Monera

Abstract: Drawing on documents both published and archival, this paper explains how the prokaryote-eukaryote dichotomy of the 1960s was constructed, the purposes it served, and what it implied in terms of classification and phylogeny. In doing so, I first show how the concept was attributed to Edouard Chatton and the context in which he introduced the terms. Following, I examine the context in which the terms were reintroduced into biology in 1962 by Roger Stanier and C. B. van Niel. I study the discourse over the subsequent decade to understand how the organizational dichotomy took on the form of a natural classification as the kingdom Monera or superkingdom Procaryotae. Stanier and van Niel admitted that, in regard to constructing a natural classification of bacteria, structural characteristics were no more useful than physiological properties. They repeatedly denied that bacterial phylogenetics was possible. I thus examine the great historical irony that the "prokaryote," in both its organizational and phylogenetic senses, was defined (negatively) on the basis of structure. Finally, we see how phylogenetic research based on 16S rRNA led by Carl Woese and his collaborators confronted the prokaryote concept while moving microbiology to the center of evolutionary biology.

Abstract: A system of broad classification which recognized a plant kingdom of four divisions and an animal kingdom of ten to fifteen phyla was for many years stable and standardized. Significant changes have occurred, or are now proposed. Among these, three major lines of development are discussed: a. Classification of the algae has been fundamentally revised; seven or more algal series are distinguished primarily by characteristics of cells. The phylum concept, long established in zoological classification, has been brought into botanical classification in the systems of Pascher (1931) and Tippo (1942), in which the major algal series, the Bryophyta, and the Tracheophyta are regarded as phyla. b. Many authors have advocated recognition of a kingdom of lower organisms, to mneet the difficulty of dividing these between the plant and animal kingdoms. Two major possibilities for such a third kingdom are the Protista of Haeckel (1866, 1894), essentially identified with the unicellular organisms, and the Proctoctista of Hogg (1860) and Copeland (1947, 1956), comprising the nucleate, "acellular" organisms, including protozoa, algae, and fungi. c. Study of the fungi has led to the view that these are probably derived from colorless flagellates as a line of evolution independent of true plants. The bacteria are better regarded as an ancient complex of many nutritive types, than as a group derived from the blue-green algae. In natural communities bacteria and fungi together form a major functional group (reducers) distinct from the green plants (producers) and animals (consumers). It is consequently appropriate to conceive the broad relations of the living world in terms of three modes of nutrition and directions of evolution rather than two-the photosynthetic of the green plants, the ingestive of the animals, and the absorptive of the bacteria and fungi. These three directions of evolution appear on three major levels of organization-the Monera, or bacteria and blue-green algae, which lack nuclear membranes; the Eunucleata, or unicellular organisms with nuclear membranes; and the multicellular and multinucleate higher plants, animals, and fungi. On this basis four kingdoms are here proposed: the Protista, or unicellular organisms; the Plantae, or multicellular plants; the Fungi; and the Animalia, or multicellular animals. Among the Protista the subkingdoms Monera and Eunucleata are distinguished. Among the higher organisms the less widely successful lines of evolution into the multicellular and multinucleate conditions are recognized as the subkingdoms Rhodophyta and Phaeophyta among the plants, Myxomycota among the fungi, and Parazoa and Mesozoa among the animals.

Abstract: Since schemes of classification attempt to reflect the true interrelationships between the various groups of organisms (Blackwelder, 1959; Michener, 1957; Richards et al., 1952), each new approach to the study of evolution and phylogeny necessitates a reexamination of existing systems for the purpose of perfecting them in the light of new knowledge. At the present time much dissatisfaction with the principal scheme now in vogue is being demonstrated. Copeland (1956) has made the attempt to overcome its shortcomings by proposing four kingdoms. One, which he calls Mychota, is erected for organisms such as the bacteria and blue-green algae, in which typical nuclei are wanting. A second, named the Protoctista, includes those nucleated organisms which lack the characters of both plants and animals and embraces the Protozoa, red and brown algae, and the fungi. In the third, the Plantae, is contained all the green plants, and in the fourth, the Animalia, are placed the Metazoa. Although this system is a practical one, differing from an earlier one principally in changing the name of the anucleate kingdom from Monera and in giving a somewhat broader basis to the former "Kingdom" Protista, it still fails to show interrelationships between the various groups. Smith (1950) goes even further in subdividing just the plant realm. First he proposes grouping the yellow and golden algae, together with the diatoms, into a division called the Chrysophyta. The red, brown, green, and blue-green algal groups, as well as the euglenophytes and dinophytes, secondly are each placed in a separate division. Finally, he states that these six divisions listed above represent six kingdoms, all plantlike in structure, and that the higher green plants should be placed with the green algae. As his concern is solely with pigmented forms, he makes no attempt to place the yeasts, bacteria, and other colorless organisms within his suggested framework. Many other systems (Tippo, 1942; Whittaker, 1957, 1959; Corliss, 1959; Kerkut, 1960), for one segment of the living world or another, have been advanced during the past 20 years. While none of these proposals is without merit, all fail to take into consideration newer knowledge of the organisms gained through the electron microscope or other information garnered since the basic concepts were originally advanced. Recently it has been suggested that, on the basis of the internal morphology of the cell including the ultrastructure of its parts, all living things are members of a single kingdom (Dillon, 1962). If the structure of the cell organelles might be taken to be of some significance and a phylogeny based upon these data to be of any validity, it is essential that a new outline of classification be advanced which will better reflect the relationships disclosed through that approach. And if the existing concept of the cell theory is accepted, namely that the organism's morphology and functioning are products of its cells, then cytological structure may indeed be deemed significant. For it is quite likely that the activities of cells are themselves correlated to their internal com-

Abstract: The results of comparative sequence analysis, mainly of small subunit (SSU) ribosomal (r)RNA sequences, have suggested that all of cellular life can be placed in one of three domains: the Archaea, Bacteria or Eucarya. There is some evidence that the Archaea may not be a monophyletic assemblage, but as yet this issue has not been resolved. Most of the lineages, and all of the deepest ones, in the tree based upon SSU rRNA sequences, are microbial. Traditional ideas of classification such as Whittaker's five kingdom scheme do not adequately describe life's diversity as revealed by sequence comparisons. There are many microbial groups that demonstrate much greater amounts of SSU rRNA sequence divergence than do members of the classical kingdoms, Animalia, Plantae and Fungi. The old microbial kingdoms Monera and Protista are clearly paraphyletic but as yet there is no consensus as to how they should be reorganized in taxonomic terms. New data from environmental analysis suggests that much of the microbial world is unknown. Every environment which has been analysed by molecular methods has revealed many previously unrecorded lineages. Some of these show great divergence from the sequences of cultured microorganisms suggesting that fundamentally new microbial groups remain to be isolated. The relationships of some of these new lineages may be expected to affect how the tree of life is organized into higher taxa, and to also influence which features will be recognized as synapomorphies. There is currently no objective measure whereby microbial diversity can be quantified and compared to the figures which are widely quoted for arthropods and other Metazoa. \` \`\`I tell you what'', said William, confidingly, \``let's say eggs for both of them. Then we shan't get so muddled.'' ' (from William the Pirate, Richmal Crompton, 1932)