Total DNA from soil samples was isolated using DNeasy PowerSoil. DNA concentrations were measured on the Qubit 1 fluorimeter using the Qubit DNA HS kit. Variable 16S rRNA regions were amplified with two primer combinations, V3-V4 and V4-V5 (341F 5CCTAYGGGRBGCASCAG3 and 806R 5GGACTACNNGGGTATCTAAT3; 515F 5GTGCCAGCMGCCGCGGTAA3 and 907R 5CCGTCAATTCCTTTGAGTTT3, respectively). Phusion polymerase (New England Biolabs, USA) and the following program was used for amplification: 95 C 2 min (initial DNA melting); 24 cycles as follows: 95 C 30 s,  58 C 30 s, 72 C 40 s, 72 C 5 min. Samples (distilled water) containing no DNA processed in the same laboratory were used as a negative control. Index PCR was made using Phusion polymerase (New England Biolabs, USA) and the Nextera XT Index kit (Illumina, USA) according to the manufacturer's protocols.