Lecture 1: Introduction to Microbiology Flashcards
What is microbiology?
The study of organisms that are too small to see with the naked
eye
What organisms are usually studied in microbiology?
- Bacteria
- Archaea
- Fungi
- Protozoa
Is it true that some of the organisms studied in microbiology aren’t actually that small?
Yes
Is the idea of there being ‘5 Kingdoms’ incorrect?
Yes, now it is commonly accepted that there are ‘3 domains’.
What was the 5 kingdom system replaced by?
The 3 domain system
What was included in the 5 kingdom system?
- Plantae
- Fungi
- Animalia
- Protista
- Bacteria
What is the average size of bacteria?
1-6 µm
Is it true that some of the largest bacteria can be visible to the eye?
Yes
How do you convert micrometres to millimetres?
You divide by 1000
How large is Epulopiscium
fishelsoni ?
0.7 mm
How large is Thiomargarita
namibiensis ?
0.75 mm
Which bacteria is 0.7 mm in size?
Epulopiscium fishelsoni
Which bacteria is 0.75 mm in size?
Thiomargarita namibiensis
Was it once thought that all archaea were only extremophiles?
Yes
Why aren’t archaea and bacteria the same?
Because they are different to each other at the molecular level
Are there any known pathogenic archaea?
No
When was the first known non-extreme archaeaon located?
In 2004
Do the sizes of fungi vary a lot?
Yes
How much does the largest fungal colony weigh?
Around 10,000 kg
What are most eukaryotes?
Protists
What is Paramecium?
A ciliated protozoan
What is the size range of protists?
1-150 μm
What is the estimate of the total microbial cells on earth?
4-6 x 10³⁰ cells
What does microbial carbon equal?
That of all plants
What are major portions of biomass on earth?
Bacteria and archaea
Is it true that Microbial N and P is >10X that of plant biomass?
Yes
Why are there so many microorganisms?
- Because they have a rapid growth rate
- There’s many chances of speciation through random mutations
- Due to the exchange of genetic material (lateral gene transfer)
- Every available niche is occupied by specifically adapted
microbes - Microbes have a very long evolutionary history (~3.8 billion years)
What does a phototroph do?
Obtains energy from light
What does a Chemotroph do?
Obtains energy from chemical bonds
What does an Organotroph do?
Uses organic compounds as e- donors
What does a Lithotroph do?
Uses inorganic compounds as e- donors
What do Autotrophs do?
They use Carbon dioxide as a Carbon source
What do Heterotrophs do?
They use organic carbon as a carbon source
What does a Photolithoautotroph do?
- Uses light energy
- Uses water as an electron donor
- Fixes Carbon Dioxide
Give examples of Photolithoautotrophs
- Cynobacteria
- Most plants
What do Chemoorganoheterotroph do?
- Obtain energy from chemical bonds
- Use ogranic compounds as electron donors
- Use organic carbon as a carbon source
Give example of Chemoorganoheterotrophs
- Escherichia coli
- Animals
What do Chemolithoautotrophs do?
- They obtain energy from chemical bonds
- They use inroganic compounds (reduced sulfur) as electron donors
- They fix Carbon dioxide
Give an example of a Chemolithoautotroph
Thiobacillus spp.
What is needed for the growth of microorganisms in labs?
Macronutrients and micronutrients
What are macronutrients
Carbon, either from Carbon dioxide or from Organic Carbon.
What are micronutrients ?
Trace metals, such as Iron and Zinc
What do Prototrophs do?
They synthesise all their own cellular components (including ALL amino acids, nucleotides, vitamins)
What do Fasidious bacteria need in their growth media?
organic components, such as vitamins
What is the Carbon and energy source in e coli?
Glucose
What is the e coli medium dissolved in?
1 litre of distilled water
What is the pH of the e coli medium adjusted to?
pH 7
Does the e coli medium have any complex compounds?
No
Why doesn’t the e coli medium have any complex compounds?
