Macroaggregates Serve as Micro-Hotspots Enriched With Functional and Networked Microbial Communities and Enhanced Under Organic/Inorganic Fertilization in a Paddy Topsoil From Southeastern China.

Microbial communities of soil aggregate-size fractions were explored with molecular and networking assays for topsoil samples from a clayey rice paddy under long-term fertilization treatments. The treatments included no fertilizer (NF) as control, chemical fertilizer only (CF), chemical fertilizer with swine manure (CFM), and chemical fertilizer with rice straw return (CFS). Following a wet-sieving protocol, water-stable aggregates were separated into size fractions of large macroaggregates (L-MacA, >2,000 µm), macroaggregates (MacA, 2,000-250 µm), microaggregates (MicA, 250-53 µm), fine microaggregates (F-MicA, 53-2 µm), and fine clay (F-Clay, <2 µm). Mass proportion was 32.3-38.2% for F-MicA, 23.0-31.5% for MacA, 19.0-23.1% for MicA, 9.1-12.0% for L-MacA, and 4.9-7.5% for F-Clay, respectively. The proportion of MacA was increased, but F-Clay was reduced by fertilization, whereas the mean weight diameter was increased by 8.0-16.2% from 534.8 µm under NF to 621.5 µm under CFM. Fertilization affected bacterial 16S rRNA and fungal 18S rRNA gene abundance in F-MicA and F-Clay but not in aggregates in size larger than 53 µm. However, bacterial and fungal community α-diversities and community structures were quite more divergent among the fertilization treatments in all size fractions. Organic carbon and gene abundance of bacteria and fungi were enriched in both L-MacA and MacA but depleted in F-Clay, whereas microbial Shannon diversity was rarely changed by fraction size under the four treatments. L-MacA and MacA contained more bacteria of r-strategists and copiotrophs, whereas F-MicA and F-Clay were demonstrated with a higher abundance of K-strategists and oligotrophs. Guilds of parasitic and litter saprotrophic fungi were enriched in F-MicA but depleted in L-MacA. Furthermore, most of bacterial and fungal operational taxonomic units were strongly interacted in L-MacA and MacA rather than in MicA and F-Clay. Thus, MacA acted as micro-hotspots enriched with functional and networked microbial communities, which were enhanced with organic/inorganic fertilization in the rice paddy.

[A Review of Electrical Property Tomography for Human Tissues].

In recent years,the technologies based on the electrical properties(EPs)of human tissue,such as electrical impedance tomography(EIT)and magnetic resonance electrical impedance tomography(MREIT),have become one of the most popular research subjects in biomedicine.Compared with EIT and MREIT,the magnetic resonance electrical property tomography(MR-EPT)is a new technique using nondestructive EPs method.MR-EPT reconstructs the electrical conductivity and permittivity of the biological tissues based on the radio frequency field of the magnetic resonance imaging(MRI)system.It can obtain an accurate and high resolution image without current injection.In this paper,several methods for the EPs are reviewed,especially the MR-EPT.The theory,advantages and prospects of MR-EPT's are elaborated.The method of specific absorption rate(SAR)based on it is also introduced.MR-EPT is deserved further research and should be given more attention by the researchers.All this evolution based on MREPT can give new energy to the medical diagnosis.