Characterization of xylanolytic bacteria present in the bract phyllosphere of the date palm Phoenix dactylifera

Despite the interest of phyllosphere microbiology, no studies have addressed the bacteria present in bract phyllosphere, an ecosystem that has special characteristics in palm trees because the dry bracts remain on the plant until pruning and may contain polymer-degrading bacteria involved in plant degradation. Therefore, the aim of this work was to characterize xylanolytic bacteria isolated from palm bract phyllosphere.

Twelve xylanolytic strains were isolated and characterized by phenotypic features and complete sequencing of 16S rRNA gene. The results showed that the isolates were phenotypically and genotypically diverse. Gram-positive isolates were classified into genus Paenibacillus some of them belonging to hitherto undescribed species of this genus. Gram-negative isolates were classified into genera Pseudomonas and Acinetobacter.

The results of this work confirm the complexity of the bacterial populations present in phyllospheric ecosystems and suggest that bacteria involved in plant degradation are present at the early degradation steps of this process in dry palm tree bracts.

This is the first study on bract phyllospheric bacteria able to hydrolyse vegetal polymers and offers a new perspective in the search of unexplored sources of xylanase-producing strains.