Diversity, distribution and multi-functional attributes of bacterial communities associated with the rhizosphere and endosphere of timothy (Phleum pratense L.).

AIMS

To characterize the bacterial communities of the rhizosphere and endosphere of the forage grass timothy (Phleum pratense L.) and evaluate the functional attributes with respect to growth promotion properties, antimicrobial and biosurfactant capacities.

METHODS AND RESULTS

A total of 254 culturable bacteria were identified using 16S rRNA sequencing and grouped into 16 taxa that shared high homology of 98-99% with other known sequences. A majority of the isolates were recovered from the rhizosphere soil fraction and leaf and crown tissues. Bacillus genus was the most abundant in the bulk and rhizosphere soil fractions. Isolates belonging to the Methylobacterium genus were exclusively found in leaves making them tissue-specific. A majority of the bacterial isolates exhibited multi-functional growth promotion attributes and plant stress improvement related to the production of indole 3-acetic acid, VOC and siderophores and polymer-degrading enzymes and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activities. Some demonstrated antimicrobial properties such as hydrogen cyanide and biosurfactant production and activities of fungal cell wall degrading enzymes. The internalization and spread of selected bacterial isolates in timothy seedlings under gnotobiotic conditions was confirmed using the culture-dependent method and SEM microscopy in proof-of-concept experiments.

CONCLUSIONS

The attributes of some isolates with respect to growth promotion abilities, biocontrol potential and efficient colonization of timothy make them desirable for future development as potential biofertilizer tools.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides the first evidence of bacterial endophytes that have the necessary functional attributes to protect cool-season forage grasses against abiotic stress.