Zoospore Chemotaxis in the Watermold Allomyces

The chemotactic response of the mitospores and meiospores of Allomyces macrogynus and A. abuscula to casein hydrolysate was shown to he caused by the combined action of leucine and lysine in the hydrolysate. The testing was done by counting the zoospores that attached to a membrane through which substances diffused downward. The action of leucine and lysine was shown to be synergistic and to be specific for the L, forms. The optimum concentration above the membrane was 5 × 10^-2M for each amino acid. An effect was detectable down to approximately 10^-55 M. The addition of L-proline to the mixture increased the response. Proline in combination with leucine caused good attachment, although less than that by leucine and lysine, of the zoospores of A. arbuscula but not of those of A. macrogynus.     

Chemotaxis and transport of amino acids in Allomyces arbuscula

Among a number of amino acids tested, l-lysine and l-arginine are the principal attractants in the chemotaxis of the zygotes of Allomyces arbuscula. The reaction can be stimulated to a greater or lesser extent by a number of compounds chemically related to l-leucine. No relationship between transport of attracting amino acids and their effect on chemotaxis has been found.     

Loss of rRNA genes during a phenotypic, masculinizing mutation in Allomyces arbuscla

Summary Saturation hybridization of ³H rRNA from Allomyces arbuscula Bali wild-type to homologous DNA and to DNA preparations from Allomyces arbuscula Bali X-ray induced male mutant and an interspecific male hybrid (Allomyces arbusculaxAllomyces macrogynus Emerson and Wilson) has shown approximately 50–60% reduction in the cistrons coding for rRNA in the masculinized strains.     

The effect of actinomycin D on the formation of gametangia and mitosporangia in Allomyces

The effect of actinomycin on gametangium and mitosporangium production in Allomyces arbuscula and A. macrogynus has been investigated. Male gametangium production was not more sensitive to actinomycin than female development. Actinomycin at 20 g/ml added at the commencement of induction was completely inhibitory. The process became insensitive to actinomycin just before the first septum was laid down.     

STRUCTURE AND DEVELOPMENT OF HYPHAL SEPTA IN ALLOMYCES

Development of hyphal septa (pseudosepta) in Allomyces macrogynus begins with the formation of five or more discontinuous pieces of wall material that project inward from the hyphal wall. Lateral fusion of these projections leaves a central pore in the septum that is later filled in by centripetal deposition of wall material. However, lateral fusion of the projections is not complete; peripheral pores remain in the rim of the mature septum. The position of cytoplasmic microtubules corresponds to the position of actively moving cellular particles and organelles. Allomyces reticulatus and A. arbuscula have similar septa.     

Molecular phylogeny of Allomyces macrogynus: Congruency between nuclear ribosomal RNA- and mitochondrial protein-based trees

We have sequenced the nuclear and mitochondrial small subunit rRNA genes (rns) and the mitochondrial genes coding for subunits 1 and 3 of the cytochrome oxidase (cox1 and cox3, respectively) of the chytridiomycete Allomyces macrogynus. Phylogenetic trees inferred from the derived COX1 and COX3 proteins and the nuclear rns sequences show with good bootstrap support that A. macrogynus is an early diverging fungus. The trees inferred from mitochondrial rns sequences do not yield a topology that is supported by bootstrap analysis. The similarity and the relative robustness of the nuclear rns and the mitochondrial protein-derived phylogenetic trees suggest that protein sequences are of higher value than rRNA sequences for reconstructing mitochondrial evolution. In addition, our trees support a monophyletic origin of mitochondria for the range of analyzed eukaryotes. Correspondence to: B. Franz Lang     

Production of volatiles by the red seaweed Gelidium arbuscula (Rhodophyta): emission of ethylene and dimethyl sulfide

