Infection, fermentation and protection: the many faces of yeasts

Posted on June 6, 2019   by Laura Cox

Yeasts are a versatile organism and impact our lives in more ways than we may realise. But what research is being done to better understand these tiny organisms? We’ve taken a look at some of the yeast research recently published in Microbiology to find out…

Fungi is an umbrella term for moulds, macroscopic fungi (like mushrooms and toadstools) and yeasts. Yeasts have shaped our world in so many ways. Their ability to ferment is key to producing many of the foods we eat every day; bread, cheese and pickles would not be possible without yeasts. Neither would a number of alcoholic drinks.

The missing link for lager yeasts

Not even ten years ago, Saccharomyces eubayanus was discovered. This yeast is able to tolerate cold temperatures and settled a long-lasting debate on the origins of the group of yeasts essential in lager production. Lager yeasts are known as a ‘domesticated’ yeast, as no examples of these yeasts exist in the environment; they are a hybrid that first occurred in the brewery.

In this Microbe Profile, José Paulo Sampiano, from Universidade Nova de Lisboa, Portugal, discusses the new avenues that the discovery of S. eubayanus has opened up in yeast research and how it hid for so long.

Salmonella slayers

Salmonella is one of the most prevalent disease-causing bacteria in the world, with growing concerns about the shrinking treatment options for those infected due to antimicrobial resistance. To make matters worse, the antibiotics used to treat Salmonella infection can make patients even more sick, causing diarrhoea and harming the normal gut microflora which play a key role in keeping the disease at bay by competing for nutrients, preventing biofilm formation and producing antibacterial molecules.

A team from Victoria University, Australia, have published a review discussing ways in which researchers are harnessing the antimicrobial powers of yeasts. There are ways which yeasts can be used as a probiotic alongside antibiotics, keeping the normal gut microflora healthy during treatment. As well as their probiotic uses, yeasts also produce antibacterial agents which could be harnessed to produce desperately-needed new antibiotics.

Resourceful shapeshifters

Depending on their environment, many fungi can switch between hyphae (filamentous fungi) and yeasts. These dimorphic fungi will hibernate as hyphae, producing spores and spreading through the air. When the spores are breathed in by the host and become warmer, they are able to switch to yeasts and cause lung infections. These yeasts would not be able to survive or reproduce in the environment which is why they need their hyphae form.

In their review, Hazael Hernandez and Luis R. Martinez, from the University of Texas, USA,
discuss how environmental disturbances, like natural disasters or flooding can lead to epidemics of fungal disease due to the increased spread of spores. The review also discusses how fungal diseases could lead to the extinction of some animal species (including bats) and the threat to the global food supply.

Opportunistic killers

Candida albicans is probably one of the best-known pathogenic yeasts. It causes yeast infections which are usually known as thrush, and in rare cases can also infect the skin and nail beds. This is unusual for C. albicans though, which is usually a commensal microbe, meaning it lives on humans and has a mutually-beneficial relationship with its host. However, Candida has a dark side, and if the host has a weakened immune system, this yeast can get into the bloodstream and become fatal.

In their Microbe Profile, Neil Gow and Bhawna Yadav, from the University of Aberdeen, UK, discuss the evolution of C. albicans, its key features and how this yeast manipulates the immune system to cause such severe disease.

Later this month, the Microbiology Society will be hosting the annual British Yeast Group meeting at the County Hotel, Newcastle. This year, the topic of the meeting will be Discovery to Impact, and will explore how fundamental research themes are integrated with applied themes, including biotechnological applications of yeasts, yeasts as disease models, and pathogenic yeasts