[Response of soil ciliate to diammonium phosphate addition in alpine meadow of southern Gansu, Northwest China]. / ç”˜å—é«˜å¯’è‰ç”¸åœŸå£¤çº¤æ¯›è™«å¯¹ç£·é ¸æ°¢äºŒé“µæ·»åŠ çš„å“åº”.

In typical alpine meadow of southern Gansu Province, five sampling sites by fertilizer diammonium phosphate (DAP) addition ranging from 0 g·m-2 to 120 g·m-2 were set in order to examine the response of soil ciliate communities to different concentrations of DAP. An investigation on the abundance and species richness of soil ciliates was carried out by non-flooded Petri dish, observation in vivo and three-level ten-fold dilution methods. Soil physicochemical factors including soil water content, pH value, contents of soil total nitrogen, total phosphorus and organic carbon at different sites were also measured. It was found that there was a total of 129 species belonging to 9 classes, 17 orders, 31 families and 46 genera. Lower species richness and diversity but higher ciliate abundance were observed in the soils with higher concentrations of DAP compared with the control. The dominant group Haptorida was substituted by Colpodida from the control to the soils with the increase of fertilizer application. The results of redundancy analysis indicated that the gradient changes of total phosphorus, soil temperature and water content were the main driving factors for the change of soil ciliate community distribution.

Cyc17, a meiosis-specific cyclin, is essential for anaphase initiation and chromosome segregation in Tetrahymena thermophila.

Although the role of cyclins in controlling nuclear division is well established, their function in ciliate meiosis remains unknown. In ciliates, the cyclin family has undergone massive expansion which suggests that diverse cell cycle systems exist, and this warrants further investigation. A screen for cyclins in the model ciliate Tetrahymena thermophila showed that there are 34 cyclins in this organism. Only 1 cyclin, Cyc17, contains the complete cyclin core and is specifically expressed during meiosis. Deletion of CYC17 led to meiotic arrest at the diakinesis-like metaphase I stage. Expression of genes involved in DNA metabolism and chromosome organization (chromatin remodeling and basic chromosomal structure) was repressed in cyc17 knockout matings. Further investigation suggested that Cyc17 is involved in regulating spindle pole attachment, and is thus essential for chromosome segregation at meiosis. These findings suggest a simple model in which chromosome segregation is influenced by Cyc17.

[Response of the soil ciliate community to ecological restoration in Huajialing, Dingxi, Gansu].

To obtain a better understanding of the responses of soil ciliate communities to ecological restoration, a quarterly survey of the soil ciliate community and seasonal dynamics across five sampling sites of artificial spruce forest was undertaken. A contrast sampling site of wild grassland was used and live observation ciliates and the three level ten-fold dilution method was used in Huajialing, Dingxi, Gansu. A total of 127 species were identified, belonging to three classes, nine orders, 34 families and 50 genera. Results show that the species distribution had obvious differences across the sampling sites, the community structure of soil tended to be complicated and species comparability decreased gradually with the number of restoration years, and abundance, species richness and species diversity index showed an upward trend. The dominant groups of soil ciliates changed during ecological restoration. Colpodida was the dominant group in sampling site I and site II, whereas Hypotrichida was the dominant group in the late recovery sampling sites. This study shows that the dynamics of the soil ciliate community better respond to soil condition changes in the ecological restoration process. Although the soil ciliate community can be used to evaluate the effect of ecological restoration of terrestrial ecosystems, plenty of further systematic research to establish an effective and feasible evaluation index system is required.