Nanobacteria, along with their decomposition products, are common contaminants in cell cultures that coexist with cells. Antibiotics typically fail to eliminate them. Nanobacteria compete with cells for resources, hindering cell growth and potentially leading to cell death. Many cell cultures are currently affected by nanobacteria, significantly impacting cell culture and subsequent experiments. Cells contaminated with nanobacteria exhibit several distinctive traits: the medium appears clear, but under a microscope, numerous 'small black spots' are visible around cells or in the medium. These spots multiply over time and cannot be removed by changing the medium or washing cells. Contaminated cells consume nutrients rapidly, requiring frequent medium replacement. Nanobacteria-contaminated cells grow slowly, have poor cell health, and exhibit severe vacuolation, sometimes causing changes in cell morphology. Thus, it's crucial to address nanobacteria contamination in cell cultures.