2017 Fall News Update
Fungi appear in the news with surprising frequency. However, many of those stories do not provide any new information. Below is a summary of what we’ve learned about fungi from August through October 2017. Read below to learn about: ballistospory, chromosome evolution, fighting fungal pathogens (in humans, bats, and bananas), psilocybin, oil-eating fungi, and more! Visit the associated links to get the full story.
With the growing concern over untrustworthy news sources and the media’s tendency to inaccurately report scientific studies, can these sources be trusted? Yes they can, with a bit of caution. I have checked to make sure all the articles based on scientific papers draw from peer-reviewed journals and that they accurately reflect the content of the papers. For articles not linked to scientific papers, I try to stick to sources with a good track record in reporting on science or to local sources for region-specific information. However, I encourage you to do your own research and decide for yourself whether these sources are trustworthy.
Physics of Ballistospores
Researchers from Duke University recently used an inkjet printer and glass beads to examine the physics of sexual spore discharge in basidiomycetes. These fungi produce spores externally and launch them using energy stored in the surface tension of a water droplet, a process known as “ballistospory.” The droplet forms next to the spore (often referred to as a “ballistospore”) and the two eventually touch. When that happens, the droplet flows onto the surface of the spore. This sudden change in the center of mass launches the spore into the air. At least that’s what scientists assumed happened. Because that whole process happens so quickly, nobody has been able to actually capture it on camera. The Duke scientists got around this by using a model spore made from a tiny glass bead. An inkjet printer was modified to drop water next to the bead until the water touched the bead. When this happened, the bead jumped into the air, just as scientists expected it too. Because the bead was much larger than a spore, this process was much slower and could be captured on camera. Not only does this study confirm the current ideas about basidiomycete spore discharge, but it also provides a method for investigating the phenomenon further.
Sex Chromosome Evolution in Cryptococcus
Using detailed DNA analysis, scientists at Duke University have described the evolution that changed Cryptococcus from an organism with many sexes (see FFF#085 for more on fungi with multiple sexes) into an organism with only two. Originally, Cryptococcus had multiple sex genes spread across many chromosomes. Over time, these genes became concentrated onto just two – analogous to the X and Y chromosomes in humans. This happened through a process called “translocation,” where two different chromosomes swap large parts of their DNA. In Cryptococcus, most of these translocations occurred at the “centromere,” a dense area of the chromosome that helps keep chromosome pairs together during cell division. This is the first time that scientists have found evidence of translocation happening at the centromere in any organism; previously, scientists assumed the centromere was too dense for this kind of mutation. The genes were then shuffled around within the chromosome and some of them even fused, reducing both the number of sex-related chromosomes and the number of sex-related genes.
Immune Cells Tell Fungi to Self-Destruct
Researchers investigating fungal infections found that immune cells in mice kill fungal cells by activating the fungus’ “programmed cell death” pathway. Most cells that form tissues carry instructions on how to kill themselves in an orderly fashion (known as “programmed cell death”); this is important to ensure tissues develop correctly. For example, at a certain stage of development, the human fetus has webbed fingers. This webbing disappears before birth because the skin cells between the fingers kill themselves. In mice, immune cells in the lungs take advantage of this process to quickly kill inhaled fungal cells, such as spores. Once detected, the fungal cell is engulfed by a white blood cell. The white blood cell then releases proteins that instruct the fungus to kill itself. Understanding how this works is important for treating people with suppressed immune systems. These patients often develop fungal infections in the mouth or respiratory tract that are easily kept at bay in healthy people.
Engineered Molecules Attack Fungi
Yale scientists have created a new type of small molecule that recruits the immune system to kill fungal cells. The molecules, known as “antibody recruiting molecules targeting fungi” (ARM-Fs) have two ends: one end binds to chitin – the main component of the fungal cell wall – while the other binds to antibodies. The antibodies are already present in the blood stream, so the ARM-Fs just serve to alert the immune system to the presence of the fungus. The researchers hope that these molecules can be used in conjunction with other antifungals to treat difficult fungal infections.
Hypermutators Aid Pathogenic Fungi
Scientists at Duke University discovered that the fungus Cryptococcus deuterogattii has areas in its DNA that encourage mutations. These “hypermutators” increase the mutation rate in certain genes and thereby allow the fungus to evolve more quickly. This allows the fungus to easily adapt to antibiotics. Understanding how this works could help future scientists design drugs that are more difficult for the fungi to adapt to.
Commercial Mycorrhizal Supplements Need Work
A recent study examining the efficacy of commercially available mycorrhizal supplements concluded that the supplements are not effective and have the potential to cause ecological damage. Some plants do benefit from mycorrhizal supplements, but most either do not benefit or are harmed by the supplements. On top of that, there is the risk that the cultivated strains could escape into the environment and change the forest community. Very little is known about how mycorrhizal fungi spread, so the study’s authors urged restraint until long-term environmental studies could be conducted.
