Effects of a rhizobacterium on the growth of and chromium remediation by Lemna minor
- 597 Downloads
Duckweed has shown great potential for both energy and environmental applications, particularly in wastewater treatment and fuel ethanol production. A rhizobacterium, Exiguobacterium sp. MH3, has been reported to associate with the duckweed Lemna minor for symbiotic growth. The aim of this work is to study the effects of rhizobacterium MH3 on L. minor growth and chromium (Cr) remediation. It appeared to have a synergism between the rhizobacterium MH3 and duckweed; the presence of strain MH3 promoted the growth of duckweeds by increasing both the frond number and dry weight of duckweed by more than 30 %, while duckweed in turn provided essential carbon source and energy for the growth of rhizobacterium MH3. Under Cr(VI) exposure, particularly at higher Cr(VI) concentrations, Exiguobacterium sp. MH3 significantly alleviated the harmful effects of the stress on the duckweed by promoting duckweed growth and preventing duckweed from excessive uptake of Cr. Potential mechanisms were also discussed in light of the genome sequence of strain MH3, and it was speculated that siderophores and indole-3-acetic acid (IAA) secreted by strain MH3 might contribute to promoting duckweed growth.
KeywordsRhizobacterium Exiguobacterium Duckweed Chromium Growth-promoting effect
This research was funded by a Key Project of Shenzhen Emerging Industries to JM (No. JC201104210118A) and Public Science and Technology Research Funds Projects of Ocean (201305022). Authors would like to kindly acknowledge Eric Lam for providing Lemna minor 145 and Maurycy Daroch for valuable comments on the manuscript.
Conflict of interest
The authors declare that they have no conflict of interest.
- Bharti N, Yadav D, Barnawal D, Maji D, Kalra A (2013) Exiguobacterium oxidotolerans, a halotolerant plant growth promoting rhizobacteria, improves yield and content of secondary metabolites in Bacopa monnieri (L.) Pennell under primary and secondary salt stress. World J Microbiol Biotechnol 29:379–387CrossRefGoogle Scholar
- Biedermann KA, Landolph JR (1990) Role of valence state and solubility of chromium compounds on induction of cytotoxicity, mutagenesis, and anchorage independence in diploid human fibroblasts. Cancer Res 50:7835Google Scholar
- Cheng JJ, Stomp A (2009) Growing duckweed to recover nutrients from wastewaters and for production of fuel ethanol and animal feed. Clean: Soil Air Water 37:17–26Google Scholar
- Joseph B, Patra RR, Lawrence R (2007) Characterization of plant growth promoting rhizobacteria associated with chickpea (Cicer arietinum L.). Int J Plant Prod 1:141–151Google Scholar
- Tang J, Zhang Y, Meng H, Xue Z, Ma J (2013) Complete genome sequence of Exiguobacterium sp. strain MH3, isolated from rhizosphere of Lemna minor. Genome Announc 1, e01059–01013Google Scholar
- Varga M, Horvatić J, Čelić A (2013) Short term exposure of Lemna minor and Lemna gibba to mercury, cadmium and chromium. Cent Eur J Biol 8:1083–1093Google Scholar
- Wu S, Feng X, Wittmeier A (1997) Microwave digestion of plant and grain reference materials in nitric acid or a mixture of nitric acid or a mixture of nitric acid and hydrogen peroxide for the determination of multi-elements by inductively coupled plasma mass spectrometry. J Anal Atom Spectrom 12:797–806CrossRefGoogle Scholar
- Zhang Y, Zhang YY, Tang J, Ma J (2014) Characterization of reduction of hexavalent chromium by Exiguobacterium sp. MH3. Chin J Appl Environ Biol 20:791–797Google Scholar