Sensitivity of Thermotoga spp. to kanamycin. (a) Sensitive cells formed inhibition zones surrounding the paper discs loaded with various amounts of the antibiotic, as indicated in the top left panel. Gas bubbles produced by the Thermotoga cells were clearly visible in each plate. (b) Optical densities of T. maritima liquid cultures grown with kanamycin ranging from 0 to 300 μg/ml. Results of three independent tests. Tm, T. maritima; Tn, T. neapolitana; RQ7, T. sp. RQ7.