The effects of different light conditions and exogenous ethylene on the emission of volatile compounds from the alga Gelidium arbuscula Bory de Saint‐Vincent were studied. Special emphasis was placed on the possibility that the emission of ethylene and dimethyl sulfide (DMS) are related through the action of dimethylsulfoniopropionate (DMSP) lyase. The conversion of DMSP to DMS and acrylate, which is catalyzed by DMSP lyase, can indirectly support the synthesis of ethylene through the transformation of acrylate to ethylene. After mimicking the desiccation of G. arbuscula thalli experienced during low tides, the volatile compounds emitted were trapped in the headspace of 2 mL glass vials for 1 h. Two methods based on gas chromatography/mass spectrometry revealed that the range of organic volatile compounds released was affected by abiotic factors, such as the availability and spectral quality of light, salinity, and exogenous ethylene. Amines and methyl alkyl compounds were produced after exposure to white light and darkness but not after exposure to exogenous ethylene or red light. Volatiles potentially associated with the oxidation of fatty acids, such as alkenes and low‐molecular‐weight oxygenated compounds, accumu‐lated after exposure to exogenous ethylene and red light. Ethylene was produced in all treatments, especially after exposure to exogenous ethylene. Levels of DMS, the most abundant sulfur‐compound that was emitted in all of the conditions tested, did not increase after incubation with ethylene. Thus, although DMSP lyase is active in G. arbuscula, it is unlikely to contribute to ethylene synthesis. The generation of ethylene and DMS do not appear to be coordinated in G. arbuscula.     

Two different genetic strains of stalked-Ulva (Ulvales, Chlorophyta) grow on intertidal rocky shores in Ebisujima, central Japan

Stalked‐Ulva has been recognized as an ecologic form of Ulva pertusa Kjellman with narrow and extensive stipes that grows on rocky shores with strong wave action. However, it is possible that stalked‐Ulva includes more than two taxa, because it has been shown previously that some isolates of stalked‐Ulva did not cross with U. pertusa. Therefore, further crossing tests, observations of swarmer behavior, culture studies and comparison of DNA sequences were made to clarify whether or not all stalked‐Ulva are included within U. pertusa. Crossing tests showed that stalked‐Ulva contained two different types, one that crossed with U. pertusa (Up strain) and one (N strain) that did not. The biflagellate swarmers of N strains showed negative phototaxis and were slightly larger than male and female gametes of Up strains. Thalli cultured from the swarmers of N strains released the same type of swarmers again. The N strains have an asexual life history, reproducing solely by biflagellate swarmers. Internal transcriber spacer sequence analysis indicated that these two entities are U. pertusa (Up strain) and U. fasciata Delile (N strain). In culture both strains differ morphologically from wild thalli with stipes; it seems that the two different taxa both show a petiolate morphology when growing under the same environmental conditions.     

Interaction Between A1 Adenosine and Class II Metabotropic Glutamate Receptors in the Regulation of Purine and Glutamate Release from Rat Hippocampal Slices

Abstract: Electrical stimulation of rat hippocampal slices evoked the release of excitatory amino acids and purines, as reflected by a time-dependent increase in the extracellular levels of glutamate and adenosine, as well as by the increased efflux of radioactivity in slices preloaded with both [¹⁴C]glutamate and [³H]adenosine. The evoked release of excitatory amino acids and purines was amplified when slices were exposed to 8-cyclopentyl-1,3-dipropylxanthine (a selective A1 adenosine receptor antagonist), (+)-α-methyl-4-carboxyphenylglycine [a mixed antagonist of metabotropic glutamate receptors (mGluRs)], or (2S,3S,4S)-2-methyl-2-(carboxycyclopropyl)glycine (a selective antagonist of class II mGluRs). In contrast, 2-chloro-N⁶-cyclopentyladenosine (CCPA; a selective A1 receptor agonist) or (2S,1R,2R,3R)-(2,3-dicarboxycyclopropyl)glycine (DCG-IV; a selective agonist of class II mGluRs) reduced the evoked release of excitatory amino acids and purines. CCPA and DCG-IV also reduced the increase in cyclic AMP formation induced by either forskolin or electrical stimulation in hippocampal slices. The inhibitory effect of CCPA and DCG-IV on release or cyclic AMP formation was less than additive. We conclude that the evoked release of excitatory amino acids and purines is under an inhibitory control by A1 receptors and class II mGluRs, i.e., mGluR2 or 3, which appear to operate through a common transduction pathway. In addition, although these receptors are activated by endogenous adenosine and glutamate, they can still respond to pharmacological agonists. This provides a rationale for the use of A1 or class II mGluR agonists as neuroprotective agents in experimental models of excitotoxic neuronal degeneration.     

