Cadmium adsorption characteristics and mechanisms of cadmium-resistant strains
The focus of this study was the mechanism of cadmium resistance of three previously screened bacterial strains,i.e.,Stenotrophomonas sp.Cd-2,Achromobacter sp.Cd-3,and Staphylococcus sp.Cd-7.The characteristics of bacterial adsorbents for Cd2+and the secretion of extracellular polymeric substances(EPS)of the three strains under Cd2+stress were investigated.The gene expression profile of strain Cd-3 was examined using transcriptome sequencing technology after exposure to Cd2+stress,with the aim of investigating the mechanisms underlying the resistance to Cd.The results showed that the strains exhibited the highest adsorption rate of Cd2+,reaching over 90%,under the following conditions:pH,7;temperature,30℃;contact time,120 min;Cd2+concentrations,20～100 mg·L-1;bacterial biosorbent concentrations,1 g·L-1(Cd-7)and 8 g·L-1(Cd-2,Cd-3).The adsorption processes followed the Langmuir model and pseudo-second-order kinetic model,indicating that the adsorption of Cd2+by these three strains is via a single molecular layer,with the adsorption rate mainly limited by chemical adsorption.The EPS assay revealed that,under conditions of Cd2+stress,the three strains primarily inhibited the entry of Cd2+into cells through extracellular protein complexation.The transcriptome sequencing results showed that strain Cd-3 exhibited a response to Cd2+stress by upregulating genes associated with growth metabolism,redox reactions,and transmembrane transport,indicating that strain Cd-3 was resistant to Cd2+stress by regulating the expression of these genes.
heavy metalcadmiumadsorptionmicrobial remediationtranscriptome
万方数据
维普
