This revision of the classification of unicellular eukaryotes updates that of Levine et al. (1980) for the protozoa and expands it to include other protists. Whereas the previous revision was primarily to incorporate the results of ultrastructural studies, this revision incorporates results from both ultrastructural research since 1980 and molecular phylogenetic studies. We propose a scheme that is based on nameless ranked systematics. The vocabulary of the taxonomy is updated, particularly to clarify the naming of groups that have been repositioned. We recognize six clusters of eukaryotes that may represent the basic groupings similar to traditional ''kingdoms.'' The multicellular lineages emerged from within monophyletic protist lineages: animals and fungi from Opisthokonta, plants from Archaeplastida, and brown algae from Stramenopiles.

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The new higher level classification of eukaryotes with emphasis on the taxonomy of protists

A mechanism for gene conversion is proposed which overcomes many of the difficulties that any copy choice model encounters. It is suggested that along with general genetic pairing of homologous genomes at meiosis, effective pairing over short regions of the genetic material occurs at the molecular level by the separation of the strands of the DNA double helices, followed by the annealing of strands from two homologous chromatids. If the annealed region happens to span a heterozygous site, mispairing of bases will occur. Such a situation may be analogous to that in DNA which is damaged by mutagens; the same or similar repair mechanisms may operate, and these, by adjusting the base sequences in order to restore normal base pairing, would bring about gene conversion in the absence of any genetic replication. The model indicates how precise breakage and rejoining of chromatids could occur in the vicinity of the conversion, so that conversion would frequently be accompanied by the recombination of outside markers. The model also proposes that the distance between two mutant sites on a fine structure map depends not so much on the frequency of a recombinational event occurring between them, but rather on the degree of inhibition of the processes of genetic pairing by the mutants themselves. The model will explain almost all the data in a formal way, and it has the advantage over copy choice mechanisms for gene conversion in (1) being compatible with semi-conservative replication of DNA, (2) not invoking DNA synthesis during or after genetic pairing, (3) providing a molecular mechanism for close specific pairing, (4) making it unnecessary to postulate sister strand exchange or a process akin to this, (5) suggesting why rates of gene conversion in opposite directions are sometimes unequal and (6) providing an explanation of the clustering of mutant sites, a basis for map expansion and for the apparently capricious departure of fine structure maps from additivity. Although the model proposed is a general rather than a specific one, it suggests that the process of conversion and intragenic recombination is more complex than is usually believed, since it depends on several interacting factors. Nevertheless, it is hoped that the introduction of a model with this complexity will help to stimulate specific experiments, and that these will provide definitive information which would never be obtained if simpler models of conversion and intragenic recombination were believed to explain the genetic data sufficiently well.

/pdf/a-mechanism-for-gene-conversion-in-fungi-1tp9iv58rz.pdf

A mechanism for gene conversion in fungi.

The subkingdom Protozoa now inclues over 65,000 named species, of which over half are fossil and approximately 10,000 are parasitic. Among living species, this includes approximately 250 parasitic and 11,300 free-living sarcodines (of which approximately 4,600 are foraminiferids); approximately 1,8000 parasitic and 5,100 free-living flagellates; approximately 5,600 parasitic "Sporozoa" (including Apicomplexa, Microspora, Myxospora, and Ascetospora); and approximately 2,5000 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unnamed. Seven phyla of PROTOZOA are accepted in this classification--SARCOMASTIGOPHORA, LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and reporesentative genera of each are named. The present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of nex taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporatesmost of the major changes that will be made for some time, and that it will be used for many years by both protozoologist and non-protozoologists.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1550-7408.1980.tb04228.x

