Diversity of alkane hydroxylase genes on the rhizoplane of grasses planted in petroleum-contaminated soils.

Shun Tsuboi,Toshiaki Nakajima-Kambe,Kazuhiro Iwasaki,Shigeki Yamamura

doi:10.1186/s40064-015-1312-0

Abstract

The study investigated the diversity and genotypic features of alkane hydroxylase genes on rhizoplanes of grasses planted in artificial petroleum-contaminated soils to acquire new insights into the bacterial communities responsible for petroleum degradation in phytoremediation. Four types of grass (Cynodon dactylon, two phenotypes of Zoysia japonica, and Z. matrella) were used. The concentrations of total petroleum hydrocarbon effectively decreased in the grass-planted systems compared with the unplanted system. Among the representative alkane hydroxylase genes alkB, CYP153, almA and ladA, the first two were detected in this study, and the genotypes of both genes were apparently different among the systems studied. Their diversity was also higher on the rhizoplanes of the grasses than in unplanted oil-contaminated soils. Actinobacteria-related genes in particular were among the most diverse alkane hydroxylase genes on the rhizoplane in this study, indicating that they are one of the main contributors to degrading alkanes in oil-contaminated soils during phytoremediation. Actinobacteria-related alkB genes and CYP153 genes close to the genera Parvibaculum and Aeromicrobium were found in significant numbers on the rhizoplanes of grasses. These results suggest that the increase in diversity and genotype differences of the alkB and CYP153 genes are important factors affecting petroleum hydrocarbon-degrading ability during phytoremediation.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-1312-0) contains supplementary material, which is available to authorized users.

Highlights

The exploration, extraction, refining, transport, and use of petroleum and derivative products has resulted in soil pollution with petroleum hydrocarbons, which is of critical environmental concern worldwide (Khan et al 2013)
Decrease in total petroleum hydrocarbon (TPH) concentration Total petroleum hydrocarbon concentration in the soils showed decrease in all planted systems during 856 or 891 days, respectively, while it was nearly unchanged in the unplanted system (Fig. 1)
Cloned 255 CYP153 gene sequences were grouped into 44 operational taxonomic units (OTUs), four of the sequences obtained were positioned outside the outgroup (Pseudomonas putida linC, accession No AAA25810)

Summary

Introduction

The exploration, extraction, refining, transport, and use of petroleum and derivative products has resulted in soil pollution with petroleum hydrocarbons, which is of critical environmental concern worldwide (Khan et al 2013). Techniques for cleaning these soils include physicochemical/chemical treatments such as chemical oxidation using ferrous compounds and soil thermal desorption (Langbehn and Steinhart 1995; Ferguson et al 2004), but these are expensive and environmentally invasive (Pandey et al 2009; Segura et al 2009). This study aims to acquire novel insights into the community structures and diversity of alkane-degrading bacteria on the rhizoplanes of grasses, based on culture-independent molecular approaches

Objectives

Methods

Results

Conclusion