Cells grown to the stationary phase in M9 succinate minimal liquid medium were harvested and washed three times with M9 medium without carbon sources. A 1 : 1 mixture of the mutant (LacZ−) and control cells

(ATCC17616cox::lacZ; LacZ+) was inoculated into 2.7 g of soil sample in a 50-mL test tube, and the water content was adjusted to 60% of the maximum water-holding capacity. Approximately 50 tubes were prepared for each mixture, and three tubes were used for each time point. At different time points after the incubation at 30 °C, M9 minimal medium was added to the tube, vigorously vortexed, and treated mildly by sonication. The sample was left standing still for 30 min, and the supernatant was recovered and plated onto an M9 succinate minimal agar plate containing X-gal. find more The colony-forming units (CFUs) g−1 of soil were measured, and the ratio of white (mutant) to white plus blue (control) colonies was calculated. The LacZ activities of cells in the soil and in the laboratory medium were measured as described previously (Nishiyama et al., 2010). For the measurement of LacZ activity

in the laboratory medium, one-percent volume of an overnight culture (M9 succinate minimal medium) was transferred to fresh M9 medium, and the cells were incubated for 24 h and harvested. For the measurement of LacZ activity click here in the soil, the cells in the soil were harvested as described (Nishiyama et al., 2010). In brief, the tube, into which M9 medium was added, was vortexed vigorously for 30 s, shaken for 30 min, and mildly sonicated for 15 s. After leaving for 30 min for sedimentation of

the soil particles. the cells were collected from the supernatant by Chlormezanone centrifugation at 7500 r.p.m. (5500 g) for 6 min. The harvested cells were disrupted by sonication, and cell debris was removed by centrifugation. The crude extract thus obtained was used to measure the LacZ activity. The activity was normalized by the amount of protein in the reaction mixture that was measured using a Protein Assay kit (Bio-Rad Laboratories). Genomic sequence of ATCC 17616 predicted a pathway for the catabolism of tryptophan and anthranilate (Fig. 1b). In this pathway, the three enzymes KynA (tryptophan 2,3-dioxygenase), KynB (kynurenine formamidase), and KynU (kynureninase) convert tryptophan to anthranilate, which is next converted to catechol by the four-component anthranilate dioxygenase (AndAc AndAd AndAb AndAa). Catechol is then converted to TCA cycle compounds by the activities of CatA, CatB, and CatC. The genomic locus for the catabolism of anthranilate and catechol in ATCC 17616 is shown in Fig. 1a. An andAc mutant (17616ΔandAc) of ATCC 17616 was tested for its ability to utilize tryptophan and anthranilate as a sole carbon source. The wild-type strain, but not 17616ΔandAc, grew on both compounds.