Diversity of bacterial community in Suaeda roots rhizosphere growth in PAHs-contaminated saline soil estimated by high throughput sequencing method

Abstract:

[Objective] Analysis and comparison of the bacterial community diversity in Suaeda roots rhizosphere and non-rhizosphere polycyclic aromatic hydrocarbons (PAHs) contaminated saline soil to provide the basis for plant-microbial remediation of PAHs contaminated saline soil. [Methods] Soil samples were collected from Suaeda roots rhizosphere and non rhizosphere at an oil well site in Shengli oil field. Bacterial community structures were analyzed by high throughput sequencing, and further the abundance of PAH-ring hydroxylating dioxygenase (PAH-RHDα) genes in soil was detected by Real-time PCR. [Results] The salt content of Suaeda roots rhizosphere soil is 22.51 g/kg, which is significantly lower than the salt content (40.03 g/kg) in non rhizosphere soil. The pH of rhizosphere and non-rhizosphere soil were basically the same, which were 8.20 and 8.22. The organic matter content and total nitrogen content of rhizosphere soil is 24.41 g/kg and 1.59 g/kg, respectively, which made C/N 15. These contents of non rhizosphere soil are 18.80 g/kg and 0.71 g/kg, respectively, which made C/N 26. The bacterial communities were analyzed and at least 53 854 and 30 312 sequencing were obtained for rhizosphere and non-rhizosphere soil samples. At 97% similarity level, the OTU number, Chao 1 index and ACE index are 5 934, 11 461 and 15 555 respectively in rhizosphere soil sample, which are higher than the index values in non-rhizosphere soil (4 262, 8 262 and 11 186). The rhizosphere soil contains 32 phyla and 758 genera of bacteria, more than those in the bare soil (28 phyla and 676 genera). Bacteria abundance and diversity of Suaeda roots rhizosphere soil were higher than that of the non-rhizosphere soil. There are rich resources of haloalkaliphilic microorganisms in PAHs-contaminated saline alkali soil, such as Thioalkalispira, Halothiobacillus, Thiohalophilus, and the PAH-RHDα genes were detected in the rhizosphere soil. [Conclusion] Haloalkaliphilic bacteria such as Thioalkalispira, Halothiobacillus, and Thiohalophilus were the dominant microorganism in PAHs-contaminated saline alkali soil. Suaeda can reduce the salt content and improve the C/N value of rhizosphere soil effectively, simultaneously increase the diversity of microbial communities structure and the abundance of PAH-RHDα genes. Therefore, Suaeda was beneficial to promote halophilic PAHs degrading microorganisms play a role in bioremediation of PAHs-contaminated saline-alkali soil.

Key words:Saline soil, PAHs, Bioremediation, Suaeda, Bacterial community