Sharon T. Broadwater

Molecular and morphological characterization of ten polar and near-polar strains within the oscillatoriales (Cyanobacteria)

An approximately 1400‐bp region of the 16S rRNA gene was sequenced for 10 polar or near‐polar strains putatively placed in the Oscillatorialean genera Oscillatoria, Phormidium, and Lyngbya obtained from the University of Toronto Culture Collection to assess phylogenetic relationships. The strains were also examined for thylakoid structure and cell division type with TEM as well as traditional morphology with LM. Phylogenetic trees constructed using parsimony, distance, and maximum likelihood methods were similar in topology. If the original epithets applied to the sequenced strains (both polar and those from GenBank) were used, it was clear that taxa were not monophyletic. However, using the revised taxonomic system of Anagnostidis and Komárek, we were able to reassign these strains to their current correct taxa (species, genus, and family). When these assignments were made, it was determined that the molecular sequence data analyses were congruent with morphology and ultrastructure. Nine of the polar strains were found to be new species, and eight were described as such: Arthronema gygaxiana Casamatta et Johansen sp. nov., Pseudanabaena tremula Johansen et Casamatta sp. nov., Leptolyngbya angustata Casamatta et Johansen sp. nov., Phormidium lumbricale Johansen et Casamatta sp. nov., Microcoleus glaciei Johansen et Casamatta sp. nov., Microcoleus rushforthii Johansen et Casamatta sp. nov., Microcoleus antarcticus Casamatta et Johansen sp. nov., Microcoleus acremannii Casamatta et Johansen sp. nov. Some genera (Leptolyngbya and Microcoleus) were clearly not monophyletic and require future revision.

CHOREONEMA (CORALLINALES, RHODOPHYTA): 18S rDNA PHYLOGENY AND RESURRECTION OF THE HAPALIDIACEAE FOR THE SUBFAMILIES CHOREONEMATOIDEAE, AUSTROLITHOIDEAE, AND MELOBESIOIDEAE

Phylogenetic analyses of 18S rDNA gene data for Choreonema thuretii (Corallinales, Rhodophyta) and available data for other coralline red algae indicated that Choreonema belongs to the same lineage as other taxa of Corallinales possessing tetra/bisporangial conceptacles with multiporate plates. These results, when integrated with extant morphological/anatomical data, ultrastructural data, and taxonomic data led to the conclusion that all taxa of Corallinales possessing multiporate conceptacles belong to a distinct family, the Hapalidiaceae. Recognition of the Hapalidiaceae as a distinct family was supported both phylogenetically and phenetically. The Hapalidiaceae includes those taxa of Corallinales whose tetrasporangia produce zonately arranged spores and whose tetra/bisporangia are borne in conceptacles, produce apical plugs, and develop beneath multiporate plates. The Hapalidiaceae includes the subfamilies Choreonematoideae, Melobesioideae, and Austrolithoideae, formerly placed in the Corallinaceae sensu lato. The Choreonematoideae lack cell connections between adjacent vegetative filaments and have a multiporate plate that is acellular at maturity, consisting only of a calcium carbonate matrix. The Austrolithoideae and Melobesioideae both have cellular pore plates; taxa of Melobesioideae have cell fusions between cells of adjacent vegetative filaments, whereas taxa of Austrolithoideae lack cellular connections between adjacent vegetative filaments. Inclusion of the Austrolithoideae in the Hapalidiaceae was based entirely on morphological/anatomical evidence; molecular evidence currently is lacking. Relevant historical and nomenclatural data are included.

ULTRASTRUCTURE OF VEGETATIVE ORGANIZATION AND CELL DIVISION IN THE UNICELLULAR RED ALGA DIXONIELLA GRISEA GEN. NOV. (RHODOPHYTA) AND A CONSIDERATION OF THE GENUS RHODELLA1

This study suggests that the genus Rhodella be restricted to that set of features currently observed only in Rhodella maculata Evans and Rhodella violacea (Korn‐mann) Wehrmeyer, that a new genus Dixoniella be established to accommodate the unicellular red alga, Rhodella grisea (Geitler) Fresnel, Billard, Hindák et Pekár‐ková, and that Rhodella cyanea Billard et Fresnel be further studied for probable reclassification. These conclusions are based on ultrastructural comparisons of Dixoniella grisea with published information on the genus Rhodella. The presence of thylakoids in the pyrenoid, a peripheral encircling thylakoid in the chloroplast, a dictyosome/nuclear envelope association, and the lack of a specialized pyrenoid/nucleus association in D. grisea separate this alga from the genus Rhodella. Cell division in D. grisea is not demonstrably different from that in Rhodella, although the unusually well‐defined material of the presumptive microtubule organizing center (MTOC) made it possible to follow the development and behavior of the MTOC to a greater degree than in previously studied red algal cells. The surprising amount of conformity in cell division characters between D. grisea and the genus Rhodella prompted a comparison of cell division characteristics in all red algal unicells studied to date.

