Remnants Of Walls Research Articles

Type and strain variation in induction of L forms of Neisseria gonorrhoeae.

Strains of Neisseria gonorrhoeae were inoculated onto brain heart infusion (Difco) agar supplemented with penicillin and polyvinylpyrrolidone (PVP) as a stabilizer and cultivated in a candle extinction jar. L-form colonies became visible after a few days. They continued to grow and were viable for up to 38 days. The extent of inducibility of L forms of N. gonorrhoeae was examined semiquantitatively. It was found to be constant for each type and strain and to depend only slightly on the amount of penicillin added to the medium. None of the types of one strain produced L-form colonies. In another strain, avirulent types (T3, T4) showed more ability to produce L forms than virulent types (T1, T2) and no L forms were produced by the subtypes of T1 and T2-T1a and T2a. In a third strain, only T4 produced L forms. Electron microscopic studies showed that the L forms consisted of a number of membranous vesicles and a variety of cell types such as those completely lacking cell walls and those with only remnants of cell walls. The results indicate the existence of subtypes of T1 and T2 of gonococci and the intrinsic inducibility of gonococcal types and strains to produce L forms.

The isolation of protoplasts of the fission yeast Schizosaccharomyces by Trichoderma viride and snail enzymes.

The formation of protoplasts of the fission yeasts Schizosaccharomyces pombe and Schizosaccharomyces versatilis after the combined application of snail enzymes and Trichoderma viride enzymes in an osmotic stabilizer (0.4M KCl, pH 5.5) was studied by light and electron microscopy. The effect of the enzymes used leads during 30 min to the formation of 100% protoplast population. Using electron microscopy no original walls or wall remnants were detected in the suspension of protoplasts. Protoplasts are viable and in liquid nutrient medium they regenerate cell walls and revert into normal cells. Such a protoplast population may be useful for biochemical study of protoplast metabolism by quantitative methods as well as for the chemical study of regenerating cell walls.

Extraction of lipids from cottonseed tissue: VI. Ultrastructural morphology of isolated pigment glands

AbstractCottonseed pigment glands, isolated from the underflow fraction of the liquid cyclone process, were examined with an electron microscope. The glands were circumscribed by a layer of tangentially flattened cells. Subjacent to the flattened cells were partially lysed cells containing recognizable remnants of cell walls. Within the lumens or matrices of the glands were myriads of pigment spherules measuring 0.1–1.5 µ in diameter. These spherules remained within the glands, even though gland walls were ruptured mechanically. Since aggregates of pigment spherules devoid of gland walls were observed in the gland‐rich fraction, it was concluded that maintenance of intact pigment glands was not a requisite for successful separation of gossypol from other cottonseed components with the liquid cyclone process. Avoiding dispersion of aggregated spherules from the glandular matrix was probably just as important as maintaining intact gland walls during mechanical separation of gossypol from other cottonseed components.

Reversion of protoplasts and spheroplasts in the yeast Nadsonia elongata.

The time rate of regeneration of the cell wall and reversion of protoplasts of the yeast Nadsonia elongata to cells of normal shape and size has been compared with the capability for regeneration of spheroplasts of this yeast. Nearly all protoplasts in a given culture were able to regenerate new walls and had usually reverted to cells of normal appearance by the 30th h of cultivation. Spheroplasts required only half this time to do this. These results can be interpreted as evidence that regeneration of a wall by protoplasts does not depend upon the presence of a cell wall primer, because the proportion of reverting protoplasts (which lack wall remnants) was the same as that of reverting spheroplasts (which possess them). The presence of wall remnants in spheroplasts appears to have merely an accelerating effect on the formation of a new wall and on subsequent reversion of the spheroplasts to complete cells of normal shape and size.

Further observations on hydrolysis of the cell wall in the xylem

Hydrolyzed walls (birefringent, Periodic acid/Schiff negative, remnants of primary walls that also lack polyuronides with free carboxyl groups) are demonstrated in the primary xylem of wheat and bean leaves. Walls with similar properties have been found in the primary xylem of a variety of tissues from different species, and are believed to be ubiquitous. It is shown that the pit membrane of intervessel pits between tracheary elements of willow is also a hydrolyzed wall. Combined with the observation byLiese (1965) it seems likely that the removal of non-cellulosic polysaccharides from primary walls unprotected by lignin is a general phenomenon that occurs late in the autolysis of all tracheary elements. Parenchyma cells that abut autolyzing tracheary elements appear to react to hydrolytic attack in a number of ways that are illustrated and discussed.

