Mycoplasma: the invisible contaminant of cell culture (and how to detect it with the naked eye)

Wednesday, July 1, 2026

Regardless of the type of laboratory, if you work with cell cultures, you must be aware of Mycoplasma, as it can contaminate your samples undetected. It can silently spread throughout a laboratory for weeks, altering results long before anyone suspects anything is wrong.

What is Mycoplasma and why is it so difficult to detect?

Mycoplasma cells are the smallest bacteria capable of autonomous replication. Their most distinctive feature is the absence of a cell wall, which allows them to adopt variable shapes and, above all, to pass through the 0.22 µm filters commonly used to sterilize media and serums. In other words, one of the standard methods for maintaining a sterile culture is insufficient to stop them.

Added to this is their minuscule size: they are not visible with a conventional optical microscope and, unlike other contaminants, they do not usually cloud the medium or cause obvious changes in its appearance. A heavily contaminated culture can look exactly the same as a clean one. Therefore, the contamination goes unnoticed unless actively and regularly sought.

A problem for reproducibility

Given its basic structure, its behavior is parasitic. Mycoplasma exploits host cells in cell cultures and competes with them for nutrients in the medium, altering their metabolism, nucleic acid synthesis, gene expression, and proliferation rate, and potentially inducing changes in morphology or even chromosomal alterations. The result is experiments that are no longer reproducible and data that cannot withstand scrutiny. Furthermore, cross-contamination between cultures in the incubator is common.

Prevention and screening: the two sides of control

The best defense against Mycoplasma begins before it arrives, with good cell culture practices that reduce contamination pathways. Among the most important are: not processing different cell lines simultaneously in the same cabinet, keeping flasks organized by line in incubators to avoid cross-contamination, and establishing regular checks to detect and isolate any contaminated cultures promptly.

To ensure our preventative measures are effective and we maintain good control, we need verification through regular screening. The problem is that traditional methods don't always make this easy: microbiological culture is slow and doesn't detect all species, conventional PCR requires specialized equipment and personnel, and fluorescence staining requires a microscope. To address this need for fast and accessible screening, AssayGenie has developed the GenieColor Mycoplasma Detection Kit.

A colored response, without instrumental reading

The kit proposes a one-step colorimetric assay that detects Mycoplasma DNA directly in the sample. The reagent changes color depending on the presence of the contaminant, so the result is interpreted visually, without amplification curves or thresholds to analyze. Its specifications make it ideal for the routine monitoring of virtually any cell line.

Three reasons why it fits into the routine flow

1. Visual and without instruments. The result is a color change, not a graph. You don't need a thermocycler with probes or a plate reader to know if your cultures are clean.

2. Fast and one-step. Dispense sample and reaction mixture into a single tube, incubate for 60 minutes at 65 °C —in a water bath or thermocycler— and read.

3. Sensitive and validated. Detects more than 100 copies of Mycoplasma plasmid per µl and has demonstrated excellent compatibility in a selection of common cell lines.

Maintaining Mycoplasma-free cultures through routine checks is a key aspect of cell culture development. Using GenieColor, contamination control becomes a quick and easy process, and the reproducibility of your results is no longer left to chance.