The Morphology and Cytology of Myxococcus xanthus , N. Sp

Abstract

Knaysi (1938) states that there are three current points of view relative to the presence and nature of the bacterial nucleus. One group of investigators holds that the bacterial cell contains no nucleus. Knaysi argues, however, that the fact that a nucleus has not been seen is no indication that it does not exist. A second group maintains that nuclear material is present but in a highly dispersed condition and is therefore not easily seen. The third group takes the stand that the presence of a nucleus is logical, and is indicated by granular bodies often noted within the bacterial cell. These bodies are frequently observed to behave both functionally and chemically as nuclei are supposed to behave. In general, this latter view, that a more or less definite nucleus does exist, at least during certain stages of the life cycle of the bacterial cell, seems to be favored by many investigators today. Stoughton (1929) observed the presence of stainable bodies in the cells of Bacterium malvacearum. Just before cell division occurred these bodies split, the halves migrating toward opposite ends of the cell, and finally were included in the new daughter cells. The dye reactions of these intracellular bodies were typically nuclear, and the author concluded that they should be considered as nuclei. Much of the work published by the Hollandes (1930, 1932) favors the theory of a compact nucleus. Lindegren and Mellon (1932) described a type of reduction-division that took place

The Formation and Germination of Microcysts in Myxococcus xanthus

“…Descriptions of the germination process have not always agreed. Various accounts have invoked the formation of germ tubes (Thaxter, 1897; Beebe, 1941 ;Loebeck & Ordal, 1957), siniple elongation (Quehl, 1906;Klieneberger-Nobel, 1947) and elongation preceded by the casting off of a mucoid shcath (Krzemieniewslta, 1930;Stanier, 1942;Grace, 1951). As a prelude to a physiological investigation of these processes, we felt that an unequivocal demonstration of the morphological sequence of events in microcyst formation and germination would be invaluable.…”

MICROCYST OF MYXOCOCCUS XANTHUS

“…Hutchinson and Clayton in 1919 observed that some cells of cytophaga became shorter and thicker until finally the "sporoids" were spherical and stained very intensely; Krzemieniewska in 1930 and 1933 also observed these changes and after watching the cells during germination concluded that the microcysts were surrounded by a mucoid sheath which was shed as the vegetative rod emerged (Stanier, 1942). Beebe (1941) described the resting cells of M. xanthus as "spherical, with thick outer wall or membrane, highly refractile when unstained" and staining very easily. In the process of changing to a resting cell the vegetative thin bacillus became shorter and wider and the cell wall began to thicken and stain more heavily.…”

Ultracentrifugation and Cytology of Spirillum volutans

“…Good reviews of the nature of the chromatin material and the methods of division in bacteria are available and need not be repeated here (Guilliermond, 1907;Dobell, 1911;Lindegren, 1935;Stille, 1937;Knaysi, 1938;Lewis, 1940;and Beebe, 1941). Suffice to say that there are at present five views concerning the nature of the nuclear apparatus in bacteria as follows: (1) Nuclei similar to those demonstrated in higher plants and animals are absent.…”

“…This is somewhat similar to the conditions described by Schaudinn (1902) who held that in Bacillus biitschlii the chromatin was differentially scattered in the vegetative cell but present as a "true" nucleus in the spores. Beebe (1941) has described the nucleus as a compact Feulgen-positive mass in Myxococcus xanthus. This nucleus breaks up into chromosomes during division and undergoes autogamy before spore formation and meiosis during germination of the spores.…”