Abstract
The goal of this research was to determine the effects of the growth of invasive plant Amur Honeysuckle (Lonicera maackii) on the rhizosphere bacterial community composition, and diversity in an urban wetland forest ecosystem. Bacterial communities from the rhizosphere of 5 L. maackii plants and control bulk soils that did not have any L. maackii were investigated at Nina Mason Pulliam EcoLab (NMPE) using a culture-independent pipeline. Bacterial communities were characterized by PCR amplification and cloning 16S rRNA gene fragments following total DNA isolation from the soil samples. Microbial communities associated with both L. maackii rhizosphere and control sites showed high bacterial diversity within each site and taxa unique to individual sites were observed. Phylogenetic analyses revealed 80% of 400 16S rDNA clones were classified as α-, β- and γ-Proteobacteria, Acidobacteria, Actinobacteria, Cytophaga-Flexibacter-Bacteroides (CFB) group, and Verrucomicrobia. Members of the Proteobacteria and Acidobacterium represented 66.5% and 14.5% of the clone library, respectively, whereas the remaining bacterial divisions each comprised less than 7% of the clone library. Twenty-five 16S rDNA clones could not be classified into any known bacterial divisions. Statistical analyses showed significant differences in the presence of L. maackii on the proportions of 16S rDNA clones affiliated with Proteobacteria and Acidobacterium, suggesting bacterial community composition and structure does significantly change in the presence of L. maackii. However, sequence-based community analysis and the corresponding lack of intact microbial cultures limit understanding of the potential influences of enriched microbial taxa on plant hosts and their roles in ecosystem functioning.
Highlights
Soil bacterial communities have significant impact on plant cover as pathogens, decomposers, or beneficial mutualists, influence nutrient cycling and solubilization, as well as have potential to induce production of plant hormones in plants [1]
Identical or nearly identical bacterial 16S rRNA gene fragments have been recovered from non-rhizosphere forest soil samples from the Nina Mason Pulliam EcoLab (NMPE) site
We addressed two main questions about NMPE soils: 1) What the bacterial community profile is in the L. maackii rhizosphere soils? 2) Does this profile differ from the control soils devoid of L. maackii? The 16S rDNA clone library from NMPE LM rhizosphere soils represented seven known bacterial divisions
Summary
Soil bacterial communities have significant impact on plant cover as pathogens, decomposers, or beneficial mutualists, influence nutrient cycling and solubilization, as well as have potential to induce production of plant hormones in plants [1]. These impacts can range from highly positive to negative for the plants. The relative abundance of plant species in a Canadian meadow was correlated with the extent to which soil microbes are associated with each plant species This relationship conferred positive impacts on host plant biomass; abundant plant species were more likely to experience positive feedbacks with their rhizosphere-associated microflora, while rare species tended to experience negative feedbacks [2]. Compared with culture-based methods, sequence-based analyses provide a means for exploring plant-associated microbial communities that is more representative of their phylogenetic complexity, providing the potential for identifying novel plant-associated taxa while broadening our understanding of the diversity of plant-microbe associations
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