- Volume 62, Issue 2, 1970
Volume 62, Issue 2, 1970
- Article
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The Structure and Formation of Lomasomes
More LessSUMMARY: Saprolegnia ferax and Dictyuchus sterile contain lomasomes and plasma-lemmasomes whose structure and distribution are described. It is suggested that plasmalemmasomes are produced when plasmalemma production is not balanced by cell expansion. When plasmalemmasomes become sequestered in developing cell walls they may be termed lomasomes.
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Centriole Replication and Nuclear Division in Saprolegnia
More LessSUMMARYPaired centrioles in the hyphae and young sporangia of Saprolegnia ferax and Dictyuchus sterile were aligned end to end at 180° to each other. At the end of interphase new centrioles were replicated on the proximal end of each parent centriole. Each pair of centrioles was associated with a characteristic region of the nuclear envelope, termed the pocket. As the centriole pairs moved apart the mitotic spindle developed between these pockets. Kineto- chores, initially found at the equator of the spindle, became polarized as the nucleus elongated. A characteristic association between the nuclear envelope and astral microtubules is described and its role in nuclear division discussed. Mitochondria frequently lay along tracts of microtubules. The processes of centriole replication, spindle formation and nuclear division are discussed in relation to reports of the ultrastructure of these processes in other organisms.
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Entomophthora Conidia in the Air-spora
More LessSUMMARY: At Silwood Park, Berkshire, in 1958, the largest concentration of each of five ‘types’ of Entomophthora conidia in the air typically occurred at 05·00 to 07·00 h. and was associated with humid air and sunrise. The smallest concentration occurred between 14·00 and 17·00 h. when the air was usually driest.
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The Effect of Nickel on a Marine Bacterium, Arthrobacter marinus sp.nov.
More LessSUMMARY: An unbalanced growth situation, resulting in large, plasmolysed sphero-plasts (megalomorphs) produced by the addition of nickel to the growth medium of a marine bacterium, Arthrobacter marinus sp.nov., is described.The effect of increasing nickel concentrations was gradual. Under the cultural conditions used, a slight effect was noted on size in 1 × 10−4 m-NiCl2, but in 4 × 10−4 m-NiCl2 the cells formed megalomorphs attaining a size of 10 to 15 μm. Cell division did not occur in 5 × 10−4 m-nickel. The lag phase of the culture increased from about 3 h. without added nickel to more than 70 h. at 4 × 10−4 m-nickel. Concurrently, the maximum population decreased as the nickel concentration was increased. The classification of the marine bacterium is described and the organism is designated as A. marinus sp.nov.
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The Characterization of Hyalochlorella marina gen. et sp.nov. a New Colourless Counterpart of Chlorella
More LessSUMMARY: Hyalochlorella marina is described as the type species of a new colourless genus of the chlorococcalean algae. It is a morphological and developmental counterpart of Chlorella and analogous to Prototheca, the known colourless counterpart. Hyalochlorella is distinguishable from Prototheca by its mode of autospore discharge, its possession of a large centric or eccentric vacuole, a Ruthenium Red positive wall and its lack of pectinaceous interstitial ground substance in the mature sporangium. Its developmental cycle is simple, involving a period of growth followed by cytokinesis. Nuclear division occurs concomitantly with growth; cytokinesis involves the segmentation of a multinucleate protoplast into uninucleate daughter protoplasts (preautospores) by simultaneous multiple fission. Daughter cell number, although variable, is usually an integral of 2 n or 2 n - 2 n-2 . Numbers in the 2 n – 2 n - 2 series are believed to result from the degeneration of one nucleus in the tetranucleate stage followed by subsequent growth and division.
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The Isolation and Occurrence of Hyalochlorella marina
More LessSUMMARY: Three out of five methods currently employed in the isolation of lower marine fungi have been effective in the isolation of Hyalochlorella marina from the marine environment. Isolation attempts from locations on the Atlantic, Pacific and Gulf of Mexico Coasts (U.S.A.) indicate that H. marina is ubiquitous, occurring in nature either attached to algal filaments or free- floating. Its incidence in the eulittoral and intertidal zones is highest between 14 and 20°. There is no correlation between incidence and the salinities commonly encountered in sea water and numerous attempts at isolation from fresh water have been unsuccessful. It is preferentially attached to algal filaments but exhibits no specificity with regard to particular algae.
