Nobutaka Hanagata

Tolerance of microalgae to high CO2 and high temperature

We have screened five green freshwater microalgae for tolerance to high CO2 concentrations. Scenedesmus and Chlorella showed much higher log phase growth rates than the other three strains tested. Scenedesmus was better able to tolerate very high CO2 concentrations than Chlorella. However, both algae had about the same growth rate when the CO2 concentration was in the range 10–30%. Chlorella was better able to tolerate elevated temperatures. The two algae had very similar light response curves. Scenedesmus was completely inhibited by 100% CO2. This inhibition was reversible since growth was resumed when the CO2 concentration was returned to 20%.

Phylogeny of the subfamily Scotiellocystoideae (Chlorophyceae, Chlorophyta) and related taxa inferred from 18S ribosomal RNA gene sequence data

Nuclear‐encoded small subunit ribosomal RNA gene (18SrDNA) sequences were determined for Coelastrella multistriata (Trenkwalder) Kalina et Punčochářová, two species of Scotiellopsis (S. oocystiformis (Lund) Kalina et Punčochářová and S. terrestris (Reisigl) Kalina et Punčochářová) and two species of Muriella (M. aurantiaca Vischer and M. terrestris Boye‐ Petersen). Coelastrella and Scotiellopsis are members of the subfamily Scotiellocystoideae, and Muriella is a member of the subfamily Chlorelloideae in the family Chlorellaceae. Phylogenetic trees were constructed based on these sequence data and on previously known 18SrDNA sequences of 25 taxa. Coelastrella and Scotiellopsis were closely related to each other and formed a cluster with Scenedesmus vacuolatus (Shihira et Krauss) Kessler et al. This cluster shared a monophyletic ancestry with other Scenedesmus species. Muriella aurantiaca formed a sister relationship with the monophyletic lineage of Scenedesmus. However, another species, M. terrestris, was placed in the Trebouxiophyceae and was strongly related to Chlorella. The genus Mychonastes belonging to the Scotiellocystoideae was also not monophyletic. This study suggests that the subfamily Scotiellocystoideae should be removed from the Chlorellaceae.

Behavior of cell aggregate of Carthamus tinctorius L. cultured cells and correlation with red pigment formation

The formation processes of Carthamus tinctorius cell aggregates in a growth medium and the correlation of red pigment formation with cell aggregate sizes were investigated. About 80% of cell aggregates in the growth medium were > 1.00 mm in size. The growth rate of large cell aggregates was more rapid than that of small cell aggregates. Most cell aggregates > 0.50 mm in size became larger or smaller than their original sizes during the culture. A high level of red pigment formation was observed when cell aggregates obtained by the preculture using cell aggregates < 1.00 mm in size were cultured in the production medium.

Reconsideration of the taxonomy of ellipsoidal species of Chlorella (Trebouxiophyceae, Chlorophyta), with establishment of Watanabea sen. nov.

Subcultures of SAG 211–9b and 1AM C‐211, ultimately derived from CCAP 211/9b, a strain isolated by Pringsheim in 1939 and identified as Chlorella sac‐charophila (Kruger) Migula were observed using light and electron microscopy. Their morphology proved to be basically identical. Both have two forms of cells, one (E‐form) narrowly to broadly ellipsoidal, the other (S‐form) ovoid to spheroidal. The cell wall of both forms is composed of a single smooth layer. The chloroplast of young cells is trough‐like or saucer‐shaped with a smooth margin, while that of mature cells is band‐ or cup‐shaped with deep incisions. The thylakoid lamellae are loosely stacked and neither form has a pyrenoid. Both types of cells are capable of producing autospores: eight to 16 in E‐form cells, two to four in S‐form cells. These morphological features are different from those of C. saccharophila, which has a pyrenoid and produces only one form of autospores. In the absence of any existing genus that includes Chlorella‐like algae with a simple cell wall, no pyrenoid, and two forms of mature cells and autospores, a new genus, Watanabea, is proposed with the type species W. reniformis.

