Effects of Volatile Organic Compounds on Biofilms and Swimming Motility of Agrobacterium tumefaciens

Volatile organic compounds (VOCs) emitted by bacteria play an important role in the interaction between microorganisms and other organisms. They can inhibit the growth of phytopathogenic microorganisms, modulate plant growth, and serve as infochemicals. Here, we investigated the effects of ketones, alcohols, and terpenes on the colony biofilms of plant pathogenic Agrobacterium tumefaciens strains and swimming motility, which can play an important role in the formation of biofilms. It was shown that 2-octanone had the greatest inhibitory effect on biofilm formation, acting in a small amount (38.7 g/m³). Ketone 2-butanone and unsaturated ketone β-ionone reduced the formation of biofilms at higher doses (145.2–580.6 and 387.1–1548.3 g/m³, respectively, up to 2.5–5 times). Isoamyl alcohol and 2-phenylethanol decreased the formation of biofilms at doses of 88.7 and 122.9 g/m³ by 1.7 and 5 times, respectively, with an increased effect at 177.4 and 245.9 g/m³, respectively. The agrobacteria cells in mature biofilms were more resistant to the action of ketones and alcohols. These VOCs also suppressed the swimming motility of agrobacteria; the radius of swimming zones decreased ~from 2 to 5 times. Terpenes (−)-limonene and (+)-α-pinene had no significant influence on the colony biofilms and swimming motility at the doses used. The results obtained represent new information about the effect of VOCs on biofilms and the motility of bacteria.