If you are doing cell culture, it is important to keep your cultures clean and free from contamination. Contaminants can be chemical, such as impurities from media and reagent components, water sources, cleaning agents, detergents etc. and include metal ions, free radicals, and plasticizers leaching from plasticware and others. These can alter the cell morphology or growth rate, decrease their viability or cause cell death. Biological contaminants include bacteria, viruses, fungi, mycoplasma, or cross-contamination from other cell lines, leading to abnormal cell growth or death, and ultimately lost time and resources.
Bacterial-infected cultures usually appear cloudy, and can be detected under the microsope. Virally-infected cultures can be detected via electron microscopy, immunostaining, ELISAs, or PCR. Fungal contamination is usually from yeasts and molds. Molds grow as filaments called hyphae, and a collection of these filaments is referred to as a mycelium. Mold spores can survive harsh environments when they are dormant, but can reactivate when suitable growth conditions are favorable. Mycoplasmas belong to a unique genus of bacteria without cell walls, but their small size and ubiquitous distribution allows them to go undetected in seemingly sterile cell cultures. Cross contamination from other cell lines is not as common but is a serious issue if it occurs, so it is recommended to obtain your cell lines form a reputable source. According to a recent paper, rough estimates suggest that the number of published papers that used problematic cell lines is around 16.1% (Weiskirchen et al, 2023). For reliable detection of Mycoplasma contamination in cell culture, our PCR Mycoplasma Detection Kits can be used. Alternatively, for prevention or elimination of Mycoplasma contamination, our De Plasma™ kits are available.
Cell lines can be classified into 3 groups: a) finite cell lines, b) continuous cell lines, and c) stem cell lines. Finite cell lines are derived from primary cultures and have slow growth rates. They are contact-inhibited and form a monolayers. Continuous cell lines are typically from transformed cells and divide rapidly. They are not contact-inhibited and may form multiplayers. Stem cells are undifferentiated pluripotent cell types. Stem cells can be extended to make the same type or triggered to make certain cell types. Recently, 3D cell cultures, where you culture cells within a defined scaffold, are interesting for studying cell-cell interactions.
Introduction of foreign DNA or other nucleic acids into cells is called transfection. DNA is introduced into eukaryotic cells via chemical or physical methods. Physical methods include electroporation or sonoporation. To verify whether the DNA integrated into the genome, a selective marker is co-transfected with the gene, which allows it to be resistant to the antibiotic. Stress, or ‘selection pressure’ is applied to the transfected cells, using a selection antibiotic, and only the cells that contain the desired gene along with the resistance gene will grow.
If you are planning to use antimicrobials for contamination control, gene selection or transfection, your choice of antimicrobial will depend on your cell line, media type, and your research purpose. Our CulturePure® products are highly purified and tested to ensure they are safe for cell culture.
Our cell-culture database is also a useful tool to help you select the most effective media and antibiotics for your cell line, determine the most suitable antibiotics for selection and transfection, and even locate relevant citations specific to your cell line, and your plasmid/vector.
Your journey to healthy cell cultures is within reach. We invite you to explore our antimicrobials and products for cell culture research.
References:
Barone PW et al (2020) Viral contamination in biologic manufacture and implications for emerging therapies. Nat Biotechnol38:563–572 Link
Weiskirchen S et al (2023) A beginner's guide to cell culture: Practical advice for preventing needless problems. Cells. 12(5):682 Link