Isolation and Biochemical Characterization of Six Anaerobic Fungal Strains from Zoo Animal Feces

Abstract

Anaerobic fungi are prime candidates for the conversion of agricultural waste products to biofuels. Despite the increasing interest in these organisms, their growth requirements and metabolism remain largely unknown. The isolation of five strains of anaerobic fungi and their identification as Neocallimastix cameroonii, Caecomyces spec., Orpinomyces joyonii, Pecoramyces ruminantium, and Khoyollomyces ramosus, is described. The phylogeny supports the reassignment of Neocallimastix californiae and Neocallimastix lanati to Neocallimastix cameroonii and points towards the redesignation of Cyllamyces as a species of Caecomyces. All isolated strains including strain A252, which was described previously as Aestipascuomyces dubliciliberans, were further grown on different carbon sources and the produced metabolites were analyzed; hydrogen, acetate, formate, lactate, and succinate were the main products. Orpinomyces joyonii was lacking succinate production and Khoyollomyces ramosus was not able to produce lactate under the studied conditions. The results further suggested a sequential production of metabolites with a preference for hydrogen, acetate, and formate. By comparing fungal growth on monosaccharides or on the straw, a higher hydrogen production was noticed on the latter. Possible reactions to elevated sugar concentrations by anaerobic fungi are discussed.

Phylogenomic analysis of the Neocallimastigomycota: Proposal of Caecomycetaceae fam. nov., Piromycetaceae fam. nov., and emended description of the families Neocallimastigaceae and Anaeromycetaceae

“…Similarities in specific microscopic traits (zoospore flagellation, thallus development, and rhizoidal growth patterns) across genera have been identified; and the significance of using such traits for proposing higher order relationship has been debated [4][5][6]. As well, phylogenetic analysis using two ribosomal loci: the internal transcribed spacer region 1 (ITS1) and D1/D2 region of the large ribosomal subunit (D1/D2 LSU) has yielded multiple statistically-supported supra-genus groupings, although such topologies were often dependent on the locus examined, region amplified, taxa included in the analysis, and tree-building algorithm employed [7][8][9]. Therefore, while phenotypic and phylogenetic analyses suggest the existence of supragenus relationships within the Neocallimastigomycota, the exact nature of such groupings is yet unclear.…”

“…The clade is circumscribed by phylogenomic analysis, AAI values, and confirmed by LSU and RPB1 phylogenetic analyses, as well as morphological characteristics. The emended family encompasses the genera Neocallimastix(Braune 1913 [61],Vavra and Joyon 1966[62],Heath et al 1983) [22], Orpinomyces(Breton et al 1989, Barr et al 1989 [70, 71], Pecramyces (Hanafy et al 2017)[32], Feramyces [33],Ghazallomyces (Hanafy et al 2020)[5], and Aestipascuomyces (Stabel et al 2020)[8].Type genus: Neocallimastix Braune 1913 [61], Vavra and Joyon 1966 [62], Heath et al 1983, [22]. Mycobank ID: MB25486.…”

Taxonomy of the anaerobic gut fungi (Neocallimastigomycota): a review of classification criteria and description of current taxa

“…In addition to its phylogenetic distinction from N. frontalis (Fig. 6b-c) [38,101]. The species is characterized by bifurcated rhizoidal system at the base of sporangia (Fig.…”

“…Occurrence. Isolates belonging to the genus Pecoramyces have been isolated from faecal samples of cow and sheep [12,35], goat rumen [123,124], oryx [28,101], and nilgiri tahr (Nilgiritragus hylocrius) faeces. Culture-independent diversity surveys suggest a widespread distribution pattern and a preference to foregut fermenters [35], although occurrence in hindgut samples has also been observed [28] as an occasional minor fraction of the community.…”

“…Phylogenetic analyses using ITS1 and D1/D2 LSU loci often provide conflicting tree topologies. For example [37] and [101] place Cyllamyces as an internal node within the broader Caecomyces in ITS1 [37], and D1/D2 LSU [37,101] phylogenetic trees, respectively. Such pattern has led to suggestions of either splitting the genus Caecomyces into two genera [66], or reassigning Cyllamyces isolates as members of the genus Caecomyces.…”