Bacterial diversity in paclobutrazol applied agricultural soils

Abstract

The aim of this study was to investigate the bacterial communities on paclobutrazol [(2RS, 3RS)-1-(4-Chlorophenyl)-4, 4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-ol]–applied agricultural soils by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rDNA gene fragments. Three different agricultural soil samples were collected from paclobutrazol applied mango and waxapple orchards, peanut fields and untreated rice fields as a control for DGGE analysis. The DGGE pattern of PCR- generated 16S rDNA gene fragments indicated that the bacterial populations from four paclobutrazol–applied soils of peanut fields were closely related to each other and two paclobutrazol–applied soils of mango and waxapple orchards harbored closely related bacterial communities. But, paclobutrazol–free agricultural soils comprised relatively a different bacterial group. However, the bacterial populations of mango and waxapple orchard are completely different from the bacterial communities of peanut field. Further purification and sequence analysis of 40 DGGE bands followed by phylogenetic tree assay showed similar results that soil bacteria from paclobutrazol applied mango and waxapple orchard are phylogenetically related. Based on the phylogenetic analysis, the clone M-4 was clad 100 % (bootstrap value) with Mycobacterium sp. The Mycobacterium sp. has been proved to degrade the phenolic compounds such as phenol, 4-chlorphenol, 2,4-dichlorophenol and paclobutrazol molecule containing chlorobenzene ring.

Keywords:

• Bacterial diversity
• denaturing gradient gel electrophoresis (DGGE)
• paclobutrazol
• agricultural soil

Acknowledgments

The authors thank Dr. Subbiyan Maruthasalam, Dr. Palaniappan Selvakumar, Department of Life Sciences, National Chung Hsing University, Dr. Shu-Ying Liu, Department of Molecular Biotechnology, DaYeh University and Dr. Yung-Sen Huang, Institute of Biotechnology, National University of Kaohsiung, for critical reading of the manuscript.

Notes

^aDenaturing gradient gel electrophoresis (DGGE) band, number as indicated on Figure 1.

^b Number indicates the nucleotide length of the clone.

^a These two authors have contributed equally to this paper.