Microbiology

Question 1

Saprophytic

Answer 1

feed on dead or decaying matter eg fungi

Question 2

Parasitic

Answer 2

feed on living matter eg athletes foot

Question 3

Aerobic

Answer 3

needs oxygen for growth

Question 4

Anaerobic

Answer 4

oxygen is not needed for growth

Question 5

Faculatitive

Answer 5

these microbes will grow with or without oxygen

Question 6

Psychrophiles

Answer 6

these microbes prefer low temperatures 5-20 degrees

Question 7

Mesophiles

Answer 7

most microbes thrive at this temperature 20-45 degrees

Question 8

Thermophiles

Answer 8

prefer temperatures above 45 degrees

Question 9

Moisture

Answer 9

necessary for all microbes to metabolise
low water content can reduce the growth of microbes in food

Question 10

pH level

Answer 10

most prefer a neutral pH

Question 11

Moulds

Answer 11

multicellular
contaminate many foods
start as single celled spore

Question 12

conditions required for the growth of moulds

Answer 12

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

Question 13

Structure of Moulds

Answer 13

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

Question 14

Asexual Reproduction

Answer 14

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

Question 15

Types of moulds

Answer 15

Phycomycetes
Ascomycetes

Question 16

Sexual Reproduction

Answer 16

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

Question 17

Phycomycetes

Answer 17

reproduces sexually & asexually
produce sporangia
most favourable temp 30 degrees
examples are mucor & rhizopus

Question 18

Mucor

Answer 18

Found on: soil, bread, meat, cheese
Characteristics: saprophyte, greyish, sporangium
Example: bread mould

Question 19

Rhizopus

Answer 19

Found on: soil, bread, soft rot on fruit & veg
Characteristics: saprophyte, black, sporangium
Example: rot on mushrooms

Question 20

Ascomycetes

Answer 20

Optimum temp: 20-25 degrees
Asexual reproduction only contain cross walls
Produce conidia
Examples: penicillium & aspergillis

Question 21

Penicillium

Answer 21

Found on: cheese, fruit, bread
Characteristics: saprophyte, crumbly green/blue, mould
Example: ripening cheeses and production of antibiotics

Question 22

Aspergillis

Answer 22

Ascomycetes
Found on: fruit,veg, grain
Characteristics: saprophyte, blak or green mould

Question 23

Yeasts

Answer 23

single celled
saprophytic
found on air, soil, on fruit
fruit, meat and meat can be spoiled by yeasts
used in production of some foodstuffs

Question 24

Conditions for growth of Yeast

Answer 24

Food: feeds on carbs eg sugar
Oxygen: faculative
Temperature: 25-30 degrees, 60+ destroys yeast
Moisture: moist conditions
pH: acidic conditions ( 4-5)

Question 25

Budding

Answer 25

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

Question 26

Varieties of Large Fungi

Answer 26

Field Mushrooms
Truffles
Amanita

Question 27

Reproduction of large fungi

Answer 27

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

Question 28

Advantages of fungi

Answer 28

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

Question 29

Disadvantages of Fungi

Answer 29

Can causes food spoilage
Can cause plant diseases
Can causes human diseases

Question 30

Conditions needed for Bacteria

Answer 30

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

Question 31

Binary Fission

Answer 31

Reproduce Asexually
Bacteria cell elongates amd its nuclear material duplicates
Cell wall and membrane develop and seperate cell into two halves

Question 32

Growth Phase of Bacteria

Answer 32

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

Question 33

Endospore Forming Bacteria

Answer 33

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

Question 34

What destroys Endospores?

Answer 34

Moist heat- 121 degrees celcius for 15 minutes
Dry heat- 150 degrees celcius for one hour