Morphology, ultrastructure, and small subunit rDNA phylogeny of the marine heterotrophic flagellate Goniomonas aff. amphinema.

Marine goniomonads have a worldwide distribution but ultrastructural information has not been available so far. An isolate of the heterotrophic marine nanoflagellate Goniomonas (G. aff. amphinema) from North Wales (UK) has been studied, providing information on its morphology and cellular structure using video, electron, laser scanning confocal microscopy (LSCM), and atomic force microscopy. Here, we describe a new feature, a granular area, potentially involved in particle capture and feeding. The binding of the lectin wheat germ agglutinin to the granular area of cells with discharged ejectisomes indicates the adhesive nature of this novel feature. The presence of a microtubular intracellular cytopharynx, apparently also used for feeding, has been revealed by LSCM. The small subunit rRNA gene of the isolate has been sequenced (1,788 bp). Phylogenetic results corroborate significant genetic divergence within the marine members of Goniomonas. This work highlights the need for integrated morphological, ultrastructural, and molecular investigation when describing and studying heterotrophic nanoflagellates.

Ciliate contributions to bioaggregation: laboratory assays with axenic cultures of Tetrahymena thermophila.

Protists, mainly ciliates, play several essential roles in biological wastewater treatment, such as the transfer of matter and energy, bacterial predation, and the removal of organic material. Moreover, during the treatment process, the formation of bioaggregates-flocs and biofilms-is essential to obtaining high-quality effluents. In the present study, Tetrahymena thermophila was used as a model organism to demonstrate the contribution of ciliates to bioflocculation. Axenic cultures of this species were exposed to chemical and mechanical stimuli that promote bioaggregation. In either case, the secretion of a capsulate mucous material by the ciliates or by particle aggregation was detected. Numerous, small, loosely compacted flocs were observed under shaking conditions and in the presence of latex beads. The composition of the exopolymeric material secreted by ciliates was analyzed by a series of fluorochromes and colorimetric methods, which showed that carbohydrates and nucleic acids were the main components involved in matrix formation and particle adhesion.

Classification of the peritrich ciliate Opisthonecta matiensis (Martín-Cereceda et al. 1999) as Telotrochidium matiense nov. comb., based on new observations and SSU rDNA phylogeny.

New observations on Opisthonecta matiensis Martín-Cereceda et al. [1999. Description of Opisthonecta matiensis n. sp. (Protozoa, Ciliophora), a new peritrich ciliate from wastewater. J. Eukaryot. Microbiol. 46, 283-289] especially the lack of an epistomial membrane, reveal that the species does not belong to the genus Opisthonecta, but to Telotrochidium, the other genus within the family Opisthonectidae Foissner, 1975. The contractile vacuole and the cytopyge are on the dorsal wall of the vestibulum and the trochal band is limited distally and proximally by rows of narrowly spaced pellicular pores. Thus the species is redefined as Telotrochidium matiense nov. comb. The morphological, cortical and nuclear events occurring during conjugation are illustrated, compared with those in other species, and phylogenetically discussed. Invariably, the microconjugants attach to and penetrate the lateral side of the macroconjugants. Nuclear processes are very similar to those reported from other peritrichs. The small subunit rRNA gene (SSU rDNA) is sequenced and the phylogeny within Opisthonectidae and peritrichs examined. T. matiense is more closely related to Epistylis (63% Maximum Parsimony (MP), 85% Maximum Likelihood (ML)) than to any other genus, while another representative of the family, viz., Opisthonecta henneguyi, is closely related to Vorticella microstoma, Astylozoon enriquesi and clone RT3n18 (100% MP, 100% ML). Morphology and gene sequences suggest that Telotrochidium and Opisthonecta have derived from different lineages of stalked peritrichs: Opisthonecta could have arisen from peritrichs with stalk myonemes, while Telotrochidium probably evolved from peritrichs without stalk myonemes.

Ciliate contributions to bioaggregation: laboratory assays with axenic cultures of Tetrahymena thermophila

Protists, mainly ciliates, play several essential roles in biological wastewater treatment, such as the transfer of matter and energy, bacterial predation, and the removal of organic material. Moreover, during the treatment process, the formation of bioaggregates-flocs and biofilms-is essential to obtaining high-quality effluents. In the present study, Tetrahymena thermophila was used as a model organism to demonstrate the contribution of ciliates to bioflocculation. Axenic cultures of this species were exposed to chemical and mechanical stimuli that promote bioaggregation. In either case, the secretion of a capsulate mucous material by the ciliates or by particle aggregation was detected. Numerous, small, loosely compacted flocs were observed under shaking conditions and in the presence of latex beads. The composition of the exopolymeric material secreted by ciliates was analyzed by a series of fluorochromes and colorimetric methods, which showed that carbohydrates and nucleic acids were the main components involved in matrix formation and particle adhesion (AU)

No disponible

Direct visualization of the microtubular cytoskeleton of ciliated protozoa with a fluorescent taxoid.

Visualization of the infraciliature, which is an essential tool for the identification of ciliate species, has traditionally been obtained with silver proteinate methods. Since infraciliature is mainly composed of microtubules, we used the synthetic fluorescent taxoid FLUTAX as a method for ciliate identification. The main advantages of this method are the facility and rapidity of its application and the fact that no previous fixation and permeabilization processes are required. FLUTAX may also be used as a probe to follow morphogenetical changes in the microtubular cytoskeleton during the ciliate life cycle.