Identification of manganese-resistant strains and their regulatory effects on manganese accumulation by hyper-enriched plants
The synergistic effect of rhizosphere microorganisms on heavy metal hyperaccumulation in plant remediation of contaminated soils has significant potential for application.We identified a strain of bacteria with the ability to produce siderophores and indole-3-acetic acid(IAA)from a historically contaminated site of electrolytic manganese slag.Based on 16S rDNA analysis,the isolate was identified as Serratia marcescens A-4.This strain was able to grow on a selective LB medium containing Mn2+concentrations up to 20 000 mg/L.The strain A-4 was inoculated into the substrate of the hyperaccumulator Commelina communis,with substrates treated with low,medium,and high manganese(LM,MM,HM)groups,where electrolytic Mn residues accounted for 15％,30％,and 50％,respectively.The study investigated the effects of A-4 on the growth,Mn accumulation,and rhizosphere microbial community of C.communis.Results showed that,compared to the blank control groups,the LM,MM,and HM groups inoculated with A-4 increased the biomass of C.communis by 15.7％,39.6％,and 70.2％,respectively.The manganese enrichment ability of the aboveground parts of C.communis increased significantly,with Mn concentration rising by 1.62 times(P＜0.05),1.68 times(P＜0.05),and 1.07 times,respectively.The transport factors of the experimental groups increased from 8.73±2.77,8.93±1.55,and 6.17±1.17 to 14.15±0.70(P＜0.05),26.73±0.10(P＜0.05),and 31.04±16.47(P＜0.05),respectively.Additionally,the Shannon index revealed significant differences in microbial community diversity between the MM and HM treatment groups,and principal coordinate analysis(PCoA)indicated significant clustering differences among the treatment groups.Microbial community analysis showed that strain A-4 significantly impacted the abundance of key bacteria in the rhizosphere of C.communis,increasing the relative abundance of Abditibacteriota and Gemmatimonadetes while decreasing the relative abundance of Parcubacteria.KEGG functional gene analysis indicated that the abundance of genes regulating glutathione S-transferase and iron complex outer membrane receptor protein significantly increased in the LM and MM treatment groups.These genes may be key to the growth and Mn absorption in C.communis.This study demonstrates that inoculation with A-4,which can produce siderophores and IAA,significantly regulates the growth,Mn uptake,rhizosphere microbial community,and functional genes of C.communis.It provides a theoretical reference for understanding microbial enhancement of plant growth and Mn uptake,and related research on joint remediation of Mn-contaminated soil by hyperaccumulating plants and microorganisms.
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