bacterial diversity and differentiation Flashcards
what is meant by the term diversity
the level of taxonomic classification
how many major bacterial phyla are there and what is the largest
18
proteobacteria
what are the four focused bacterial phyla on this course
1) cyanobacteria
2)actinobacteria
3)firmicutes
4) proteobacteria
outline the characteristics of proteobacteria phylum
1) largest bacterial phylum
2) gram negative bacteria
3)pathogenic
outline the characteristics of firmicutes phylum
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
outline the characteristics of actinobacteria phylum
1) many are gram positive
2) morphologically diverse
3) widley distributed in soil
4) some are very pathogentic such as mycobacterium tuberculosis
outline the characteristics of cyanobacteria
1) gram negative
2) photosynthetic
3) harvest energy for light and produce oxygen as a by product
4) some produce toxins
what are some toxins produced by cyanobacteria
hepatoxins, cytotoxins, neurotoxins
define differentiation
the process by which prokaryotes undergo changes in form and function in order to survive and disperse better in the environment
give an example of changes in form/structure
prokaryotes can form multicellular structures by clumping together to survive environmental changes
why would a single cell differentiate into a different version of itself
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
what is a biofilm
an example of differentiation found whenever there is a solid surface bathed in water
outline how a biofilm is formed
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
what does the EPS matrix in biofilms also allow other than acting as a cement
1) absorbs water and nutrients
2) allows waste to exit
3) provides a protective armour
how come some lab strains of bacteria lose the ability to form biofilms
1) genes responsible mutate
2) absence of environmental pressures mean the mutation persists
outline how communal life within biofilms offers advantages
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
what is an exospore
an example of differentiation where actinobacteria show filamentous growth and produce external spores
what is an endospore
some cells produce intracellular spores which act as survival structures allowing cells to survive in a metabolically inert state
what is endospore production restricted to
a phylum of gram-positive bacteria
outline some features of an endospore
- 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
outline how an endospore is formed
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
outline the process of endospore staining
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
what is a swarmer/sessile cell
gram negative bacteria which thrive in low nutrient environments differentiate into one of the two cells
outline a swarmer cell
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
what happens to swarmer/sessile cells when nurtients availability changes
available= cell remains sessile
low= sessile cell produces a swarmer by asymmetric cell division allowing movement to a regions with increases nutrients
what are myxospores
predatory bacteria which feed on fungi, yeasts, protoza and bacteria by moving over solid surfaces killing and consuming other microbes in their path
outline how myxobacteria assimilate their prey
1) secrete antibiotics to kill their prey
2) secrete enzymes to lyse their prey and digest macromolecules of the prey
why do myxobacteria produce myxospores
when prey is scarce they form resting cells= myxospores
= survival structures
outline the formation of myxospores
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
what are resting structures produced by cyanobacteria
nutritional limitation and stress tempers cause some cells in the filament to form large resistant cells = Akinetes
what are the specialized structures produced by cyanobacteria
heterocysts which fix nitrogen when scarce and are connetect to neighbouring cells by channels providing nitrogen in exchange for photosynthetic products
what are dispersal cells produced by cyanobacteria
hormogonia which is attracted to a signal produced by plants
they enter specialised pockets in the plant and differenciate into heterocycsts to fixate nitogen
