| Polychlorinated biphenyls (PCB) are very stable chloroorganic compound that have been widely used for industrial purposes because of their excellent stability, insulation properties, and resistance to combustion. Many studies discuss in more detail the extent of PCB influence in different human diseases such as cancer, neurobehavioural effects, abnormal thyroid and immune function. The overall toxicity of some PCB congeners in many soil and aquatic animals is well documented as a serious environmental problem. Biphenyl/PCB could inhibite septum formation, block cell division and lead to bacterial filamentation, even affect the protein expression.Rhodococcus sp. R04, a PCB (Polychlorinated biphenyl) degrader, was used to investigate the effect of biphenyl/PCB on bacterial morphology and division. The results showed that R04 growth was inhibited by biphenyl, and displayed concentration-dependent manners (21 to 60 mM of biphenyl). Aroclors1221 strongly inhibited the bacterial growth, and had a clearly long exponential growth phase. The length of R04 filaments increased with increase of biphenyl concentration. When the concentration of biphenyl was up to 42 mM, the longest filament was 14.72±0.66 μm, and it was approximately twice the length of cell cultured in the glucose-medium.The bacterial septum formation was influenced by biphenyl or PCB. The cell membrane was stained clearly both in the control and 3 mM biphenyl, and the fluorescence intensity of cell membrane was higher than that of cytoplasm. Complete septa were normally observed in the cells grown both on the control and 3 mM biphenyl. However, when the concentrate of biphenyl was up to 21 mM, only partial septa were observed. Incubated with 42 mM of biphenyl, no septa were watched in the cells and the cellular outline became ambiguous. The cell contour was visible, but only partial septa on the cell membrane were observed in the medium containing Aroclors1221. Real-time PCR was performed to measure the expression of cell division protein FtsZ, the result showed that the expression of ftsZ decreased with increasing of biphenyl concentration. These results clearly suggested that biphenyl/PCB inhibited septum formation, blocked cell division and led to bacterial filamentation.By analyzing the transcriptome data, we found that compared to the control, the expression of the genes related to biphenyl metabolism were up-regulated about 4 to 60 times. Be interesting, the expression of gas vesicle proteins in R04 grown with biphenyl were up-regulated about 40 to 80 times.This paper verified this result by using RT-PCR. Light-refractile, intracellular bodies that contain gas and provide cells with buoyancy were discovered in many bacteria, these gas vesicles (GVs) were formed solely of proteins. The scientists found that there were gas vesicle gene clusters in Rhodococcus sp. R04 by genome sequencing. The small protein GvpA is the major constituent and assembles to form the ribbed wall of GV. The gene gvpJ sequence is similar to gvpA, and it inferred that the gas vesicle protein GvpJ involved in the formation of the cap structure of GVs. Several soil actinomycetes also contain gvp clusters. Whether these organisms actually synthesize gas vesicles remains to be established. In recent years, the study of the physiological function of gas vesicle protein has become the hot research field.To visualize gas vesicle protein GvpA and GvpJ in living E.coli cells, the reconstructed plasmids were constructed that contained GFP. This research is helpful for the further study on the physiological function of gas vesicle protein. We have not found the gas vesicle structure in R04 yet. |
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