ULTRASTRUCTURE OF EARLY DEVELOPMENT IN THE FEMALE REPRODUCTIVE SYSTEM OF POLYSIPHONIA HARVEYI BAILEY (CERAMIALES, RHODOPHYTA)1

Prefertilization and immediate postfertilization development in the female reproductive branch of Polysiphonia harveyi (Bailey) was studied with the electron microscope. Results pertaining to prefertilization morphology and development are consistent with those established in earlier light microscopic studies, but several unexpected ultrastructural characteristics were discovered. The mature carpogonium was found to have double membrane‐bound vacuoles of nuclear origin and the carpogonial nucleus contained a nucleolus with a distinctive crystalline lattice. Trichogynes lacked a nucleus. Of particular interest was the discovery of a highly structured channel of smooth endoplasmic reticulum (SER) which extended uninterrupted, except for pit connections, through the carpogonial branch. It is suggested that the message of fertilization is conducted through the SER channel from the carpogonium to the support cell. Few observations were made on postfertilization branches, but evidence of direct fusion between the carpogonium and auxiliary cell was fairly conclusive. Pit plugs in the female branch were found to be of three morphological types differing by the presence and number of pit membranes. We have designated these plugs Type I–III since differential functioning was not fully ascertained. Our data suggest that pit membranes may serve to stabilize the plug and that those plugs without membranes are more readily dismantled to allow cytoplasmic continuity between cells.

Ultrastructure of unicellular red algae

The phylum Rhodophyta is an enigmatic as semblage of organisms whose phylogenetic relationships with other eukaryotes are shrouded in uncertainty. The group was long held to be among the most primitive eukaryotes due to the lack of a centriole complex and the similarities between the red algal chloroplast and cyanobacteria (Garbary and Gabrielson 1990). This view was given further impetus when the analysis of red algal 5s ribosomal RNA indicated an early divergence from other eukaryotes (Lim et al. 1986; Hori and Osawa 1987). However, there is equally compelling evidence that red algae are not more primitive than other algal phyla. Acceptance of the endosymbiotic origin of chloroplasts renders the resemblance of red algae and cyanobacteria to be superficial (Gabrielson et al. 1985) while ultrastructural studies show typical eukaryotic cell organization (Pueschel 1990). In addition, recent studies of the 18s ribosomal subunit (Bhattacharya et al. 1990) indicate divergence of red algae to be at the same time as that of ‘plants, fungi, animals and most protists’.

ULTRASTRUCTURE OF VEGETATIVE AND DIVIDING CELLS OF THE UNICELLULAR RED ALGAE RHODELLA VIOLACEA AND RHODELLA MACULATA1

Rhodella violacea (Kornmann) Wehrmeyer and Rhodella maculata Evans were investigated for ultrastructural details of vegetative and dividing cells. Rhodella violacea has a nuclear projection into the pyrenoid similar to that found in R. maculata, although the nuclear projection in R. maculata traverses a starch‐lined area before contacting the pyrenoid. Unlike most, red algae, the two Rhodella species lack a peripheral encircling thylakoid in the chloroplast and have dictyosomes associated solely with endoplasmic reticulum (ER) instead of with both mitochondria and ER. Both species also have a well‐developed peripheral system of ER connected to the plasmalemma by tubules, a situation found only in red algal unicells, Cell division was studied primarily in R. violacea; a less thorough examination of R. maculata showed no essential differences. Both have small, double‐ringed, nucleus‐associated organ files (NAOs) surrounded by moderately electron‐dense material, metaphase–anaphase polar gaps in the nuclear envelope, absence of perinuclear ER. and short interzonal spindles. This pattern of mitosis is similar in most respects to that reported in the unicell Flintiella. Following mitosis, microtubules extend from the region of each NAO to its associated nucleus and to the undivided pyrenoid. The NAOs appear to apply tension to the nuclei and the pyrenoid and may be the mechanism for ensuring equal partitioning of both organdies. Two different forms of pyrenoid‐nucleus association occur during mitosis. Nuclear projections into the pyrenoid, prevalent during interphase and early stages of mitosis, recede at metaphase. Then, the pyrenoid extends protrusions into the nuclear polar areas, forming a cup that partially surrounds the nucleus. Cell division and vegetative characters confirm the close taxonomic affinity of these two species of Rhodella and support their separation from the genus Porphyridium.

