The minimisation of exposure of mammalian cell lines to potential microbial contaminants is handled by routine adherence to quality laboratory procedures. Mycoplasma, are capable of sustainable intracellular existence, are not visible in light microscopy and must be tested for, using dedicated methods. Bacterial contamination is usually detectable by relatively simple optical, spectroscopy and pH methodology. Symbiont occupation assumes an evolved mutually beneficial relationship and does occur with many eukaryote-prokaryotes, but rarely mammals. Other, purely intracellular low density, low energy and relatively stable and non-visible bacterial occupation of mammalian cytoplasm, assumes the existence of new intra-genus relationships and associated mechanisms. In this study, preliminary microscopy and sequence data has been collated implying the presence of low density cocci in the cytoplasm of hepatocyte lines with negligible impact on cell function and behaviour.