaliphilic Sodiomyces alkalinus, obtained from the same type of soils but which showed a narrower preference towards high pH.

Keywords: Acremonium; Emericellopsis; alkaline soils; molecular phylogeny; pH tolerance; soda soils.

Fig. 1.

Phylogenetic reconstruction of Acremonium species in Bionectriaceae as inferred from the partial LSU gene sequences. New isolates from the soda soils are marked with colour boxes. Clade delineation is from Summerbell et al. (2011). Bayesian topology with the ML/PP support values over each node is displayed. Thickened branches indicate strong combined support (ML>90, PP>0.94). T – type/ex-type strains.

Fig. 2.

Four-gene phylogeny of the new alkalitolerant isolates within the Emericellopsis-clade based on partial sequences for ITS (including 5.8S rDNA), β-tub, RPB2 and TEF1-α genes. All strains studied are in bold. Bayesian topology is displayed with the ML/PP support values over each node. Thickened branches indicate strong combined support (ML>90, PP>0.94). T – type/ex-type strains. Representative strains from each delineated clade are shown on AA medium plates (11-d-old).

Fig. 3.

Growth patterns of the representative strains at pH 4 through 11.2 based on MYA medium. A. strains from the T, M and soda soils clades within the Emericellopsis lineage including intermediate Acremonium sp. isolates A105 and A111; B. isolated alkalitolerant strains from the sister clade of the Emericellopsis lineage.

Fig. 4.

Emericellopsis alkalina (CBS 127350). A–E. 11-d-old (28 °C, dark regime, 9 cm Petri dish) colony on alkaline agar (AA), Czapek agar (CZ), potato dextrose agar (PDA), oatmeal agar (OA), malt yeast extract agar (MYA). F–G. Hyphal bundles with acremonium-like conidiation (SEM). H. Conidiogeous cells emerging from single hypha (SEM). I. Conidial head on a single conidiogenous cell emerging from the hyphal bundle (SEM). J. Matured conidial heads (SEM). K. Single conidiogenous cell with young conidial head (SEM). L. Conidial head (LM). M. Conidia (SEM). Bars F–G = 20 μm; H, J and L = 10 μm; I and K = 5 μm; and M = 2 μm.

Fig. 5.

Emericellopsis alkalina (CBS 127350). A. Cleistothecia (SEM). B. Cleistothecium surrounded by the asexual sporulation (SEM). C. Open cleistothecium (SEM). D. Magnified view on the multilayered peridium (SEM). E. Open cleistothecium (LM). F. Young asci (LM). G. Young asci (SEM). H–J. Lysing asci (SEM). K–M. Ascospores with alar appendages (SEM). Bars: A and E = 100 μm; B = 20 μm; C = 10 μm; D, F–H, and J = 5 μm; I and M = 2 μm; and K–L = 1 μm.