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Persistence in Mice of the L-Phase of Three Streptococcal Strains Adapted to Physiological Osmotic Conditions
More LessSUMMARYInability of the L-phase of Gram-positive bacteria to persist in vivo is explainable by its need for osmotic protection. Adaptation to physiological osmotic conditions did not enhance the ability of the L-phase to survive in vivo after intravenous or intraperitoneal injection in mice. One ‘low-salt’ L-strain survived in mice for 8 days in vivo when protected against phagocytosis by a filter box, whereas under the same conditions its ‘high-salt’ parent L-strain died in a few hours. The decrease of the number of surviving colony-forming units of this low-salt L-strain in the filter box contrasts sharply with the increase in number shown by the parent bacterial strain protected in the same way.
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The Ultrastructural Architecture of the Walls of Some Hyphal Fungi
More LessSUMMARY: The appearance of the walls of apical and sub-apical regions of hyphae of predominantly 5 day cultures of Neurospora crassa, Schizophyllum commune and Phytophthora parasitica as seen with the electron microscope, employing shadowed or sectioned material, is illustrated and described in detail. The appearance of untreated or control material in buffer is compared with that exposed to various single and sequential treatments with enzymes, including laminarinase, Pronase, cellulase and chitinase, as well as various chemical treatments.
From these observations is inferred the co-axial distribution of polymers such as β1,3-, β1,6-glucans, glycoproteins, proteins, chitin and cellulose in the walls of each species. The distributions have both similarities and differences between the species. The significance of all these features for the growth, mechanical rigidity and integrity of a hypha is briefly discussed.
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Lactobacillus jensenii sp.nov., a New Representative of the Subgenus Thermobacterium
More LessSUMMARY: Seven strains of homofermentative Lactobacillus newly isolated from human sources were found to possess all of the usual phenotypic characters of Lactobacillus leichmannii. However, a subsequent comparative study of the electrophoretic mobilities of their lactic dehydrogenases showed that these seven newly isolated strains were markedly different from collection strains of L. leichmannii. Determination of the mean DNA base composition of a representative sample of the new isolates (36·1 ± 1·2 moles % G + C) clearly indicates that they cannot be considered as L. leichmannii (50·8 ± 0·5 moles % G + C). The newly isolated strains have been assigned to a new species, L. jensenii.
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Electrophoretic Characterization of Lactic Dehydrogenases in the Genus Lactobacillus
More LessSUMMARY: Crude extracts of 146 strains of different species of Lactobacillus have been submitted to starch gel electrophoresis and the gels developed specifically for lactic dehydrogenases, d or l, NAD-dependent or NAD-independent. Each species contained at least one NAD-dependent lactic dehydrogenase specific for d(−) or for l( + ) lactic acid; some species contained both enzymes. For each species there was a strict correlation between the stereospecificity of the NAD-dependent lactic dehydrogenases found in extracts and the type of lactic acid produced during growth, i.e. d(−), l ( + ) or dl. The l-lactic dehydrogenases (NAD-dependent) of Lactobacillus casei and L. fermenti were not reversible and consequently could not be detected after electrophoresis. Only those NAD-independent lactic dehydrogenases able to reduce phenazine methosulphate could be detected by the method of development used. Such enzymes were found in extracts of some homofermentative lactobacilli.
The number and the nature of the lactic dehydrogenases and their respective electrophoretic mobilities are constant within a species. Therefore the electrophoretic migration of lactic dehydrogenases of lactobacilli is a useful taxonomic marker for species differentiation.
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Purification and Properties of NAD-dependent Lactic Dehydrogenases of Different Species of Lactobacillus
More LessSUMMARY: Six nicotinamide adenine dinucleotide (NAD)-dependent lactic dehydrogenases, four specific for D( − ) lactate and two specific for l( + ) lactate have been purified from different Lactobacillus species. Four of these enzymes appeared to be pure by several criteria. Some of the physical and catalytic properties of these enzymes are described and compared with those previously reported for the d- and l-lactic dehydrogenases of Lactobacillus plantarum.
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A Simple Method to Obtain the Mycococcus Form of Mycobacterium phlei
More LessSUMMARYA method for the isolation of mycococci directly from cultures of Mycobacterium phlei is described. The method consists of the cultivation of M. phlei in Middlebrook’s 7H9 liquid medium without the addition of any enrichments. The medium was distributed in screw-capped bottles, plugged for 3 weeks with cotton-wool only and then for another 4 weeks with the caps screwed on top of the cotton-wool plugs. The mycococci were then isolated on subcultures on nutrient agar. A streptomycin-resistant variant of M. phlei yielded a mycococcus that was streptomycin-resistant. Frequent subcultivation of the parent strain probably prevented the development of mycococci. Evidence is submitted that the mycococci were not contaminants.
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