Mycology: Fungi, Molds, Viruses, and Prions

• Chapter focuses on fungi, viruses, and prions

Fungi Basics

• Absorptive heterotrophs that are eukaryotes
• Not plants, nor animals
• They lack chlorophyll and are non-photosynthetic
• They do not have true roots, stems, or leaves
• Non-motile
• Organic material is broken down by releasing digestive enzymes
• Act as decomposers and nutrient recyclers
• Can live on dead organisms as saprobes
• Store food energy as glycogen
• Produce organic acids, antibiotics, enzymes, and hormones
• Can cause disease and also poisonous toxins
• Fungal kingdom: Myceteae
• Fungal phyla include -mycota

Molds

• Identification and classification relies on shape, size, and spore color
• Spores range from 2 µm to 100 mm in size
• Spore shape can be globose, barrel-shaped, lemon-shaped, club-shaped, elliptical, curved, etc.
• Attachment and septation are key characteristics
• Walls can be smooth, granular, warty, spiny, cup-shaped, etc.
• Spores can be hyaline (colorless) to deeply pigmented

Effects of Mold

• Molds can have beneficial and harmful effects
• Molds are used for; microbial enymes, producing Penicillin, griseofulvin, cyclosporine, cephalosporin
• Can cause plant diseases, mycotoxins etc
• Mycotoxins are toxins made by molds on cereals, nuts, fruits, and vegetables
• Corn, peanuts, and tree nuts are common foods
• More than 100 species of molds produce mycotoxins, aflatoxin is most common
• Aspergillus flavus and Aspergillus parasiticus are types of aflatoxin
• Aflatoxins are potent carcinogens
• Mycosis is mold/fungal infections
• They develop slowly and recur more often than bacterial infections
• The body does not produce immunity to them
• Dermatomycosis, an infection of the skin, hair, and nails, is one category
• The other category is systemic mycosis, an infection of the entire body

Important Genera of Mold

• Ashbya gossypii colonies are flat and similar appearance to hair to the naked eye, pale to vibrant yellow color
• Sexual spore-bearing cells are long, thin, and can produce riboflavin (vitamin B2) and cobalamin (vitamin B12)
• Alternaria can cause damage before and after harvest
• Common in cereal grains, fruits, and vegetables
• Produces secondary metabolites, including phytotoxins and mycotoxins
• Ascomycota classification is Aspergillus spp. that has hundreds of species
• A. oryzae hydrolyzes starch to produce sake
• A. niger is responsible for producing galactosidase, citric and gluconic acids from sucrose and starch
• A. carbonarius produces pectinases
• A. flavus and A. parasiticus produce aflatoxin
• Penicillium spp. are Ascomycota fungi and produce food and drugs, also play role in food spoilage
• Penicillium spp. in food manufacturing is P. roqueforti
• Roquefort cheese spots are from it and also come from fermented sausages and salami
• P. roqueforti and P. camemberti produce proteases and lipases
• P. chrysogenum and P. notatum produce penicillin
• Mycotoxins types include: Citreoviridin, Cyclopiazonic acid, Ochratoxin, and Patulin

Yeasts

• Saprophytic fungus
• Eukaryotic and unicellular.
• Glycogen or fats are form of reserving food.
• Exist in nectar of flowers, sugarcane juice ,and sugary mediums
• Average size is 3-15 μm in length and 2-8 μm in diameter
• Cell color is in pearl grey(hyaline)
• They do not consist of flagella
• They are non-motile
• They are saprophytic
• Reproduction can either be vegetative or sexual

Vegetative reproductions:

• Binary fission
• Budding (Gemmation),

Sexual reproductions:

• Haplobiontic lifecycle

• Diplobiontic lifecycle

• Haplodiplobiontic lifecycle

• Characteristics include, Producing Vitamins, Minerals also Nutrients.

• They can be fermentative,oxidative, or even both.