A Newly Revised Classification of the Protozoa

are those who consider questions in science which have no unequivocal , experimentally determined answer scarcely worth discussing. Such feeling, along with conservatism, may have been responsible for the long and almost unchallenged dominance of the system of two kingdoms-plants and animals-in the broad classification of organisms. The unchallenged position of these kingdoms has ended, however; alternative systems are being widely considered (1-18) and are appearing in many introductory biology texts (19-24). My purpose in this article is to discuss the merits of two classifications which depart from the traditional two kingdoms, the systems of Copeland (1-3) and Whittaker (4, 5). Two-Kingdom System Man is terrestrial, and he sees around him two major groups of organisms of very different adaptation to nutrition on land-the photosynthetic, rooted, higher plants, and the food-ingesting, motile, higher animals. So distinct in way of life, direction of evolution, and kind of body organization are these groups that a concept of dichotomy-plants versus animals-is almost inescapable if they are considered by themselves. The two groups became the nuclei around which concepts of the plant and animal kingdoms were developed by early naturalists. The kingdoms have been part of the formal classification of living things since Linnaeus (25). Mosses, liverworts, and macroscopic algae are clearly plants in their photo-synthetic and nonmotile way of life, and (though the photosynthetic process itself was not understood by early naturalists) these forms were grouped 150 with the higher land plants. The higher fungi on land are nonmotile, and their apparently \"rooted\" manner of growth suggested the plants. It thus seemed reasonable to assign fungi to the plant kingdom, and some students believed that they had evolved from algae. The wealth of unicellular life discovered by microscopists offered greater difficulty. Some forms were motile and ingested food, however, and were naturally regarded as one-celled animals or proto-zoans. Others were nonmotile and photosynthetic, hence one-celled plants. There remained a wide range of uni-cellular forms in which nonmotility and flagellate or pseudopodial motility, and ingestive, photosynthetic, and absorp-tive nutrition, were combined in various ways which were neither clearly plant-like nor animal-like. In a number of cases plant-like and animal-like unicells were connected by a series of closely related intergrading forms within the same major taxon. There remained also the bacteria which, though few are pho-tosynthetic and many are motile, seemed better treated as plants because of their walled cells. The plant and animal kingdoms …

https://science.sciencemag.org/content/sci/163/3863/150.full.pdf

New concepts of kingdoms of organisms

Colletotrichum - current status and future directions.

http://science.sciencemag.org/content/sci/120/3107/105.full.pdf

Ascomycete spore mutants and their use in genetic studies.

The Protostelid Genus Schizoplasmodiopsis

Aggregating cells of the cellular slime mold Fonticula alba form a volcano-shaped fruiting structure which at maturity bears its spores apically in a globose mucous mass. Numerous dictyosomes forming in the sorogenic cells are involved in the accumulation and deposition of stalk material.

https://science.sciencemag.org/content/sci/213/4507/561.full.pdf

Role of Golgi Apparatus in Sorogenesis by the Cellular Slime Mold Fonticula alba.

Sorogena stoianovitchae is an unusual ciliated protozoan with a life cycle characterized by the aggregation of individual trophic cells to form a multicellular sorogen that rises from the liquid culture medium surface by the secretion of a stalk The noncellular stalk is a tapered, longitudinally furrowed structure composed of a fibrillar matrix that is initially hydrated, but with time dehydrates, the stalk becoming thin and brittle This dehydration is of importance from the earliest stages of stalk formation since it results in the formation of the outer sheath-like region of the stalk that appears to provide much of the support of the stalk Cytochemical tests of the stalk for polysaccharides (including acidic mucopolysaccharides) and proteins are positive Proteolytic enzymes degrade the stalk Lectins specific for glucose and N-acetyl-D-glucosamine bind to the stalk Gas chromatography analysis detected the presence of fucose, glucose, glucosamine, and arabinose, as well as a variety of amino acids, predominantly glycine The cytochemical and biochemical tests, the ultrastructural data, and the behavior of the stalk material suggest that the staik is composed of a matrix of complex protein-polysaccharide molecules

The Structure and Composition of the Stalk of the Ciliated Protozoan Sorogena stoianovitchae

