Geosiphon pyriforme,a fungus forming endocytobiosis withNostoc (Cyanobacteria), is an ancestral member of the glomales: Evidence by SSU rRNA Analysis

Geosiphon pyriforme inhabiting the surface of humid soils represents the only known example of endocytobiosis between a fungus (Zygomycotina; macrosymbiont) and cyanobacteria (Nostoc; endosymbiont). In order to elucidate the taxonomical and evolutionary relationship ofGeosiphon pyriforme to fungi forming arbuscular mycorrhiza (AM fungi), the small-subunit (SSU) ribosomal RNA genes ofGeosiphon pyriforme andGlomus versiforme (Glomales; a typical AM fungus) were analyzed and aligned with SSU rRNA sequences of several Basidiomycetes, Ascomycetes, Chytridiomycetes, and Zygomycetes, together with all AM-fungal (Glomales) sequences published yet. The distinct group of the order Glomales, which includesGeosiphon, does not form a clade with any other group of Zygomycetes. Within the Glomales, two main lineages exist. One includes the families Gigasporaceae and Acaulosporaceae; the other one is represented by the genusGlomus, the members of which are very divergent.Glomus etunicatum andGeosiphon pyriforme both form independent lineages ancestral to the Glomales. The data provided by the present paper confirm clearly thatGeosiphon represents a fungus belonging to the Glomales. The question remains still open as to whether or notGeosiphon is to be placed within or outside the genusGlomus, since this genus is probably polyphyletic and not well defined yet.Geosiphon shows the ability of aGlomus-like fungus to form a “primitive” symbiosis with a unicellular photcautotrophic organism, in this case a cyanobacterium, leading to the conclusion that a hypothetical association of aGlomus-like fungus with a green alga as a step during the evolution of the land plants appears probable. Correspondence to: H. Gehrig     

Geosiphon pyriforme,an Endosymbiotic Consortium of a Fungus and a Cyanobacterium (Nostoc), Fixes Nitrogen

The bladders of Geosiphon pyriforme, an endosymbiotic consortium of a fungus and the cyanobacterium Nostoc punctiforme, show nitrogenase activity. This suggests that the organism is capable of nitrogen fixation.     

SYNUROPHYCEAE CLASSIS NOV., A NEW CLASS OF ALGAE

The silica-scaled algae (Synuraceae, Chrysophyceae sensu lato) are compared to other Chrysophyceae, Phaeophyceae and Bacillariophyceae with occasional comparisons to other chlorophyll c-containing algae, scaled protozoa and oomycete fungi. The silica-scaled algae have several unique characters which separate them from the above groups and based upon these differences a new order, Synurales ord. nov., and a new class, Synurophyceae class. nov., are described. The major distinguishing characters of the Synurophyceae class. nov. are: they have chlorophylls a and c₁ but lack chlorophyll c₂; their flagellar apparatus includes a microtubular root that loops around two parallel flagella and a flagellar root system which occurs in four absolute orientations; the photoreceptor consists of paired flagellar swellings which are not associated with the cell membrane and chloroplast; no eyespot is present; the nuclear envelope is not or is only weakly associated with the chloroplast endoplasmic reticulum. The Synurophyceae class. nov. are about equally distinct from the Chrysophyceae sensu stricto, Phaeophyceae and Bacillariophyceae when the class level characters are compared. Although the Phaeophyceae have a long history of being placed by themselves in the division Phaeophyta, and the Bacillariophyceae and Chrysophyceae have recently been placed alone in the Bacillariophyta and Chrysophyta, respectively, the similarities found among these classes suggest these algae are not so distinct that they require separate divisions. Tentatively, therefore, the Synurophyceae are placed in the division Phaeophyta along with the Bacillariophyceae and Chrysophyceae sensu stricto.     

