Low-intensity microwave radiation and the virulence of Agrobacterium tumefaciens strain B6.

When virulent cells of Agrobacterium tumefaciens strain B6 were exposed to low-level microwave radiation at a frequency of 10,000 MHz and an intensity of 0.58 mW/cm2 for 30 to 120 min, a 30 to 60% decrease in their ability to produce tumors on potato and turnip disks was observed. This microwave exposure did not affect the viability of these bacteria or their ability to attach to a tumor-binding site nor did it induce thermal shock. This loss of virulence was reversible within 12 h.