Background: Saccharibacteria (formerly TM7) are ultrasmall bacteria with highly reduced genomes that belong to the Patescibacteria superphylum, which represents over one-quarter of microbial diversity. Nanosynbacter lyticus TM7x, isolated from the human oral cavity, was the first cultured representative and displays an obligate episymbiotic lifestyle with Schaalia odontolytica XH001. TM7x undergoes a horizontal transmission phase where cells detach from hosts, yet how these metabolically restricted bacteria maintain viability and infectivity during this stage remains unclear. Methods: To investigate energy-generating strategies in TM7x, we constructed and validated targeted knockout mutants and evaluated substrate utilization under defined conditions. We assessed host attachment using binding assays, analyzed metabolic activity with Raman spectroscopy, and measured viability under nutrient supplementation with SYTOX Green assays. Quantitative real-time PCR was performed to determine gene expression changes associated with energy metabolism. Results: Deletion of the TM7x-encoded arginine deiminase system (ADS) markedly reduced ATP levels and impaired attachment to S. odontolytica. Raman spectroscopy confirmed metabolic flexibility of TM7x. Furthermore, we provided the first experimental evidence that TM7x can take up and metabolize glucose via glycolysis. Viability assays demonstrated that both arginine and glucose supplementation enhanced survival of free-floating TM7x. Gene expression analysis supported the role of glycolytic enzymes in energy generation during host-free phases. Conclusion: Our findings reveal that TM7x employs both ADS and glycolysis to sustain viability and infectivity across diverse environments when disassociated from its hosts. This dual strategy supports survival during horizontal transmission, a critical phase of the Saccharibacteria life cycle.