Microbiology

Question 1

Example of eukaryotic microbe?

Answer 1

Fungi, protists

Question 2

Why are there so many microorganisms?

Answer 2

Rapid growth in environment, many chances of speciated through random mutations (ability to adapt), lateral gene transfer, very long evolutionary history (3.8b years)

Question 3

When did bacteria / archaea first originate?

Answer 3

Around 3.8b years ago

Question 4

How was the history of the earth driven by microbial processes?

Answer 4

Earth slowly became oxygenated - origin of oxygenic photosynthesis by cyanobacteria. oxygen accumulates in atmosphere allowing for origin of eukaryotes

Question 5

What are nutritional categories based on?

Answer 5

Sources of energy, electron donors and cell carbon

Question 6

Organotroph?

Answer 6

utilises organic compounds as electron donors. (already fixed carbon sources) e.g. glucose, methanol

Question 7

Lithotroph?

Answer 7

Utilises inorganic compounds as electron donors, eg. reduced compounds, NH3, CO, H

Question 8

Autotroph?

Answer 8

CO2 as carbon source, fix carbon dioxide (photosynthesis)

Question 9

Heterotroph?

Answer 9

organic carbon as carbon source (glucose) e.g. humans

Question 10

Prototrophs?

Answer 10

Synthesise all their own cellular components (all amino acids, nucleotides) -can turn one carbon source into anything

Question 11

Fastidious bacteria?

Answer 11

Need organic compounds (diet), vitamins, to grow in a media

Question 12

How does bacteria grow and multiply?

Answer 12

Using binary fission, cells double in size and split into 2, EXPONENTIAL GROWTH

Question 13

Why is exponential growth of bacteria good?

Answer 13

an efficient way of growth when plenty of nutrients are available

Question 14

How is bacterial growth limited?

Answer 14

all environments are limited - space and nutrients, max. carrying capacity

Question 15

What is the lag phase on bacterial growth curve?

Answer 15

no growth first - bacteria need time to adapt to new media / conditions to grow in (switch on genes)

Question 16

What is the log phase on bacterial growth curve?

Answer 16

growing as fast as they can - exponential growth, abundance of nutrients and space

Question 17

What is the stationary phase on bacterial growth curve?

Answer 17

growth stopped: media has become too crowded / too many waste products / running out of nutrients

Question 18

What is the death phase on bacterial growth curve?

Answer 18

bacterial cells die, but remaining living cells can use energy released from dying cells

Question 19

How can we measure bacterial growth?

Answer 19

Haemocytometry - microscope + grid to estimate number of cells, Turbidmetry - bacteria scatter light shone through beaker - optical density used to see how cloudy solution is
Dilution plating - create dilutions and measure how many cells are in beginning and end of exp. phase

Question 20

Problems with identifying microorganisms?

Answer 20

limited morphological diversity - microbes look similar down a microscope

Question 21

What is differential media?

Answer 21

contains compounds which allow groups of microorganisms to be visually distinguished - certain compound produced by bacteria interacts with compound in media e.g. colour change of media

Question 22

What is selective media?

Answer 22

selects for certain characteristic of bacteria = if certain bacteria only grows in one sugar

Question 23

Methods of identifying microorganisms?

Answer 23

Microscope and staining, growth on sel / diff media, testing substrate spectrum supporting growth, testing of enzyme activities (e.g. antibiotic resistance enzyme), cell chemical constituents
MODERN: sequencing of specific genes - but have to compare to something we already know

Question 24

Why is selective media used in clinical diagnostics?

Answer 24

only a few organisms are associated with certain symptoms, so easy to grow and identify + find treatment

Question 25

When is differential media used?

Answer 25

Used to determine whether a culture is pathogenic / benign or malignant - colour change shows results

Question 26

How can enzyme activity be used to find pathogens?

Answer 26

Colour change based on benign / malignant enzyme present

Question 27

Why is it unlikely that cellular life evolved on the surface?

Answer 27

Hostile conditions - harsh UV light, no ozone layer, volcanic activity - not liveable

Question 28

Why is it more likely that cellular life evolved subsurface?

Answer 28

More stable conditions, in hydrothermal vents in ocean floor + constant source of energy from reduced inorganic compounds