RHIZOMUCOR (Lucet & Cost.) Wehmer ex Vuill., 1931 (Les Champignons parasites et les mycoses de l’hommes, p.19); 7 spp + 2 var. (Schipper, 1978—monograph).
Mucor Micheli ex L.: Fr. sect. Rhizomucor Lucet & Cost., 1899 (Compt. Rend. Hebd. Séances Acad. Sci 129:1033; fide Schipper, 1978).
Mucor Micheli ex L.: Fr. subgen. Rhizomucor (Lucet & Cost.) Sacc. & Syd. 1902 (In Saccardo, Syll. Fung. 16:385; fide Schipper, 1978).
Rhizomucor (Lucet & Cost.) Wehmer, 1907 (In Lafar, Handb. Techn. Mykol. 4:459; fide Schipper, 1978).

Rhizomucor consists of Mucor -like fungi that produce nonapophysate sporangia and branched sporangiophores but unlike Mucor they form rhizoids. Zygospores have an ornamented and pigmented zygosporangial wall, and they are formed between opposed, more or less equal suspensors that are not appendged. Mesophilic and thermophilic taxa are included in Rhizomucor.

Type species: R. pusillus

Species of Rhizomucor:
R. endophyticus Zheng & Jiang, 1995 (Mycotaxon 56:456).
R. meihei (Conney & Emerson) Schipper, 1978 (Studies in Mycology 17:58).
R. nainitalensis Joshi, 1982 (Sydowia 35:100).
R. pakistanicus Qureshi & Mirza, 1979 (in Mirza, Khan, Begum & Shagufta, Mucorales of Pakistan, p. 100), and later described by Qureshi & Mirza, 1983 (Biologia 29:343).
R. pusillus (Lindt) Schipper, 1978 (Studies in Mycology 17:54).
R. tauricus (Mil’ko & Schkurenko) Schipper, 1978 (Studies in Mycology 17:62).
R. variabilis var. variabilis Zheng & G.-q. Chen, 1991 (Mycosystema 4:47).
R. variabilis var. regularior Zheng & G.-q. Chen, 1993 (Mycosystema 6:2).

Rhizomucor, as monographed by Schipper (1978), contains three species [R. miehei, R. pusillus, R. tauricus] that are thermophilc. Two additional thermophilc species, R. nainitalensis (Joshi 1982), R. pakistanicus (Mirza et al., 1979; Qureshi and Mirza, 1983), have been described. Recently, two species were described that are mesophilic, R. endophyticus (Zheng and Jiang, 1995) and R. variabilis (with two varieties: R. variabilis var. regularior and R. variabilis var. variabilis (Zheng and Chen, 1991, 1993). These latter species are either endophytes of wheat (R. endophyticus) or the cause of mucormycosis in humans (both varieties of R. variabilis).

Voigt et al. (1999) have shown that Rhizomucor is polyphyletic, with the thermophilic taxa, R. pusillus and R. miehei, being in the same clade with Syncephalastrum racemosum and the mesophilic R. variabilis being in the clade with some Mucor spp. Recent research has questioned the validity of R. tauricus (Vágvölgyi et al. 1999); these workers believe that it is an unusual isolate of R. pusillus. Rhizomucor miehei and R. pusillus are recognized as distinct species (Vastag et al., 1998, 2000) using carbon and nitrogen source utilization and isoenzymes, and RAPD analysis. Species of Rhizomucor are either homothallic (R. endophyticus, R. miehei, R. nainintalensis) or heterothallic or presumably heterothallic (R. pakistanicus, R. variabilis) but one species (R. pusillus) is known to have both heterothallic and homothallic strains (Schipper 1978).

Joshi, M. C. 1982. A new species of Rhizomucor from India. Sydowia 35:100-103.

Mirza, J. H., S. M. Khan, S. Begum, and S. Shagufta. 1979. Mucorales of Pakistan. University of Agriculture, Faisalabad, Pakistan. 183 p.

Qureshi, M. S. A., and J. H. Mirza. 1983. Rhizomucor pakistanicus Qureshi & Mirza sp. nov. Biologia 29:343-344.

Schipper, M.A.A. 1978. On the genera Rhizomucor and Parasitella. Studies Mycol. (Baarn) 17:52-71.

Vágvölgyi, C., M. Vastag, K. Ács, and T. Papp. 1999. Rhizomucor tauricus: a questionable species of the genus. Mycol. Res. 103:1318-1322.

Vastag, M., T. Papp, Z. Kosza, and C. Vágvölgyi. 1998. Differentiation of Rhizomucor species by carbon source utilization and isoenzyme analysis. J. Clin. Microbiol. 36:2153-2156.

Vastag, M., T. Papp, Z. Kosza, and C. Vágvölgyi.. 2000. Intraspecific variation in two species of Rhizomucor assed by random amplified polymorphic DNA analysis. J. Basic Micorbiol. 40:269-277.

Voigt, K., E. Cigelnik, and K. O’Donnell. 1999. Phylogeny and PCR identification of clinically important Zygomycetes based on nuclear ribosomal-DNA sequence data. J. Clin. Microbiol. 37:3957-3964.

Zheng, R.-y., and G.-q. Chen. 1991. A non-thermophilic Rhizomucor causing human primary cutaneous mucormycosis. Mycosystema 4:45-57.

Zheng, R.-y., and G.-q. Chen. 1993. Another non-thermophilic Rhizomucor causing human primary cutaneous mucormycosis. Mycosystema 6:1-11.

Zheng, R.-y., and H. Jiang. 1995. Rhizomucor endophyticus sp. nov., an endophytic Zygomycetes from higher plants. Mycotaxon 56:455-466.

Updated Mar 13, 2005