Synthesis of hexafluoroisopropylidene-containing polyimide-silver nanocomposite films evolving specularly reflective metal surfaces

Highly reflective surface-metallized flexible polyimide films have been prepared by the incorporation of the soluble silver ion complex (1,1,1-trifluoroacetylacetonato)silver(I) into dimethylacetamide solutions of the poly(amic acid) prepared from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (4-BDAF). Thermal curing to 300 °C of solution cast silver(I)poly(amic acid) films leads to cycloimidization of the amic acid with concomitant silver(I) reduction and formation of a reflective surface-silvered film from 6–13% weight percent silver. The reflective surfaces evolve only when the cure temperature reaches 300 °C. After achieving a maximum value the reflectivity abruptly drops with further heating at 300 °C and the polyimide suffers oxidation degradation. The metallized films are thermally stable and maintain mechanical properties similar to those of the parent polyimide. TEM reveals that the interior of the composite films have ca. 5–20 nanometer-sized silver particles. SEM shows surface silver particles from ca. 50–1000 nm whose size varies with cure time at 300 °C. Neither the bulk nor the surface of the films is electrically conductive. There is strong interfacial adhesion of metal to polyimide.

Ultrastructure of vegetative organization and cell division in the freshwater red algaCompsopogon

SummaryUniseriate filaments of the freshwater red algaCompsopogon coeruleus were examined by transmission electron microscopy for details of vegetative organization and cell division with the goal of providing useful taxonomic characters. Each cells single, complex chloroplast contains a peripheral encircling thylakoid, and unlike the vast majority of red algae, the cis-regions of dictyosomes are not consistently juxtaposed with mitochondria. These subcellular features, which are present in all examined genera in theCompsopogonales, Erythropeltidales, andRhodochaetales, along with certain unique reproductive characteristics, unify these three orders. During mitosis in uncorticated axial cells, a small, ring-shaped nucleus associated organelle (NAO) is located at each division pole, an intranuclear spindle comes to a moderately acute focus at the flattened, fenestrated metaphase-anaphase division poles and perinuclear ER partially encloses dividing nuclei, including a well-developed interzonal midpiece. The cleavage furrow penetrates the large, central vacuolar region to separate daughter nuclei. These cell division features most closely resemble the pattern described for the orderCeramiales. Our observations of vegetative and dividing cells ofC. coeruleus supplement the growing volume of evidence in favour of uniting all red algae into a single class without subclass designations.

Ultrastructure of meiosis in Dasya baillouviana (Rhodophyta). I: Prophase I

This first of two papers on ultrastructural observations of meiosis in the red alga Dasya baillouviana (Gmelin) Montague describes stages of prophase I of meiosis. Although the five stages of prophase were originally derived from light microscopic studies, the same stages were utilized for this study based on the developmental sequence of the synaptonemal complex, which has the same morphology and mode of development as those reported for other red algae. The cytoplasm in early prophase sporocytes was typically less electron dense than either vegetative cells or sporocytes in later stages of meiosis. The reduction in density suggests clearing of ribosomes and other cytoplasmic components prior to conversion from sporophyte to gametophyte control. Leptotene cells often had an amorphous, chromatin‐free area, function unknown, which was not obviously associated with any specific nuclear region. Diplotene cells were characterized by nuclei containing prominent ring‐shaped nucleoli composed of a dark staining ring of material surrounding an electron‐translucent “vacuole.” Packets of electron‐dense, fibrillar material were often noted in the cytoplasm of late prophase cells. These packets are thought to he “nuage,” a term applied to large cytoplasmic aggregations of RNA in germ cells of several other phyla. It is suggested that nuage may represent a new infusion of ribosomal and messenger RNA for post‐meiotic development. The division pales are established by late prophase and a single polar ring is found within each large “exclusion zone” in close association with a pore‐free area of nuclear envelope. Both annulate lamellae and small, numerous vesicles are located in the exclusion zones. The significance of the various aspects of prophase I is discussed with the overall observation that this phase of meiosis in red algae is very similar to the process in higher plant and animal cells.

PARASITIC INTERACTIONS AND VEGETATIVE ULTRASTRUCTURE OF CHOREOAEMA THURETII (CORALLINALES, RHODOPHYTA)1

The monotypic coralline red alga, Choreonema thuretii (Bornet) Schmitz (Choreonematoideae), grows endophytically within three geniculate genera of the Corallinoideae. Although the thallus of Choreonema is reduced, lacks differentiated plastids, and is endophytic except for its conceptacles, its status as a parasite has been questioned because cellular connections to the host had not been ob served. Transmission electron microscopy, however, disclosed a previously undescribed type of parasitic interaction in which Choreonema interacts with its host through specialized cells known as lenticular cells. These small, lens‐shaped cells are produced from the single file of host‐penetrating vegetative cells. Pit plug morphology between vegetative and lenticular cells is polarized. Plug caps facing the vegetative cell have normal coralline morphology, while those facing the lenticular cell are composed of three layers. Regions of lenticular cells near host cells protrude toward the host cell; upon encountering the host cell wall, the prolrusion produces numerous finger‐like fimbriate processes that make cellular connections with the host cell. Lenticular cells may extend several protrusions toward a host cell or penetrate more than one host cell; two or more lenticular cells may also penetrate the same host cell. The lack of secondary pit connections, cell fusions, and passage of parasitic nuclei suggest that this parasitic relationship may be evolutionarily older than previously reported cases of parasitism in red algae.