PHOTOSYNTHETIC ACTIVITY OF TWO DEVELOPMENTAL STAGES OF A NOSTOC STRAIN (CYANOBACTERIA) ISOLATED FROM GEOSIPHON PYRIFORME (MYCOTA)1

Sessile colonies and motile hormogonia, the two main developmental stages in the life cycle of a Nostoc strain isolated from the endocytobiosis with Geosiphon pyriforme (Kützing) F. v. Wettstein, were investigated for their photosynthetic competence. Large-scale fractionation of the two stages is presented. Photosynthetic parameters were assessed by measurement of chlorophyll fluorescence and oxygen evolution. Hormogonia were as photosynthetically competent as the colonial stage. In addition, hormogonia showed an enhanced capability for nonradiative dissipation of absorbed light energy, a feature that might be important for their function as propagula. Data for the quantum yield of photosystem II of the isolated Nostoc strain were compared to the values determined in situ in G. pyriforme and indicated the possibility of a higher photosynthetic capacity of the endosymbiotic as compared to the isolated cyanobacterium.     

Geosiphon pyriforme,an Endosymbiotic Association of Fungus and Cyanobacteria: the Spore Structure Resembles that of Arbuscular Mycorrhizal (AM) Fungi

The zygomycete Geosiphon pyriforme is the only known endocyanosis of a fungus. The Nostoc spp. filaments are included in photosynthetically active and nitrogen fixing, multinucleated bladders, which grow on the soil surface. The spores of the fungus are white or slightly brownish. They are about 250 μm in diameter and develop singly on hyphal ends or, less frequently, intercalarly. The wall of the spores consists of a thin innermost layer, a laminated inner layer with a thickness of about 10–13 μm, and an evanescent outer layer. The laminated layer is composed of helicoidally arranged microfibrils, and is separated from the evanescent outer layer by a thin electron-dense sublayer. Polarisation microscopy indicates the occurrence of chitin. Shape and wall ultrastructure of the Geosiphon spores and their cytoplasm resemble that of Glomus spores, but are different from that of other genera of the Glomales and Endogonales. Germination occurs by a single thick hyphal outgrowth directly through the spore wall. Like various AM forming fungi, Geosiphon pyriforme contains endocytic bacteria-like organisms, which are not surrounded by a host membrane. Our observations indicate that Geosiphon is a potential AM fungus.     

A NEW PHYLOGENY FOR CHROMOPHYTE ALGAE USING 16S-LIKE RRNA SEQUENCES FROM MALLOMONAS PAPILLOSA (SYNUROPHYCEAE) AND TRIBONEMA AEQUALE (XANTHOPHYCEAE)1

The 16S-like ribosomal RNA genes from Mallomonas papillosa Harris et Bradley (Synurophyceae) and Tribonema aequale Pascher (Xanthophyceae) were sequenced and compared to those of other eukaryotes. Mallomonas is closely related to Ochromonas (Chrysophyceae) and supports the general hypothesis of a close phylogenetic relationship between the Synurophyceae and Chrysophyceae. Tribonema is specifically related to Costaria costata (C. A. Agardh) Saunders (Phaeophyceae) demonstrating an unexpected phylogenetic relationship between the Xanthophyceae and Phaeophyceae. Distance and parsimony analysis place these four chromophyte genera in a complex evolutionary assemblage that includes the Bacillariophyceae and Oomycetes but excludes the Dinophyceae. The close relationship between the chromophyte algae and the Öomycete fungi supports the hypothesis that protists with tripartite hairs form a natural assemblage.     

Microglena butcheri nov. sp., a flagellate from the English Lake District

Summary Microglena butcheri nov. sp. (Chrysophyceae) is described and figured. Morphology and asexual reproduction were investigated by light microscopy. It was not possible to maintain this organism in culture.

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Zusammenfassung Microglena butcheri nov. sp. (Chrysophyceae) wird beschrieben and abgebildet. Die Morphologie and die ungeschlechtige Vermehrung wurden durch Lichtmikroskopie untersucht. Es war nicht möglich, diesen Organismus zu kultivieren.

