To investigate the effect of microbial inoculum on soil heavy metal immobilisation, pot experiments were conducted with paddy soils contaminated by cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg), respectively. The results showed that the inoculation of Rhodopseudomonas palustris was more effective in the immobilisation of Pb and Cd in soils than the composite of R. palustris and Bacillus subtilis. Interestingly, a lower dosage of inoculum immobilised significantly more heavy metals than the higher dosage, potentially due to the competition of bacteria with limited nutrients. The heavy metal contents in rice grains also supported this finding, as less Pb and Cd were accumulated under the lower dosage. However, there were limited effects of microbial inoculations on the immobilisation of Hg and As. In general, our study indicated the effectiveness of R. palustris in immobilising Pb and Cd in soils and highlighted the importance of determining the optimal dosage of inoculum in bioremediation.
Abriouel H., Franz C.M.A.P., Omar N.B., Gálvez A. (2011): Diversity and applications of Bacillus bacteriocins. Fems Microbiology Reviews, 35: 201–232. https://doi.org/10.1111/j.1574-6976.2010.00244.x
Cheng C., Wang Q., Wang Q.X., He L.Y., Sheng X.F. (2020): Wheat-associated Pseudomonas taiwanensis WRS8 reduces cadmium uptake by increasing root surface cadmium adsorption and decreasing cadmium uptake and transport related gene expression in wheat. Environmental Pollution, 268: 115850. https://doi.org/10.1016/j.envpol.2020.115850
Griffiths B.S., Kuan H.L., Ritz K., Glover L.A., McCaig A.E., Fenwick C. (2004): The relationship between microbial community structure and functional stability, tested experimentally in an upland pasture soil. Microbial Ecology, 47: 104–113. https://doi.org/10.1007/s00248-002-2043-7
Haskett T.L., Tkacz A., Poole P.S. (2020): Engineering rhizobacteria for sustainable agriculture. The ISME Journal, 2020: 1–16.
He X.L., Li B.K., Chen Y.Y., Wu J.W. (2016): Correlations between soil microbial distribution and soil factors in the rhizosphere of Ammopiptanthus mongolicus. Journal of Arid Land Resources and Environment, 212: 53–57.
Jallad K.N. (2015): Heavy metal exposure from ingesting rice and its related potential hazardous health risks to humans. Environmental Science and Pollution Research, 22: 15449–15458. https://doi.org/10.1007/s11356-015-4753-7
Lakshmi K., Indiragandhi K., Somasundari R. (2014): Biosorption of heavy metals by using free and immobilised cells of Bacillus subtilis and Pseudomonas aeruginosa. Scientific Transactions in Enviornment and Technovation, 7: 118–120. https://doi.org/10.20894/STET.116.007.003.003
Liu J., Zhang X.H., Tran H., Wang D.Q., Zhu Y.N. (2011): Heavy metal contamination and risk assessment in water, paddy soil, and rice around an electroplating plant. Environmental Science and Pollution Research, 18: 1623. https://doi.org/10.1007/s11356-011-0523-3
Ndeddy A.R.J., Babalola O.O. (2016): Effect of bacterial inoculation of strains of Pseudomonas aeruginosa, Alcaligenes feacalis and Bacillus subtilis on germination, growth and heavy metal (Cd, Cr, and Ni) uptake of Brassica juncea. International Journal of Phytoremediation, 18: 200–209. https://doi.org/10.1080/15226514.2015.1073671
Pei J., Xu D. (2011): Progress in the application of photosynthetic bacteria to the treatment of heavy metal wastewater. Industrial Water Treatment, 31: 13–17.
Peng W.H., Li X.M., Song J.X., Wei J., Liu Y.Y., Fan W.H. (2018): Bioremediation of cadmium- and zinc-contaminated soil using Rhodobacter sphaeroides. Chemosphere, 197: 33–41. https://doi.org/10.1016/j.chemosphere.2018.01.017
Puga A.P., Abreu C.A., Melo L.C.A., Paz-Ferreiro J., Beesley L. (2015): Cadmium, lead, and zinc mobility and plant uptake in a mine soil amended with sugarcane straw biochar. Environmental Science and Pollution Research International, 22: 17606–17614. https://doi.org/10.1007/s11356-015-4977-6
Wang T., Sun H.W., Mao H.J., Zhang Y.F., Wang C.P., Zhang Z.Y., Wang B.L., Sun L. (2014): The immobilization of heavy metals in soil by bioaugmentation of a UV-mutant Bacillus subtilis 38 assisted by NovoGro biostimulation and changes of soil microbial community. Journal of Hazardous Materials, 278: 483–490. https://doi.org/10.1016/j.jhazmat.2014.06.028
Xiao X., Zhao Y., Zhou Q., Wang L.Y., Zhang X.J., Zhao L.H., Zhang S. (2019): Alleviating the cadmium toxicity and growth-promotion in paddy rice by photosynthetic bacteria. CLEAN – Soil, Air, Water, 47: 1800382. https://doi.org/10.1002/clen.201800382
Xie X.G., Zhang F.M., Wang X.X., Li X.G., Dai C.C. (2019): Phomopsis liquidambari colonization promotes continuous cropping peanut growth by improving the rhizosphere microenvironment, nutrient uptake and disease incidence. Journal of the Science of Food and Agriculture, 99: 1898–1907. https://doi.org/10.1002/jsfa.9385
Yang Y., Deng L. (2005): Effects of heavy metals in the paddy soil in Sichuan province on rice grain. Journal of Agro-Environmental Science, 24: 174–177.
Zeng J., Li X.Y., Wang X.X., Zhang K.H., Wang Y., Kang H.Y., Chen G.D., Lan T., Zhang Z.W., Yuan S., Wang C.Q., Zhou Y.H. (2020): Cadmium and lead mixtures are less toxic to the Chinese medicinal plant Ligusticum chuanxiong Hort. than either metal alone. Ecotoxicology and Environmental Safety, 193: 110342. https://doi.org/10.1016/j.ecoenv.2020.110342