Research On The Molecular Mechanism Of Viable But Non-culturable State Of Rhodococcus Erythropolis And Its Degradation Potential For Benzene And Toluene

In Marine,river,sediment and soil environments,due to the stress of various environmental factors such as pH,organic pollutants,heavy metals and antibiotics,functional bacteria tend to enter the viable but non-culturable(viable but non-culturable,VBNC)state.In this state,the bacteria are still active but no longer grow and divide.And the metabolism and bioremediation ability at low levels.The physiological characteristics of bacteria are different,and the molecular mechanisms by which they enter the VBNC state also have obvious differences.Therefore,this study selected the Rhodococcus erythropolis with the potential of petroleum pollution degradation as the research object,and carried out degradation experiments on benzene and toluene at different pHs to reveal the molecular mechanism of benzene and toluene causing Rhodococcus erythropolis to enter the VBNC state at different pHs,and discussed the degradation potential of Rhodococcus erythropolis in the VBNC state to petroleum pollutants.It provides a theoretical basis for the evaluation of degradation ability and practical application of functional bacteria in environmental governance.The main conclusions of this study are as follows:(1)Under the condition of pH=3,all Rhodococcus erythropolis entered the VBNC state within 5 days.It could maintain its culture ability at pH=5 and pH=9,but some of the bacteria entered the VBNC state and the total number of cells and the number of viable bacteria showed a downward trend.(2)The degradation rate of benzene and toluene by Rhodococcus erythropolis was the highest at pH=7,followed by pH=9 and pH=5.Under the condition of pH=3,Rhodococcus erythropolis in the VBNC state could not play their degradation function.(3)Based on the analysis of transcriptome data,under the condition of pH=5 and the presence of benzene and toluene,some Rhodococcus erythropolis entered the VBNC state through the synergistic action of stringent response,pyruvate metabolism pathway and protein synthesis pathway.In the presence of benzene and toluene at pH=9,some of them entered the VBNC state through the synergistic action of DNA replication pathway,ABC transporter pathway and protein synthesis pathway.At both pH levels,benzene and toluene stimulated the expression of catabolic genes of Rhodococcus erythropolis in the system,enhancing their ability to decompose and metabolize xenobiotics under these conditions.