     

THE OCCURRENCE OF CHLOROPHYLLS C1 AND C2 IN THE CHRYSOPHYCEAE1

We analyzed 34 strains representing 25 species of Chrysophyceae for chlorophylls c₁ and c₂ using thin-layer chromatography. Most organisms had both chlorophylls c₁ and c₂ in addition to chlorophyll a but 17 strains of 9 species of Synura and Mallomonas possessed only chlorophylls a and c₁. These are the first chlorophyll c-bearing algae which lack chlorophyll c₂. We postulate that at least some of the silica-scaled algae including Mallomonas and Synura may be distinct from other Chrysophyceae based upon pigmentation and other characters described in the literature.     

A morphological study of the phytoflagellate Chrysococcus Rufescens Klebs in culture

Cells of the freshwater nannoplankton flagellate Chrysococcus rufescens Klebs (Chrysophyceae or Chrysomonadida) were isolated from a pool in the English Lake District and the clonal cultures established were used for a morphological investigation by light and electron microscopy. A novel feature was a system of flattened sacs and tubules just below the cell surface, possibly connected with the formation of the thick fibrous lorica. The structure and disposition of the main organelles however resembled those of other members of the Chrysophyceae investigated.     

A new species of Pavlova from Madeira

Light microscope observations on Pavlova pinguis sp. nov. (Chrysophyceae), a marine flagellate, are described and it is compared with the type species P. gyrans. Recent observations on P. gyrans are given and the diagnoses of the genus and type species emended.     

A study of the nannoplankton flagellate Pedinella hexacostata vysotskii by light and electron microscopy

A strain of Pedinella hexacostata Vysotskii (Chrysophyceae, or Chrysomonadida) was grown in culture and examined by light and electron microscopy. Behaviour, phagotrophy and division have been observed and salinity tolerance tested experimentally. Pedinella is discussed with relation to Pseudopedinella and other members of the Pedinellaceae. The fine structure of the tentacles is compared with that of tentacles in some other Protozoa.     

Die Feinstruktur kristalloider Einschlüsse in Mitochondrien von Porterioochromonas stipitata

Summary The matrix of the mitochondria of Porterioochromonas stipitata Lewin (Chrysophyceae) often contains crystalloid inclusion bodies that are composed of hexagonally packed fibrils (or tubules). The fibrils have a diameter of 10 nm, their center-to-center spacing is 13,5 nm.     

John Bishop Duncan

Abstract

Atrichum undulatum (Hedw.) Beauv., Physcomitrium pyriforme (Hedw.) Hampe, Cyclodictyon blumeanum (C. Muell.) O. Kuntze and Tristichella spiculifera Dix., representing four genera of mosses new to Peninsular Malaysia, are reported and the latter two species described and illustrated. Features of ecological and distributional interest are also discussed. The sporophytes of Tristichella spiculifera are described and figured for the first time.     

Chrysosphaerella (Pseudochrysosphaerella)solitaria,spec. nova (Chrysophyceae)

A new unicellular species of the genusChrysosphaerella (Chrysophyceae) was found in fresh-water ponds in Switzerland, Japan, and the U.S.A. It is described asC. solitaria. The genus is divided into two subgenera:Chrysosphaerella, comprising the colonial species, andPseudochrysosphaerella, the unicellular ones.     

Synuraceae (Chrysophyceae) in the Netherlands

Summary Investigations of phytoplankton biomass development and species succession in the Oude Waal near Nijmegen revealed the importance of the Chrysophyceae (Table I).Submicroscopical structures of the Chrysophyceae are known to be species-specific. So electronmicroscopical observations have been introduced into the research program. Special attention has been paid to the (scale-bearing) Synuraceae. The analysis of weekly taken samples in the year 1979 revealed a typical temporal distribution pattern of the Synuraceae, mainly controlled by temperature. Particulary the genusSynura showed a succession of four species:S. uvella dominated at water temperatures from 10–14°C,S. glabra from 14–16°C,S. curtispina from 10–19°C andS. petersenii occurred at water temperatures ranging from 0–21°C.     

