Researchers reveal how one bacterium inhibits predators with poison

February 22, 2018, Ulsan National Institute of Science and Technology
SEM image of B. bacteriovorus HD100, attacking pathogen. Credit: UNIST

Infections caused by gram-negative bacteria such as salmonella, pneumococcus, and cholera are a major problem for patients with compromised immune systems, as well as for premature babies. Bdellovibrio and like organisms (BALOs) are bacterial predators that attack and feed on other gram-negative bacteria without harming humans. Therefore, the use of predatory bacteria has been suggested as an alternative approach to tackle a range of drug-resistant, gram-negative bacterial infections that can develop in hospitalized patients. However, recent studies have revealed that some gram-negative bacteria appear to be resistant to BALOs.

A research team affiliated with UNIST has reported that the bacterium Chromobacterium piscinae produces cyanide, an inhibitory molecule, to defend itself in the battle against Bdellovibrio bacteriovorus HD100. This breakthrough has been led by Professor Robert J. Mitchell and his team in the School of Life Sciences at UNIST.

In the study, the research team found that the amount of cyanide produced by C. piscinae was sufficient enough to inhibit predation, but not overtly toxic toward B. bacteriovorus HD100. Their results also showed that C. piscinae produced the protective cyanide when provided nutrients in the form of dilute nutrient broth (DNB). Through a series of experiments, the research team also identified that C. piscinae is preyed upon by B. bacteriovorus HD100 when provided in HEPES buffer, but that it was resistant when the tests were performed in DNB.

"Our study suggests microbes may have means for resisting predation that only show up in certain environments," says Wonsik Mun in the School of Life Sciences, the first author of the study. "This study also suggests caution in defining bacterial strains that are susceptible to predation and those that are resistant, as secondary metabolites clearly can play a role."

To test whether cyanide alone was responsible or whether some other compound also acted as an inhibitor, the research team also performed additional experiments, purging and treatment of the supernatant with vitamin B12a. Their results confirmed that cyanide is the main, if not sole, inhibitor responsible. Further experiments also showed that vitamin B12a has detoxifying properties that help with the activation of B. bacteriovorus HD100. In this way, B. bacteriovorus HD100 can avoid these defensive mechanisms and deal with pathogens.

"Studying such mechanisms may lead scientists to better understand how some pathogenic protect themselves against antibiotics," says Professor Mitchell. "To understand how germs may resist treatment, we need to look at the actual conditions in the host."

The research team now plans to look at how other respond to , as well as other factors that can potentially inhibit or negatively impact predatory activity in microbes.

Explore further: The cyanide defense: How one bacterium inhibits predators with poison

More information: Wonsik Mun et al, Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio bacteriovorus HD100 Predation, mBio (2018). DOI: 10.1128/mBio.01370-17

Related Stories

Predatory bacteria—the quest for a new class of antibiotics

October 11, 2017

In 2016, the World Health Organization named antibiotic resistance as "one of the biggest threats to global health, food security, and development today." The announcement cited a growing list of infections, such as tuberculosis ...

E. coli survives predatory bacteria by playing hide and seek

February 22, 2016

The majority of disease-causing bacteria in the body are rendered harmless by the protective effects of the immune system. Those that manage to escape the immune system can be killed by antibiotics, but bacteria are becoming ...

Recommended for you

Can China keep it's climate promises?

March 26, 2019

China can easily meet its Paris climate pledge to peak its greenhouse gas emissions by 2030, but sourcing 20 percent of its energy needs from renewables and nuclear power by that date may be considerably harder, researchers ...

In the Tree of Life, youth has its advantages

March 26, 2019

It's a question that has captivated naturalists for centuries: Why have some groups of organisms enjoyed incredibly diversity—like fish, birds, insects—while others have contained only a few species—like humans.

Cellular microRNA detection with miRacles

March 26, 2019

MicroRNAs (miRNAs) are short noncoding regulatory RNAs that can repress gene expression post-transcriptionally and are therefore increasingly used as biomarkers of disease. Detecting miRNAs can be arduous and expensive as ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.