The bacteria apparently boost the production of essential oils, and also they change the molecular structure of the oil, giving it different flavours and properties, that include termicidal, insecticidal, antimicrobial and antioxidant.
The researchers, led by microbiologists Pietro Alifano and Luigi Del Giudice, the plant biologist Massimo Maffei, focussed their study on the tropical Vetiver grass through interdisciplinary research.
They found that Vetiver root cells produce a few oil precursors, which are then metabolised by the root bacteria to build up the complexity of the Vetiver oil.
The researchers found the bacteria in the oil-producing cells as well as in root locations that are closely associated with the essential oil.
Vetiver grass is the only grass cultivated specifically for its root essential oil, which is made up of chemicals called sesquiterpenes, which are used in plants as pheromones and juvenile hormones.
Also present in the essential oils, are alcohols and hydrocarbons, which, together with the sesquiterpenes are primarily used in perfumery and cosmetics.
The perfumery and flavouring industry could benefit from the increased variety that these bacteria provide to the smells and tastes of these oils.
Bacteria responsible for this transformation include alpha-, beta- and gamma-proteobacteria, high-G+C Gram-positive bacteria as well as microbes which belong to the Fibrobacteres / Acidobacteria group.
"This research opens new frontiers in the biotech arena of natural bioactive compounds. Pharmaceutical, perfumery and flavouring industries may now exploit the selected microbial strains and widen their metabolic libraries," said Professor Alifano.
"The ecological role of plant-microbial associations shows another fascinating aspect. The metabolic interplay between a plant, which offers a few simple molecules, with root bacteria, that biotransform them into an array of bioactive compounds, increases fitness and reveals new cost-efficient survival strategies," said Professor Maffei.