Study On The Anti-cadmium Mechanism Of Beauveria Bassiana And The Activity Of Fermentation Broth Activity

Industrial emissions lead to heavy metal pollution,which accumulates in plants,animals and human body through food chain,posing a serious threat to the ecological environment and human health.Among all kinds of heavy metals,cadmium is the most toxic and widely distributed,which is harmful to human body.In vivo,cadmium can induce tumor proliferation by promoting DNA methylation,inhibiting DNA repair,inducing oxidative stress,influencing cell cycle regulation and inhibiting apoptosis.Previous studies found that filamentous fungi can not only absorb heavy metals,but also inhibit tumor cells.However,due to the low adsorption capacity of filamentous fungi to heavy metals and the low inhibition rate of fermentation broth to tumor cells,the application of filamentous fungi in biomedical field is limited.Therefore,we plan to carry out the screening of Beauveria bassiana,a highly cadmium tolerant fungus,to investigate the mechanism of cadmium ion adsorption based on RNA transcriptome sequencing,to explore the gene regulation of filamentous fungi in the process of resisting and adsorbing heavy metal cadmium,and to reveal the inhibition response of fermentation broth to tumor cells,as well as the interaction between the adsorption characteristics and the inhibition rate of tumor cells The main conclusions are as follows:1.The screening of Beauveria bassiana with high resistance to cadmium and its adsorption characteristics for heavy metals were studied.Cd²⁺tolerant filamentous fungus was isolated from heavy metal contaminated soil.The strain was identified as Beauveria bassiana Z1 by its sequence alignment.The cadmium tolerance of strain Z1was tested.The results showed that strain Z1 could still grow on the plate containing9000mg/L Cd²⁺,which was much higher than that of the reported strain3900 mg/L.The adsorption capacity of strain Z1 for Cd²⁺in liquid culture was investigated.The results showed that the strain Z1 showed high adsorption capacity for cadmium ions at the concentrations of 20 mg/L?100 mg/L and 200 mg/L?1000 mg/L.the adsorption rate of strain Z1 could reach 97.4%in the liquid medium containing 40 mg/L cadmium,and92.1%in the liquid medium containing 1000 mg/L Cd²⁺.2.The adsorption mechanism of Beauveria bassiana under high concentration of Cd²⁺stress was studied.The transcriptome changes of strain Z1 under Cd²⁺stress were analyzed by Illumina sequencing technology,and the adaptive mechanism of strain Z1 to cadmium was studied at m RNA level.Through annotation and functional analysis of differential genes,2022 genes related to heavy metal resistance were screened,among which 1104 genes were up-regulated and 918 genes were down regulated compared with the control group.Through go and pathway enrichment analysis of differentially expressed genes,it was found that these genes were mainly enriched in 7077 GO entries and 3716 KEGG pathways.Among them,active oxygen scavenging enzyme gene and heavy metal resistance gene(P-type ATPase,heavy metal tolerance protein,cytochrome P450)are the main genes with high cadmium tolerance.The catalase gene and cytochrome P450 gene were selected for fluorescent quantitative PCR.The results showed that the expressions of CAT and CPY450 were up-regulated under Cd²⁺stress,which was consistent with the results of transcriptome.3.The interaction between the characteristics of bacteria adsorption and the inhibition rate of tumor cells in fermentation broth was studied.The ethyl acetate fraction of the fermentation broth was extracted and the inhibitory effect on MCF-7 cells was investigated.The ethyl acetate fraction of Beauveria bassiana has obvious inhibitory effect on MCF-7 cells in the range of 10?150?g/ml of ethyl acetate fraction.After 24hours of treatment,when the concentration of ethyl acetate fraction is 50?g/ml,the inhibitory effect on MCF-7 cells is the best,and the inhibitory rate reaches 48.13%,which is much higher than that in the literature.It is preliminarily proved that the high cadmium resistance of Beauveria bassiana is related to tumor inhibition rate.