Lecture 3: Microbial Systematics

Question 1

What is sytematics?

Answer 1

The study of the diversity of organisms and their relationships

Question 2

What Links phylogeny (evolutionary history) with taxonomy?

Answer 2

systematics

Question 3

What should the genus/species name be written in?

Answer 3

Italics

Question 4

What do the names of bacterial species reflect?

Answer 4

something about the organism

Question 5

Describe how Staphylococcus epidermidis gets its name

Answer 5

-Staphylo= “bunch of grapes” clusters

• coccus= coccus-shaped bacterium
• epidermidis= isolated from skin

Question 6

Describe how bacillus thermophilus gets its name

Answer 6

• Bacillus= rod-shaped bacterium
• thermophilus= grows at high temperature

Question 7

is there a unified species concept in microbiology?

Answer 7

No

Question 8

Why can’t a species in microbiology be defined in the same way as the general species definition?

Answer 8

• Because micoorganisms undergo asexual reproduction
• Because microorganisms undergo lateral gene transfer
• Phenotypic and genotypic plasticity of microorganisms

Question 9

What is the current definition of a species in microbiology?

Answer 9

a group of strains that show a high degree of overall similarity and differ considerably from related strain groups with respect to many independent characteristics

Question 10

What does a polyphasic approach to classification in microbiology include?

Answer 10

• Phenotypic analysis: morphological, metabolic, physiological and chemical characteristics
• Genotypic: comparative at the gene and genome level
• Phylogenetic:framework of evolutionary relationships

Question 11

How do you compare microorganisms using phenotypic traits?

Answer 11

• You look at the observable traits of the organism and compare with standard or type cultures.

Question 12

What is the problem with looking at phenotypic traits when comparing micoorganisms?

Answer 12

a single mutation can change the apparent definition of a species

Question 13

How can you look at the morphology of a cell?

Answer 13

• By gram staining, which allows you to look at cell shape, size and arrangement (single, chains, etc.), pleomorphism (existing in different shapes) formation of cysts, spores (shape, size, etc.)
• Looking at Presence of flagella, capsules, staining reactions, etc

Question 14

How can you determine the motility of a microorganism?

Answer 14

by using phase-contrast microscopy

Question 15

How can you test the nutrionality of a microorganism?

Answer 15

Testing for ability to grow on a range of compounds as sole sources of carbon, energy and nitrogen

Question 16

Does gram staining help visualise bacteria/archaea ?

Answer 16

Yes

Question 17

Does crytsal violet stain all cells?

Answer 17

Yes

Question 18

What is a biochemical test that can be used to test the phenotypes of microorganisms?

Answer 18

• Look at how they decompose simple carbohydrates
• Acid from glucose in anaerobic or aerobic conditions
• Fermentation produces acids (lactate, acetate) change pH, induces colour change
  CO2 collects in Durham tube

Question 19

Can testing if a microorganism uses amylase to break down starch help identify a microorganism?

Answer 19

Yes

Question 20

What are colony based characters?

Answer 20

Colony shape, margin, elevation, surface appearance, opacity, texture, pigmentation, odour and appearance of growth

Question 21

What substances inhibit growth?

Answer 21

selective media, antibiotics, dyes, toxins, etc.

Question 22

What pyhsiological properties can different bacteria have?

Answer 22

• Ability to grow in certain ph’s
• Ability to grow in high pressure environments i.e barophiles, which are organisms from the bottom of the ocean.
• Ability to grow in very salty conditions i.e halophiles
• Whether they’er aerobes, anaerobes. or microaerophile’s.

Question 23

What are microaerophiles?

Answer 23

microorganisms that require low oxygen concentrations for growth

Question 24

Which microorganisms work in low temperature environments of <15°C?

Answer 24

Psychrophiles

Question 25

Which microorganisms work in normal temperature environments of 15-45°C?

Answer 25

Mesophiles

Question 26

Which microorganisms work in high temperature environments of >50°C?

Answer 26

Thermophiles

Question 27

Which microorganisms work in very high temperature environments of >80°C?

Answer 27

Hyperthermophiles

Question 28

How are Psychrophiles adapted to live in low temperature environments?

Answer 28

Due to their protein structure and membrane fluidity, very fluid

Question 29

where do hypothermophiles live?

Answer 29

In hot springs and hydrothermal vents

Question 30

Do we tend to use more molecular techniques to identify microorganisms?

Answer 30

Yes

Question 31

How was the molecular identification of microbes done pre-sequencing?

Answer 31

• DNA-DNA hybridisation
• Fatty acid (FA) profiling
• DNA profiling
• Multilocus sequence typing (MLST)