The characteristics of rhizosphere microbes associated with plants in arsenic-contaminated soils from cattle dip sites

• Published in: The Science of the total environment 2007-06, Vol.378 (3), p.331-342
• Main Authors: Chopra, B.K., Bhat, S., Mikheenko, I.P., Xu, Z., Yang, Y., Luo, X., Chen, H., van Zwieten, L., Lilley, R. McC, Zhang, R.
• Format: Article
• Language: English
• Subjects: Acaulospora; Agrostis tenuis; Animals; Applied sciences; Arsenic; Arsenicals - analysis; Arsenicals - pharmacology; Arthrobacter; Australia; Bacillus; Bacteria; Bacteria - classification; Bacteria - isolation & purification; Biological and medical sciences; Biotechnology; Cattle; Cattle dip site; Cattle Diseases - prevention & control; Decontamination. Miscellaneous; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment and pollution; Exact sciences and technology; Ferns - drug effects; Ferns - growth & development; Ferns - microbiology; Fundamental and applied biological sciences. Psychology; Gigaspora; Industrial applications and implications. Economical aspects; Insecticides - analysis; Insecticides - pharmacology; Insecticides - toxicity; Miscellaneous; Mycorrhizae; Pennisetum - drug effects; Pennisetum - growth & development; Pennisetum - microbiology; Phylogeny; Pollution; Pollution, environment geology; Rhizome - drug effects; Rhizome - growth & development; Rhizome - microbiology; Rhizosphere; Serratia; Soil and sediments pollution; Soil contamination; Soil Microbiology; Soil Pollutants - analysis; Soil Pollutants - toxicity; Tick Control - methods; Tick-Borne Diseases - prevention & control; Tick-Borne Diseases - veterinary
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2007.02.036

Soil microorganisms and plants were studied in samples of arsenic-contaminated soil from two cattle dip sites. The aim was to delineate the parameters that will determine the feasibility of future remediation by growing arsenic-accumulating plants, including the identity and characteristics of some rhizosphere soil microbes. The soil samples contained high total, but low soluble arsenic concentrations which, together with other properties, resembled the previously reported characteristics of dip-site soils from this region of rural Australia. A glasshouse trial demonstrated that dip-site rhizosphere microbes promoted arsenic accumulation by the grass Agrostis tenuis on contaminated dip-site soil without inhibition of growth. The arsenic content of the shoots was increased by 45%. We studied the colonization of roots of dip-site plants by mycorrhizal fungi and tentatively identified six genera of other fungi present in the soil samples. Two plant species growing at the sites, Kikuyu grass (the most abundant plant) and Rainbow fern, exhibited mixed infections of their roots by endomycorrhizal fungi (tentatively identified as Acaulospora and Gigaspora) and by soil-born pathogens. Five rhizosphere bacteria were identified to genus level and we determined the effect of arsenic on their growth. The two most prevalent strains differed greatly in their growth sensitivity to arsenate; Arthrobacter sp. being the most sensitive while Ochrobactrum sp. exhibited exceptional resistance to arsenate. Of the other, less prevalent strains, two were Bacillus spp. and the last, Serratia sp., was the most resistant to arsenite. These findings show the importance of understanding plant–soil microbe interactions for developing future strategies aimed at a phytoremediation-based approach to removing arsenic from soil at dip sites.