Culture-dependent and culture-independent characterization of bacterial community diversity in different types of sandy lands: the case of Minqin County, China

Abstract

Background: Minqin is suffering from a serious desertification, whereas the knowledge about its bacterial community is limited. Herein, based on Nitraria tangutorum and Haloxylon ammodendron from Minqin, the bacterial community diversities in fixed sandy land, semi-fixed sandy land and shifting sandy land were investigated by combining with culture-dependent and culture-independent methods.

Results: Minqin stressed with high salinity and poor nutrition is an oligotrophic environment. Bacterial community in Minqin was shaped primarily by the presence of host plants, whereas the type of plant and sandy land had no marked effect on those, which displayed a better survival in the rhizospheres of N. tangutorum and H. ammodendron. The dominant groups at phyla level were Actinobacteria, Firmicutes, Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, Acidobacteria and Candidate_division_TM7. The abundance of Firmicutes with ability of desiccation-tolerance was significantly higher in harsh environment, whereas Bacteroidetes were mainly distributed in areas with high nutrient content. The abundances of Proteobacteria and Bacteroidetes were relatively high in the rhizospheres of N. tangutorum and H. ammodendron, which had more plant-growth promoting rhizobacteria. A large number of Actinobacteria were detected, of which the most abundant genus was Streptomyces. The physicochemical factors related to the diversity and distribution of the bacterial community were comprehensively analyzed, such as pH, electrical conductivity, soil organic matter, C/N and sand, and the results indicated that Minqin was more suitable for the growth of N. tangutorum, which should be one of most important sand-fixing plants in Minqin.

Conclusions: The bacterial community diversities in different types of sandy lands of Minqin were comprehensively and systematically investigated by culture-dependent and culture-independent approaches, which has a great significance in maintaining/restoring biological diversity.

Keywords: Bacteria community; Culture-dependent method; Culture-independent method; Desertification; Minqin Desert; Rhizosphere; Sandy land.

Fig. 1

Distribution of partial sequences of culturable bacteria from bulk soils and rhizospheres of N. tangutorum and H. ammodendron at fixed sandy land, semi-fixed sandy land and shifting sandy land on the level of genus, and all genera belonged to Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes. The first letter in the code represents sandy types (A, fixed sandy land; B, semi-fixed sandy land; C, shifting sandy land) and the second letter in the code represents the plant species (C, bulk soil without plant; N, N. tangutorum; H, H. ammodendron)

Fig. 2

Relative abundances of the dominant bacterial groups in all soils on the level of phylum (a) and genus (b). The first letter in the code represents sandy types (A, fixed sandy land; B, semi-fixed sandy land; C, shifting sandy land) and the second letter in the code represents the plant species (C, bulk soil without plant; N, N. tangutorum; H, H. ammodendron)

Fig. 3

PCA of the main factors affecting bacterial community distribution. (a): The effects of plant species on the bacterial community distribution: control soil, bulk soils without plant; N_rhizosphere, rhizospheres of N. tangutorum; H_rhizosphere, rhizospheres of H. ammodendron. (b): The effects of types of sandy lands on the bacterial community distribution: A, fixed sandy land; B, semi-fixed sandy land; C, shifting sandy land. The first letter in the code represents sandy types and the second letter in the code represents the plant species

Fig. 4

Distribution heatmap of microbial orders arranged by hierarchical clustering of samples from fixed sandy land (a), semi-fixed sandy land (b) and shifting sandy land (c) at the phylum level. The first letter in the code represents sandy types (A, fixed sandy land; B, semi-fixed sandy land; C, shifting sandy land) and the second letter in the code represents the plant species (C, bulk soil without plant; N, N. tangutorum; H, H. ammodendron)

Fig. 5

Comparison of the distribution of control samples and rhizosphere samples at the phylum level. Proportional Venn diagram showing the number of OTUs found only in the soil (soil_only), only in the rhizosphere N. tangutorum (RN_only) (a) or H. ammodendron (RH_only) (b), and in both locations. These OTUs were used to create the abundance bar graphs and the relative abundance of raw reads for different phyla belonging to the OTUs depicted under the panel Venn

Fig. 6

Redundancy analysis between the bacterial communities and the environmental factors present in the rhizosphere soil and bulk soil in three types of sandy lands. The first letter in the code represents sandy types (A, fixed sandy land; B, semi-fixed sandy land; C, shifting sandy land) and the second letter in the code represents the plant species (C, bulk soil without plant; N, N. tangutorum; H, H. ammodendron)

Fig. 7

Location of the study area, Minqin County, China