Ultrastructure of Onion Roots Infected with Pyrenochaeta terrestris, a Fungus Parasite

Onion roots of varieties ‘951’ and ‘Excel’ were infected under artificial conditions by a virulent isolate of the onion pink-root fungus, Pyrenochaeta terrestris. Roots of variety ‘951’ were penetrated initially at the tip while roots of variety ‘Excel’ were penetrated initially 2 cm or more back from the tip. Ultrastructural observations of infected roots of both varieties indicated that the fungus penetrated primarily or entirely by dissolution of host cell walls, rather than by pressure of fungal cells. In both varieties the fungus caused cell disruption one to several cells in advance of the fungus. In addition, the same isolate of the pink-root fungus was grown on paper consisting primarily of gymnosperm cells. The remnants of cell walls were dissolved by the fungus with no evidence of physical pressure by the fungus.

ULTRASTRUCTURE OF ONION ROOTS INFECTED WITH PYRENOCHAETA TERRESTRIS, A FUNGUS PARASITE

Onion roots of varieties ‘951’ and ‘Excel’ were infected under artificial conditions by a virulent isolate of the onion pink‐root fungus, Pyrenochaeta terrestris. Roots of variety ‘951’ were penetrated initially at the tip while roots of variety ‘Excel’ were penetrated initially 2 cm or more back from the tip. Ultrastructural observations of infected roots of both varieties indicated that the fungus penetrated primarily or entirely by dissolution of host cell walls, rather than by pressure of fungal cells. In both varieties the fungus caused cell disruption one to several cells in advance of the fungus. In addition, the same isolate of the pink‐root fungus was grown on paper consisting primarily of gymnosperm cells. The remnants of cell walls were dissolved by the fungus with no evidence of physical pressure by the fungus.

Kinetic and morphological observations on Saccharomyces cerevisiae during spheroplast formation.

A strain of Saccharomyces cerevisiae which produced elongated cells under our growth conditions was investigated. By digestion of the cell walls with snail enzyme, the cells became spheroplasts after a transient state which we termed "prospheroplast." The prospheroplast could be lysed like the spheroplast, but it retained the shape of the original yeast cell if osmotically protected. Prospheroplasts and spheroplasts were prepared, and thin sections of samples taken throughout the process of wall removal were studied in the electron microscope, at regular intervals up to the time of complete conversion to spheroplasts. In addition, cell wall remnants recovered from spheroplast preparations were shadow cast for electron microscopy. This material revealed structures resembling bud scars with attached membranous matter. The kinetic studies showed that after a certain period of time all cells were transformed into prospheroplasts, whereas spheroplast formation started later, depending on the enzyme concentration. In sections, the prospheroplasts appeared to be formed by detachment of the cell walls. Both the prospheroplasts and the spheroplasts showed asymmetric cytoplasmic membranes in which the outer leaflets appeared coated with a dense fibrillar layer. The experiments suggest that, after enzyme digestion, the cytoplasmic membrane retains a coating which is rigid in the prospheroplast but which loses rigidity when the cell is transformed into a spheroplast.

Cell grouping and primary wall generations in the cambial zone, xylem, and phloem in Pinus

The use of the term cambium, or equivalent terms, in modern literature is discussed. The term cambial zone adopted in this paper includes the cambial initial and the dividing and enlarging cells. The tissue mother cell produced at each division of the initial produces a group of four cells in xylem or two cells in phloem. Theoretical constructs have been made for xylem and phloem production by associating the concepts that xylem and phloem are produced in alternate series of initial divisions and that a new primary wall is deposited around each daughter protoplast at each cell division. Correlations are derived from the theoretical constructs for the thickness of primary wall layers lying in the tangential direction and of those lying in the radial direction at progressive histological levels. Deductions from theoretical constructs are made when the initial is producing xylem, when it changes its polarity from xylem to phloem production, and when the reverse change occurs. Most of the theoretical deductions are supported by photographic evidence. The chief point of this study is the demonstration of generations (multiplicity) of primary parental walls. The term intercellular material proposed in this paper includes the cell plate plus any remnants of ancestral primary walls between the current primary walls surrounding the adjacent protoplasts. This term is still applicable to cells where secondary wall deposition is taking place or has been completed.