The genus Schizoplasmodium is a member of the Protostelia, a primitive subclass of mycetozoans. It has previously been known only from the commonly occurring type species, S. cavostelioides Olive and Stoianovitch. Two additional species of rare occurrence are described here-S. obovatum, found on bark of living trees in Florida and Uganda, and S. sechellarum, found in the Seychelles Islands and Papua New Guinea on old corn and leguminous capsules. All three members of the genus produce reticular plasmodia but lack flagellate cells. The most unusual feature of the group is the production of ballistospores that are discharged from their stalks by the development and explosion of gas bubbles. SCHIZOPLASMODIUM is a genus of the subclass Protostelia of the Eumycetozoa (Olive, 1975). It is unique in having the spores of its single-spored fruiting bodies discharged by the force of a bursting gas bubble mechanism (Fig. 1-5, 10). A single valid species, S. cavosteliolides Olive and Stoianovitch (1966a), has been recognized. The present paper describes two new species of rare occurrence and provides a key to the genus. In addition to having ballistospores, Schizoplasmodium species also produce thin reticular plasmodia that feed on yeast or bacterial cells or both. Food vacuoles containing the ingested cells may be observed within the plasmodia. However, plasmodia often appear to crawl over the food cells, partially enveloping them in groups between plasmodium and agar medium but not completely surrounding them. It is possible that some digestion may occur without complete ingestion of the cells into food vacuoles. Spores and cysts are typically plurinucleate, and each on germinating produces a single protoplast with slender filopodia that, by anastomosis, may begin to produce a reticular configuration before germination is complete. Plasmodia enlarge by fusion with each other and by growth and nuclear division unaccompanied by division of the protoplast. The reticular nature continues to be enhanced by further proliferation and anastomosis of filopodia (Fig. 9, 15). Also, smaller plasmodia may develop from larger ones by plasmotomy. In S. sechellarum single plasmodia may reach a breadth of 2.5 cm. Feeding plasmodia migrate slowly through colonies of food organisms on agar media. They usually have a distinctly reticular posterior region 'Received for publication 20 January 1975. Supported by National Science Foundation grants GB35964X and BMS-72-02392 and a grant from the BrownHazen Fund of the Research Corporation. The senior author is grateful to Dr. Ian Frost, Head of the Veterinary Division, Department of Agriculture, Mahe, Seychelles for the use of laboratory facilities. and a nearly continuous anterior area from which numerous fine filose pseudopodia extend into the food supply (Fig. 15). As the food decreases, the plasmodia may become entirely reticular. Particularly at the edge of a colony or in parts of it where the food organisms have become more or less depleted, rhizopodia, which often anastomose into reticulopodia, extend into the agar medium (Fig. 16). Protoplasmic movement within the plasmodium is generally quite active but not coordinated into the shuttle movement characteristic of most myxomycetes. Movement in a single relatively narrow strand often occurs in opposite directions simultaneously. Numerous contractile vacuoles and nuclei, each with a single centrally located nucleolus, are present (Fig. 9, 17). The nuclei constantly shift in position in the moving cytoplasm. The onset of sporulation is recognizable by the concentration of the plasmodial protoplasm into a number of small masses, which are at first connected by narrow strands that later snap apart and leave separate prespore cells on the substrate surface (Fig. 18). These develop directly into stalked fruiting bodies in the manner characteristic of the protostelids (Olive and Stoianovitch, 1966b; Olive, 1975). The entire process of sporogenesis from prespore cell to mature sporocarp requires only about one hour. Since prespore cells and mature spores contain about the same range of nuclear numbers, it is unlikely that mitosis occurs in the process. The sporocarp consists of a single spore on a slender tubular stalk and is enveloped entirely by a distinct sheath that spreads out at the base into a wrinkled supportive disc (Fig. 20, 21). The frequent irregular appearance of the stalk results from irregularities in the stalk tube and sheath. When sporocarps are placed in water or pushed over onto the agar, the stalk tube tends to become less distinct, possibly deliquescing. The sheath in

Lindsay S. Olive

Papers

Ascomycete spore mutants and their use in genetic studies.

The Protostelid Genus Schizoplasmodiopsis

Role of Golgi Apparatus in Sorogenesis by the Cellular Slime Mold Fonticula alba.

The Structure and Composition of the Stalk of the Ciliated Protozoan Sorogena stoianovitchae

The ballistosporic protostelid genus schizoplasmodium