Mucor Fresen.
The zygomycota is an artificial grouping of related basal clades comprising the subphyla Mortierellomycotina Kerst. Hoffm. et al., Mucoromycotina Benny, Kickxellomycotina Benny and Zoopagomycotina Benny (Muszewska et al. 2014). The genus Mucor is the largest within the Mucoromycotina and includes more than 50 species several of which have important economical application, including the production of enzymes, fumaric acid, fatty acid, and also antifungal agents for plants (Dexter and Cooke 1984; Alves et al. 2002; Roa Engel et al. 2008). It is characterized by fast-growing colonies, simple or branched sporangiophores without basal rhizoids, nonapophysate sporangia, and zygospores which are borne from opposed suspensors, possess a thick pigmented and ornamented zygosporangium and are seldom produced (Schipper 1978; Benny 2013). This genera has a worldwide distribution, with most species described as saprobes commonly isolated from soil, stored grains, fruits, vegetables and the excrement of herbivores (Schoenlein-Crusius et al. 2006; Jacobs and Botha 2008; Santiago et al. 2011; 2013).
According to Álvarez et al. (2011) Mucor has the greatest number of described species among Mucorales. In a series of studies, Schipper (1973, 1975, 1976, 1978) monographed this genus and described 39 species, four varieties and 11 forms. Subsequently, 17 species have been proposed (Mehrotra and Mehrotra 1978; Mirza et al. 1979; Subrahamanyam 1983; Chen and Zheng 1986; Schipper and Samson 1994; Watanabe 1994; Zalar et al. 1997; Pei 2000; Alves et al. 2002; Jacobs and Botha 2008; Hermet et al. 2012; Madden et al. 2012).
Molecular studies have shown that Mucor is polyphyletic (O’Donnell et al. 2001; Kwasna et al. 2006; Jacobs and Botha 2008; Budziszewska and Piatkowska 2010; Álvarez et al. 2011). Based on phylogenetic relationships inferred from data of LSU and ITS regions (rDNA), and morphological characteristics, Walther et al. (2013) concluded that Mucor and Backusella Hesselt. & J.J. Ellis species represents a natural group characterized by transitorily recurved sporangiophores. Therefore, all Mucor species with this feature were transferred to Backusella [B. grandis (Schipper & Samson) G.Walther & de Hoog, B. indica (Baijal & B.S. Mehrotra) G.Walther & de Hoog, B. oblongielliptica (H. Nagan., Hirahara & Seshita ex Pidopl. & Milko) G. Walther & de Hoog, B. oblongispora (Naumov) G. Walther & de Hoog, B. recurva (E.E. Butler) G. Walther & de Hoog, B. tuberculispora (Schipper) G. Walther & de Hoog, and B. variabilis (A.K. Sarbhoy) G. Walther & de Hoog]. Considering that some of the characteristics traditionally used to separate Zygorhynchus Vuill. from Mucor, such as the unequal suspensors of the zygospores and the Zygorhynchus zygospore production pattern (two suspensors originating from the same hypha) do not represent synapomorphies of the genus Zygorhynchus, and seem to be convergent characters within Mucor, Walther et al. (2013) recombined all Zygorhynchus species in Mucor as follows: M. exponens (Burgeff) G. Walther & de Hoog, M. fusiformis G. Walther & de Hoog, M. heterogamus Vuill., M. japonicus (Komin.) G. Walther & de Hoog, M. megalocarpus G. Walther & de Hoog, M. moelleri (Vuill.) Lendn. and M. multiplex (R.Y. Zheng) G. Walther & de Hoog. Nonthermophilic Rhizomucor endophyticus and Circinella rigida were reclassified as M. endophyticus (R.Y. Zheng & H. Jiang) J. Pawłowska & G. Walther and M. durus G. Walther & de Hoog, respectively.
Recently, molecular data have been used to evaluate mucoralean species (Hoffmann et al. 2013; Walther et al. 2013). During studies on the Mucorales from Brazil and Korea, taxa of Mucor that differs morphologically and molecularly from the other species was isolated and are thus described as new. The phylogenetic tree for Mucor are presented in Figs. 1, 2, 3 and 4.
Fig. 1 a Phylogenetic tree of M. amphibiorum group constructed using the ITS rDNA sequences. Mortierella parvispora was used as outgroup. b Phylogenetic tree of M. hiemalis group constructed using the ITS rDNA sequences. Mucor gigasporus was used as outgroup. Sequences are labeled with their database accession numbers. Support values are from Bayesian inference and maximum likelihood analyses (values above and below of the branches, respectively). Sequences with only ITS1 and 5.8 s rDNA are marked with *. New taxa are in blue and ex-type strains in bold.
Fig. 2 Phylogenetic tree of Mucor constructed using the large subunit (LSU) rDNA sequence data. Circinella species were used as outgroup. Sequences are labeled with their database accession numbers. Support values are from Bayesian inference and maximum likelihood analyses (values above and below the branches, respectively). The sequences obtained in this study are annotated in blue.
Fig. 3 Phylogenetic tree for Mucor koreanus EML-QT1 and EMLQT2 based on Maximum likelihood analysis of ITS rDNA sequence. Sequence of Syncephalastrum racemosum was used as outgroup. Bootstrap support values >50 % are indicated at the nodes. The bar indicates the number of substitutions per position. New taxa are in blue and ex-type strains in bold.
Fig. 4 Phylogenetic tree for Mucor koreanus sp. nov. EML-QT1 and EML-QT2 and related species based on Maximum likelihood analysis of multi-genes of 18S and 28S rDNA, actin (Actin-1) and translation elongation factor (EF-1α). Sequences of Umbelopsis nana and U. isabellina were used as outgroups. Numbers at the nodes indicate the bootstrap values (>50 %) from 1000 replications. The bar indicates the number of substitutions per position.
Species