STRUCTURE AND REPRODUCTION OF THE ALGAL SYMBIONTS OF HYDRA VIRIDIS(1).

The algal symbionts of Hydra viridis are found within vacuoles of the gastrodermal digestive cells of the host. Electron microscopy reveals that the symbionts possess cell walls, and that their reproductive cycle follows the general pattern of free-living Chlorella. Nuclear and chloroplast divisions arc followed by formation of new cell walls, the Golgi apparatus being quite active during cell wall synthesis. Autospores are released when the parent wall ruptures. The autospores are then usually segregated into separate animal vacuoles. Remnants of the ruptured parent wall persist in the vacuoles for an indefinite period. The ruptured parent walls curl at the breakage clefts, forming double-layered scroll-like structures. The fate of these wall remnants has not been firmly established. Long-term starvation of the animals does not result in a detectable change in the structure of the symbionts, and they continue to divide and to store carbohydrate as starch grains.

CONTRIBUTIONS TO OUR KNOWLEDGE OF AMBROSIA FUNGI. I. ASCOIDEA HYLECOETI SP. NOV. (ASCOMYCETES)

BATRA, LEKH R. (U. Kansas, Lawrence), and HELENE FRANCKE-GROSMANN. Contributions to our knowledge of ambrosia fungi. I. Ascoidea hylecoeti sp. nov. (Ascomycetes). Amer. Jour. Bot. 48(6): 453-456. Illus. 1961.-The genus Ascoidea Bref. & Lindau in Brefeld (1891) belongs to the family Ascoideaceae (Endomycetales, Hemiascomycetidae). Ascoidea differs from all other ascomycetes by its possession of characteristic multispored asci which proliferate, the newer asci being formed through the collar-like wall remnants of older asci. Ascogenous hyphae are absent. The present fungus differs in many ways from the type and the only species of the genus, A. rubescens Bref. & Lindau. Ascoidea hylecoeti reproduces asexually by chlamydospores. The asci are conical and many spored. They are aggregated in thick clusters of 50-200 individual asci. The number of ascospores per ascus is much larger than that of A. rubescens and their size is much smaller. Ascoidea hylecoeti is known to occur only in association with the genus Hylecoetus, one of the ambrosia beetles. AMBROSIA fungi are a group of fungi which live symbiotically with some genera of insects. Most of these fungi live saprophytically on plant and in. sect material. although some may have a rather complex and parasitic role together with the insect partner in the formation of so-called ambrosia galls on some plants. Generally, these fungi serve as a major source of food for the developing larvae. Ambrosia fungi are predominantly ectosymbiotes. They are characterized by having mucilaginous spores and fragrant colonies when grown on common laboratory media or when observed in the field. Some of these fungi cause blue staining of logged timber. resulting in heavy economic losses in some parts of the world. These fungi usually overwinter in the form of oidia, thick-walled chlamydospores, or dried, shiny. and mucilaginous crusts of ascospores. The female ambrosia beetles carry the fungi in special structures and the inocula are deposited during oviposition along with the eggs (FranckeGrosmann 1952, 1956, 1957). Taxonomically, most of the ambrosia fungi belong to the Endomycetales, Ophiostomatales and other ascomycetous orders and Fungi Imperfecti (Batra, 1959). Some unidentified Basidiomycetes have also been isolated by the present authors, although no Phycomycetes have so far been observed. Ascolidea hylecoeti was isolated during our studies of symbiotic relationships between ambrosia fungi and ambrosia beetles. Like many other such fungi, this fungus lives as an ectosymbiote and is

A New Embedding Medium for Electron Microscopy

THE introduction of n-butyl and methyl meth-acrylates as embedding media1 constituted an important development in the preparation of ultra-thin sections of biological material; but their use is attended by various major difficulties. Shrinkage occurs on polymerization, hard objects are not penetrated by the monomer so that the plastic shrinks away and does not provide sufficient support, and sometimes there is an unaccountable appearance of bubbles around the specimen. Moreover, the polymerization process is not uniform and sometimes causes severe damage. This is perhaps most strikingly seen in bacteria where often only empty remnants of cell walls remain.