Topic 5 - Microbial growth Flashcards
What are growth requirements?
- Temperature
- pH
- Osmotic pressure
- Trace elements
- Nitrogen, Carbon, Hydrogen, Oxygen, Phosphorus and Sulphur
What are the optimum temperature for:
- Psycrophiles
- Psycrotrophes
- Mesophiles
- Thermophiles
- Hyperthermophiles
- 15 degrees
- 25
- 37
- 63
- 95
What are acidophiles and alkaliphiles?
Acidophiles are microbes that grow in acidic environments and alkaliphiles are microbes which grow in alkaline environments.
What is a hypertonic environment?
When the solute is higher
What is plasmosis?
When the cell loses water in hypertonic solution. This is seen with a addition of sugar and salt.
What are halophiles?
Microbes which require salt and extreme halophiles require high osmotic pressure.
What are saccharophiles?
Organisms that require sugar. Most organisms are inhibited by 50-70% sugar.
What are the chemical requirements for growth?
Nitrogen - DNA, RNA, protein and AA
Carbon - Carbs, DNA, RNA, AA’s and as carbon source for catabolism and anabolism.
Hydrogen - proton source for ETC
Oxygen - Terminal electron acceptor
Phosphorus - phosphate for DNA, RNA, NADP and ATP
Sulphur - AA’s methionine and cystine
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What are the trace elements?
Ian Makes Zena Cry Cobalt Iron - needed for cytochromes in ETC Magnesium - enzyme cofactor Zinc Copper Cobalt
What are enzyme cofactors?
They assist enzymes during catalyse reactions.
Which enzymes break down oxygen?
Catalase, superoxide dismutase and peroxidase.
What are microaerophiles?
They require oxygen but at a lower concentration to that found in the atmosphere.
What is the difference between:
Facultatice anaerobes
Obligate anaerobes
Aerotolerant anaerobes
Facultative - use oxygen when present but continue to reproduce and ferment in it’s absence (E.coli and yeasts).
Obligate anaerobes - very sensitive to oxygen since they dont produce SOD and catalase (clostridium).
Aertolerant- tolerate oxygen but can’t reproduce in its presence (lactobacilli is cheese fermentation).
What are organic growth factors?
AA’s, vitamins, purine, pyrimidine.
some organisms cant make their own while some bacteria can synthesis their own.
What are:
Culture mediums
Pure cultures
Colonies
Culture mediums are mediums prepared for microbial growth
Pure cultures are cultures with only one species or strain
Colonies are populations arising from one single cell or spore
What does sterile mean?
No living organisms.
What is inoculum?
microbes in medium
What does CFU means?
The number of living things in a sample.
What are the different forms of agar?
Deep- in a test tube
Plate/medium - in a dish
Slanted - on an angle
Why is agar useful?
Because it isnt metabolised, solidifying agent, solidifies at 40 degrees and liquidifies at 100 which is very useful for thermophiles.
What is selective media?
Media that suppresses unwanted microbe growth for example adding penicillin which inhibits bacterial growth but allows for fungal. This is also seen in MacConkey’s agar where it allows for gram negative bacteria only.
What is differential media?
This detects traits, for example it detects bacteria that has the ability to haemolysis in blood agar plates.
What is enrichment cultures?
This encourages the growth of bacteria which is present in small numbers. They can also be selective as they allow for growth of specific microbe.
What is used for anaerobic media?
Cystenine, sulphide and thioglycolate which react with oxygen. Also boiling reduces the presence of oxygen.
What is oxyrase and how is it used?
It is an enzyme which when combined with oxygen produces hydrogen and water.