Regulation of amino acid synthetic enzymes in Neurospora crassa in the presence of high concentrations of amino acids

Summary Ornithine carbamoyl transferase and leucine aminotransferase of Neurospora crassa represent two of many amino acid synthetic enzymes which are regulated through cross-pathway (or general) amino acid control. In the wild-type strain both enzymes display derepressed activities if the growth medium is supplemented with high (mM range) concentrations of l-amino acids derived from branched pathways, i.e. the aspartate, pyruvate, glycerophosphate and aromatic families of amino acids. A cpc-1 mutant strain, impaired in cross-pathway regulation i.e. lacking the ability to derepress, shows delayed growth under such conditions. In the presence of glycine, homoserine and isoleucine various cpc-1 isolates do not grow at all. Derepression of the wild-type enzymes and the retarded growth of the mutant strain can be reversed if certain amino acids are present in the medium in addition to the inhibitory amino acids.     

Olfactory discrimination of complex mixtures of amino acids by the black bullhead Ameiurus melas

On the basis of previous findings of behavioural discrimination of amino acids and on the knowledge of electrophysiology of the catfish (genera Ictalurus and Ameiurus) olfactory organs, behavioural experiments that investigated olfactory discrimination of amino acid mixtures were carried out on the black bullhead Ameiurus melas. Repeated presentations of food‐rewarded mixtures released increased swimming activity measured by counting the number of turns >90° within 90 s of stimulus addition. Non‐rewarded amino acids and their mixtures released little swimming activity, indicating that A. melas discriminated between the conditioned and the non‐conditioned stimuli. Two questions of mixture discrimination were addressed: (1) Are A. melas able to detect components within simple and complex amino acid mixtures? (2) What are the smallest differences between two complex mixtures that A. melas can detect? Three and 13 component mixtures tested were composed primarily of equipotent amino acids [determined by equal electroolfactogram (EOG) amplitude] that contained L‐Cys at ×100 the equipotent concentration. Ameiurus melas initially perceived the ternary amino acid mixture as its more stimulatory component alone [i.e. cysteine (Cys)], whereas the conditioned 13 component mixture containing the more stimulatory L‐Cys was perceived immediately as different from L‐Cys alone. The results indicate that components of ternary mixtures are detectable by A. melas but not those of more complex mixtures. To test for the smallest detectable differences in composition between similar multimixtures, all mixture components were equipotent. Initially, A. melas were unable to discriminate the mixtures of six amino acids from the conditioned mixtures of seven amino acids, whereas they discriminated immediately the mixtures of four and five amino acids from the conditioned mixture. Experience with dissimilar mixtures enabled the A. melas to start discriminating the seven‐component conditioned mixture from its six‐component counterparts. After fewer than five training trials, A. melas discriminated the mixtures of nine and 10 amino acids from a conditioned mixture of 12 equipotent amino acids; however, irrespective of the number of training trials, A. melas were unable to discriminate the 12 component mixture from its 11 component counterparts.     

Factors Influencing the Growth of Glaucoma chattoni in a Chemically Defined Medium*

SYNOPSIS. Glaucoma chattoni strain A has been grown in the chemically defined medium previously used for Colpidium campylum and Tetrahymena pyriformis. It was necessary to modify the amino acid, nucleotide and other components of the medium in order to obtain optimum growth. The modified medium contained 17 amino acids, nucleic acid components, fatty acids, stigmasterol, sodium acetate, a mixture of B-vitamins and several inorganic salts.     

Minutes of the Ninth Annual General Meeting

In unialgal culture, Gymnodinium pseudopalustre Schiller (G.p.) and Woloszynskia apiculata sp. nov. (W.a.) multiply respectively by binary fission in the motile state and by motionless zoosporangia, releasing 2, 4 or 8 zoospores. Both species are isogamous, but G.p. is homothallic, W.a. heterothallic. Fusion of the planogametes leads to long-lived planozygotes, which retain two posterior flagella and, while enlarging, assume specific morphologies. The motile stage of the zygotes is terminated by formation of hypnozygotes (resting spores), globular and spiny in G.p., grossly fusiform (‘horned’) and tubercled in W.a. The composition of the hypnozygote walls is described. After their dormancy has been broken by a cold treatment of several weeks in the dark, hypnozygotes of both species germinate when brought back to higher temperature and light. In so doing, those of G.p. excyst one posteriorly biflagellate swarmer as a meiocyte, which, after a stage of nuclear cyclosis or, in karyological terms, zygotene through postzygotene, undergoes two steps of binary fission in the motile stage, separated by several days. In W.a., cyclosis as well as the first meiotic cell division occur inside the closed wall of the hypnozygote (now a meiocyte); thereafter either two swarmers escape and undergo the second meiotic division in a separate zoosporangium or, alternatively, second meiotic nuclear and cell divisions also take place inside the spore wall and four swarmers are finally excysted. Some aspects of dinoflagellate life cycles and taxonomic questions are discussed.     