SECONDARY CAROTENOID ACCUMULATION IN SCENEDESMUS KOMAREKII (CHLOROPHYCEAE, CHLOROPHYTA)

As Scenedesmus komarekii Hegewald was cultured under high light intensity and nitrogen limitation, the color of cells progressed from green to brown, and finally through orange to brick red. The secondary carotenoids astaxanthin and canthaxanthin, as well as apolar carotenoids, were detected in the brown and orange cells. These carotenoids were contained in lipoidal globules that were first formed at the periphery of the cell and progressively propagated toward its inside, eventually filling most of it. The chloroplast was single and parietal in the green cells. As the cells turned brown, the chloroplast divided into several small lobes and was pushed toward the interior by the accumulating lipoidal globules. Sometimes the outer layer of the wall of the brown cell developed one or two diametrically opposed swellings. Once the cells became orange or red, neither lipoidal globules nor any major organelles were distinguishable. The cell wall in the orange cells became thick because of the formation of electron‐dense granules between its outer and inner layers. The mode of the secondary carotenoid accumulation in S. komarekii differs from that of Haematococcus, an alga well known for its ability to accumulate secondary carotenoids, but resembles that of “Chlorella”zofingiensis (=Mychonastes zofingiensis (Dönz) Kalina et Punčochářová).

Elicitor for red pigment formation in Carthamus tinctorius cultured cells

Abstract Effective elicitors for formation of red pigment in Carthamus tinctorius cultured cells were screened. In the commercially available polysaccharides, xanthan gum and fucoidan were found to elicit pigment formation approx. 6-times greater than the control. In the autoclaved algae, blue-green algae such as Anabaena cylindrica, Anabaena variabilis and Nostoc linckia had a large elicitor effect, while the green algae tested had no effect. When the cell wall of N. linckia was used as elicitor, the pigment formed was approx. 10-times that of the control. In addition, an extracellular polysaccharide from a culture of unknown fungus strain SE-801 elicited pigment formation approx. 13-times that of the control. This extracellular polysaccharide consisted of two fractions, a 0–20% EtOH precipitating fraction and a 20–40% EtOH precipitating fraction. Both fractions possessed similar elicitor effects. The 0–20% EtOH precipitating fraction was decomposed by cellulase and glucoamylase. Following decomposition by these enzymes the elicitor effect of the 0–20% EtOH fraction was reduced.

SALT/WATER RELATIONSHIPS IN MANGROVES

ABSTRACT Mangroves form extensive, unique communities in tropical coastal areas and tidal lowlands, dominating 60–75% of tropical shorelines. The aim of the present review is to summarize the current knowledge concerning the mechanisms underlying the most striking feature of these plants—their unique ability to obtain water from the surrounding sea. Mangroves are thought to accomplish this by rejecting potentially harmful salts. Some species actively excrete those salts leaking into the plant by means of specialized salt glands in their leaves. Mangroves are rooted in anaerobic soils, a condition giving rise to the spectacular aerial roots, such as pneumatophores and stilt roots, characteristic of mangroves, that provide oxygen to submerged tissues. We shall also discuss recent studies that have focused on physiological issues in mangroves, such as oscillatory behavior of their stomata, the structure and function of salt glands, and the compatible solutes in their leaves, which balance the osmotic pressur...

Eukaryotic picoplankton, Mychonastes homosphaera (Chlorophyceae, Chlorophyta), in Lake Kinneret, Israel

Eukaryotic picoplankton was isolated from Lake Kinneret, Israel. This green picoplankton is spheroidal or ovoidal in shape. The cell wall has a network of ribs on its surface. The chloroplast is cup‐ or mantel‐shaped without a pyrenoid. The morphology and cellular structure of this autosporic alga is identical with Mychonastes homosphaera (Skuja) Kalina et Punčochářová. The phylogenetic tree based on 18S ribo‐somal RNA gene sequence data showed that M. homosphaera is placed in the Chlorophyceae and located at the base of a branch leading to the other algae possessing directly opposed orientation of the flagellar apparatus.

Red pigment production by Carthamus tinctorius cells in a two-stage culture system

Abstract Reactor configuration was investigated for optimal production of red pigment by Carthamus tinctorius cells in a two-stage culture. For the first stage, growth levels of cells in an Erlenmeyer flask on a rotary shaker and a seesaw type reactor were higher than those in an STR and bubble column. Cells grown at high k L a conditions possessed high pigment forming capacity in the second culture stage. Product inhibition was observed for pigment formation in the second culture stage. High pigment production levels were achieved by periodical removal of pigment from the reactor. Production medium in the second culture stage could be reused by removal of the pigment formed.

Effect of medium used in first stage culturing on red pigment formation in suspension culture of Carthamus tinctorius

Abstract In red pigment formation by suspension cultures of Carthamus tinctorius cells, the effect of the first culture stage conditions on red pigment formation in the second culture stage were investigated. In the medium composition for the first culture stage, CaCl2·2H2O, MgSO4·7H2O and KH2PO4 was found to affect red pigment formation. When the concentrations of these nutrients was increased to 2-, 3- and 8-fold, respectively, that of the MS medium, the level of red pigment formation in the second culture stage increased by about 5-times that of MS medium.