Microbial Diversity

Question 1

Define a strain - how are bio- morpho- and sero- vars differentiated

Answer 1

Variant of the same species
Bio - biochemically
Morpho - morpholgically
Sero - different antigenic properties

Question 2

3 main classification methods

Answer 2

Phenotypic
Genotypic
Phylogenetic

Question 3

Phenetic classification is based on how organisms look or behave - what are the 3 sections of this

Answer 3

Morphologically - shape, size and structural features
Physiologically - what an organisms does
Ecologically - Life-cycle patterns

Question 4

Give 3 limitations of phenetic classification

Answer 4

Behavioural groupings may be wrong due to convergent evolution
Unculturables cannot be studied phenotypically
Microbes can tranfer DNA leading to a change in phenotype

Question 5

What does genotypic classification compare

Answer 5

Genetic similarity

Question 6

How does nucleic acid base composition work

Answer 6

50% more energy is required to break the bonds between G-C in comparison to A-T so measuring energy input to denature DNA tells you the base composition

Question 7

What piece of equipment is used to measure how much energy was required to melt the DNA

Answer 7

Spectrophotometer

Question 8

Why does less than 10% difference not necessarily correlate to relatedness

Answer 8

Base proportions maybe similar but sequences may be different

Question 9

Give 1 advantage and disadvantage of NABC

Answer 9

Unculturables can be studied
Must have enough pure DNA

Question 10

Define hybridisation

Answer 10

Act of annealing 2 different single strand of DNA together

Question 11

How does nucleic acid hybridisation work

Answer 11

If single strands of DNA from two different organisms are hybridised the proportion of binding shows how similar the 2 sequences are

Question 12

Outline how the first organisms DNA is prepared

Answer 12

DNA is denatured and a single strand is affixed on to a filter or membrane

Question 13

Outline how the second organisms DNA is prepared

Answer 13

DNA is sheared and labelled with a detectable molecule then denatured

Question 14

How is the unhybridised DNA removed once the fragments and the strand have been mixed

Answer 14

Removal by washing of the filter

Question 15

What is NAH effective at and give 1 disadvantage

Answer 15

Separating closely related organisms
Shows similarities but not what those similarities are

Question 16

What is phylogenetic classification based on

Answer 16

Predicted evolutionary relationships

Question 17

What mutations considered as in terms of time - what does more mutations infer

Answer 17

Molecular chronometers - more mutations suggest more time passed

Question 18

Give 1 disadvantage of molecular chronometers

Answer 18

Rate of sequence change can vary overtime - assumes that amount of change increases linearly with time

Question 19

Give 2 advantages of phylogenetic classification

Answer 19

• Can study unculturables
• Labs work only has to occur once - comparisons can be made once you have the genetic sequence

Question 20

What rRNA is used is used for P and E

Answer 20

P - 16s rRNA
E - 18s rRNA

Question 21

Give 2 reasons why rRNA are used in phylogenetic classification

Answer 21

• Universally distributed
• Moderately well conserved - too much and they wouldn’t change enough for differences to be observed - too little and changed would be too rapid and there would be no similarities

Question 22

How are enough 16s rDNA genes accquired

Answer 22

Amplification using PCR

Question 23

In the phylogenetic tree of life - what does more mutations mean

Answer 23

More distantly relatedness

Question 24

Why does denaturing gel electrophoresis work on 16s rDNA whereas normal gel electrophoresis doesn’t

Answer 24

There is an addition of a gradient of denaturing chemicals - where the DNA denatures is controlled by the DNA sequence
Normal gel electrophoresis wont work as it functions on the size of molecules - all of the 16s rDNA molecules from PCR will be the same size

Question 25

Why will denatured rDNA move slower in electrophoresis

Answer 25

The rDNA is less aerodynamic

Question 26

Why is rRNA more advantageous than rDNA (2)

Answer 26

• rRNA can be examined without breaking open the sample
• PCR not required as there are many more ribosomes hence more rRNA

Question 27

What is the name given to short sections of nucleotides that are unique to different taxonomic ranks

Answer 27

Oligonucleotide signature sequences

Question 28

How are oligonucleotide sequences detected - FISH

Answer 28

A probe (small strand of complementary nucleic acid) is labelled with a fluorescent dye and hybridises with the sequence
Fluorescent in-situ hybridisation