[Comparison of Bacterial Community Structure and Functional Groups of Paddy Soil Aggregates Between Karst and Non-karst Areas].

Studying the similarities and differences in microbial community structure and functional groups in soil aggregates between karst areas (KA) and non-karst areas (NKA) can provide a theoretical basis for revealing the interaction mechanism between soil organic microorganisms and soil aggregate structure stability in KA. The surface soils (0-20 mm) were collected from paddy fields both in KA and NKA. The aggregates were divided into macro-aggregates (Mac, 0.25-2 mm), micro-aggregates (Mic, 0.053-0.25 mm), and silt-clay fractions (SC,<0.053 mm) using the wet sieving method. The microbial community structure of soil aggregates was analyzed using high-throughput sequencing. The keystone taxa were analyzed by the co-occurrence network, and their functions were predicted by FAPROTAX. The results showed that:① the proportion of Mac, mean weight diameter, and geometric mean diameter of aggregates in KA were 30.94%, 0.41 mm, and 0.15 mm, respectively. These three factors in KA were significantly higher than those in NKA, indicating that the environment in the KA was conducive to the formation of aggregates. ② The relative abundances of Acidobacteria, Proteobacteria, Acidobacteria(Gp3, Gp4, and Gp6), and in three particle size aggregates in KA were higher than those in NKA. The relative abundance of Chloroflexi (6.13%) in Mic in KA was significantly higher than that in SC (2.79%). ③ Co-occurrence network analysis showed that Proteobacteria and Acidobacteria were keystone taxa in three particle size aggregates. The positive correlation edge (65.5%) of bacteria in KA was the highest, and most of the correlation was synergistic. ④ Chemoheterotrophy (15.52%, 15.30%, and 16.89%) and aerobic chemoheterotrophy (14.62%, 14.38%, and 15.97%) were the most dominant functional groups in the three particle size aggregates in KA, and their relative abundance was significantly higher than those in NKA. The relative abundance of chitinolysis in Mac in KA (0.46%) was significantly higher than that in SC (0.39%). The results showed that the soil environment in KA can improve the stability of the aggregates, and the bacterial community structure, key groups, and functional groups in the three particle size aggregates in KA were significantly different from those in NKA.