Because E. coli can make them all itself.
How many different components does the Neisseria gonorrhoeae require?
35
What is the source of glucose in the Neisseria gonorrhoeae medium?
Glucose
Apart from the components, what else is needed in the Neisseria gonorrhoeae medium?
- The many sterile components are mixed
- Then the pH is adjusted to 7
- Then the Neisseria gonorrhoeae is grown in 3-10 % Carbon dioxide.
Describe the complex medium for E. coli and some Neiserria spp.
How do bacteria grow?
By asexual reproduction, either through binary fission or budding
Do bacteria grow exponentially?
Yes
Do bacteria cells double in size, then split?
Yes
What happens when bacteria don’t separate properly?
- Pairs are produced
- Larger assemblies of bacteria are produced
- Both of these are problematic for the bacteria
How quickly does e coli double ?
Once every 20 minutes
What is the growth of bacteria limited by?
Space and availability of nutrients
Which microbes grow differently?
- Those that have very strict requirements for growth
- Slow growing Anaerobes
What happens in the lag phase?
- Bacteria are adapting to the new condition of having nutrients available to them.
- Genes are switched on, new proteins are made that enable them to grow
What happens in the exponential phase?
- Bacteria grow as fast as they possibly can
- Straight line, as the number of microbes is being measured on a log scale
why is the exponential phase a straight line?
because the number of microbes is being measured on a log scale
What does the gradient of the exponential phase tell you?
How quickly the bacterial cells doubles in mass
How can you work out how quickly bacterial cells double in mass?
By working out the gradient of the exponential phase
What happens in the stationary phase?
- Run out of nutrients.
- There is a build-up of waste products which inhibits growth.
- Too crowded to be able to make anymore cells and so the cells stop growing.
- Many cell pathways are switched off.
What happens in the death phase?
- Cells start to die
- Cells that are still living can utilise some of the energy that is released by the dying cells.
What’s one way of counting bacteria cells?
Using haemocytometry, use grid and microscope to estimate how many cells there are in the culture.
What’s one way of measuring optical density?
Using turbidmetry
When do you measure how much DNA and protein is in the culture?
- If the cells clump together so that you can’t measure optical density properly.
- If the cells stick to the surface of the flask, rather than being in the liquid culture.
What are the ways in which bacterial growth can be measured?
- By measuring cell number
- By measuring optical density
- By measuring the fresh/dry weight
- By measuring the amount of protein
- By measuring the amount of DNA
Do round bacteria scatter less or more light?
Less
Do rod-shaped bacteria scatter less or more light?
More
What is the problem with identifying microbes from one another when looking down a microscope?
They have a limited morphological diversity, and so most microbes look similar down a microscope
What are some traditional ways of identifying microorganisms?
- Microscopy and staining
- Growth on selective/ differential media
- Testing substrate spectrum supporting growth
- Testing of enzyme activities (antibiotic resistance).
- Characterisation of cell chemical constituents (lipids, cell wall components, DNA base ratio, quinones)
Will some bacteria only grow on specific sugars?
Yes
What is modern identification of microorganisms based upon?
The sequencing of specific conserved genes
What does selective media allow to happen?
Selective media allows for the growth of only certain types of organism
In diagnostic clinical microbiology, what is selective media used for?
Identifying presumed pathogens from clinical specimens.
Does penicillin affect more gram negative or more gram positive bacteria?
More gram positive bacteria
What does differential media allow to happen?
- Differential media allows for the identification of organisms based on growth and appearance on that medium (often based on colour differences).
- Used to determine if a culture is potentially pathogenic
How can enzyme activities in bacteria be tested?
- A culture of the organism is grown
- The cells are resuspended in a buffer
- The test wells are inoculated
- The resulting colour in the test strip is compared against a database
- This can help to distinguish between pathogenic and benign strains
What test is commonly used for testing enzyme activity in microorganisms?
ApiZym
