Comparison Of Diversity And Structure Of Soil Actinobacteria Communities Across The Main Grasslands In Northern China

Soil actinobacteria, as a dominant bacteria taxa, plays an important role in nutrient cycling and energy flow. Majority of previous studies about Actinobacteria just focused on the changes of soil Actinobacteria relative abundance, but rarely concerning about its diversity, community structure and main driving factors. The studies about the classes of Actinobacteria also needed to be further investigated.Our studies were conducted in five different grassland types in northern China, which included plain meadow, typical steppe, meadow steppe, alpine meadow and de sert steppe. High-throughput sequencing method was used to measure the Actinobacterial community diversity, community structure and their main driving factors in the five grasslands types. We also analyzed the variation and influencing factors for the classes of soil Actinobacteria, revealing the changes in Actinobacteria community diversity, community structure and main driving factors in landscape scales. Based on the above analysis, we got the results as follows:(1) Our study totally sorted 127 kinds of Actinobacteria which belonged to five classes, including Actinobacteria, Acidimicrobia, Rubrobacteria, Thermoleophilia and Nitriliruptoria. We also detected two other classes TakashiAC-B 11 and MB-A2-108. The predominant classes were Acidimicrobia, Thermoleophilia and Actinobacteria in five grassland types.(2) The phylotype richness and diversity of soil Actinobacteria in five grassland types existed significant differences (P<0.01), in which the diversity of Actinobacteria in plain meadow was lower than that four grassland types. The relative abundance of the five classes were greatly different (P<0.05). Actinobacteria (class) has different distribution in five grassland types and its abundance was the highest in alpine meadow and the lowest in typical steppe; The relative abundance of Acidimicrobia was higher in plain meadow than other four grasslands while Thermoleophilia has the opposite distribution; The relative abundance of Rubrobacteria was the highest in desert steppe; A little of Nitriliruptoria just existed in plain meadow.(3) The Actinobacteria diversity was significantly negatively correlated with soil pH value (r2=0.219, P<0.01) and electric conductivity (r2=0.219, P<0.01). Actinobacteria diversity was mainly driven by soil pH on the basis of RDA. It was proved that different classes were controlled by different factors. The relative abundance of the class of Actinobacteria was affected by soil physic-chemical parameters, in which Actinobacteria (class) was correlated with soil organic carbon, total nitrogen, C:N ratio, N:P ratio, pH value and electric conductivity; Soil pH value and electric conductivity were the main driving factors for the classes of Acidimicrobia and Thermoleophilia; Rubrobacteria was mainly manipulated by soil moisture and nutrient contents; A little of Nitriliruptoria just existed in plain meadow, and its relative abundance was influenced by soil pH value and electric conductivity, indicating that Nitriliruptoria was suitable for growing in saline-alkali soil.In summary, in landscape scale, different grassland types had significant different soil Actinobacteria diversity and community structure. Actinobacterial diversity was mainly influenced by soil pH value. The relative abundance of Actinobacteria, Acidimicrobia, Rubrobacteria, Thermoleophilia and Nitriliruptoria were all different in five grassland types, and these classes were driven by different soil physic-chemical factors. The study explicited the changes of soil actinobacteria community diversity, structure and the drivers, provided much knowledge for understanding the variation of Actinobacterial classes, which provides a theoretical basis for soil microbial distribution across the main grasslands in northern China.