Bacteria Spews Cyanide To Fend Off Predators

A team of scientists in South Korea have revealed how one bacterium inhibits predators with cyanide.

AsianScientist (Mar. 1, 2018) – In a study published in mBio, researchers in South Korea have discovered that some bacteria produce cyanide to ward off predators.

Infections caused by Gram-negative bacteria, such as Salmonella, Pneumococcus and Cholera have continued to be 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.

In the present study, a research team led by Professor Robert J. Mitchell at the Ulsan National Institute of Science and Technology (UNIST) reported that the bacterium Chromobacterium piscinae produces cyanide, an inhibitory molecule, to defend themselves against Bdellovibrio bacteriovorus HD100.

The researchers found that the amount of cyanide produced by C. piscinae was sufficient enough to inhibit predation, but was not overtly toxic toward B. bacteriovorus HD100. Their results also showed that C. piscinae produced the protective cyanide when provided with nutrients in the form of dilute nutrient broth.

“Our study suggests that microbes may have means for resisting predation that only show up in certain environments,” said Dr. Mun Wonsik of UNIST, who is the first author of the study. “This study also suggests that caution should be taken in defining bacterial strains that are susceptible to predation and those that are resistant, as secondary metabolites clearly can play a role.”

Further experiments showed that Vitamin B12a has detoxifying properties that help B. bacteriovorus HD100 overcome inhibition by cyanide. Compounds in the environment may therefore affect the efficacy of predation.

“Studying such mechanisms may lead scientists to better understand how some pathogenic bacteria protect themselves against antibiotics,” said 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 predatory bacteria respond to cyanide, as well as other factors that can potentially inhibit or negatively impact predatory activity in microbes.

The article can be found at: Mun et al. (2017) Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio bacteriovorus HD100 Predation.


Source: Ulsan National Institute of Science and Technology.
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