Growth Effects in Oregano Plants ( L.) Assessment Through Inoculation of Bacteria Isolated from Crop Fields Located on Desert Soils

Bacteria can establish beneficial interactions with plants by acting as growth promoters and enhancing stress tolerance during plant interactions. Likewise, bacteria can develop multispecies communities where multiple interactions are possible. In this work, we assessed the physiological effects of three bacteria isolated from an arid environment (, , and ) applied as single species or as a consortium on oregano ( L.) plants. Moreover, we assessed the quorum-sensing (QS) signaling activity to determine the molecular communication between plant-growth-promoting bacteria. The plant inoculation with showed a positive effect on morphometric and physiologic parameters. However, no synergistic effects were observed when a bacterial consortium was inoculated. Likewise, activation of QS signaling in biofilm assays was observed only for interspecies interaction within the genus, not for either interaction with . These results suggest a neutral or antagonistic interaction for interspecific bacterial biofilm establishment, as well as for the interaction with oregano plants when bacteria were inoculated in a consortium. In conclusion, we were able to determine that the bacterial interactions are not always positive or synergistic, but they also might be neutral or antagonistic.