Microbiology Flashcards
Saprophytic
feed on dead or decaying matter eg fungi
Parasitic
feed on living matter eg athletes foot
Aerobic
needs oxygen for growth
Anaerobic
oxygen is not needed for growth
Faculatitive
these microbes will grow with or without oxygen
Psychrophiles
these microbes prefer low temperatures 5-20 degrees
Mesophiles
most microbes thrive at this temperature 20-45 degrees
Thermophiles
prefer temperatures above 45 degrees
Moisture
necessary for all microbes to metabolise
low water content can reduce the growth of microbes in food
pH level
most prefer a neutral pH
Moulds
multicellular
contaminate many foods
start as single celled spore
conditions required for the growth of moulds
Food- most are saprophytic
Oxygen- generally aerobic
Temperature- most are mesophiles
Moisture- moist & humid conditions
pH- acidic environment ( 4-6 pH)
Time- needed for growth
Structure of Moulds
spore lands on suitable conditions produces a hypha
hypha grows down to absorb nutrients for growth
as hypha grows into many hyphae
hyphae become interwined and form a branched mycelium
when mycelium is established, some hyphae will grow upwards and produce sporangium or conidia
Asexual Reproduction
occurs when the mycelium is well established on the food
head can either br conidia or sporangium
wen ripe sporangium bursts releasing the spores
conidia breaks off releasing the spores
spores are carried by air until they reach a suitable food
Types of moulds
Phycomycetes
Ascomycetes
Sexual Reproduction
two hyphae grow side by side
each hypha sends out branching hyphae to each other which grow and meet eachother and fuse together
zygospore produced
spore develops imside zygospore, can last long periods of time inside due to thick wall
under suitable comditions the spores germinate and hyphae develop
Phycomycetes
reproduces sexually & asexually
produce sporangia
most favourable temp 30 degrees
examples are mucor & rhizopus
Mucor
Found on: soil, bread, meat, cheese
Characteristics: saprophyte, greyish, sporangium
Example: bread mould
Rhizopus
Found on: soil, bread, soft rot on fruit & veg
Characteristics: saprophyte, black, sporangium
Example: rot on mushrooms
Ascomycetes
Optimum temp: 20-25 degrees
Asexual reproduction only contain cross walls
Produce conidia
Examples: penicillium & aspergillis
Penicillium
Found on: cheese, fruit, bread
Characteristics: saprophyte, crumbly green/blue, mould
Example: ripening cheeses and production of antibiotics
Aspergillis
Ascomycetes
Found on: fruit,veg, grain
Characteristics: saprophyte, blak or green mould
Yeasts
single celled
saprophytic
found on air, soil, on fruit
fruit, meat and meat can be spoiled by yeasts
used in production of some foodstuffs
Conditions for growth of Yeast
Food: feeds on carbs eg sugar
Oxygen: faculative
Temperature: 25-30 degrees, 60+ destroys yeast
Moisture: moist conditions
pH: acidic conditions ( 4-5)
Budding
parent cell develops a bulge
nucleus of parent cell moves towards the bulge
nuclues divides in two
wall forms which seperates the new bud from the parent cell
bud seperates
Varieties of Large Fungi
Field Mushrooms
Truffles
Amanita
Reproduction of large fungi
Mushrooms start as spores
Produce hypha which grow and produce mycelium
increase in size and opens as mushroom develops
pink gills can be seen under cap
these change to brown as mushroom gets older inside gills pores are produced
when mushroom is ripe spores are released
Advantages of fungi
Used in production of alternative protein foods
Many are edible
Some moulds used in cheese production & antibiotic production
Yeast used in bread production and beer
Disadvantages of Fungi
Can causes food spoilage
Can cause plant diseases
Can causes human diseases
Conditions needed for Bacteria
Food- can be saprophytic (lactic acid) or parasitic (staphyloccus aureus)
Oxyegen- aerobic ( mycobacterium tuberculosis), anaerobic (clostridium botulinum), faculative ( e- coli)
Temperature- psychrophilic (listeria), thermophillic (e-coli), hyperthermophillic (thermotogo maritima)
moisture- needed for all bacteria to grow
pH level- slightly acidic or neutral (pH6-7)
Time- ideal conditions double very 20 minutes
Binary Fission
Reproduce Asexually
Bacteria cell elongates amd its nuclear material duplicates
Cell wall and membrane develop and seperate cell into two halves
Growth Phase of Bacteria
Lag Phase- adapting to new environment. Little increase
Log Phase- multiplying quickly in ideal conditions. Rapid increase seen
Stationary Phase- no increase. Production of new canclled out by death of old. Slows due to lack og food, space, moisture and oxygen. Build up of toxic waste products
Decline Phase- bacteria dying is greater than the reproduction rate. Small number survive and remain dormant as endospores
Endospore Forming Bacteria
During deline phase some bacteri die while others form endospores
-endospores are tough dormant cells that form around duplictaed dna strand
-cell distintergrates and endospore remains dormant
-when favourable conditions return the endospore breaks down its tough wall
-DNA dup;icates iteslf and normal cell forms
-reproduce by binary fision
What destroys Endospores?
Moist heat- 121 degrees celcius for 15 minutes
Dry heat- 150 degrees celcius for one hour
