PS 26-104
Metagenomic sequencing reveals shifts in soil microbial communities: Do these shifts suggest a mechanism for the success of non-native plants after sucrose amendment?
Metagenomic sequencing reveals shifts in soil microbial communities: Do these shifts suggest a mechanism for the success of non-native plants after sucrose amendment?
Tuesday, August 12, 2014
Exhibit Hall, Sacramento Convention Center
Background/Question/Methods
Puget Sound lowland prairies have been reduced to less than 3% of their original area. This ecosystem was invaded by Scotch broom, which associates with nitrogen-fixing bacteria and elevates nitrogen levels. Invasion of other non-native plants after control of the Scotch broom threatens the remaining prairies. Carbon amendment has been used as a way to lower soil nitrogen because microbial communities will no longer be limited by carbon and sequester available nitrogen. Through carbon amendment and lowered soil nitrogen, native species might be released from any competitive impact from non-natives. Past sucrose amendments in these prairies reduced non-natives initially, but after four years, non-native species rebounded to become more abundant than on control soils. This unexpected result suggests that sucrose amendment may have altered the microbial community in unanticipated ways. To assess the changes in the bacterial and fungal communities, we established control and sucrose-amended plots in mounded prairie at Glacial Heritage Preserve in western Washington state. We extracted genomic DNA from these soils over a six-week period and also from soils treated with sucrose four years earlier. We used metagenomic sequencing to compare the microbial communities between control and sucrose-amended plots over these shorter and longer time frames.
Results/Conclusions
Principal component analysis of the metagenomic data showed that soil bacterial and fungal communities responded differently between mounds and swales in the prairie. Sucrose-amendment led to an overall decrease in relative abundance of bacteria. In the mounds, Elusimicrobia, Fibrobacteres, and Gemmatimonadetes decreased over time with sucrose-amendment as compared to control plots. In the swales, Acidobacteria, Elusimicrobia, Gemmatimonadetes, Planctomycetes, and Verrucomicrobia decreased over time due to sucrose-amendment. In contrast, fungi increased in relative abundance over time in sucrose-amended plots. In mounds, groups representing Ascomycota (Helotiales, Eurotiales, Capnodiaceae, Dothioraceae), Basidiomycota (Ceratobasidiaceae), Glomeromycota, and Zygomycota (Mucorales) increased in relative abundance. Many of these fungal groups include opportunistic molds that may be able to metabolize the added sucrose more efficiently than bacteria, and Glomeromycota including arbuscular mycorrhizae that aid in plant success. Surprisingly, soils to which sucrose was added four years earlier showed almost identical shifts in fungal communities, with more dramatic increases in opportunistic Ascomycota and Glomeromycota in mounds than in swales. Non-native plant species also rebounded much more dramatically in mounds than in swales on these same soils. These correlated patterns suggest that opportunistic and mycorrhizal fungi may play a role in the observed plant responses.
Puget Sound lowland prairies have been reduced to less than 3% of their original area. This ecosystem was invaded by Scotch broom, which associates with nitrogen-fixing bacteria and elevates nitrogen levels. Invasion of other non-native plants after control of the Scotch broom threatens the remaining prairies. Carbon amendment has been used as a way to lower soil nitrogen because microbial communities will no longer be limited by carbon and sequester available nitrogen. Through carbon amendment and lowered soil nitrogen, native species might be released from any competitive impact from non-natives. Past sucrose amendments in these prairies reduced non-natives initially, but after four years, non-native species rebounded to become more abundant than on control soils. This unexpected result suggests that sucrose amendment may have altered the microbial community in unanticipated ways. To assess the changes in the bacterial and fungal communities, we established control and sucrose-amended plots in mounded prairie at Glacial Heritage Preserve in western Washington state. We extracted genomic DNA from these soils over a six-week period and also from soils treated with sucrose four years earlier. We used metagenomic sequencing to compare the microbial communities between control and sucrose-amended plots over these shorter and longer time frames.
Results/Conclusions
Principal component analysis of the metagenomic data showed that soil bacterial and fungal communities responded differently between mounds and swales in the prairie. Sucrose-amendment led to an overall decrease in relative abundance of bacteria. In the mounds, Elusimicrobia, Fibrobacteres, and Gemmatimonadetes decreased over time with sucrose-amendment as compared to control plots. In the swales, Acidobacteria, Elusimicrobia, Gemmatimonadetes, Planctomycetes, and Verrucomicrobia decreased over time due to sucrose-amendment. In contrast, fungi increased in relative abundance over time in sucrose-amended plots. In mounds, groups representing Ascomycota (Helotiales, Eurotiales, Capnodiaceae, Dothioraceae), Basidiomycota (Ceratobasidiaceae), Glomeromycota, and Zygomycota (Mucorales) increased in relative abundance. Many of these fungal groups include opportunistic molds that may be able to metabolize the added sucrose more efficiently than bacteria, and Glomeromycota including arbuscular mycorrhizae that aid in plant success. Surprisingly, soils to which sucrose was added four years earlier showed almost identical shifts in fungal communities, with more dramatic increases in opportunistic Ascomycota and Glomeromycota in mounds than in swales. Non-native plant species also rebounded much more dramatically in mounds than in swales on these same soils. These correlated patterns suggest that opportunistic and mycorrhizal fungi may play a role in the observed plant responses.