Deep-sea polymetallic nodules are valuable for their high abundance of metals,such as manganese,nickel,cobalt and copper.Microorganisms were known involved in the geochemical formation of nodules.Yet it is poorly understood what kinds of microorganisms are involved in this process.Previously,we compared microbial community composition inside polymetallic nodules and in their surrounding sediments from three sampling sites in the Pacific Ocean.Principal component analysis indicated that microhabitat(i.e.,nodule or sediment)seemed to be a major factor influencing microbial community composition,rather than sampling locations or distances between locations.To better understand the relationships between metals and microbial communities in deep-sea polymetallic nodules and surrounding sediments,we investigated samples of 20deep-sea polymetallic nodules and 9 surrounding sediments from the Pacific Ocean and Indian Ocean.The results of metal composition showed that manganese,cobalt,copper,and nickel are much more abundant in the nodules than those in the surrounding sediments.Several kinds of metals have significant high correlation,such as copper and nickel(r=0.96,p-value<0.001).Relative abundance of taxa in the microbial communities was investigated by using culture-independent high-throughput sequencing,followed by classification and statistic analysis.Principal component analysisshowed the microbial communities in the nodules are strikingly different with those in surrounding sediments.Correlation-based network analysis was performed,which helped usobtaina comprehensive understanding ofrelationships between metals and microorganisms.The order Rhizobiales,to which some Mn(Ⅱ)-oxidizing microorganisms belong,shows high correlation(r > 0.6,p-value < 0.001)with manganese,nickel and copper.The order Solirubrobacterales shows high correlation(r > 0.6,p-value < 0.001)with manganese and cobalt.The results suggest that the microorganisms belonging to these two orders may play important roles in the geochemical formation of nodules.This study shed light on further studies concerning the formation of the deep-sea polymetallic nodulesand the isolation of the uncultured microorganisms involved in this geochemical process.