Berkeley Pit. Credit: NASA

Fungi From a Toxic Mine Pit Have Teamed Up to Produce a New Type of Antibiotic

We've never seen bacteria killed like this before.

BEC CREW
3 MAY 2017
 

Two species of fungus isolated from a highly toxic mine pit in Montana have been thrown together in the lab with unexpected results - the duo teamed up to synthesise a compound that kills four antibiotic-resistant strains of MRSA.

This never-before-seen compound resembles a known class of antibiotic, except for one major detail - the way it kills bacteria is unlike anything scientists have documented, and it's already proven effective against the bugs that cause anthrax and strep throat.

 

The two fungal species were collected from the Berkeley Pit - an abandoned open pit copper mine in Montana that's more than 540 metres deep (1,780 feet), and contains water that's as acidic as lemon juice, and laced with arsenic.

This stagnant pit of toxic waste is so dangerous, it's become known as a death trap for migrating snow geese - just a few months ago, thousands were forced to take refuge in the pit to get away from a snowstorm, only to perish in the metal-laden waters.

Autopsies of the 342 geese found floating in the pit back in 1995 revealed that their insides were ravaged with burns and festering sores - symptoms of exposure to high concentrations of copper, cadmium, and arsenic. 

But not everything falls victim to the Berkeley Pit death trap. An array of fungal and bacterial species have been found to thrive here, and for two decades now, University of Montana chemists Andrea A. Stierle and Donald B. Stierle have been analysing the unusual compounds produced by these hardy extremophiles.

So far, they've identified a fungus with cancer-killing qualities called Taxomyces andreanae, plus organisms that can synthesise molecules with anti-inflammatory and anti-ageing qualities.

This time, they decided to see what would happen if they cultured two species of Penicillium fungus together, and after six days, found that these bizarre lake inhabitants had cooperated to produce new compounds that neither could make on their own.

 

The molecular structure of these compounds resembled a known class of antibiotics called macrolides, and when the researchers observed how one of these new compounds - called berkeleylactone A - attacked a number of harmful bacteria, the result was like nothing they'd seen before.

"Mode of action studies have shown that, unlike other macrolide antibiotics, berkeleylactone A does not inhibit protein synthesis nor target the ribosome, which suggests a novel mode of action for its antibiotic activity," the team reports.

When they examined the structure of berkeleylactone A, they found that it lacked both sugars and a double bond, which sets it apart from similar antibiotic compounds.

As Melissae Fellet explains for Chemical & Engineering News, those two structural features are "thought to be important to the antibiotic properties of other 16-member macrolides isolated from bacteria or fungi".

So without them, how did berkeleylactone A manage to extinguish four antibiotic-resistant strains of MRSA, plus Bacillus anthracis (the anthrax bacterium), Streptococcus pyogenes (strep throat), Candida albicans, and Candida glabrata (pathogenic yeasts in humans)?

It's not yet clear exactly how the new antibiotic works, but we could be onto something here in the fight against antibiotic-resistant pathogens, which are expected to kill millions in the coming decades if current trends continue.

While we're a long way from seeing this compound form the basis of new medications, if its potential bears out in further tests, toxic pond bugs could end up being our best shot.

The research has been published in the Journal of Natural Products.

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