1.
Microbial taxonomic, nitrogen cycling and phosphorus recycling community composition during long-term organic greenhouse farming.
Ding, GC, Bai, M, Han, H, Li, H, Ding, X, Yang, H, Xu, T, Li, J
FEMS microbiology ecology. 2019;(5)
Abstract
Understanding the interplay between the farming system and soil microbiomes could aid the design of a sustainable and efficient farming system. A comparative greenhouse experiment consisting of organic (ORG), integrated (INT) and conventional (CON) farming systems was established in northern China in 2002. The effects of 12 years of organic farming on soil microbiomes were explored by metagenomic and 16S rRNA gene amplicon sequencing analyses. Long-term ORG shifted the community composition of dominant phyla, especially Acidobacteria, increased the relative abundance of Ignavibacteria and Acidobacteria Gp6 and decreased the relative abundance of Nitrosomonas, Bacillus and Paenibacillus. Metagenomic analysis further revealed that relative abundance of ammonia oxidizing microorganisms (Bacteria and Archaea) and anaerobic ammonium oxidation bacteria decreased during ORG. Conversely, the relative abundance of bacteria-carrying periplasmic nitrate reductases (napA) was slightly higher for ORG. Long-term organic farming also caused significant alterations to the community composition of functional groups associated with ammonia oxidation, denitrification and phosphorus recycling. In summary, this study provides key insights into the composition of soil microbiomes and long-term organic farming under greenhouse conditions.
2.
[Efficient and Stable Operation of Shortcut Nitrification by Entrapping Ammonia Oxidizing Bacteria].
Yu, MY, Liu, Y, Tian, YB, Shi, H, Xu, F, Yang, H
Huan jing ke xue= Huanjing kexue. 2017;(7):2925-2930
Abstract
In order to improve the efficiency of shortcut nitrification by entrapping ammonia oxidizing bacteria, the technique of ammonia oxidizing bacteria(AOB) enrichment culture was studied. The continuous operation method was used to inhibit the growth of nitrite-oxidizing bacteria(NOB) by free ammonia, at the same time, the NOB was gradually washed out of the system through the technology of sludge discharge. Polyvinyl alcohol(PVA) was used as the embedding material to immobilize the ammonia oxidizing bacteria after enrichment culture. The embedding rate of the reactor was 8%. The ammonia oxidation rate was increased by improving ammonia nitrogen loading in the continuous operation mode. The results showed that the ammonia oxidation rate(NH4+-N/VSS)was as high as 2.028 g·(g·d)-1 and the nitrite nitrogen accumulation rate was stabilized at more than 90%. High-throughput sequencing analysis was conducted on the bacterial community composition before and after enrichment culture, and the experimental result indicated that the culture diversity of raw sludge was larger. Nitrosomonas and Nitrospirae, which have nitrification function, accounted for 0.24% and 2.7%, respectively. The diversity of the activated sludge decreased significantly after the enrichment culture, Nitrosomonas(18%) became the dominant bacteria whereas Nitrospira occupied only 0.02%. After he embedding of ammonia oxidizing bacteria, the shortcut nitrification was realized rapidly. Finally, the shortcut nitrification rate reached 50 mg·(L·h)-1and the nitrite nitrogen accumulation was above 90%.