Microbes and Environment: Sporulation, vectors, quorum

Question 1

Define Ecosystem

Answer 1

The sum total of all organisms and abiotic factors in a particular environment.

Question 2

Define Habitat

Answer 2

Portion of an ecosystem where a community could reside.

• An ecosystem contains many habitats

Question 3

Define Parasitism

Answer 3

when one member in the relationship is harmed and the other benefits

Question 4

Define Mutualism

Answer 4

Both species benefit

Question 5

Define Commensalism

Answer 5

One species benefits, the other is neither harmed not helped

Question 6

Define Species Richness

Answer 6

total number of different species present

Question 7

Define Species abundance

Answer 7

proportion of each species in an ecosystem

Question 8

Define Guilds

Answer 8

Metabolically related microbial populations

Question 9

Define Niche

Answer 9

Habitat shared by a Guild, supplies nutrients as well as conditions for growth

Question 10

Define Biogeochemistry

Answer 10

The study of biologically mediated chemical transformations

Question 11

Define Microenviroment

Answer 11

The immediate environmental surroundings of a microbial cell or group of cells

Question 12

Define Biofilms

Answer 12

Assemblages of bacterial cells adhered to a surface and enclosed in an adhesive matrix excreted by the cells

Question 13

What are biofilms made up of

Answer 13

-The matrix is typically a mixture of polysaccharides

Question 14

Give three reasons bacteria form biofilms

Answer 14

• Self-defence- Biofilms resist physical forces that sweep away unattached cells, phagocytosis by immune system cells, and penetration of toxins e.g. antibiotics
• Allows cells to remain in a favourable niche
• Allows bacterial cells to live in close association with one another

Question 15

What is Pseudomonas aeruginosa?

Answer 15

Biofilm producing, gram negative, rod shaped bacterium.

Question 16

What intracellular signaling molecules does Pseudomonas aeruginosa use?

Answer 16

acylated homoserine lactones

Question 17

Define Quorum sensing

Answer 17

mechanism by which bacteria asses their population density
-Ensures that a sufficient number of cells re present before initiating a response that, to be effective, requires a certain cell density (e.g. toxin production in pathogenic bacterium.

Question 18

What are the main properties of autoinducer molecules that allow quorum sensing to take place?

Answer 18

• Diffuses freely across the cell envelope
• Reaches high concentrations inside cell only if many cells are near
• Binds to specific activator protein and triggers transcription of specific genes

Question 19

What is Acyl homoserine lactone (AHL) an example of

Answer 19

An autoinducer molecule

Question 20

What encodes for bioilluminesence in becteria such as Aliivibrio fischeri?

Answer 20

Lux operon

Question 21

Give two examples of quorum sensing

Answer 21

• Virulence factors

- Switching from free-living to growing as a biofilm

Question 22

Is quorum sensing sensing present in microbial eukaryotes?

Answer 22

some eukaryotes

Question 23

Is quorum sensing sensing present in archaea?

Answer 23

Likely

Question 24

What is the name given to the process by which prokaryotic cells respond to other cells of the same species

Answer 24

Quorum sensing

Question 25

Give two examples of Virulence factors

Answer 25

Escherichia Coli

Staphylococcus aureus

Question 26

What does straphylococcus aureus do to the host?

Answer 26

• -Secretes small peptides that damage host cells or alter host’s immune system

Question 27

What are endospores?

Answer 27

• Highly differentiated cells resistant to heat, harsh chemicals and radiation
• ‘Dormant’ stage of bacterial life cycle

Question 28

Are endospores present in gram-positive bacteria

Answer 28

Present in some gram-positive bacteria