Phosphate solubilizing uranium tolerant bacteria associated with monazite sand of a natural background radiation site in South-West coast of India

Abstract

Uranium contamination is a topic of concern due to its toxicity to the environment and human health. Bioremediation has gained importance as a feasible and eco-friendly strategy. Bacteria tolerant to uranium and with phosphate solubilizing ability have proven to be important candidates in the development of bioremediation technology. In this context, we have isolated bacteria from the actinide-metal-containing monazite sand of Someshwara beach, Karnataka (South-West coast of India) with special reference to phosphate solubilizers. Phylogenetic analysis by 16S rRNA gene sequencing grouped the 32 bacteria into 14 genera belonging to four phyla, namely Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. Out of 32 bacteria, 7 solubilized 252.1 ± 14.8 to 1,312.9 ± 53.2 mg L−1phosphate from 5 g L−1tri-calcium phosphate. When tested for uranium sensitivity, all seven selected bacteria showed significant tolerance to uranium compared to the reference strain Escherichia coli ATCC 25922T. Therefore, further investigation of these natural soil isolates, well adapted to complex environmental conditions could lead to prospective applications in remediation of uranium or other heavy metal contaminated sites.