Fungi
History
Fungi are ancient organisms, there is evidence to believe that they appeared around 1 billion years ago, however this is hard to prove due to their perishable nature there is little evidence in the fossil record and certainly no DNA available to test the fossils for proof. There is fossil evidence dating back approximately 400-450 million years ago of what initially were thought to be tree's, which are now believed to be prototaxites an ancient terrestrial fungus that stood up to 8 meters tall and 1 meter in diameter (Honegger, 2018), long before trees dominated the landscape.
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It is thought that fungi originated from a single celled fungus chytridiomycota, which was a unicellular, aquatic based fungus that had flagellated gametes which enabled them to swim, similar to protists (Lücking et al., 2009). Its suggested that throughout time Fungi have evolved to lose the flagella as they moved to land and no longer needed to be motile, as chytrids are the only fungi that still have flagella.
There are constantly new species being identified and so entirely new families of fungi are being found. Since 2007 there has been over 350 new families of fungi and approximately 2000 new species of fungus are identified each year (Willis, 2018). This is part of the attraction of fungal research with so many discoveries to be made and the advancement of DNA sequencing technology it’s a fast developing study area with great potential to make new discoveries.
Lemon infected with Penicilium mould
Image credit: University of Derby, Microbiology students (2018).
Medicine
Fungi are most famous in the world of medicine for penicillin which was discovered by mistake by Alexander Fleming when he noticed mould growing on a petri dish that he hadn’t disposed of and noticed that the surrounding bacteria was receding away from the mould, he knew that there must be a method of bacterial resistance. It took over a decade to isolate, test and produce it before finally getting its first use during WW2 (Santesmases and Gradmann, 2011), it has potentially saved 200 million lives since.
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However, Penicillin is only one of many incredibly important medicinal uses for fungi, well the secondary metabolites of fungi which are responsible for the antibiotic’s penicillin and cephalosporin’s (Demain, 2014). Furthermore, they are responsible for immunosuppressant drugs such as cyclosporine, which are used after organ transplants to reduce the risk of organ and tissue rejection.
Fungi are widely used in medical research due to them being eukaryotic, yeasts for example have genes similar to humans that can modify and produce proteins (Mager and Winderickx, 2005), with their fast reproduction and ease of culturing, they're a model organism for medical research. Another fungus Neurospora crassa commonly called red bread mould has widely been used in genetic analysis due to its haploid life cycle that`s easy to perform genetic analysis on as its offspring will show recessive traits. Currently yeasts are widely used in genetic studies such as cancer research (Natter and Kohlwein, 2013).
Prototaxites, an ancient fungus that stood up to 8 meters tall and 1 meter in diameter.
Image credit: Skymushrooms, http://picdeer.com/media/1879968275472140323_4004836144.
Importance of fungi
Key points
Fungi have a vast number of applications ranging from medicine, to food, and farming. Fungi not only produce medicine but are useful for the field of medical research of humans and animals e.g. yeast (Mager and Winderickx, 2005). Another fungus, Fusarium is used as a substitute for meat in popular brands of vegetarian/ vegan foods and is also sold as a cooking ingredient worldwide. Fungi are of massive importance in agriculture and land management, as there are mutualistic plant-fungi interactions, fungi are useful as natural pesticides, and as biofertilisers.
Food
Fungi have long been a part of the human diet, mushrooms, mouldy cheese, and truffles have become delicacies. The genus penicillium is to thank for almost all the mouldy cheese as it is left to encompass the cheese and aid in the ripening process, it has a second more important purpose too which will be mentioned shortly. Fermentation has been traced back as far as 7,000BC, and yeast has been around for at least 80 million years, so humans have a great history of utilising yeast in their food and beverages. This would have been done by leaving the items exposed to the air, thus allowing wild yeasts to accumulate converting sugar into CO2 and ethanol.
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This process eventually became the focus of a famous French scientist Louis Pasteur, who developed the commonly used brewer’s yeast Saccharomyces cerevisiae also known as baker’s yeast. Louis Pasteur known as "The father of microbiology" during his work on fermentation worked on germ theory and established the process now known as pasteurisation (Barnett, 2000). This led to massive improvements in the life expectancy of milk, cheese and all products that contain bacteria such as lactobacillus and staphylococcus that would otherwise spoil quickly, pasteurisation made it possible for foods to be sent all over the world. The process heats the product until it reaches 72degrees centigrade, at which point it is kept there for a set time enough to kill of the bacteria.
Agriculture
Fungi have countless benefits in the agricultural industry, the decomposition of organic material by fungi produces humus, a key constituent in fertile soils ideal for farming. However, this process can also be completed by bacteria such as actinomycetes, the bacteria and fungi work together alongside other microbes and invertebrates to degrade organic matter and turn it in to inorganic matter that can be utilised by plants and other organisms. Fungi are also now widely used as biopesticides (Xing et al., 2015), perhaps the most important and well known benefits are mycorrhizas and so is the focus of this resource.
Mycorrhizas can increase draught tolerance of crops by forming hyphal networks that can access places in the soil that plant roots cannot. Furthermore, they reduce the need for fertiliser input especially inorganic chemical treatments (Bhardwaj et al., 2014). Mycorrhizas can utilise atmospheric Nitrogen, a key nutrient for all plant life on earth, this is a part of the nitrogen cycle which is detailed on the following pages. Alongside the fungi, bacteria also carry out important processes involving converting unusable compounds into nutrients that the plants and microbes alike can use for energy.
Bread Mould
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The image shows Penicillium growing on bread, the image was taken using a scanning electron microscope(SEM) at 7320X magnification.
Image credit: University of Derby Microbiology students (2018)
