Submitted to: World Journal of Microbiology and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/4/2009
Publication Date: 1/1/2010
Citation: Abou-Shanab, R.I., Van Berkum, P.B., Angle, J.S., Delorme, T.A., Chaney, R.L., Ghozlan, H.A., Ghanem, K., Moawad, H. 2010. Characterization of Ni-resistant bacteria in the rhizosphere of the hyperaccumulator alyssum murale by 16S RRNA gene sequence analysis. World Journal of Microbiology and Biotechnology. 26(1):101-108. Interpretive Summary: Bacteria thrive in soil, especially where plant roots grow. The soil in close proximity to plant roots has a special name, the rhizosphere, and is especially suited for bacteria because it is rich in nutrients. The plant Alyssum (Alyssum murale) accumulates heavy metals when grown on metal contaminated soils. Therefore, it is useful for bioremediation and for extracting these metals for commercial purposes. What is not known is how the plant affects the bacteria that colonize the rhizosphere. The growth of several groups of bacteria were stimulated by the rhizosphere of Alyssum. These bacteria included those with characteristics of rhizobia. Rhizobia are beneficial bacteria that are very successful at colonizing roots of plants. However, rhizobia were not the only bacteria found in the rhizosphere. Other widely diverse groups of bacteria also were shown to be stimulated for growth in the rhizosphere of Alyssum. This information is useful for scientists working to decontaminate soils, bacterial population geneticists and taxonomists.
Technical Abstract: The diversity of 184 isolates from rhizosphere and bulk soil samples taken from the hyperaccumulator Alyssum murale, grown in a Ni-rich serpentine soil, was determined by 16S rRNA gene analysis. Among these 184 isolates 44 groups were identified. The 16S rRNA gene sequences of representatives were determined from which it was concluded that these isolates were highly diverse and were placed within the phyla Proteobacteria, Firmicutes and Actinobacteria. Among 44.6% of the isolates within the phylum Proteobacteria, 35.9% were placed within the class '-Proteobacteria and 20.7% had 16S rRNA gene sequences indicative of bacteria within genera that form symbioses with legumes (rhizobia). Of the remaining isolates, 44.6% and 5.4% were placed within the phyla Actinobacteria and Firmicutes, respectively. No placement was obtained for a small number (9) of the isolates. Bacteria of the phyla Proteobacteria and Actinobacteria were the most numerous within the rhizosphere of A. murale and represented 32.1% and 42.9% of all isolates, respectively.