An investigation of the fine structure, cell surface carbohydrates, and appeal of the diatom Extubocellulus sp. as prey for small flagellates.

The fine structure and surface exopolymers of a coastal planktonic nanodiatom of the sparsely reported genus Extubocellulus were studied respectively by scanning electron microscopy and confocal microscopy in conjunction with fluorescent lectins. Monitoring the suitability of the species as prey food for other protists was also investigated by video microscopy coupled with digital film. Cells are rectangular in girdle view, with a pervalvar axis longer than the apical axis. Valves are almost circular with a diameter of 2.8 to 3.6 microm. The valve face bears randomly distributed areolae (ca. 50 in 10 microm), which may be either open or occluded. Two small raised ocelluli occur at the apices, with a rim devoid of perforations and about 6-7 porelli. Glucose and N-acetyl-glucosamine moieties present on the surface of the live diatom were labelled with fluorescent lectins, and a differential pattern of distribution for both carbohydrates was observed. The potential role of fluorescent lectins as cellular probes of taxonomic value in small diatoms is compared with that of nucleotide and antibody probes. We provide the first illustrative evidence of the presence of Extubocellulus sp. in the cytoplasm of the nanoflagellate Goniomonas amphinema and of the egestion of diatom frustules. Results obtained are discussed in the light of the present knowledge of the role of carbohydrate-protein interactions in phagocytosis of prey by free-living protozoa.

Ciliate communities of rotating biological contactor biofilms: a multivariate approach.

Physical-chemical monitoring and characterization of ciliate communities from a full-scale rotating biological system (RBC) have been carried out for a year. RBC system operated efficiently in removing the organic matter, as the decrease of the BOD5 loading along the successive RBC units revealed. 55 species of ciliated protozoa were identified in the RBC biofilms. Differences in abundance, occurrence and type of species were found along the different units of the RBC system; the last RBC held a more stable and diverse ciliate community. The complexity of interspecific relationships among the ciliates has been outlined using multivariate methods (Cluster and Correspondence analysis). Correlation between ciliate species and physical-chemical conditions were obtained by regression analysis. Results show that 12 species of ciliates were related to an optimal efficiency in organic matter removal, Litonotus crystallinus being the most sensitive species. The presence and abundance of Litonotus crystallinus and Acineria uncinata was associated with a decrease in the organic factor. Metopus es was the only species related to a decrease in process efficiency due to its association with an increase in organic factor. The results provide statistical evidence of the use of certain ciliate species as reliable bioindicators in full-scale RBC wastewater treatment plants.

An integrated approach to analyse biofilms of a full scale wastewater treatment plant.

A rotating biological contactor (RBC) system operating in a full-scale wastewater treatment plant has been described by several approaches accounting for performance, composition and structure of biofilms in three stages through biological wastewater treatment (RBC1, RBC 2, RBC 3). RBC biofilms were effective in removing the BOD loading from 13 g BOD5 d(-1) m(-2) in RBC 1 to 6 g BOD5 d(-1) m(-2) in RBC 3. Analysis of biofilm composition showed: i) the volatile solids were similar in the three RBCs (0.6 g m(-2) VS per g m(-2) of TS); ii) the protozoan and metazoan biocenosis was mainly made up of ciliated protozoa, which were most abundant in RBC 2 (1.84 x 10(6) ciliates g(-1) VS). Relationship between ciliate species and physical-chemical profile of the system by cluster analysis indicated that the species Acineria uncinata, Amphileptus punctatus, Cinetochilum margaritaceum and Holosticha mancoidea were associated with the best RBC performance; iii) the exopolymeric matrix of the three RBC biofilms was mainly constituted by proteins, although humic substances, polysaccharides, uronic acids and DNA were also found. Analysis of biofilm structure by confocal microscopy indicated changes in biofilm organisation with depth. Results have been brought together and a graphic representation of the composition and architecture of RBC biofilms is presented.

Dynamics of protozoan and metazoan communities in a full scale wastewater treatment plant by rotating biological contactors.

Performance of a full-scale wastewater treatment plant by rotating biological contactors (RBC) system was monitored during a year by physico-chemical and microbial characterisation. Six points along wastewater treatment were selected in the plant: three points along the water line (influent, sedimentation tank and effluent) and three points along RBC system (RBC1, RBC2 and RBC3). Although a large seasonal change in the values of physico-chemical parameters was observed, operation of the plant was optimal during all year (90% of removal in BOD5 and SS influent content). Microbial characterisation was approached by determining the structure and dynamics of protozoan and metazoan communities. Protozoa were the most abundant in all stages in the plant, heterotrophic flagellates being the most representative group in the water line and ciliates in the RBC system. The same seasonal preference was only observed for heterotrophic flagellates in the water line and green flagellates in the RBC system, both groups having highest abundances in summer and spring, respectively. Identification of ciliated protozoa populations rendered 58 species of ciliates in the plant. Most of these species are typical of aerobic wastewater treatment systems except three of them, which are cited for the first time in this type of ecosystems: Chaenea stricta, Holosticha mancoidea and Oxytricha lanceolata. Along the water line 34 species were identified, and half of them only appeared occasionally (once in all the study), while along the RBC system biofilms 55 species were observed, and the majority appeared permanently in this system. Our results indicate that the type of habitat, rather than the physico-chemical water parameters, was the primary factor in determining the different distribution of protozoan and metazoan communities in the plant. In RBC biofilms, the structure of ciliate protozoa community was found to be quite sensitive to changes in physico-chemical parameters, mainly to organic loading (BOD5) variations.

Characterization of extracellular polymeric substances in rotating biological contractors and activated sludge flocs.

Extracellular polymeric substances (EPS) from biofilms of a rotating biological contactor (RBC) system and from activated sludge flocs were extracted using ultrasound and a cation exchange resin. In both wastewater treatment systems, the EPS matrix was mainly constituted of proteins, humic-like substances and polysaccharides, although other components--DNA and uronic-like substances--were also present. The composition of the biofilm EPS was different in the succesive RBC wastewater treatment stages: protein had its highest concentration in the first RBC unit, while humic substances and polysaccharides in the third RBC. Significant differences between biofilm and sludge floc EPS were also reported. The amount of proteins was 3.5 times higher for RBC biofilms than for sludge flocs, and quantities of humic substances and polysaccharides extracted from biofilms were twice as high than in sludges. Moreover, biofilm exopolymers were two times more hydrophobic than those of sludge flocs. Implications of wastewater chemistry and microbial growth strategies into EPS composition and properties are suggested.

Description of Opisthonecta matiensis n. sp. (Protozoa, Ciliophora), a new peritrich ciliate from wastewater.

Opisthonecta matiensis n. sp. was isolated from the inlet water of a wastewater treatment plant near Madrid, Spain, and studied in vivo, with silver methods, and using electronic and indirect immunofluorescence microscopy. This new species shows an amphora-like cell shape and has a size of 45-73 microns (x 58.2) x 25-40 microns (x 31.3). The oral infraciliature is formed by one haplokinety, three polykineties, and a short row of kinetosomes (epistomial membrane). The aboral infraciliature is made up of the trochal band and the scopula. From the trochal band arise three fibrillar systems: oral fibers, aboral fibers, and oblique fibers. The myoneme system is composed of a delicate peristomial ring, longitudinal branched fibers that reach the trochal band and of radial fibers extending from the scopula to the trochal band. The silverline system consists of an average of 147 lines. This new species is separated from other known forms by its smaller size, the presence of one single vacuole, and its higher number of silverlines.