Composition of cell material and biological value of the cellular protein of a Micrococcus strain grown on hydrocarbons

A Micrococcus cerificans strain was grown on simple media with n-hexadecane or gas oil as sole carbon sources. Samples of cellular material recovered from hexadecane or gas oil fermentations do not appear to differ significantly in their composition. The protein content varied from 68 to 75%. With the exception of sulfur amino acids the amino acid distribution compares favorably with the FAO standard reference protein. The biological value of cell protein recoveered from hexadecane fermentations was 67 (cascin, 70). In the case of gas oil grown cells, the cell material recovered had to be completely purified in order to improve its protein quality. After fully extraction of undersirable fraction with petroleum ether in a Soxhlet apparatus the biological value observed was 63.     

Protein increase and lysine production by a <Emphasis Type="Italic">Paecilomyces variotii</Emphasis> strain grown on two-phase olive mill waste

Two-phase olive-mill waste, the so-called “ecological”, has been treated with a Paecilomyces variotii isolate in solid state fermentation experiments. The growth of the microorganism was estimated by measuring the production of carbon dioxide, using gas chromatography. A 46% increase of the protein content was achieved at the fermented product, after molasses addition at the initial mixture. The amino acid profile of the produced protein, as far as the essential amino acids are concerned, was significantly improved, resulting in a product that has the potential to be used as animal feed. Furthermore, it contains lysine, one of the essential amino acids that did not exist at the original product and is produced during fermentation. This is the first report on solid state fermentation of the two-phase olive mill waste (TPOMW) as a substrate, using a Paecilomyces variotii strain.     

Regularity in budding mode and resultant growth morphology of the azooxanthellate colonial scleractinian Tubastraea coccinea

Scleractinia exhibit a variety of growth forms, whether zooxanthellate or azooxanthellate, according to factors that control asexual reproduction and ensuing coral growth. The azooxanthellate branching scleractinian Dendrophyllia arbuscula shows regular modes of budding in terms of the locations of budding sites, the orientations of directive septa, and the inclination angle of budding throughout colonial growth. This study reports that such regularities are also found in the apparently different growth form of the massive dendrophylliid Tubastraea coccinea, which shows the following growth features: (1) the offsets (lateral corallites) always occur near four primary septa, except the two directive primary septa, meaning that the lateral corallites do not appear in the sectors of the two directive septa; (2) the two directive septa in lateral corallites tend to be oriented subperpendicular to the growth direction of the parental corallites; (3) the lateral corallites grow approximately diagonally upwards; and (4) these regularities are seen in the axial and derived lateral corallites among all generations during colony growth. Large differences in growth form are found between the branching D. arbuscula and massive T. coccinea, irrespective of the presence of specific regularities. It is likely that subtle modifications of certain parameters (e.g., budding interval, branch length, corallite size, and inclination angle of lateral corallites) have a strong effect on the overall growth morphology. A precise understanding of such regularities, which occur regardless of generation or taxonomic position, would contribute to understanding the “shape-controlling mechanism” of corals, which are an archetypal modular organism.     

Amino acid composition of azolla as affected by strains and population density

The total nitrogen and amino acid composition of seven Azolla strains were compared at four different growth phases. Total nitrogen content of the individual strains ranged from 2.6% to 5.7% of dry matter and was not significantly influenced by growth phase or population density. The concentration of the sixteen amino acids determined was maximal during the linear growth stage and specific differences occurred among Azolla strains. AnAzolla microphylla strain was the best source of amino acids and anA. filiculoides strain the poorest under the cultural conditions used. The chemical index score demonstrated the potential of some species, such as theA. microphylla strain, as contributor of protein for animals. Strains of other species, such asA. filiculoides, had several limiting amino acids and appear more suited for use solely as a green manure. All Azolla strains contained a similar proportion of essential (55%) and non-essential (45%) amino acids. Leucine, lysine, arginine and phenylanine+tyrosine were the predominant essential amino acids whereas the sulfur containing amino acids (methionine and cystine) were present in smaller amounts.     

