Saksenaeaceae
Overview
When originally described, the family Saksenaeaceae (Ellis and Hesseltine, 1974) included two monotypic genera, Saksenaea vasiformis Saksena (1953) and Echinosporangium transversale Malloch (1967). Zygospores have not been found in either species. Ellis and Hesseltine (1974) admitted an uncertainty regarding a close relationship of Echinosporangium and Saksenaea and justified their placement of the two genera in a single family “…because neither can possibly be placed in the recognized families of Mucorales as they currently exist.” Seven reasons were given in support of grouping them together, but all of them except one “the anomalus type of sporangia”, could apply to many other Mucorales. The columellate sporangia of S. vasiformis vs. the acolumellate sporangia of E. transversale were not stressed as an important feature separating the two taxa; Echinosporangium (renamed Lobosporangium M. Blackwell & Benny — Benny and Blackwell, 2004) is currently a member of the Mortierellaceae (Mortierellales) whereas here Saksenaea is in the Saksenaeaceae (Mucorales).
Apophysomyces, Radiomyces and Saksenaea, are in clade with good support (85% BP — O’Donnell et al., 2001; 92% BP-Voigt and Olsson, 2008) but Radiomyces is not being included in the Saksenaeaceae, with Apophysomyces and Saksenaea, because of the strong support (100% BP) for the latter family.
Radiomyces has an 83% BP (O’Donnell et al., 2001) and a 92% BP (neighbor joining) and 69% (strict consensus) according to Voigt and Olsson, 2008). Radiomyces will be the only genus included in the Radiomycetaceae here because of the 100% BP for the Apophysomyces — Saksenaea clade, it is easy to grow and sporulate in culture (Benny and Benjamin, 1991) and it has not been reported to cause mucormycosis in nature. Radiomyces, however, can be the causative agent of mycomycosis in laboratory mice (Kitz et al., 1980). Apophysomyces and Saksenaea, however, are notoriously difficult to get to sporulate in culture (Ellis and Ajello, 1982; Padhyay and Ajello, 1988). Saksenaeaceae is not recognized by Cannon and Kirk (2007) and Kirk et al. (2008) but it is considered a synonym of Radiomycetaceae in both references.
Saksenaea vasiformis S.B. Saksena and Apophysomyces elegans P.C. Misra, K.J. Srivast. & Lata have been isolated from soil and are reported to cause cases of human zygomycosis (Ajello et al., 1976; Ellis and Ajello, 1982; Ribes et al., 2000). Rice also has been a source of S. vasiformis in India (Pillai and Ahmed, 1993). Alvarez et al. (2010) described three new species of Apophysomyces, A. ossiformis Alvarez, Stchigel, Cano, D.A. Sutton & Guarro, A. trapeziformis Alvarez, Stchigel, Cano, D.A. Sutton & Guarro and A. variabilis Alvarez, Stchigel, Cano, D.A. Sutton & Guarro. The new species of Apophysomyces all contained clinical isolates whereas the cultures of the type species, which included the type, A. elegans, originated from soil collected in India; no clinical isolates were available (Alvarez et al., 2010).
Classification
Saksenaeaceae Hesseltine & Ellis, 1974 (In Ellis and Hesseltine, Mycologia 66: 87).
= Saksenaeaceae Hesseltine & Ellis, 1973 (Sparrow, and Sussman (Eds.). The Fungi 4B, p. 202 (nomen nudum, without a Latin diagnosis; Art. 36.1 of the ICBN, McNeill et al., 2006)].
Mycelium abundant, generally coenocytic, fast growing, branched, aerial mycelium floccose. Sporangia apophysate, columellate, multispored, obpiriform with a deliquencescent wall or flasked-shaped, with a long neck, which deliquesces at the tip, formed singly or in pairs on a short, lateral, hyphal branch, subtended by a branched rhizoid.
Type genus: Saksenaea.