The moss genus Leptobryum and the identity of Pohlia integra

Abstract

Leptobryum Wilson (Bryaceae) consists of two species, viz., Leptobryum pyriforme (Hedw.) Wilson and L. wilsonii (Mitt.) Broth. Pohlia integra (Cardot) A.J.Shaw and three other species of Leptobryum, viz., L. escomelii Thér., L. pottiaceum Dusén, L. stellatum (Herzog) Broth. are reduced to synonomy under L. wilsonii. L. sericeum Kindb. is considered a doubtful species because no specimen could be located.     

Recent Bryological Literature

Abstract

Growing Leptobryum pyriforme (Hedw.) Wilson under ten times ambient atmospheric CO₂ concentrations showed that, while stomatal density and index decreased under elevated atmospheric CO₂, the overall number of stomata per spore capsule remained unaltered. Capsule length increased, while the size of stomata and epidermal cells decreased. This study suggests that stomatal frequency measures used to investigate the influence of varying levels of atmospheric CO₂ on angiosperms and gymnosperms may result in misleading conclusions when applied to bryophytes if considered in isolation from growth responses.     

Chrysocapsopsis rupicola: A new genus and species in the Chrysophyceae

Chrysocapsopsis rupicola gen. et sp. nov. (Chrysophyceae) is described. It differs from Chrysocapsa and the closely related genera Chrysocapselia and Tetrachrysis by possessing both epiphytic and planktonic forms within the same life-history. Reproduction is by budding which produces short irregular branches within a gelatinous mass. Four or more aplanospores are produced from each mother cell; no motile cells were observed.     

Prosthecium species with Stegonsporium anamorphs on Acer

Data from microscopic morphology, single-spore cultures, and DNA analyses of teleomorphs and anamorphs support the recognition of five species of Prosthecium with Stegonsporium anamorphs on Acer: P. acerinum sp. nov., the teleomorph of S. acerinum; P. acerophilum comb. nov., formerly known as Dictyoporthe acerophila; P. galeatum comb. nov., originally described as Massaria galeata; P. opalus sp. nov.; and P. pyriforme sp. nov., the teleomorph of S. pyriforme s. str. The morphology of both type specimens and freshly collected material was investigated. The teleomorphs have brown ellipsoidal ascospores with five distosepta and often a longitudinal distoseptum. The anamorphs of all species described here belong to Stegonsporium; their connection to the Prosthecium teleomorphs was demonstrated by morphology and DNA sequences of single spore cultures derived from both ascospores and conidia. The anamorphs and teleomorphs of all five Prosthecium species are described and illustrated by LM images, and a key to these species is provided. As perceived from this work, S. pyriforme is restricted to Europe and does not occur in North America, whereas S. acerinum is restricted to North America, not found in Europe. The host associations given in the literature are revised and evidence is provided that only A. opalus, A. pseudoplatanus, and A. saccharum are confirmed hosts of Prosthecium with Stegonsporium anamorphs. Molecular phylogenetic analyses of tef1, ITS rDNA, and partial nuLSU rDNA sequences confirm that the species with Stegonsporium anamorphs are closely related to P. ellipsosporum, the generic type species. Stilbospora macrosperma is confirmed as the anamorph of P. ellipsosporum by DNA data of single spore isolates obtained from both ascospores and conidia.     

Characterization of the glutamate/aspartate-transport system in a symbiotic Nostoc sp.

The permeability properties of the cell membrane of a symbiotic Nostoc sp. for glutamate and aspartate were investigated. These compounds were translocated across the plasmalemma by a transport system which showed a very high affinity for glutamate and a lower one for aspartate. Since a concomitant release of glutamate was observed during the uptake of these two amino acids it is concluded that the transport proceeds via a counterexchange mechanism. In addition to this counterexchange a net release of glutamate occurred in the dark. Some aspects concerning the possible function of this transport system in the symbiotic association Geosiphon pyriforme are discussed.