Tag Archives: Mold

Scientists sequence genome of Fleming’s original penicillin-producing fungus

A group of researchers successfully sequenced the genome of the mold that produced penicillin, the world’s first true antibiotic, using samples frozen alive more than fifty years ago. The team compared Alexander Fleming’s original sample of penicillium mold to two strains of mold now used to produce the substance today.

The freeze-dried Fleming strain from which the Penicillium fungus was grown and genome sequenced. Credit CABI.

Back in 1928, biologist Alexander Fleming noticed Penicillium mold growing in a culture of Staphylococcus aureus he was studying. It appeared the experiment was wrecked but Fleming noticed that where the mold grew, the bacteria didn’t. He later identified the chemical compound that was fatal to the bacteria and called it penicillin in honor of the humble mold.

Fleming froze samples of the mold that produced his first isolated samples of pure penicillin. More than 50 years later, a group of researchers at Imperial College London and the University of Oxford decided to look them up. They compared the samples with the genomes of two modern strains of Penicillium mold, now used in the United States.

“We originally set out to use Alexander Fleming’s fungus for some different experiments, but we realized, to our surprise, that no one had sequenced the genome of the original Penicillium, despite its historical significance to the field,” said Timothy Barraclaugh, co-author, in a statement.

The researchers found a subtle difference between the two genomes, which might help us better combat antibacterial resistance. Most antibiotics are based on chemicals that fungi or bacteria produce to defend themselves. If you get a dose of penicillin, it was likely produced by mold cultures, which are descendants of samples taken from moldy cantaloupes.

Over the years, antibiotics manufacturers bred their cantaloupe mold cultures to produce more penicillin. This means the genomes of modern industrial Penicillum mold are probably very different from their cantaloupe-eating ancestors.

The team looked at two sets of genes in particular. The ones that coded for chemicals called enzymes and the ones that control how much of an enzyme to make and when. They found that modern strains had more copies of the genetic instructions for making those enzymes, which meant those cells would make more enzymes and thus more penicillin.

While nature favors the traits that make mold more likely to survive and pass on its genes, artificial selection by humans cares about penicillin production over everything else. But Fleming’s mold and the modern strains used different versions of the enzymes that make penicillin. This could be due to evolution in the lab or because the strains are from different continents and evolved different enzymes.

If that’s the case, those different enzymes might produce different versions of penicillin. Still, there’s not enough data now to say exactly how the different enzymes impact the final product. The difference could lead to more efficient penicillin production, more effective penicillin, or a way to work around at least some of the resistance certain bacteria strains have evolved to the drug, the researchers believe.

“Industrial production of penicillin concentrated on the amount produced, and the steps used to artificially improve production led to changes in numbers of genes,” Ayush Pathak, lead author, said in a statement. “But it is possible that industrial methods might have missed some changes for optimizing penicillin design, and we can learn from natural responses to the evolution of antibiotic resistance.”

The study was published in the journal Scientific Reports.

Space station mold can survive 200 times more radiation than you or me

Unlike our pinkish, frail frames, mold may be able to survive on the outside walls of our spaceships. Even when drenched in hard radiation.

Mold Cheese.

Image via Pixabay.

The International Space Station isn’t as squeaky-clean as you’d expect: in fact, it turns out that our current home in space is plagued by mold. Every week, astronauts spend several hours scrubbing and cleaning its inside walls to prevent this mold from impacting their health.

However, new research suggests that efforts to completely de-mold the ISS may be in vain. Mold spores can survive even on the outside walls of the station and can bear radiation levels thousands of times harsher than ourselves. The results also point to mold as a useful ally on space travels, which could help supply the crew with biological products such as antibiotics or vitamins.

Stowaways, cosmic rays

“We now know that [fungal spores] resist radiation much more than we thought they would, to the point where we need to take them into consideration when we are cleaning spacecraft, inside and outside,” said Marta Cortesão, a microbiologist at the German Aerospace Center (DLR) in Cologne, who presented the findings at the 2019 Astrobiology Science Conference.

“If we’re planning a long duration mission, we can plan on having these mold spores with us because probably they will survive the space travel.”

Mold spores can withstand extreme temperatures, ultraviolet light, chemicals and dry conditions. This resiliency makes them hard to kill. Spores of the two most common mold types on the ISS — Aspergillus and Pennicillium — can survive exposure to X-ray levels at over 200 times the deadly dose for humans, the team found. The findings show how important planetary protection protocols designed to prevent spacecraft from contaminating other planets with Earth-borne life are, and that we need to reconsider how much of a threat fungi spores are from this point of view.

The good news is that these two species aren’t generally harmful to humans. They can impact people with weakened immune systems in cases of extreme exposure (i.e. when inhaling a large quantity of these spores). However, Cortesão believes we can coax these molds to work in our favor. Fungi are more similar to us, genetically, than bacteria: they’re made up of complex cells with a structure resembling ours, and they come equipped with the biochemical machinery to synthesize polymers, food, vitamins, and other useful molecules astronauts may need on extended trips beyond Earth.