Seed-Fungal Interactions and Rainforest Diversity
In recent years, scientists have recognized that fungi are important as regulators of plant diversity in tropical forests. A recent study from the Smithsonian Tropical Research Institute suggests that fungi begin influencing tropical forest diversity even before tree seeds germinate. When a seed falls on the forest floor, it will quickly be colonized by fungi. Different seed and fungus combinations produced different results. In many cases, a fungus that was parasitic on one seed actually benefitted another. This demonstrates a new method through which soil fungi can regulate forest diversity.
Can Genetic Engineering Save Bananas from Fusarium Wilt?
A field trial is underway in Australia to test a genetically engineered banana that will hopefully be resistant to the TR4 strain of Fusarium Wilt (also called Panama Disease, see FFF#107). The Cavendish banana – the variety found in nearly every grocery store – is the best banana for consumers but also is very susceptible to TR4. The engineered bananas were created by adding a few genes from another variety of banana that is resistant to TR4. Researchers hope that the new strain will both be resistant to the fungus and as tasty and portable as the normal Cavendish. Creating such a banana – whether through genetic engineering or conventional breeding – is likely the only way to save the world’s favorite fruit.
Magic Mushrooms & Depression
Researchers at the Imperial College London conducted a small study examining the effects of psilocybin (see FFF#098) on brain activity in depressed patients. This was one of the first studies to use MRI technology to visualize the effects of psilocybin on brain activity. In general, the researchers found that psilocybin “reset” the brain, reducing activity in the amygdala and stabilizing activity in the default-mode network. Of course, this study used a small sample size and researchers are just beginning to examine how psilocybin effects the brain, so this study cannot be used to support recreational use of the drug.
Gene Drive Developed to Research Antibiotic Resistance in C. albicans
Candida albicans is a common fungal pathogen of humans (see FFF#162) and is becoming more difficult to treat as it develops resistance to antifungal drugs. Historically, C. albicans was difficult to study because it is diploid and scientists did not have a method for knocking out both copies of a gene. Now, researchers have developed a method to do just that using a rare haploid strain of C. albicans and a system known as a “gene drive.” In a gene drive, the DNA-editing proteins CRISPR and Cas9 are added to the haploid strain, which is then mixed with a diploid strain. When a haploid cell fuses with a diploid cell, CRISPR and Cas9 identify the targeted gene and cut it out of the DNA strand. The molecules then insert the genes encoding the CRISPR-Cas9 system. The cell is now diploid and both copies of the targeted gene have been removed. This process will repeat whenever the cell fuses until the DNA of every cell in the population has been edited. The new gene drive system will make it easier for researchers to study C. albicans and should lead to new strategies for fighting antibiotic resistance.
Fungus Degrades Oil
Researchers from the University of Saskatchewan discovered a fungus that helps plants grow in soil contaminated with oily residues. The fungus was isolated from the roots of dandelions growing in coarse tailings from surface-mined bitumen. This type of mining contaminates nearby areas with oils that are inhospitable to most life. However, plants like the dandelion begin growing in contaminated areas after a decade or so. The newly-discovered fungus appears to be a crucial factor in this initial colonization. The fungus can degrade and extract energy from complex hydrocarbons – including crude oil – but also grows in some kind of symbiosis with a variety of plants, allowing the plants to grow where they otherwise couldn’t. Researchers hope that this fungus will be useful in bioremediation efforts by degrading harmful molecules while supporting plant growth.
Forest Service Funds Bat Fungus Research
The U. S. Forest Service recently awarded grants totaling over $410,000 to four research teams working to fight the spread of White Nose Syndrome, a fungal disease of bats that has caused massive bat die-offs across eastern North America (see FFF#026 for more). In Missouri, scientists are working to identify naturally-occurring bacteria that can be used to fight the disease. A team in Wisconsin will investigate whether ultraviolet light can be used to kill the fungus while bats hibernate. Researchers in South Carolina are assessing how susceptible tri-colored bats are to the disease. One of the scientists in Wisconsin was also awarded money to improve protocols aimed at preventing humans from transporting the fungus between bat hibernation areas.
Computer Game Helps Fight Aflatoxin
One of the most difficult things for biologists to do is predict the structures of proteins. To make this easier, scientists developed a computer game called Foldit. This game lets the public solve puzzles relating to protein shapes. The solutions players come up with are then used to predict how proteins will fold. Currently, the game is being used to design enzymes that could neutralize aflatoxin (FFF#202), one of the most common and most dangerous mycotoxins found in food. You can help by downloading and playing the game here.