Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
39 Cards in this Set
- Front
- Back
What are the main characteristics of fungi? |
Eukaryotes - mainly multicellular Chitin in cell wall Heterokaryotic stage Form hyphae (network is called a mycelium) Zygotic life cycle Reproduce through spores Non-photosynthetic Non-motile Heterotrophic Macro and microscopic appearance Mostly in terrestrial habitats (lands) |
|
Which reproduction is predominant? |
Asexual if conditions are favourable - less energy needed for it |
|
What's the main role in ecosystem of fungi? |
Decomposers - clean higher level of food chain (predators) and anything in between |
|
What is ecophysiolohy? |
Deals with adaptation of the physiology of an organism to environmental conditions |
|
What's ecophysiology of moulds? |
Fermentation C assimilation - carbs, organic acids N assimilation - amino acids, nitrate Volatiles production - esters, acetaldehyde Growth at high sugar, low aw, high salt - osmotolerance Growth at broad pH range (2-10) Growth at low temperature Enzyme activities - lipolytic, pectinolytic etc. Resistance to preservatives |
|
What's traditional classification based on? |
Reproductive structures Nowadays based on philogeny |
|
What is holomorph? |
"whole fungus" = anamorph (asexual reproduction) + telomorph (sexual reproduction) *Pleomorph - has more phenotypes |
|
What's the simple classification of fungi? |
Zygomycetes (lower fungi) Higher fungi: Basidiomycetes (mushrooms) Ascomycetes Fungi imperfecti (deuteromycetes) - artificial phylum because sexual cycle was unknown (deuteromycetes) - artificial phylum because sexual cycle was unknown |
|
What are main characteristics of zygomycetes? |
Terrestrial (but humid) Form zygospores (sexual) Non septated vegetative hyphae Coenocytic (many nuclei in a shared cytoplasm) Asexual reproduction by the formation of sporangiospores - formation sporangia Implicated in food spoilage!! |
|
What are characteristic of reproductive cycle of zygomycetes? |
Mycelium of a mating type + and - (2 types of nuclei) -> gametangia with haploid nuclei -> young zygosporangium (heterokaryotic) -> karyogamy -> ... |
|
What are names of Rhizopus spores? |
Sporangiospores for asexual Zygospores for sexual |
|
What are characteristics of Rhizopus? |
Rhizoids - root like structures "Black bread mould" - R. stolonifer Rhizopus oryzae - tempeh fermentation |
|
What are characteristics of ascomycota? |
Terrestrial (also dry regions) Sexual spores (ascospores) contained in ascus Septated vegetative hyphae Sometimes asexual reproduction via conidia Complete life cycle not always known and in that case fungi imperfecti (deuteromycetes)Food spoilage and mycotoxins!! Eg.Aspergillus flavus |
|
What's the contamination pathway? |
1) sporulation 2) release of spores 3) spores distribution 4) landing and attachment of spores |
|
What happens in sporulation? |
Produced in asexual cycle (vegetative) - majority Conidia - ascomycota Sporangiospores - zygomycota |
|
How release of spores happen? |
Passive: Dry - gravity or agitation (shaking, vibration) Wet - mist pickup, rain drops
Active: Dry - deflation (bursting) Wet - bellows (ballistospores), hygroscopic effect |
|
How spores distribution happens? |
Air currents In water Attached to dust particles Eddy movements Depends on size, shape, smooth or rough surface, specific mass, electrostatical charge |
|
What happens after spore attachment? |
Mycelium outgrowth - hydrophobins play a role in mycelium distribution, they are surface-active molecules which lower surface tension of their aqueous environment enabling hyphae to grow into the air -8 conserved cysteine residues -100 a.as. long -Self assemble at hydrophobic interfaces |
|
What does botyris cinerea do to grapes? |
Noble rot: Botyris punctures healthy mature grapes skin -> increased dehydration -> elevated sugar content -> inhibition of mould growth -> SWEETER wine Same done to not mature grapes - spoilage |
|
When yeasts overcomplete bacteria? |
Ecological niche for growth of moulds: Ph < 4.5 (no bacterial growth) Aw < 0.9 (no bacterial growth, except for halophilic) |
|
Why are fresh fruit perfect niche for fungi? |
Low pH (high acidity), sweet |
|
What happens in food with low aw? |
Below 0.9 only fungi and no bacteria - eg. In molasses, dried fruit, confections |
|
What happens in pasteurised products niche? |
Canned fruit, bottled fruit, cartoned fruit -Heat resistance of ascospores (sexual spores) -Pectolytic enzymes to break down plant tissue |
|
What are characteristic of byssochlamys Nivea? |
Anamorph- paecilomyces niveus Soil inhabitant Heat resistant ascospores Requires inactivation temp above 90°C Resistant to acid, chlorine and alcohol Spoils processed fruit products Mycotoxins: patulin |
|
What are techniques to combat spoilage fungi? |
High pressure processing Ultrasound Heat Usually combo Combo of sonication and heat - rapid decrease but after 10 minutes still quite a lot HPP + heat - very good inhibitory effect |
|
What type of effects may occur when combining treatments? |
Additive Synergistic (more than additive) Antagonistic |
|
What happens in products with chemical preservatives? |
Fruit juice and mayo - monillela acetobutans grows in 4% acetic acid Sliced rye bread - P. Roqueforti, aspergillus etc. grow on sorbic acid Cheese rind - penicillium discolor resistant to natamycin |
|
What are mycotoxins? |
Toxic 2ndary metabolites produced by moulds Among the most toxic compounds Cause chronic and acute diseases, in man and animal, severe symptoms |
|
What are 2 most important groups of mycotoxins? |
A. Flavus - aflatoxins (infants and vegans at risk - milk and nuts) Fusarium toxins - fumonisins, deoxynivalenol |
|
Where can mycotoxins be found? |
Oil seeds, milk, grains, peanuts, figs |
|
What are measured to control mycotoxins in food chain? |
Prevention: GAP - good agricultural practice Controlled storage of agricultural products
End of pipeline: Decontamination - chemical methods (not effective), physical (moderate effective and impact on product quantity), biological (fermentation, decrease toxicity by metabolic conversion but you'll end up with a different product) |
|
What's the enumeration process for fungi? |
Sampling (uneven distribution, spores presence, fragmentation mycelium - impossible to count!) - measure level of chitin instead Sample processing (dilution in 0.1%) peptone, mild heat treatment) Plating (antibiotics, osmotic value) |
|
What are ways to detect fungi? |
Classical - selective plating, colony morphology, microscopy Immunological - ELISA, latex agglutination DNA based methods - random amplified polymorphic DNA (RAPD)(no absolute ID though), sequencing conserved regions 18S rRNA (slow, identification), RT PCR (fast, identification, presence unique genes) |
|
How latex agglutination test work? |
1)Mix sample with latex beads covered in antibodies 2) if target for antibodies present - latex beads will clump (agglutinate) Qualitative not quantitative |
|
What part can Elisa detect? |
Immunologically active EPS - more quantitative Negatives - also detects non living moulds and it's more detection than identification (multiple species not detected separately) |
|
What does government do in therms of quality assurance? |
Inspection for mycotoxins or unlawful use of mouldy ingredients, risk assessments, inform enterprise and general public - eg. Inspect factories, analyze samples |
|
What does public private sector do in therms of quality assurance? |
Internal monitoring among members of trade organisation, aflatoxins level controls in feed (feed manufacturers) |
|
What do private enterprises do in therms of quality assurance? |
Quality management, GMP, HACCP use |
|
Which fungi has the least complicated structure? |
Phycomyces (lower fungi) |