bacterial diversity and differentiation

Question 1

what is meant by the term diversity

Answer 1

the level of taxonomic classification

Question 2

how many major bacterial phyla are there and what is the largest

Answer 2

18
proteobacteria

Question 3

what are the four focused bacterial phyla on this course

Answer 3

1) cyanobacteria
2)actinobacteria
3)firmicutes
4) proteobacteria

Question 4

outline the characteristics of proteobacteria phylum

Answer 4

1) largest bacterial phylum
2) gram negative bacteria
3)pathogenic

Question 5

outline the characteristics of firmicutes phylum

Answer 5

1) bacteria which live in the gut
2) first colonizers of the intestine in newborns
3) mostly gram positive
4) obligate aerobes
5) genetic exchange is common and non-selective
6) the only bacteria which can form endospores
e.g. bacillus subtilis

Question 6

outline the characteristics of actinobacteria phylum

Answer 6

1) many are gram positive
2) morphologically diverse
3) widley distributed in soil
4) some are very pathogentic such as mycobacterium tuberculosis

Question 7

outline the characteristics of cyanobacteria

Answer 7

1) gram negative
2) photosynthetic
3) harvest energy for light and produce oxygen as a by product
4) some produce toxins

Question 8

what are some toxins produced by cyanobacteria

Answer 8

hepatoxins, cytotoxins, neurotoxins

Question 9

define differentiation

Answer 9

the process by which prokaryotes undergo changes in form and function in order to survive and disperse better in the environment

Question 10

give an example of changes in form/structure

Answer 10

prokaryotes can form multicellular structures by clumping together to survive environmental changes

Question 11

why would a single cell differentiate into a different version of itself

Answer 11

1) adaptive to the environment
2) reversible- if conditions become favourable again the cell can revert to their original structures unlike plant or animal cells

Question 12

what is a biofilm

Answer 12

an example of differentiation found whenever there is a solid surface bathed in water

Question 13

outline how a biofilm is formed

Answer 13

1) cells attach to the surface and stay there (sessiloe phase)
2) cells secrete a matrix of exopolymeric substances (EPS matrix) which functions as a cement to start building the multicellular structure
3) some cells disperse to seek new territories or if conditions are favourable the whole film will dissolve

Question 14

what does the EPS matrix in biofilms also allow other than acting as a cement

Answer 14

1) absorbs water and nutrients
2) allows waste to exit
3) provides a protective armour

Question 15

how come some lab strains of bacteria lose the ability to form biofilms

Answer 15

1) genes responsible mutate
2) absence of environmental pressures mean the mutation persists

Question 16

outline how communal life within biofilms offers advantages

Answer 16

1) EPS matric limits diffusion of harmful substances so cells beneath are protected
2) cells can express enzymes conferring resistance to antibiotics or toxins
3) harder to treat pathogens forming biofilms

Question 17

what is an exospore

Answer 17

an example of differentiation where actinobacteria show filamentous growth and produce external spores

Question 18

what is an endospore

Answer 18

some cells produce intracellular spores which act as survival structures allowing cells to survive in a metabolically inert state

Question 19

what is endospore production restricted to

Answer 19

a phylum of gram-positive bacteria

Question 20

outline some features of an endospore

Answer 20

• contains no ATP or reducing power
  -interior is 3 times drier than a vegetative cell
• only takes up water upon germination
• contributes to disease transmission due to resistance to stressors

Question 21

outline how an endospore is formed

Answer 21

1) while replicating the chromosome the nuceloid lengthens which signals sporulation
2) a sporulation septum forms a point a quater way down the cell (the large portion is the mother cell)
3) the mother cell englufs the developing endospore
4) the endospore is then surrounded by two membranes and a layer of murein is synthesised between them
5) ensospore is surrounded by exosporium
6) the mother cell lyses releasing it

Question 22

outline the process of endospore staining

Answer 22

1) bacteria stained with malachite green dye
2) treated with steam allowing dye to penetarte endospore coat
3) slide is rinsed with water
4) counter stain of safranin added

Question 23

what is a swarmer/sessile cell

Answer 23

gram negative bacteria which thrive in low nutrient environments differentiate into one of the two cells

Question 24

outline a swarmer cell

Answer 24

1) cycle starts with mobile swarmer cells which has a polar flagellum and pili
2) the cell flagellum and pili are los porducing a sessile cell
3) cell projects a cell structure consisting of a stalk and holdfast terminal orgain which allows attachment to a solid surface

Question 25

what happens to swarmer/sessile cells when nurtients availability changes

Answer 25

available= cell remains sessile
low= sessile cell produces a swarmer by asymmetric cell division allowing movement to a regions with increases nutrients

Question 26

what are myxospores

Answer 26

predatory bacteria which feed on fungi, yeasts, protoza and bacteria by moving over solid surfaces killing and consuming other microbes in their path

Question 27

outline how myxobacteria assimilate their prey

Answer 27

1) secrete antibiotics to kill their prey
2) secrete enzymes to lyse their prey and digest macromolecules of the prey

Question 28

why do myxobacteria produce myxospores

Answer 28

when prey is scarce they form resting cells= myxospores
= survival structures

Question 29

outline the formation of myxospores

Answer 29

1) when prey is scarce cells aggregate
2) aggregated cells form multicellular structures called the fruiting body
3) half the cells lyse releasing nutrients which survivor cells use to differentiate into myxospres
4) spores germinate when conditions become optimal again

Question 30

what are resting structures produced by cyanobacteria

Answer 30

nutritional limitation and stress tempers cause some cells in the filament to form large resistant cells = Akinetes

Question 31

what are the specialized structures produced by cyanobacteria

Answer 31

heterocysts which fix nitrogen when scarce and are connetect to neighbouring cells by channels providing nitrogen in exchange for photosynthetic products

Question 32

what are dispersal cells produced by cyanobacteria

Answer 32

hormogonia which is attracted to a signal produced by plants
they enter specialised pockets in the plant and differenciate into heterocycsts to fixate nitogen