The Fine Structure of Eadie's Ovals Isolated from Sheep Rumen

Abstract

SUMMARYThe structure of two strains of the Gram-negative rumen organism, Eadie's Oval, was examined with the electron microscope. Despite their large size, their fine structure indicated that they were bacteria. They had a cell envelope consisting of two membranes separated by a dense layer which could be solubilized by lysozyme. They possessed characteristic bacterial flagella, and lacked internal organization with ribosomes and DNA-li ke material dispersed throughout the cytoplasm.The outer membrane was corrugated and each strain had a characteristic pattern of corrugations. One strain had sheathed flagella, the other did not. Both strains were coated with fibrils up to 660 nm long, but which apparently contracted to give an unusual cross-banded layer when treated with lysozyme. I N T R O D U C T I O NTwo ovoid, motile, Gram-negative organisms, which occur in the rumen of sheep, goats and cattle, are known colloquially as 'Ovals'. Neither has been fully characterized or allocated a taxonomic position or scientific name, and the relationship of the one to the other is not known. The smaller of the two has maximum axial dimensions of 2.5 to 3-0 ,urn by 4.0 to 9.oprn (Hungate, 1966) and was originally described by Woodcock & Lapage (I 9 I 3), who thought that it was similar or identical to Selenomonas ruminantiurn. Quin ( I 943) proposed that it was a yeast, but this was rejected by McGaughey & Sellers (1948) and van der Westhuizen, Oxford & Quin ( I 950). Wicken & Howard (I 967) found diaminopimelate and muramic acid in the cell walls of this organism, now known by the colloquial name of Quin's Oval (Q.O.), and therefore concluded that it was a bacterium. The other Oval was first described by Eadie (1962); it has average axial dimensions of 8.5 x 12.2 ,um (Orpin, 1972) and thus is substantially larger than Quin's Oval. It has been observed in ruminants in several countries (Eadie, 1962;Abou Akkada & El-Shazly, 1964;Warner, 1962Warner, , 1966Orpin, 1972). Quin (1943) in South Africa also mentioned the presence of oval organisms larger than the ones which are now given his name, but gave no details. The photomicrograph he presented of Quin's Oval appears, in fact, to be of a mixed population containing both Quin's and larger Ovals, possibly the same as those described by Eadie (1962), and which have subsequently been referred to as Eadie's Ovals (E.O.). This organism has been observed in the rumen of 90 % of the sheep we have examined, in populations ranging from 4-5 x 105 to 1 -1 x Io8/ml, and appears to be a normal member of the rumen microbial population. Light microscopy of living and stained organisms has shown that E.O. is probably a bacterium, despite its large size (Orpin, 1972). This contention is supported by the results presented in this paper in which we describe the fine structure of two strains of E.O. which were first distinguished on the basis of differing substrate utilization patterns (Orpin, I 972). Prepdrdtion of 'starved' E. 0. Suspensions of freshly harvested E.O. were incubated for 48 h at ...

Hydrogenosome, Pairing Anaerobic Fungi and H2-Utilizing Microorganisms Based on Metabolic Ties to Facilitate Biomass Utilization

“…Under transmission electron microscopy, the electron density of the vesicles was slightly higher than that of the matrix [84]. The number, size, and electron density of the vesicles varied in different microorganisms [11,[84][85][86]. These vesicles may be related to the storage of calcium and other cations and change at different metabolic states.…”

“…In 1975, Orpin first reported the presence of anaerobic fungi in the rumen of sheep [11]. Since then, many researchers have successively found these microorganisms in the rumen, foregut, and hindgut of many herbivores, suggesting their widespread presence in the digestive tract of herbivores.…”

“…Early after the discovery of anaerobic fungi, they were considered to be protozoa with flagella due to their zoospores [11]. In the 1970s, Orpin suggested that these flagellates were actually the transmission stage of fungal zoospores [13], and that chitin components in their cell walls [14] further confirmed their correct location in the fungal kingdom.…”

Novel microbial and chemical components of a specific black-band region in the cockroach hindgut

“…The size of this rod almost approaches that of J. BACTERIOL. the large procaryotic organisms Quin's oval and Eadie's oval found in the rumen (23). The cytoplasm of Eadie's oval is full of glycogen granules which have been isolated and characterized (24).…”

“…The presence of storage granules in procaryotes is usually an indication of unbalanced growth due to the presence of some nutrients in the absence of others (12). The presence of many microorganisms in gut and rumen ecosystems with such inclusion bodies, Eadie's oval (23), the large rod, the rod with the helically striated surface reported in this paper, and others from the guts of Eublaberus and Periplaneta (unpublished data) may be an indication that the gut environment is not one of bounteous plenty, but that, in fact, nutrients become available in local small spurts and that growth is not similar to that in continuous culture (11) but very discontinuous. The presence of significant numbers of sporulating bacteria in vivo (4) may also be an indication of unbalanced growth.…”