“Mold can be used to produce important things, compounds like antibiotics and vitamins. It’s not only bad, a human pathogen and a food spoiler, it also can be used to produce antibiotics or other things needed on long missions,” Cortesão said.

In the lab, Cortesão exposed fungal spores with ionizing radiation, high-frequency ultraviolet light, and heavy ions to see how they fared. Ionizing radiation kills cells by damaging their DNA and other essential cellular infrastructure but gets blocked by our planet’s magnetic field (the ISS also benefits from this shielding). Earth’s ozone layer protects us from high-energy UV down here on the surface. However, spacecraft going to the Moon or Mars would be exposed to both.

Cortesão reports that the spores survived exposure to X-rays up to 1000 gray, exposure to heavy ions at 500 gray and exposure to ultraviolet light up to 3000 joules per meter squared. Gray is a measure of absorbed dose of ionizing radiation (joules of radiation energy per kilogram of tissue). Half a gray is the threshold for radiation sickness in humans, while five gray is the lethal threshold.

A 180-day voyage (about as long as we’d need to get to Mars) is estimated to expose passengers to around 0.7 gray. In other words, it could cause some issues for the human crew, but not for the mold.

In the future, the team plans to expand its search to understand how the combination of radiation, vacuum, low temperature, and low gravity in space affects the fungi.

The findings ” Fungal Spore Resistance to Space Radiation” have been presented at the 2019 Astrobiology Science Conference (AbSciCon 2019) on the 28th of June.

You don’t need a brain to learn, scientists found

A new study from the University of Toulouse found that intelligence and learning aren’t limited to organisms with brains. By studying the mold Physarum polycephalum they found it can, over time, learn to navigate even irritating environments.

Physarum polycephalum.
Image via flikr user frankenstoen.

People have been arguing for ages on exactly what “intelligence” is. For some, it’s reflected in academic results, so intelligence can be measured by how well you can solve a math problem for example. Others think of it as the basis for flexibility and adaptation, and for them, one’s intelligence is measured by how well they perform when faced with novel and unfavorable conditions. Or it could be emotional intelligence, musical intelligence, the list goes on. All of these definitions, however, start from the assumption that intelligence is a product of the brain’s ability to rely on past experience to interpret present events. That’s just not true.

On Wednesday, scientists announced a discovery that turns this basic assumption on its head. A new study of Physarum polycephalum, the “many-headed slime,” found that this mold can learn about its environment despite lacking any type of central nervous system. This is the first demonstrated case of habitual learning in a brainless organism.

“Tantalizing results suggest that the hallmarks for learning can occur at the level of single cells,” the team wrote.

Habitual learning is the process through which behavior is altered as a response to repeated stimulus. Similar to physical adaptation — how calluses form on a guitarist’s fingertips to adapt to their pressing the strings over time — habitual learning is learning by doing. It’s what allows you to walk or drive or talk without you having to put too much mental effort into it. In more extreme circumstances, it helps people with phobias overcome the object of their fear through gradual but repeated exposure to it.

P. polycephalum cells merge into a single yellow blob when food becomes scarce and has previously shown a type of proto-memory in navigating its environments (and there are other examples of cells banding together in rough times or cellular memory that we’ve previously covered.) The Toulouse University team wanted to see if it could also learn from experience and alter its behavior in response.

This slime-blob grows fine root-like protrusions called pseudopods to move through its environment as it searches for food or shade. The team grew slime samples in petri dishes containing a gel made of agar, and placed these near other petri dishes with food — oatmeal in agar gel. The dishes were connected through a bridge of agar gel, which the mold would learn to crawl over to feed in about two hours. The researchers then coated this bridge with quinine or caffeine in concentrations that weren’t toxic but P. polycephalum found irritating.

The blob creates filaments in search of food.

At first, they note that the mold “showed a clear aversive behavior” — it halted for a short time, then started advancing at a much slower pace. Overall, it took more than three hours for the pseudopods to cross the bridge, seeking narrow paths to avoid the irritating substances. But as the days passed the mold overcome its initial reticence and started crossing much quicker, evidence that it had “habituated” to the quinine and caffeine, the team said — in essence, it learned to navigate through unfavorable environments.

“Our results point to the diversity of organisms lacking neurons,” they wrote, “which likely display a hitherto unrecognized capacity for learning.”

The findings suggest that life could learn way before it developed any type of nervous system. This discovery could offer us new insight into the behavior of other molds, even viruses and bacteria.

The full paper, titled “Habituation in non-neural organisms: evidence from slime molds ” Has been published online in the journal Proceedings of the Royal Society B and can be read here.