Topic 16 - Mycotoxicosis - human and animal poisonings of microfungi

Question 1

Fungi

Answer 1

Unicellular, or multicellular organisms (without tissues) developing hyphae

Sessile, heterotroph organisms feeding on dead matter, or living tissues

Secrete extracellular digestive enzymes into the environment and adsorb dissolved molecules

1.5-10 million species worldwide’

Question 2

Symbiotic fungi

Answer 2

Two thirds of all fungi

Mutualists or parasites

Question 3

Fungal community role in predators (humans)

Answer 3

community of anaerobic microfungi in the intestines; pathogenic microfungi (digestion, parasites)

Question 4

Fungal community role in herbivorous animals (livestock)

Answer 4

community of anaerobic microfungi in the intestines, in the rumen; pathogenic microfungi (digestion, parasites)

Question 5

Fungal community role in photosynthetic plants (crop plants)

Answer 5

community of mycorrhizal fungi, endo-phytic microfungi (nutrient uptake, com-mon mycorrhizal network, protection)

Question 6

Fungal community role in community of terricolous saprotrophic fungi

Answer 6

mineralization (ammonification), biological weathering, sharing of nutrients among plants

Question 7

Production of secondary metabolites

Answer 7

Produced primarily when sources of nutrients become limited in the environment

Support (stabilise) the primary metabolism

Biosynthesised from the primary metabolites → strictly regulated

Number of secondary metabolites is generally high, once produced do not considerably affect the stability of primary metabolism

Question 8

alternative origin of secondary metabolites

Answer 8

Horizontal gene transfer from bacteria

Question 9

Biological functions of secondary metabolites in fungi

Answer 9

Support the acquisition and defence of nutrient sources against other organisms

Protection from UV radiation

During sexual reproduction, attract the hyphae of the opposite sex then play a key role in cell differentiation during ontogeny

Question 10

Toxic heavy metals and poisonous chemical compounds

Answer 10

Depend on environment and the species identity of the fungus

Pb: passive accumulation along roadsides (in the past, from exhaust fume)

Some fungal genera are characterised by the active accumulation of Cd (from the brake pads of vehicles)

Hg: some Agaricus species (with a yellowing flesh) and puffballs accumulate it specifically; it can also be accumulated passively in many other taxa growing on crop fields

Accumulation of insecticides and herbicides

Question 11

Radioactive materials in fungi

Answer 11

Fungi able to accumulate large amounts of radioactive isotopes within a short time period due to extensive mycelia and the huge total surface of hyphae

K+ ions can be replaced with cesium ions → can be taken up easily from acidic soils

fungi preferring acidophilus haibitats → higher in cesium

Question 12

Toxins

Answer 12

concentration of toxins accumulated by soil fungi increases towards the higher trophic levels (thus highest in comminites in predators)

Food safety should be considered from the soil microbes

Question 13

Health hazards caused by fungi

Answer 13

Allergy

Mycetism

Mycotoxicosis

Mycosis

Question 14

Allergy

Answer 14

allergic reactions to fungal spores and/or to other fungal substances

Question 15

Mycetism

Answer 15

mushroom poisoning; ingestion of toxic substances present in macro fungal sporocarps

Question 16

Mycotoxicosis

Answer 16

Poisonings caused by the toxic compounds of microfungi (mainly holds) that readily colonise crops and human foods

Question 17

Mycosis

Answer 17

Infection of animals and humans by pathogenic microfungi (mainly holds, yeasts)

Question 18

Mycosis in fish

Answer 18

Saprolegnia: Caused by saprolegnia species through wounds

Generally secondary pathogens affecting usually overfed individuals with other infections, and kept in dirty and too cold water

Question 19

Symptoms of mycosis in fish

Answer 19

Skin with cotton-like structures

Often covered by algae

Question 20

Treatment of mycosis in fish

Answer 20

Quarantine

alteration of circumstances suitable for fungal infections

Question 21

Mycosis in amphibians

Answer 21

Devastating amphibian populations worldwide

Batrachochytrium dendrobatidis and B. salamandrivorans cause lethal skin infections in frogs and salamanders, respectively

Question 22

Mycosis in reptiles

Answer 22

Infections difficult to recognise, often overlooked

Circumstances perfect for fungal infections: many individuals are crowded in a small box, and kept in sub-optimal temperatures with high air humidity

Most frequently, their skin and mucous membranes are affected

Question 23

Mycosis in birds

Answer 23

Aspergillosis most frequently affect respiratory system including air sacs

Poultry highly susceptible

Cryptococcosis rarely develop in birds, but a large population of Cryptococcus neoformans lives int heir intestines → humans can be infected in cities from the droppings of pigeons

Question 24

Mycosis in humans (mammals)

Answer 24

Fungal infection in case of Immune deficiency: HIV infection, long-term application of broad-spectrum antibiotics, radioactive radiation, cancer, autoimmune diseases, neutropenia, diabetes, skin burns, catheter, intravenous drug use

infect skina nd mucous membranes

Subcutaneous infections (injuries)

Infection of internal organs

They are often difficult to cure → prevention

Question 25

Mycotoxicosis

Answer 25

Never induce immune response

Symptoms: often occur when major organ damage is developed

approx. 150 micro fungal taxa

Question 26

Most important mycotoxins detected in forages and human foods

Answer 26

Aflatoxins
Ochratoxins
Trichothecenes 
Zearalenon 
Rubratoxins
Ergot alkaloids

Question 27

Aflatoxins

Answer 27

Produced mainly by Aspergillus flavus and A. parasiticus

grow mainly on fleshy forages and oil plants damaged by insects

Question 28

Effects of microfungi producing aflatoxins

Answer 28

mutagens, teratogens, immunosuppressives, cause hepatic impairments (hepatitis, liver chirrosis and cancer)

Question 29

Ochratoxins

Answer 29

Nephrotoxins causing necrosis of renal tubules, immunosuppressive, carcinogenic

Fat-soluble compounds → pork fat is rich in ochratoxins;

too much consumption of coffee and rye bread should be avoided

By A. ochraceus, A. carbonarius, Penicillium verrucosum

Question 30

Fumonisins

Answer 30

Affecting white matter of horse brain → leucoencephalomalacia

Structural analogues of sphingosine → disruption of sphingolipid metabolism → erosion of myelin sheath of axons

Carcinogenic

Question 31

Trichothecenes

Answer 31

Inhibit protein synthesis

Large subunit of ribosomes is affected

Produced by fusarium species

All cereals and gras species are potential hosts

Question 32

Zearalenon

Answer 32

Interferes with sexual maturation

Pigs particularly sensitive, humans not

Enlarged outer genitals; atrophic ovaries → sterility

In corn flakes and beers made of maize

Produced by fusarium species

Question 33

Rubratoxins

Answer 33

Cause damage in liver and kidneys; also affecting the CNS

Trigger the effects of aflatoxins

Eggs, dairy and meat products can be rich rubratoxins

Produced by penicillium and Aspergillus species