[Ultrastructural description of Euglena pailasensis (Euglenozoa) from Rincón de la Vieja volcano, Guanacaste, Costa Rica].

The euglenoids are unicellular eukaryotic flagellates living in a diversity of soils and aquatic environments and ecosystems. This study describes the ultrastructure of an euglenoid isolated from the surface of a boiling mud pool with temperatures ranging from 38 to 98 degrees C and pH 2 - 4. The hot mud pool is located in Area de Pailas de Barro, Las Pailas, Rincón de la Vieja Volcano, Guanacaste, Costa Rica.

Role of the oxidized secondary acceptor QB of photosystem II in the delayed 'afterglow' chlorophyll luminescence.

Leaf discs of dark-adapted tobacco plants were excited by 2 flashes and kept in darkness at 20 degrees C for various time periods, then thermoluminescence emission was recorded without freezing the sample. The B band at 30 degrees C decreased with a half-time t1/2 approximately 1 min and the AG band at 45 degrees C with a t1/2 approximately 5 min. This corresponds to the decay kinetics of S2/3 in PS II centres in the state S2/3 QB - (B band) or S2/3 QB.

Copper effect on cytochrome b of photosystem II under photoinhibitory conditions.

Toxic Cu (II) effect on cytochrome b(559) under aerobic photoinhibitory conditions was examined in two different photosystem II (PSII) membrane preparations active in oxygen evolution. The preparations differ in the content of cytochrome b(559) redox potential forms. Difference absorption spectra showed that the presence of Cu (II) induced the oxidation of the high-potential form of cytochrome b(559) in the dark.

Characterization of a photosynthetic Euglena strain isolated from an acidic hot mud pool of a volcanic area of Costa Rica.

Abstract Conspicuous green patches on the surface of an acidic hot mud pool located near the Rincón de la Vieja volcano (northwestern Costa Rica) consisted of apparently unialgal populations of a chloroplast-bearing euglenoid. Morphological and physiological studies showed that it is a non-flagellated photosynthetic Euglena strain able to grow in defined mineral media at temperatures up to 40 degrees C and exhibiting higher thermotolerance than Euglena gracilis SAG 5/15 in photosynthetic activity analyses. Molecular phylogeny studies using 18S rDNA and GapC genes indicated that this strain is closely related to Euglena mutabilis, another acid-tolerant photosynthetic euglenoid, forming a clade deeply rooted in the Euglenales lineage.