Marine microbes play an important role in the biogeochemical cycling of nutrients which governs the primary productivity that supports the biodiversity and fisheries of the Ocean. These microbial-mediated processes are not solely dependent on the availability of macronutrients, but also on the bioactive trace metals- manganese, iron, nickel, cobalt, copper, and zinc –which are "essential" for the growth of organisms. Most of the trace metal amendmentstudies have primarily focused on the responseof autotrophic phytoplanktonto ironthanother biogeochemically relevant metals. Studies on the response of heterotrophic prokaryotes to iron and other trace elements are limited. We performed microcosm studiesin conjecture withnext-generationsequencing to target the phylogenetic response of the heterotrophic bacterial community to trace metal enrichments: iron, manganese, zinc and copper (individually and mixed); using samples from the chlorophyll maxima region of the open-ocean waters in the Indian Ocean. The microcosm experiments were incubated on board for a period of five days followed by filtration through 0.22µm cartridge filters, DNA extraction and V3-V4 amplicon sequencing using the Illumina MiSeq platform. The dominant phylum across all the experiments wasProteobacteria, with the abundance increasing in response to metal additions. In particular, hydrocarbon-degrading bacteria (Alcanivorax and Marinobacter) benefitted the most from the metal additions revealing a predominant role in the cycling of metals. Additionally, the hydrocarbonoclastic bacterium Porticoccuslitoralis, was only stimulated in the treatment where the trace metals were amended as a mixture. Bacteroidota were the second abundant phylum in the treatments amended with iron, manganese and the mixture, whereas in treatments using copper and zinc Proteobacteria was followed by Planctomycetota (Planctomycetia and Phycisphaerae). Desulfotobacterota (Bradymonadales) were stimulated when amended with copper, iron, manganese and a mixture of trace metals. Bradymonadales are a bacterial predator group with a high preference for Bacteroidetes and Proteobacteria, and hence are an indispensable selective force in microbial community structure and dynamics. Predation by bacteria can release nutrients and also affect biogeochemical cycling.In the control experiment, Proteobacteria (44.19%) was the most abundant phylum, followed by Actinobacteria (27.21%) and Cyanobacteria (8.67%). The abundance in Cyanobacteria (Synechococcus and Prochlorococcus) decreased drastically in the experiments amended with the trace metals as compared to the control. This could provide insights into the inhibitory effects of metals (and consequently high-flux aerosol deposition) on Cyanobacteria due to metal toxicity. The most susceptible population to trace metal additions was the uncultured bacteria SAR 324.