Role of gut microbiome in multiple myeloma. Targeting the microbiome may be a useful method to disrupt pathogenic processes mediated by gut microbes, such as the production of glutamine and ammonium (which activates osteoclasts) by the nitrogen-recycling bacteria E cloacae and K pneumoniae, or interleukin-17–mediated potentiation of tumor microenvironment via Th17 cells and eosinophils by P heparinolytica. Retrospective studies suggest strategies to increase the relative abundance of butyrate producers (eg, E hallii or F prausnitzii) or diversity may augment treatment responses. OC, osteoclasts; Th17, T-helper 17. Figure created with BioRender.com.