Innovative Static Culture Method for Microbial Growth and Analysis

Growing microorganisms in the lab is known as culture, a fundamental yet essential technique in microbiology research. It is common practice to cultivate microorganisms in a liquid media that supplies vital nutrients; this method is straightforward and very successful.

For aerobic microbes to flourish, oxygen availability is just as important as nutrients. However, in a liquid media, oxygen is difficult to dissolve. The medium must therefore be forcefully aerated, typically by shaking.

Numerous methods have been devised to improve the aeration of “shake” cultures, such as providing air bubbles to bioreactors and using “baffled” shake flasks, which include indentations intended to facilitate oxygen transport. However, by exposing microorganisms to physical (shear) stress, these traditional shake cultures present a serious problem.

A group of researchers from Kindai University in Japan, led by Professor Motomu Akita and Dr. Kenji Ito (who are also connected to Cell Film Lab. Co. Ltd.), have now shown a novel technique for “static” culturing of bacteria in a liquid medium in a study that was published in the journal Scientific Reports.

They accomplished this by using TPX, a polymer that is extremely permeable to gases with modest molecular weights, such as oxygen. To create a thin layer of media suitable for growing, a small amount of liquid medium was placed in a TPX film bag, inoculated with bacteria, and placed on a level surface.

The researchers successfully cultivated Escherichia coli using this method, and it grew similarly in the film bag and liquid shake cultures. They also cultivated Komagataella phaffi, which needs a lot of oxygen to grow, to see if this method provided enough oxygen availability, and they found that K. phaffi grew slightly less in the film bag than in the traditional shake cultures.

There are various benefits to using a film bag as opposed to traditional culturing techniques.

Our method enables easy observation of biological phenomena that were previously unobservable. Until now, microorganisms have not been cultured in liquid conditions where sufficient oxygen was supplied and physical stress was absent.”

Motomu Akita, Professor, Kindai University

Researchers may now closely study the behavior of microorganisms in the absence of shear stress, thanks to this technique.

One noticeable occurrence in this context is the development of “biofilms,” which are gel-like layers created when bacteria stick to a surface. Typically, stirring liquid cultures prevents the formation of biofilms. Nonetheless, the current investigation showed that Bacillus species cultured statically formed “biofilm” along the film bag's bottom.

The possibilities for this new culturing method are enormous. For starters, reducing the space, energy, and resources needed to culture bacteria could promote more sustainable research activities. This means experiments could be conducted even in limited physical spaces, or when culturing equipment is constrained.”

Motomu Akita, Professor, Kindai University

The novel approach may find use in a variety of scientific, medical, and industrial research domains, such as space exploration, education, healthcare, and food production. It might be used, for instance, to carry out investigations in far-off places like space stations or even the polar areas.

Additional possible uses include improving research in low-budget labs, streamlining processes in hospitals, permitting on-site culture while conducting fieldwork, and supporting educational experiments in classrooms.