Microcyst Formation and Germination in Spirillum lunatum

Abstract

SUMMARY: Spirillum lunatum has been shown to possess a life cycle in which there is an alternation between a vegetative and a microcyst stage. Microcyst formation may occur from the spiral vegetative cell by: (1) fusion of two entwined organisms to form one or more microcysts ; (2) the production of a protuberance a t some point along the organism into which the entire organism is gradually absorbed; (3) the gradual shortening and rounding of the organism to form an oval to spherical body. Microcyst formation begins, in a typical broth culture, a t c. 24 hr. after inoculation and the majority of the organisms are in the microcyst stage after a 4-day incubation period. When microcysts from an old culture are inoculated into fresh media, they germinate to form the spiral vegetative organism. Germination occurs by either unipolar or bipolar emergence of the germ tube.During a taxonomic study of the genus SpiriZZurn Ehrenberg (Williams, 1952), it was found that three species of the marine spirilla and two of the freshwater species exhibited morphological changes during the growth of the cultures. Young cultures, which consisted entirely of spiral organisms, gradually changed until only oval or spherical bodies (0*8-5*0p. in diameter, depending on the species) were found in old cultures. When these bodies were inoculated into fresh media, the normal spiral organism germinated from them. Since the entire organism is involved in the formation of these oval to spherical bodies, in a manner similar to the formation of the microcysts of the Sporocytophuga (Stanier, 1942; Grace, 1951), these bodies have been called ' microcysts '. Because of its relatively large size, S. Zunaturn was chosen as the experimental organism. The morphological changes which occur in this species are similar, although not identical, to those occurring in the other two marine spirilla and in the two freshwater species. METHODSThe spirillum was grown in sea-water nutrient broth of the following composition: peptone, 5.0 g.; beef extract, 3.0 g.; yeast autolysate, 3.0 g.; and sea water, 1000 ml. Broth tubes were inoculated with old cultures, ranging in age from 2 to 6 weeks, and incubated at 30". Organisms removed from the broth cultures at appropriate times between 8 and 72 hr. were used for microcultures. Cultures less than 24 hr. old were centrifuged and the harvested organisms re-suspended in a small amount of sterile sea water. Cultures older than 24 hr.

PROTOPLASTS AND L-TYPE GROWTH OF ESCHERICHIA COLI

“…For example, the cycle of transformable competence of the pneumococcus (Fox and Hotchkiss, 1957) is patently due to some imbalance of growth of cellular constituents, for which the wall and other envelopes would be the first candidates. For another, the microcysts of Spirillum lunatum, as figured by Williams and Rittenberg (1956) show at least a superficial resemblance to the cycle of evolution and reversion of protoplasts. The spontaneous occurrence of large bodies and the osmotic fragility of marine luminous bacteria (Johnson and Gray, 1949) also have to be related to the rigidity of the cell wall.…”

Microbulbifer variabilis sp. nov. and Microbulbifer epialgicus sp. nov., isolated from Pacific marine algae, possess a rod-coccus cell cycle in association with the growth phase

“…Formation of coccoid bodies, spherical bodies, spherical forms or round bodies in older cultures has been reported for various Gram-negative bacteria (Krieg, 1976(Krieg, , 1984. They exhibited unusual features: an unusual method of formation in 'Spirillum lunatum' (Williams & Rittenberg, 1956) and 'Spirillum serpens' (Aquaspirillum serpens; Terasaki, 1970), loss of viability in 'Desulfovibrio aestuarii' (Desulfovibrio desulfuricans subsp. aestuarii; Levin & Vaughn, 1968) and Vibrio sp.…”

Biology of the chemoheterotrophic spirilla.

“…With an electron microscope the DNA was seen a linear molecule 13.25 ,um long; from this length a molecular weight of 2.6 x 107 was calculated. COCCOID BODIES AND LIFE CYCLES In 1956 Williams and Rittenberg (197) photographed the formation of coccoid bodies, which they termed "microcysts," in a marine spirillum, S. lunatum. (This organism was quite different than that presently occurring in the type strain ATCC 11337, since the latter does not require seawater and does not form coccoid bodies.…”