LB 29-251 - Recent precipitation diversifies the root and rhizosphere bacterial microbiome of two Texas prairie grasses: Implications for future field sample analysis

The long-term impacts of annual precipitation on the plant rhizosphere and endophytic microbiome have been thoroughly investigated, but the short-term impacts of precipitation events have received less focus. Understanding the shifts in the plant microbiome in response to short-term perturbances like rain events may reveal a key confounding factor in microbiome studies, and understanding how the reactions of the microbiome differ between species may elucidate differences in how those species interact with their environment. In this study, leaf, root, and rhizosphere samples from two Texas prairie grass species – King Ranch bluestem (Bothriochloa ischaemum (L.) Keng.), an invasive species, and little bluestem (Schizachyrium scoparium (Michx.) Nash.), a native species – were collected from sites across the state of Texas with varying periods of time passing since a rain event. Upon sequencing the 16S rRNA gene to reveal bacterial microbiomes of those samples, a strong increase in diversity immediately following a rain event was found in the rhizosphere. The root endophytic microbiomes of the two grasses showed a similar, but weaker, response, with class Alphaproteobacteria enriched in root samples of both species collected during a rain event. The leaf endophytic microbiome showed the weakest response to the number of days since precipitation, but a strong increase in bacterial diversity was seen in samples that experienced a high amount of precipitation in the previous month. The observed strong difference in the root and rhizosphere microbiomes reveals time since precipitation as a key factor in microbiome composition in grass roots and the near-root microbiome, one that should be considered by field studies moving forward.