The effects of Eisenia fetida and Metaphire guillelmi on the soil micro-food web in a microcosm experiment.

Numerous studies have shown that the function of earthworms may depend on their ecotype and density, which affects how they impact soil microbial and nematode communities. However, it is unclear how different earthworm species and densities alter the composition of soil microbial and nematode communities and how these modifications impact the soil micro-food web. The structural equation model (SEM) is a more accurate tool for identifying the intricate relationships between various trophic levels in the soil micro-food webs than the widely used bivariate data analysis. In order to ascertain the effects of earthworm species, including epigeic earthworm Eisenia fetida and anecic earthworm Metaphire guillelmi, as well as varying densities on the composition of main microbial groups, soil nematodes and their relationships, a microcosm experiment was conducted in a greenhouse. After nine weeks of observation, compared with the control treatments, Eisenia fetida increased the biomasses of total microorganism and bacteria, whereas Metaphire guillelmi decreased the biomasses of total microorganism, bacteria, and gram-positive bacteria, but showed an increase in AMF biomass. Additionally, both two earthworm species decreased the abundance of total soil nematode, bacterivores, and omnivore-predators, which is in contrast with the control treatments. The SEM results indicated that the addition of Eisenia fetida at different densities had indirect negative effects on the abundance of omnivore-predators, as it significantly increased the content of soil organic carbon, ammonium nitrogen, and nitrate nitrogen. The bottom-up effects were found to be the dominant forces, which promoted bacterial-dominated decomposition channels. The addition of Metaphire guillelmi with different density had direct negative impact on bacterivores and fungivores. Moreover, it had indirect negative effects on omnivore-predators by altering the soil properties. The dominant forces were still the bottom-up effects. Our study suggests that different earthworm species have distinct mechanisms that affect the soil micro-food web in different ways.

Novel SLC12A3 mutations in Chinese patients with Gitelman's syndrome.

BACKGROUND: Inactivating mutations of the SLC12A3 gene are the most common cause of Gitelman's syndrome (GS), a disorder inherited as an autosomal recessive trait. In a minority of cases, GS-like phenotypes are caused by mutations in the CLCNKB gene. METHODS: We searched for SLC12A3 and CLCNKB gene mutations in 13 Chinese patients (9 males and 4 females, age 35 +/- 14 years) from 8 unrelated families with the clinical and biochemical features of GS. All coding regions, including intron-exon boundaries, were analyzed using PCR followed by direct sequence analysis. RESULTS: We identified 10 mutations distributed throughout the SLC12A3 gene. Seven are novel variants, including 4 missense mutations (Gly196Val, Cys430Gly, Gly439Val and Leu571Pro), 2 deletions (1384delG and 346-353delACTGATGG) and 1 in-frame insertion (997insCys). Three mutations were recurrent, including 2 missense mutations (Thr60Met and Asp486Asn) and 1 deletion (2883-2884delAG). The homozygous or heterozygous mutation Thr60Met was found in 8 of 13 patients. There were no mutations detected in the CLCNKB gene. CONCLUSIONS: Thr60Met may be the most common mutation in Chinese patients with GS. Possible specific genotype-phenotype correlations were difficult to identify.