An axenic culture is a laboratory culture containing a single microbial species grown free of all other living organisms, including bacteria, fungi, protozoa and viruses.
Methods and maintenance
Obtaining and maintaining an axenic culture requires strict aseptic technique to prevent contamination from ubiquitous environmental microorganisms. Isolation begins by streaking or dilution plating on selective and differential media to separate individual cells, followed by selection of a single colony for subculture. Alternatively, micromanipulation or filtration can be used to physically separate a target organism from contaminants. Cultures are grown in sterilized media and incubated in clean environments such as laminar flow cabinets. Antibiotics, antifungals or heat pretreatment may be applied to eliminate unwanted organisms, but these treatments can stress the target microbe. Regular monitoring by microscopy and plating onto rich media helps detect contaminants, and subculturing at defined intervals reduces the risk of overgrowth by adventitious microbes. For organisms requiring specialized conditions, like anaerobes or obligate symbionts, axenic culture may be challenging or impossible.
Applications and examples
Axenic cultures enable researchers to study the physiology, genetics and metabolism of a microbe without interference from other species. Pure cultures are essential for identifying pathogens using Koch’s postulates, testing antibiotic susceptibility and characterizing new species. In cell biology, axenic cultures of protozoa such as Acanthamoeba and Giardia lamblia have facilitated research on cell division and pathogenic mechanisms. Germ‑free animal models are maintained under sterile conditions to examine host–microbe interactions by introducing defined microbial communities. Plant scientists use axenic callus cultures or algae cultures to investigate growth regulators and photosynthesis without microbial contaminants. However, many microbes form obligate mutualistic associations and cannot be maintained in isolation; studying them requires co‑culture systems or genomic approaches.
Axenic culture serves as a cornerstone of microbiological research, providing controlled systems to examine the properties of individual organisms and establish causal relationships between microbes and phenotypes.
Related Terms: Pure culture, Sterile technique, Contamination, Isolation, Microbiome