Effect Of Low Temperature Stress On Physiology And Degradation Of Estradiol Hormone In Rhodococcus (R.D-001)

In the cold zone north of my country's 40 degrees north latitude,the temperature is generally low throughout the year,the lowest temperature is below-30°C,and the average water temperature is about 10°C.The cold climate conditions are extremely unfavorable for the biological purification of sewage.Low temperature in sewage treatment plants mainly affects the metabolic function of microorganisms in sewage activated sludge.Studies have shown that low temperature is the most important factor affecting the physiology and function of microorganisms.Therefore,studying the degradation mechanism of microorganisms under low temperature stress is the key to improving the biological purification efficiency of sewage treatment plants in cold winter areas.In recent years,the research on the degradation mechanism of estrogen-degrading bacteria under low temperature stress has not been deep enough.In order to further explore the effect of low temperature stress on the physiology and degradation of estradiol hormone of strain RD-001,this article uses high-efficiency estrogen-degrading bacteria Rhodococcus equi DSSKP-R-001(RD-001)is the target strain,which was cultured at 30°C and 10°C.The morphological changes of strain RD-001 were observed by scanning electron microscopy;the strain RD-001was tested against females by high performance liquid chromatography.The degradation rate of glycol hormones;the changes of fatty acids were detected by gas chromatography;the gene expression level of strain RD-001 under low temperature stress was analyzed by transcriptomics sequencing technology,and the reasons for the changes in the above phenomena were revealed from the perspective of genes.The specific research conclusions are as follows:1.Low temperature stress inhibits the growth of strain R.D-001 and the degradation of estradiolStrain RD-001 was cultured at 30°C,and the cells grew rapidly,with the highest cell OD₆₀₀value of 0.195 at 72 h,and then entered the cell growth equilibrium phase;cultured at 10°C,the cell growth was slow,and the OD₆₀₀value was the highest at 60 h It was 0.137,after which the number of cells no longer changed significantly.The cell density affects the degradation rate of the strain.At 30°C,the degradation rate of strain R.D-001 to estradiol is 94.8%,and at10°C,the degradation rate only reaches 54.8%.It can be seen that as the culture temperature decreases,the cell growth and estradiol degradation of strain R.D-001 are significantly inhibited.2.Low temperature stress changes the morphology and fatty acid composition of strain R.D-001Strain RD-001 was cultured at 30°C and 10°C,and the cell morphology changed from a spherical shape to an irregular short rod shape,and regular depressions appeared in the contact part of the cell and the cell.This may be due to the low temperature changing the strain RD-001 The composition of the cell wall,so the cell morphology has changed.By detecting the changes in fatty acid content of strain RD-001 at different temperatures,it was found that the overall fatty acid content increased at low temperatures,and the relative content of unsaturated fatty acids was higher than saturated fatty acids,which may increase the fluidity of cell membranes,lower the melting point of fatty acids,and make Cells are more likely to adapt to low temperature environments..3.The effect of low temperature stress on the differentially expressed genes of strain R.D-001By analyzing the changes of differentially expressed genes in strain R.D-001 at different temperatures,we found that 525 differentially expressed genes were up-regulated and 1100were down-regulated under low temperature stress.The GO database,KEGG database and COG database were used to enrich and analyze these differential genes.The results showed that most of the genes up-regulated were related to gene expression,protein complex production and energy metabolism.Changes in cell morphology and function may be affected by gene regulation.This study found that the key genes of fatty acid degradation and synthesis pathways are significantly up-regulated at low temperatures,which may be the main reason for the changes in fatty acid content;the decrease in estrogen degradation may also be coded for dehydrogenation.Enzymes and oxygenase genes are down-regulated;however,some genes in related pathways such as amino acid metabolism pathway and energy metabolism are activated at low temperature.The expression of these genes may be a self-protection strategy of strain R.D-001 in response to low temperature environment,which is helpful Because it survives in a low temperature environment.In short,this experiment explained the relationship between cell physiological functions and gene expression by analyzing the physiological functions and differential genes of Rhodococcus R.D-001 under low temperature stress.The research results will help advance the research on the degradation mechanism and functional regulation mechanism of cryogenic bacteria,and provide a theoretical basis for improving the winter sewage biological treatment effect in cold winter areas.