DNA nucleotide sequence homologies between some zoosporic fungi

Summary Representative species from the monoflagellate Blastocladiales and the biflagellate Saprolegniales were studied for their DNA base composition, heterogeneity, nucleotide sequence homology and divergence. Intergeneric, intrageneric and interstrain DNAs of Blastocladiales were heterogenous. The G+C values for their main component (average 64 percent) and two minor ones (average 52 and 44 percent) were found to be significantly higher than the corresponding values from the biflagellate Saprolegnia ferax (55, 46 and 36 percent respectively). In Allomyces species, the two hybrid, male and female strains were found to have closer homology with their parental types than these last between themselves. Among Blastocladiales, interspecific similarities between the epigynous A. macrogynus and the hypogynous A. arbuscula were higher (average 75 percent) than intergeneric similarities between Allomyces and Blastocladiella (average 58 percent). The biflagellate S. ferax was found to be distantly related to the uniflagellate Allomyces (average 48 percent similarity). The nucleotide sequence divergences obtained from thermal elution data correlated the hybridization values.     

Specificity of the amino acid transfer reaction inE. coli strains carrying different alleles of the RNA control (RC) gene

Summary The idea has been tested here that the aberration in amino acid controlled regulation of RNA synthesis in a mutant strain ofE. coli might reflect a major breakdown in the specificity of transfer of amino acids to S-RNA. For this purpose, S-RNA and amino acid activating enzymes were extracted from bacteria carrying either the normalRC ^st or the aberrantRC ^rel allele of the RNA control gene. The purified S-RNA preparations were first charged enzymatically with one or more of the 20 standard amino acids, then oxidized with periodate, and finally reisolated and retested for their residual capacity to accept an amino acid that was absent from the preliminary charging mixture. If preliminary charging transferred an amino acid to a non-cognate S-RNA species belonging to an absent amino acid, then the acceptor capacity for the missing amino acid would survive periodate oxidation and reveal its presence on recharging with that amino acid after post-periodate reisolation of the S-RNA. The results presented here show that there does not appear to exist any such major breakdown of transfer specificity in eitherRC ^st orRC ^rel bacteria: preliminary charging of the S-RNA fromRC ^rel bacteria with 19 of the 20 standard amino acids by use of the homologous amino acid activating enzymes does not afford protection against periodate oxidation for any appreciable fraction of the acceptor capacity for the absent 20th amino acid (when that amino acid is either methionine or arginine). It is unlikely, therefore, that thecatholic inducer, postulated to explain the continued RNA synthesis ofRC ^rel amino acid auxotrophs in the absence of their growth requirement, is one of the 20 standard amino acids.This investigation was supported by Public Health Service Research Grant CA 02129, from the National Cancer Institute.     

Nitrogen storage forms in nine boreal understorey plant species

Storage forms of N were studied in below-ground structures of nine boreal forest understorey plants. The ericaceous shrubs Vacciniumvitis-idaea and V.myrtillus, the fern Gymnocarpium dryopteris, the grass Deschampsia flexuosa, and the herbs Epilobium angustifolium, Maianthemum bifolium, Solidago virgaurea, Geranium sylvaticum and Trientalis europaea were sampled in early summer and late autumn from plots fertilised with a complete mixture of nutrients and from non-fertilised control plots. Concentrations of total nitrogen, insoluble and soluble proteins, free amino acids and nitrate were measured, and changes in absolute and relative concentrations of these N fractions between early summer and late autumn were used to identify the forms in which the plants store N. In all species studied, the concentration of free amino acids increased both between summer and autumn and in response to fertilisation, while the concentration of protein N increased only in response to fertilisation. Thus, free amino acids appear to have a central role in N storage. In all of the species except G. dryopteris, D. flexuosa and S. virgaurea, arginine dominated the pool of free amino acids and thus arginine was the major form of stored N in most species. In D. flexuosa and S. virgurea, however, asparagine and arginine together were the major forms of stored N, while glutamine was the major free amino acid, and N storage form, in G. dryopteris. Received: 10 March 1996 / Accepted: 22 December 1996