Phyllosphere microbiome in arid environments, its relation to spatial, temporal, microclimate and plants physiological stress. Acacia Phyllosphere

Phyllosphere microbiome interactions with their host plant and environment is of high importance especially in arid regions where resources are scarce. Acacia raddiana and A. tortilis are major components of savannas and arid regions in the Middle East and Africa, where they are considered long living and drought enduring keystone species and are widely spread in arid Arava (southern Israel) desert. In this study, we investigated the phyllosphere microbiome of A. raddiana and A. tortils trees along with thirteen other different shrubs species . A total of 186 different leaf samples were taken from plants in the central arava Sheizaf reserve, to investigate the ecological effect of plant species, microclimate (different area within the canopies), site and season on the variability of the associated endo and exosphere microbiome. Additional samples included leaves from a nearby site where a recent oil spill was assumed to affect local acacia trees.Result shows endosphere bacteria diversity to be half of that found on the exosphere, and possessed a different bacterial community composition. Both acacia species (A. raddiana and A. tortilis) showed to have a separate clusters within the endosphere bacterial communities samples but not in the exosphere samples. Interestingly, exosphere but not endosphere bacterial communities showed to significantly affected by both seasonality and temperature. Acacia tress microclimate, also showed to have a significant effect, A. tortilis (often called the ‘‘umbrella thorn’’ for its distinctive spreading crown) had a higher canopy variation than in A. raddiana (trees up to 20 m tall with rounded crowns) and often shows a significant community composition in either hot or cold months. Along with species, temporal and microclimate variation, tree under physiological oil spill stress also exhibited changes in both endo- and exosphere microbiome. These results shed the importance of phyllosphere microbiome and their interaction to ecological, abiotic and host physiological condition such as a holistic approach is needed to understand phyllosphere microbiome their ecosystem services.