• When there are no oxygen present the yeasts fermentation occurs which is anaerobic respiration.

• Industrial applications include: food and beverages (Beer, Wine, Sake).

• Yeast diseases, Candida albicans is a cause of systemic infections

• It contains an initial flu symptom of coughs, fever, also skin rashes.

• it penetrates organs, such as joins-bone, in rare cases leads to ulcers or abscesses

• It comes about via air not food therefore inhalation.

• Coccidioidomycosis results from Coccidioides immitis yeast

Some important Genera:

• Brettanomyces includes: Typical species: B. bruxellansis also B. lambicus
• It can also trigger beer, fruit drinks, wine, juice, and soda etc Spoilage.
• While Candida, if its mesophilic it causes spoilage of food.
• When salt, sugar and even high acids are inclusive it creates liquids.
• Debaryomyces is commonly used as starter cultures.
• It comes in many forms:Cheese ripening, sausage, production with Xylitol. It can cause spoilage in yogurts, milk also, meets but fruits, seafoods, salads/mayo and Vegetables most concentrated.
• Lastly, Debaryomyces Kloecker grows on cheese, drying also fruits even sausages.
• Saccharomyces’s produces
• Oval shaped and elongated cells.
• It also have many species that are lactose ferment, glucose.
• Top yeast grows fast.
• Evaluation allows CO2 to go to the peak, it grows 20 degree C greatest.
• It grows 10-15degrees C better

Virus Basics

• Viruses are obligate intracellular parasites, having only limited host specificity
• Bacteriophages are viruses that infect only bacteria, unable to infect human cells
• A mutation can allow a virus to jump to a new species
• They contain only DNA or RNA (but not both) and are simple
• Viruses that have no envelope are called naked viruses
• Attachment proteins are a basic component of virus
• They also receptor protein of a given host cells binds to specific carbohydrates expressed on cells

Viral LifeCycle

• With prokaryote it has 2 cycles; The Lytic Cycle and The Lysogenic Cycle
• With animal hosts includes:
  • Viral attachment/entry
• Penetration
• Intracellular trafficking and uncoating
• Transcription
• Translation
• Replication
• Integration
• Budding/Maturation
• Release

Viral foodborne illnesses

• Gastroenteritis, and extra-intestinal (systemic) infections

Norwalk Virus

• Has been a major cause when it comes to illnesses from food.
• Infective dose: not known (10-100 particles)
• incubation period: 24-48 h
• It lasts 1 -3 days on duration
• It has 2 stages; the 1st Diarrhea with out liver symptoms. In other words its intestinal .
• Then the colonizations start. The phase lasts a weak.
• 2nd extensive liver Damage. As well as colonization of intestines .

Hepatitis A Virus

• Is the infection with the liver
• It occurs by both hepatitis (6-7)
• There are recognized infections
• They are associated intestinal colonization
• There isn't a relate to this phase or symptoms to it

Beneficial applications of the virus

• Medicine and agriculture
• Production of vaccines, vectors, gene modifications
• Desirable characteristics resistance to biotic and abiotic stresses
• Nanomaterial production to perform Deposition of specific metals

Prions Basics

• Proteinaceous infectious particle” propagates through protein misfolding due lack of nucleic acid
• PrPC is the ability of converting abnormal form of normal.
• The are high resistant to heat ,also chemical treats for reactions
• TSE, also know as Transmissible Spongiform is Progressive and fatal.
• They can cause brain/dysfunction, Coma, also death
• Bovine food relations can be Spongiform Encephalopathy or known as “mad cow disease”

TSE can affect humans and animals

• It causes:
• Creutzfedlt-Jakob sickness
• Gerstmann-Straussler Sheinker
• Fatal insomnia
• Kuru
• As for animal the following are:
  • scrapie
  • Minks from transmissible
  • spongiform Encephalopathy
  • wasting sickness.
  • spongiform bovine And feline spongiform are included.