Biofilm-producing bacteria can decrease Cd uptake in vegetables,but mechanisms under-lying this effect are poorly characterized.In this study,two mutant strains B12ΔYwcc and B12 ΔSlrR were constructed from a biofilm-producing Bacillus subtilis strain B12.Then,the im-pacts of strain B12 and its high biofilm-producing mutant strain B12ΔYwcc and low biofilm-producing mutant strain B12ΔSlrR on Cd availability and uptake in Chinese cabbage and the related mechanisms were investigated in the Cd-polluted soil.Strain B12 and its mutants B12ΔYwcc and B12ΔSlrR increased the dry biomasses of edible tissues by 54％-130％com-pared with the controls.Strain B12 and its mutant B12ΔYwcc reduced the soil available Cd content by 36％-50％and root and edible tissue Cd contents by 23％-50％compared with the controls.Furthermore,the mutant strain B12 ΔYwcc reduced the edible tissue Cd content by 40％and increased the polysaccharide content by 23％,invertase activity by 139％,and gene copies of the cumA by 4.5-fold,epsA by 7.1-fold,and cadA by 4.3-fold,which were involved in Cd adsorption in the rhizosphere soils,respectively,compared with strain B12.The polysac-charide content and cumA,epsA,and cadA gene copy numbers showed significantly reverse correlations with the available Cd content.Notably,the mutant strain B12ΔYwcc showed better ability to colonize the vegetable root surface than strain B12.These findings demon-strated that the biofilm-overproducing mutant strain B12ΔYwcc increased the polysaccha-ride production and Cd-immobilizing related cumA,epsA,and cadA gene copies,resulting in lower Cd availability and accumulation in Chinese cabbage in the Cd-polluted soil.

Yanyan Ge;Zhanbiao Ge;Jinwei Zheng;Xiafang Sheng;Linyan He

College of Life Sciences,Nanjing Agricultural University,Key Laboratory of Agricultural and Environmental Microbiology,Ministry of Agriculture,Nanjing 210095,China

环境科学学报（英文版）

[1]Yanyan Ge;Zhanbiao Ge;Jinwei Zheng;Xiafang Sheng;Linyan He-.Biofilm-overproducing Bacillus subtilis B12ΔYwcc decreases Cd uptake in Chinese cabbage through increasing Cd-immobilizing related gene abundance and root surface colonization)[J].环境科学学报（英文版）,2022(10):84-93

overproducing,Ywcc,SlrR,cumA,cadA

Biofilm,Bacillus,subtilis,B12,decreases,Cd,uptake,Chinese,cabbage,through,increasing,immobilizing,related,gene,abundance,root,surface,colonization,bacteria,vegetables,but,mechanisms,under,lying,this,effect,poorly,characterized,In,study,two,strains,were,constructed,from,biofilm,Then,pacts,its,high,availability,investigated,polluted,Strain,mutants,increased,dry,biomasses,edible,tissues,by,controls,reduced,available,contents,compared,Furthermore,polysaccharide,invertase,activity,copies,fold,epsA,which,involved,adsorption,rhizosphere,soils,respectively,copy,numbers,showed,significantly,reverse,correlations,Notably,better,colonize,than,These,findings,demon,strated,that,production,resulting,lower,accumulation

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