A shake-up in cell culturing: Flame sterilization may affect the culture

July 01, 2020

Tsukuba, Japan - Researchers commonly culture bacteria for many purposes, such as to screen pharmaceuticals and manufacture vaccines. In these cases, shake flasks have been commonly and generally used for over 90 years to cultivate microbes.

To keep track of what's going on in the shake flask, researchers must use stringent sterilization techniques while extracting a sample of cells. A common sterilization technique is to expose the plug and flask to a flame at several time points during cell extraction. However, if this sterilization affects the cell culture in any way, you may inadvertently hinder production of the vaccine or whatever substance you want from the culture.

In a study recently published in Scientific Reports, researchers from the University of Tsukuba have shown that flame sterilization introduces carbon dioxide into shake flasks. This excess carbon dioxide can considerably affect cell growth.

Carbon dioxide is a product of methane combustion in the flame. The researchers found that flaming the flask for even a few extra seconds, or tilting the flask a few extra degrees, considerably increased the carbon dioxide concentration in the flask.

"For example, at a flame exposure time of only 5 s, increasing the inclination angle from 15° to 25° increased the carbon dioxide concentration in the headspace by approximately 50%," says Professor Hideki Aoyagi, senior author of the study. "Computational modeling confirmed our findings."

These increases in carbon dioxide concentration are induced over the course of only a few seconds of flame sterilization. But do they substantially affect cell growth? To test this hypothesis, the researchers needed to add excess carbon dioxide while keeping the flasks shaking, because interrupting the shaking can itself affect cell growth.

"We introduced intermittent carbon dioxide at concentrations similar to those expected by flame sterilization," explains Professor Aoyagi. "The ultimate oxygen demand of Acetobacter pasteurianus--known to spoil wine-- increased by up to 70%. Pelomonas saccharophila increased by up to 35%, whereas the other two microbes were not clearly affected in terms of growth."

The researchers do not yet know how common it is for flaming a shake-flask to alter cell culture growth. Nevertheless, seemingly minor experimental sterilization variables--too subtle for most researchers to even notice at first glance--may actually be pertinent. Culturing microbes in shake flasks and producing valuable products in the culture--perhaps relevant to COVID-19 research--may be substantially more complicated than previously appreciated.

University of Tsukuba

Related Microbes Articles from Brightsurf:

A new look at deep-sea microbes
Microbes found deeper in the ocean are believed to have slow population turnover rates and low amounts of available energy.

Microbes might manage your cholesterol
Researchers discover a link between human blood cholesterol levels and a gene in the microbiome that could one day help people manage their cholesterol through diet, probiotics, or entirely new types of treatment.

Can your gut microbes tell you how old you really are?
Harvard longevity researchers in collaboration with Insilico Medicine develop the first AI-powered microbiomic aging clock

What can be learned from the microbes on a turtle's shell?
Research published in the journal Microbiology has found that a unique type of algae, usually only seen on the shells of turtles, affects the surrounding microbial communities.

Life, liberty -- and access to microbes?
Poverty increases the risk for numerous diseases by limiting people's access to healthy food, environments and stress-free conditions.

Rye is healthy, thanks to an interplay of microbes
Eating rye comes with a variety of health benefits. A new study from the University of Eastern Finland now shows that both lactic acid bacteria and gut bacteria contribute to the health benefits of rye.

Gut microbes may affect the course of ALS
Researchers isolated a molecule that may be under-produced in the guts of patients.

Gut microbes associated with temperament traits in children
Scientists in the FinnBrain research project of the University of Turku discovered that the gut microbes of a 2.5-month-old infant are associated with the temperament traits manifested at six months of age.

Gut microbes eat our medication
Researchers have discovered one of the first concrete examples of how the microbiome can interfere with a drug's intended path through the body.

Microbes can grow on nitric oxide
Nitric oxide (NO) is a central molecule of the global nitrogen cycle.

Read More: Microbes News and Microbes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.