Fig. 1

Efficient biodegradation of PNP by strain Rhodococcus sp. 21391. a Degradation kinetics of 300 μM PNP by cells of strain 21391. The depletion of PNP (green triangle), cell density (OD600 of culture, green square), and nitrite released in the medium during the 18-h culture were monitored. b HPLC analysis of PNP catabolic intermediate by strain 21391. Comparison of retention times and spectra with standards of PNP (upper) and p-nitrocatecol (middle) show that p-nitrocatecol is an intermediate product of PNP degradation. c Effect of PNP concentrations (0.1–1.6 mM) on PNP biodegradation by strain 21391. d Neighbor-joining phylogenetic tree showing the evolutionary relationship between Rhodococcus sp. 21391 and other Rhodococcus spp. e Chemotaxis response of strain 21391 in the drop assay. PNP (1 µL) at a concentration of 1 mM was spotted onto the plate containing cells of strain 21391 and incubated for 24 h at 30 °C. The plates were prepared from MSM medium supplemented with 0.4% (m/v) agarose. The plate without PNP spotting was used as a negative control. f Degradation of different benzenes by strain 21391. Cells of strain 21391 were resuspended in MSM medium to OD600 = 0.1, while pyrene, fluorene, β-naphthol, biphenyl, 2-chloro-4-nitrophenol, dibromodiphenyl ether, and diphenyl ether were added to a final concentration of 300 μM. The content of residual benzenes was detected by HPLC after incubation for 72 h at 25 °C and 100 rpm shaking. Three replicates were set up for all the tests