Cell wall development, microfibril and pyrenoid structure in type strains of Chlorella vulgaris, C. kessleri, C. sorokiniana compared with C. luteoviridis (Trebouxiophyceae, Chlorophyta)

Abstract

Ultrastructural examination of three glucosamine-type Chlorella species (C. vulgaris var. vulgaris, C. kessleri, C. sorokiniana), forming a related group in phylogenetic trees inferred from 18S rRNA gene sequences (FRIEDL 1995, Huss et al. 1999), revealed a similar cell ultrastructure but some differences in early and later stages of the cell wall development. All species mentioned above contain the monosaccharide glucosamine as the main constituent of the rigid cell wall (TAKEDA 1991, 1993a, 1993b). A thin electrondense layer is the first visible' structure covering the young daughter protoplasts of C. vulgaris and C. sorokiniana. Layered microfibrils can be observed in cross-sections of adult cell walls. Remnants of the broken maternal cell walls (MCW) persist in a culture medium. In C. kessleri the initial electrondense layer was not found. The cell wall is hardly visible, no rrricrofibrillar structure was detected. No MCW remnants were found in the medium. Negatively stained microfibrils of all the three species obtained by IN NaOH and 2M TFAA treatment are straight or slightly bent. The pyrenoid is transversed by two thylakoids. The rigid cell wall of C. luteoviridis is composed of glucose and mannose (TAKEDA 1991, 1993a, 1993b). However some ultrastructural features of C. luteoviridis resemble that of glucosamine-type cWorellas (the thin electrondense layer covering the young daughter protoplasts, microfibrillar structure of the adult cell wall visible on cross-sections, MCW remnants persisting in a medium). Microfibrils do not form a net, they are kinked and flexuous. C. luteoviridis differs from glucosamine-type species in the pyrenoid structure (the pyrenoid is bisected by four or two thylakoids). Thickness of microfibrils in all studied species is about 5 nm.

Regeneration and maturation of daughter cell walls in the autospore-forming green alga Chlorella vulgaris (Chlorophyta, Trebouxiophyceae)

“…Most ultrastructural studies of cell division in green algae have used chemical fixatives (Krienitz et al 1999;N mcová and Kalina 2000;Handa et al 2003). However, to characterize the two distinct stages of cell-wall synthesis, we observed the regeneration and maturation of the daughter cell wall by electron microscopy, using rapid freeze fixation and freeze substitution.…”

“…Their autosporangia are 5-7 mm in diameter. Using chemical fixatives and solvent dehydration for electron microscopy, N mcová and Kalina (2000) observed that a thin electron-dense layer is the first visible structure of the newly formed cell wall of a daughter cell in the autosporangium of C. vulgaris var. vulgaris and C. sorokiniana.…”

Algal products beyond lipids: Comprehensive characterization of different products in direct saponification of green alga Chlorella sp.

“…It has also been reported that cell wall thickness depends on the growth rate [31] more specifically if the growth rate is high, the cell wall is thinner. The structure of alga in the present work is analogous to images reported by Nemcová and Kalina [31] for different Chlorella species. In addition, starch, chloroplast with thylakoid membranes, cytoplasm, nucleus and pyrenoid are clearly visible inside the cell.…”

“…has relatively thick cell walls compared to for, example another alga species Dunaliella, which has nearly no cell walls [25]. It has also been reported that cell wall thickness depends on the growth rate [31] more specifically if the growth rate is high, the cell wall is thinner. The structure of alga in the present work is analogous to images reported by Nemcová and Kalina [31] for different Chlorella species.…”

MARINICHLORELLA KAISTIAE GEN. ET SP. NOV. (TREBOUXIOPHYCEAE, CHLOROPHYTA) BASED ON POLYPHASIC TAXONOMY1

“…Common unicellular, coccoid green algae are one of the most difficult algal groups to resolve taxonomically due to the relatively low number of distinctive morphological traits (Watanabe et al 2000), which are typically the basis of a classic taxonomic treatment of related taxa (Shihira and Krauss 1965). However, several researchers have succeeded in distinguishing these simple algae at the species and genus levels using a variety of physiological, morphological, and molecular traits (Da Silva and Gyllenberg 1972, Huss et al 1989, Huss et al 1999, Kessler and Huss 1992, Nemcová and Kalina 2000, Krienitz et al 2004). Taxonomic studies of chlorellacean taxa have primarily focused on biochemical and physiological characteristics (Kessler 1984, Kessler 1992, Kessler and Soeder 1962) and pyrenoid ultrastructure (Ikeda and Takeda 1995).…”