Culturable heavy metal-resistant and plant growth promoting bacteria in V-Ti magnetite mine tailing soil from Panzhihua, China.

Xiumei Yu,Chu Zhang,Yunfu Gu,Ke Zhao,Xiaoping Zhang,Huiying Liu,Quanju Xiang,Xuejun Leng,Qiang Chen,Xia Kang,Wenwen Zheng,Jin Liu,Yanmei Li,Andrew C Singer

doi:10.1371/journal.pone.0106618

Abstract

To provide a basis for using indigenous bacteria for bioremediation of heavy metal contaminated soil, the heavy metal resistance and plant growth-promoting activity of 136 isolates from V-Ti magnetite mine tailing soil were systematically analyzed. Among the 13 identified bacterial genera, the most abundant genus was Bacillus (79 isolates) out of which 32 represented B. subtilis and 14 B. pumilus, followed by Rhizobium sp. (29 isolates) and Ochrobactrum intermedium (13 isolates). Altogether 93 isolates tolerated the highest concentration (1000 mg kg−1) of at least one of the six tested heavy metals. Five strains were tolerant against all the tested heavy metals, 71 strains tolerated 1,000 mg kg−1 cadmium whereas only one strain tolerated 1,000 mg kg−1 cobalt. Altogether 67% of the bacteria produced indoleacetic acid (IAA), a plant growth-promoting phytohormone. The concentration of IAA produced by 53 isolates was higher than 20 µg ml−1. In total 21% of the bacteria produced siderophore (5.50–167.67 µg ml−1) with two Bacillus sp. producing more than 100 µg ml−1. Eighteen isolates produced both IAA and siderophore. The results suggested that the indigenous bacteria in the soil have beneficial characteristics for remediating the contaminated mine tailing soil.

Highlights

Mining industry has caused extensive environmental and public health problems [1,2,3]
A wide variety of heavy metals such as zinc, lead, copper and cadmium have been detected in soil at mining sites presenting a major threat to the environment and population [4,5]
Basic physicochemical properties of soil samples To assess the quality of the V-Ti magnetite mine tailing soil, we first measured the soil physicochemical characteristics and heavy metal content in the soil (Table 1)

Summary

Introduction

Mining industry has caused extensive environmental and public health problems [1,2,3]. A wide variety of heavy metals such as zinc, lead, copper and cadmium have been detected in soil at mining sites presenting a major threat to the environment and population [4,5]. Heavy metals cannot be biologically degraded and indefinitely persist in the environment. Heavy metals transferred through the food chain are a serious hazard to human health [6]. Due to contamination by heavy metals, mining sites are surrounded by large barren areas. The awareness of the detrimental heavy metal contamination at mining sites has increased in recent years

Methods

Results

Conclusion