Endophytic bacterial communities in the aboveground tissue of subalpine conifers are conserved across host species and sites
Conifer species thrive on soils that are nutrient deficient; a possible hypothesis is that trees are gaining resources such as nitrogen (N) through their bacterial endophyte communities. Bacterial endophytes are bacteria that reside within the tissues of healthy plants; these bacteria are known to have beneficial effects on crop plants, such as nutrient acquisition or nitrogen fixation. A first step towards identifying the endophytic community and their functions within the host organisms is to examine the taxonomic composition of endophytes across host individuals, species and sites. Our preliminary data suggest that subalpine conifer species form associations with a highly distinct and consistent, potentially N fixing community of acetic acid bacteria (AAB) in their needles.Does Pinus flexilishost a conserved potentially N fixing endophytic community across sites in its geographic range?Does P.flexilis and Pinus contortashare a common bacterial endophytic community?Needle samples were collected from two pine species at three locations, two in California and one in Colorado. Tissues were surface sterilized and total DNA was extracted. DNA was amplified using 16S ribosomal RNA primers for bacterial identification. Samples were sequenced on an Illumina MiSeq. Sequences were processed through the QIIME bioninformatic pipeline.
Both species hosted similar communities regardless of location, with a large amount of the samples consisting of AAB, with one single OTU dominating all samples. The sequences making up this OTU were clustered at 97% similarity. When clustered and taxonomically identified at 99% similarity, it was determined that this OTU was made up of three different genera; Gluconacetobacter, Asaia, and AmeyamaeaGluconacetobacter and other members of the AAB have been found to fix N endophytically indicating a possible role N fixing in the endophytic community of pines. The conservation of this OTU across species and sites may indicate an underlying co-evolution/co-diversification of pine trees with these AAB endophytes, and/or strong host selections for their uptake.