Mycoplasma is a genus of bacteria that belongs to the class Mollicutes. What sets mycoplasmas apart from many other bacteria is their lack of a cell wall. The absence of a rigid cell wall makes them resistant to certain antibiotics that target cell wall synthesis. Meaning that even if you have antibiotics in your cell culture media, you can have a mycoplasma contamination.
Characteristics of mycoplasma:
- They are among the smallest free-living organisms. Their small size, along with their lack of a cell wall, makes them challenging to study using conventional microscopy.
- they lack a cell wall
- they are fastidious in their growth requirements
They are among the smallest free-living organisms. Their small size, along with their lack of a cell wall, makes them challenging to study using conventional microscopy.
Mycoplasma can alter many aspects of their host culture's cell, from cell metabolism to chromosomal aberrations, everything is included. Having undetected mycoplasma in your cell culture can easily falsify your research results and so invalidate your complete work.
Mycoplasma have the ability to alter their host culture's cell function, growth, metabolism, morphology, attachment, membranes, virus propagation and yield, interferon induction and yield, cause chromosomal aberrations and damage, and cytopathic effect including plaque formation.
Due to these reasons, mycoplasma is one of the most serious and devstating culture contaminants.
These 3 simple characterists, combined with their ability to alter virtually every cellular function and parameter, make mycoplasma the most serious, widespread, and devastating culture contaminants.
**It is therefore crucial to regularly check for mycoplasma contaminants in your cell cultures.**
It is therefore crucial to regularly check for mycoplasma contamination.
### Sources of mycoplasma contamination
The number one source of mycoplasma contamination is other infected cell lines. Cell lines cultured in for example the same hood can easily become infected if there is a contamination in a single one.
The second common source is the cell culturist; good training especially in aseptic techniques combined with the strategic use of a tested cell repository will greatly reduce the opportunities for contamination via this route. Talking and sneezing can generate significant amounts of aerosols that have been shown to contain mycoplasma. Also diry lab coats can be a source of contamination when a dust-laden sleeve is put into a laminar flow hood and dust particles fall into cultures.
The most common cause for mycoplasma contamination is the presence of another infected cell line in the laboratory. Sharing the same hood also for an easy spreading of the contamination between cell cultures.
Contaminated sera and other filtration products have, in the past, been a major source of contamination, but nowadays they only play a minor role in mycoplasma contaminations.
Another important cause is the cell culturist. Talking and sneezing can generate significant amounts of aerosols that have been shown to contain mycoplasma. Additionally, diry lab coats can be a source of contamination when a dust-laden sleeve is put into a laminar flow hood and dust particles fall into cultures.
However, good aseptic techniques and training will significantly reduce the risk of contamination via this route.
## Mycoplasma detection
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There are two bacis testing methods for mycoplasma:
1. Direct culture in media
Direct culture is the most effective and sensitive method for detecting mycoplasma, but it is also the most difficult and time-consuming.
2. Indirect tests that measure specific characteristics of mycoplasma
There are a wide range of indirect test methods available for mycoplasma detection, including PCR-based kits, DNA fluorochome staining, autoradiography, ELISA, immunofluorescence, and specific biochemical assays. These tests are faster than direct culture and are often commercially available as kits.
The easiest way of detection is to use a commercially available mycoplasma detection kit. They are, for example, based on PCRs, stainings or specific biochemical assays.
It is important to know what aspect of contamination the test is designed to detect, how well the test performs, its specificity (i.e., what strains of mycoplasma it detects and any likely causes of false positive or false negative reactions) and for detectable contamination, what level of sensitivity is achievable under the prescribed sampling and test conditions. Selection of test methods should be based on evaluation of the potential specificity and sensitivity of detection and the likelihood of inhibition of a positive result.
### Mycoplasma Control Kits
If you are not sure what test methods or kits to use, please do not hesitate to ask your collegues at LCSB.
If you are not sure what test methods or kits to use, please do not hesitate to ask your collegues at the LCSB.
Here are some examples of kits used by LCSB researchers:
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For more information on these preducts refer to Quarks.
### Control Intervalls
The longer the intervalls between tests, the more research has to be put into questions and the more work has to be repeated to be sure about the results.
The longer the intervalls between tests, the more research has to be put into questions and has to be repeated in case of contamination.
The LCSB, therefore, recommands to test cell cultures for mycoplasma contaminations **at time of arrival** and aftewards at **monthly intervalls**.
You do not only prevent your own research results to be invalidated, but help your colleagues' cell cultures to remain free of mycoplasma contaminations.