Synopsis of Genera
APOPHYSOMYCES Misra, 1979 (in Misra, Srivasatava and Lata, Mycotaxon 8: 377); 4 spp. (Misra et al. 1979 — illus.; Alvarez et al., 2010 — Illus. [three new species proposed]) (a synonym of Absidia according to O’Donnell, 1979; a human pathogen according to Ellis and Ajello 1982 [also report a method to induce sporulation in Apophysomyces]; Padhyay and Ajello, 1988 — technique for inducing sporulation in Apophysomyces and Saksenaea; Kimura et al., 1999 — review of mucormycosis caused by Apophysomyces. Apophysomyces has been isolated from soil in India and Nepal (Misra et al., 1979; Mikawa, 1988). New species proposed and it was discovered that the type species, A. elegans, is not pathogenic (Alvarez et al., 2010).
SAKSENAEA Saksena, 1953 (Mycologia 45: 434); 1 sp. (Saksena, 1953-ILLUS.; Ajello et al., 1976-illus. and first report as a human pathogen; Ellis and Ajello, 1982 — technique for inducing sporulation in Saksenaea; Padhyay and Ajello, 1988 — technique for inducing sporulation in Apophysomyces and Saksenaea; Vega et al., 2006 – review of mucormycosis caused by Saksenaea. Saksenaea vasiformis has been isolated from soil collected in Ethiopica, Honduras, India, Panama, and the United States — Saksena, 1953; Farrow, 1954; Hodges, 1962; Goos, 1963; Chien et al., 1992, and rice in India — Pillai and Ahmed, 1993).
Genera Not Accepted Here but Included in Saksenaeaceae by Some Authors
[Echinosporangium, see Lobosporangium Mortierellaceae (Mucorales)].
Bibliography
Alvarez, E., A.M. Stchigel, J. Cano, D.A. Sutton, A.W. Fothergill, J. Chander, V.Salas, M.G. Rinaldi, and J.Guarro. 2010. Molecular phylogenetic diversity of the emerging mucoralean fungus Apophysomyces: Proposal of three new species. Revista Iberoamericana de Micologia 27:80-89.
Ajello, L., D.F. Dean, and R.S. Irwin. 1976. The zygomycete Saksenaea vasiformis as a pathogen of humans with a critical review of the etiology of zygomycosis. Mycologia 68:52-62.
Benny, G.L., and R.K. Benjamin. 1991 [1992]. The Radiomycetaceae (Mycorales; Zygomycetes). III. A new species of Radiomyces, and cladistic analysis and taxonomy of the family; with a discussion of the evolutionary ordinal relationships in Zygomycotina. Mycologia 83: 713-735.
Benny, G.L., and M. Blackwell. 2004. Lobosporangium, a new name for Echinosporangium Malloch, and Gamsiella, a new genus for Mortierella multidivaricata. Mycologia 96:143-149.
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Ellis, J.J., and L. Ajello. 1982. An unusual source for Apophysomyces elegans and a method for stimulating sporulation of Saksenaea vasiformis. Mycologia 74:144-145.
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Misra, P.C., K.J. Srivastava, and K. Lata. 1979. Apophysomyces, a new genus of the Mucorales. Mycotaxon 8:377-382.
O’Donnell, K.L. 1979. Zygomycetes in culture. Palfrey Contributions in Botany. No. 2. Department of Botany, University of Georgia, Athens, Georgia. 257 p.
O’Donnell, K., F.M. Lutzoni, T.J. Ward, and G.L. Benny. 2001. Evolutionary relationships among mucoralean fungi (Zygomycota): Evidence for family polyphyly on a large scale. Mycologia 93: 286-296.
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Saksena, S. B. 1953. A new genus of the Mucorales. Mycologia 45: 426-436.
Vega, W., M. Orellana, L. Zaror, J. Gené, and J. Guarro. 2006. Saksenaea vasiformis infections: case report and literature review. Mycopathologia 162:289-294.
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Updated Jun 05, 2010