Ultrastructure ofDebaryomyces hansenii

Summary The ultrastructure of the extreme halotolerant yeastDebaryomyces hansenii (Zopf) van Rij was similar whether the organism was grown under normal physiological conditions or at high concentrations of NaCl (12, 20 per cent w/v). A multitude of channels often seen in association with plasma membrane and/or vacuoles occur in the cytoplasm. The vacuoles contain lipid storage material. A decrease in mitochondrial size was observed with increasing salt concentration. The ultrastructure has been discussed with respect to halotolerance.     

Ultrastructure of Lymphocystis Virus

Lymphocystis virus obtained from bluegills (Lepomis macrochirus) was cultured in the permanent bluegill cell line BF-2 and examined by electron microscopy in ultrathin sections of cell cultures and in negative-contrast preparations from cells and from centrifuged culture medium. According to negative-contrast preparations, the icosahedral virions have an overall diameter close to but not exceeding 300 mμ. Delicate filaments seem to issue from the vertices. In collapsed virions, an ordered array of morphological units was seen. Positively contrasted virions in ultrathin sections show a shell with three dark (heavy metal-stained) layers alternating with and separated by two clear layers. The acquisition of an additional outer membrane during release from the cell, as found in African swine fever virus, was never seen. Morphologically, lymphocystis virus is considered to be closely related to Tipula iridescent virus.     

Ultrastructure of incubated muscles

Morphological changes were observed in the peripheral fibres of both rat and rabbit muscles which had been incubated in vitro. These changes occurred rapidly and indicated that degenerative processes were taking place in these muscles. Consequently the morphological and physiological integrity of rat and rabbit muscles incubated in vitro is called into question.     

Ultrastructure of chickpea nodules

Summary Developing and senescing chickpea (Cicer arietinum L.) nodules formed byRhizobium sp. (Cicer) CC 1192 have been shown by light and electron microscopy to have general morphological and ultrastructural features that are characteristic of indeterminate nodules. These features included the presence of persistent meristematic tissue at the distal ends of the multi-lobed nodules, and a gradient of cells at different stages of development towards the proximal point of attachment of the nodules to the parent root. The cytoplasm of infected cells in the nitrogen-fixing region of the nodules was densely packed with symbiosomes, most of which contained a single bacteroid. Infection threads containing bacteria were noted in invaded cells from the nitrogen-fixing region of the nodules. Other features that were observed in chickpea nodules included the presence of electron-dense occlusions in intercellular spaces in the nitrogen-fixing region, and plasmodesmata that connected infected cells with other infected cells and with uninfected cells. No poly--hydroxybutyrate granules were noted in the bacteroids. In later stages of development, infected cells became enlarged and highly vacuolated, and eventually lost their contents. Uninfected cells in the central region were smaller than infected cells and were also highly vacuolated. Some of the degenerative processes that take place in senescing bacteroids were noted.     

Ultrastructure of Bacillus pulvifaciens

The ultrastructure of vegetative cells and spores of Bacillus pulvifaciens was studied by CTEM and SEM methods. The vegetative cells are rods, 1.6–4.5 m long and 0.4–0.6 m wide, exhibiting typical ultrastructural features of Gram-positive bacteria. The spores are of ellipsoidal shape, 0.6×1.2 m in size, with six longitudinal ribs reaching up to 130 nm in height. There are satelite ribs on both sides of the longitudinal ribs, reaching up to 20 nm in height. Between the longitudinal ribs, additional transversal ribs were observed in SEM. A special tubular layer, separating the outer and inner coat of the spores, was revealed in ultrathin sections. This layer seems to be a typical ultrastructural feature of Bacillus pulvifaciens spores.     

Ultrastructure of Hanseniaspora ascospores

A comparative study of the ultrastructure in sections of the ascospores of six Hanseniaspora species showed three types of spores: (1) hat-shaped in H. valbyensis and H. guilliermondii, (2) spherical with an equatorial or subequatorial ledge, smooth or rough in H. occidentalis and H. uvarum, (3) spherical with warts in H. osmophila and H. vineae. Development and germination of the spores of Hanseniaspora guilliermondii is described in more detail.This investigation was supported by the Netherlands Organization for the Advancement of Pure Research (Z.W.O.) I     

Coccolith Ultrastructure and Biomineralisation

The relationship between calcite biomineralisation and coccolith ultrastructure is analysed across the diversity of calcifying haptophytes. The emphasis is on integration of evidence from crystallographic and ultrastructural studies but additional relevant information from biochemical and phylogenetic work is reviewed. We attempt to identify aspects of ultrastructure which are most likely to be the product of self-organising processes. The principal topics reviewed are heterococcolith rim nucleation, including reassessment of the V/R model; crystal growth regulation in heterococcoliths; holococcolith biomineralisation; and the diversity of other biomineralisation modes in haptophytes. It is concluded that the diverse range of calcareous structures produced by haptophytes probably has a common phylogenetic origin and is produced via operation of a limited set of mainly shared genetic and biochemical pathways.     

Ultrastructure of Azotobacter vinelandii

Vegetative cells and cysts of Azotobacter vinelandii 12837 were prepared for electron microscopy by several methods assumed to preserve structural details destroyed by techniques previously reported in the literature. Examination of large numbers of cells and cysts by these methods revealed four structural details not reported previously: intine fibrils, intine vesicles, intine membrane, and microtubules. The intine fibrils form a network in the gel-like homogeneous matrix of the CC2 layer. Intine vesicles which seem to originate in the cell wall complex of the central body are seen in the intine and exine of cysts. Analogous structures are found on vegetative cells. The intine is divided into two chemically distinct areas by the two-layered intine membrane. Microtubules, previously reported only in vegetative cells, were found in cysts.