Morphological observations on Absidia corymbifera and Absidia blakesleeana strains preserved under mineral oil
Macro‐ and micromorphology of 30 living subcultures of Absidia corymbifera (10 strains plus three strains of Absidia ramosa) and Absidia blakesleeana (two strains) preserved under mineral oil at room temperature for periods ranging from 3 to 44 years in The Fungal Culture Collection of Instituto Oswaldo Cruz (IOC) were observed and described by permanent mycological preparations mounted in a glycerol 10% and/or Amann lactophenol solution. Vegetative and asexual reproductive structures are illustrated by drawings made with the aid of a camera‐lucida. The study showed that the period of maintenance under mineral oil and the stress which took place during the period of storage did not affect the vegetative and asexual reproductive morphology of the Absidia strains and species studied here.
Revision of the genus Absidia (Mucorales, Zygomycetes) based on physiological, phylogenetic, and morphological characters; thermotolerant Absidia spp. form a coherent group, Mycocladiaceae fam. nov.
The genus Absidia comprises ubiquitously distributed soil fungi inhabiting different growth temperature optima ranging from 20-42 degrees C. Some of the mesophilic species are important biotechnologically in the biotransformation of steroids or as producers of rennin-like components, whereas species with higher growth temperature optima are of clinical relevance as opportunistic human pathogens. The aim of this study was to investigate the phylogenetic relationships between these species and to establish a revision of their systematics. For this purpose single and combined genealogies based on distance, MP, ML, and Bayesian analyses of aligned nucleotide sequences of the nuclear-encoded genes for actin (act) and for the 5.8S ribosomal RNA flanked by the ITS regions 1 and 2 (comprising 807 and 828 characters, respectively) of 16 Absidia species were reconstructed. The phylogenetic reconstructions suggest a trichotomy of the Absidia genus consisting of a mesophilic, a fast-growing thermotolerant, and a slowly-growing mycoparasitic Absidia group. The trichotomous phylogenetic grouping is concordant with the morphology of the zygospores, which are zygotes resulting from sexual conjugation between two compatible mating partners. Whereas the mesophilic group comprises the majority of absidiaceaeous species forming sterile hair-like, mycelial appendages on the suspensors of their zygospores, the thermotolerant group is characterised by the formation of smooth-walled zygospores, and the mycoparasitic group, namely Absidia parricida and A. zychae, by Mucor-like rough-walled zygospores. Based on the phylogenetic coherence of mesophilic and thermotolerant Absidia species, we propose that the two groups are separated into two distinct genera, Absidia for the mesophilic Absidia species resembling the Absidiaceae and Mycocladus for the thermotolerant species A. corymbifera, A. blakesleeana and A. hyalospora. Because Mycocladus is physiologically, phylogenetically, and morphologically distinct from the Absidiaceae s. str. we suggest that they are classified as a separate family, Mycocladiaceae fam. nov., which comprises the three species M. corymbifer, M. blakesleeanus and M. hyalospora.
Sexual Dimorphism in Mucorales. I. Intraspecific Reactions
Introduction In a previous paper (7) experimental evidence for a strict sexual dimorphism in Cwnninghamella has been given in some detail. The literature bearing on the question of sexuality in the Mucors is there cited, especially as it offers evidence in regard to sexual dimorphism in this group of fungi. In a still earlier publication (5) detailed tests are given for a single species of A bsidia, as well as a provisional summary of tests with other forms. The methods employed in collecting the races studied, making the tests, and tabulating the reactions have already been described (6). The purpose of the present paper is to give in a series of tables the results of testing races within species other than those already recorded. In a second paper in this issue are given the results of testing together races belonging to different species. Most of the tests recorded were made during the years i9i9I923. Unless otherwise noted, the cultures were run at laboratory temperature on our standard nutrient, no. 230, consisting of 2 per cent each of agar, dry malt, and dextrose, with o.i per cent peptone. Other nutrients used were no. 360, consisting of no. 230 Plus 0.5 per cent dried horse dung decoction; no. 362, consisting of agar with addition of 2 per cent whey powder plus i per cent dextrose; no. 388, consisting of agar with 6 per cent malt and i per cent dextrose; no. 39I, consisting of 3 per cent dextrose with i per cent dried horse dung decoction. In the tables the letters A to D are used to indicate the different strengths of sexual activity measured by the relative number of zygospores produced in the given contrasts. Each race has been given a final numerical grade, made up of the average of its reactions with the testers of opposite sex (grade A having the numerical rank 4,