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Protists, ciliates in particular, play a role in ecosystem functioning by recycling microbial biomass, and thus, nutrients and energy. Studies on their secondary production in aquatic ecosystems suggest that their overall contribution to annual secondary production is relatively minor, only becoming significant during bloom episodes. It remains unclear if the ecological role of soil ciliates, as estimated by their secondary production, is similarly minor. Temporal data on ciliate abundance and biovolume among the rhizosphere of three flowering plant species were used to estimate biomass and potential secondary production of soil ciliates in a subtropical forest of Puerto Rico. Ciliate abundance, biomass, and secondary production were estimated in the top 5 cm of soil during both the dry and wet seasons. Mean ciliate abundances in these months were 5 ± 10.3 and 16 ± 16.1 (n = 93 soil samples) for nanociliates and microciliates, respectively. Mean ciliate biomass was 41,854 ± 37,055 pg C g-1 of dry weight soil. Mean nano- and microciliate biomass were 418 ± 704.4 pg C g-1 of dry weight soil and 45,315 ± 39,466.8 pg C g-1 of dry weight soil, respectively. The season in which the ciliates were collected significantly affected ciliate abundance and biomass, but this effect showed no predictable pattern, suggesting a lack of seasonality. Mean daily ciliate secondary production (the product of biomass and growth rate) was 1.74 x 104 ± 1.95 x 104 pg C g-1 of dry weigth soil d-1 (0.002 kJ m-2 d-1 or 0.047 kJ m-3 d-1), ranging from 0 to 107,804 pg C g-1 of dry weigth soil d-1. Based on monthly precipitation data, annual ciliate secondary production was estimated to be 40.0 x 105 pg C g-1 of dry weight soil yr-1, equivalent to 1.1 kJ m-2 yr-1 or 21.7 kJ m-3 yr-1. Reduced secondary production estimates, in addition to low mean consumption of microbial biomass (0.002%), indicates that ciliates have a relatively minor role in this subtropical soil ecosystem. [ABSTRACT FROM AUTHOR]

A system is devised to examine T4 phase removal by Tetrahymena thermophila and also the cellular mechanism. The results have indicated the active removal of T4 bacteriophage from fluid by macropinocytosis, followed by digestion in food vacuoles.

Abstract Background Species of Tetrahymena were grouped into three complexes based on morphological and life history traits: the pyriformis complex of microstomatous forms; the patula complex of microstome-macrostome transformers; and the rostrata complex of facultative and obligate histophages. We tested whether these three complexes are paraphyletic using the complete sequence of the small subunit rDNA (SSrDNA). Results In addition to the 16 species of Tetrahymena whose SSrDNA sequences are known, we sequenced the complete SSrDNA from the following histophagous Tetrahymena species; Tetrahymena bergeri, Tetrahymena mobilis, Tetrahymena rostrata, and Tetrahymena setosa as well as the macrostome species Tetrahymena vorax. We also included a ciliate tentatively identified as Lambornella sp., a parasite of the mosquito Aedes sp. We confirmed earlier results using SSrDNA, which showed two distinct clusters of Tetrahymena species: the australis group and borealis group. The genetic distances among Tetrahymena are in general very small. However, all nodes were supported by high bootstrap values. With the exception of T. bergeri and T. corlissi, which are both histophagous and group as sister species, all other histophagous Tetrahymena species are most closely related to a bacterivorous species. Furthermore, Lambornella sp. and T. empidokyrea, both mosquito parasites, are sister species, although there is a considerable genetic distance between them. Conclusions There has been parallel evolution of histophagy in the genus Tetrahymena and the three classical species complexes are paraphyletic. As the genus Lambornella arises within the Tetrahymena clade, it is not likely a defensible one.