Sulfate Assimilation Responses On Copper Resistance Mechanism In Cupriavidus Gilardii CR3

Copper is an essential trace element in most organisms and plays an important role in the metabolism of organisms,but excess copper is toxic.So far,it had been pointed out that the sulfate assimilation pathway plays an important role in heavy metal resistance in several omics related articles.Previous studies in our laboratory have also shown that the sulfate assimilation pathway of Cupriavidus gilardii CR3 is significantly up-regulated under copper stress.This paper aims to explore the copper resistance mechanism of C.gilardii CR3 and study its copper resistance and its internal relationship with sulfate assimilation.The work mainly includes the following aspects:1.It had no significant effect on C.gilardii CR3's growth under low concentration of Cu²⁺?0.1,0.5 mM?,but significant inhibition effect on C.gilardii CR3 under higher concentration of Cu²⁺?1.0,1.5 mM?.C.gilardii CR3 has a tendency to stabilize copper adsorption rate at 72 h.The copper tolerance mechanism of C.gilardii CR3 is the coexistence of extracellular adsorption,bioaccumulation and efflux,and intracellular accumulation is the main approach to resist to copper toxicity.2.Ultra-low temperature repeated freeze-thaw method can effectively break the wall of C.gilardii CR3 cells.Under Cu²⁺condition,intracellular cysteine content increased in the early stages of growth and then decreased with the training time.Similar Cys levels were maintained at 48 h for both lower concentrations and no copper stress.However,the Cys content remained at a higher level for 48 h under higher concentration of copper stress.The change of GSH content was synergistic with Cys.High Cys and GSH levels favor CR3 survival in high copper environments.3.The opposite change of SOD and CAT under copper stress indicated that they could coordinate with each other under copper stress.High GR activity under copper stress helps maintain high GSH content.4.In the presence of additional sulfur source,the growth of strain CR3 was significantly increased.and the Cu²⁺adsorption capacity was promoted as well,but the adsorption rate fluctuates dramatically.The presence of an external sulfur source in the early stage of copper stress helps to maintain the relative stability of the bioaccumulation copper content in bacteria CR3.However,Cu intracellular accumulation was main copper resistance type under with the prolongation of culture time.After supplementation with sodium sulfate,the similar Cys level and the higher GSH level were determined.The relative expression of sulfate assimilation genes and copper resistance genes decreased under additional sulfur conditions,indicating that C.gilardii CR3 reduced the Cu efflux demand.In all,the addition of sulfur source can increase the copper resistance capability of strain CR3.