microbial symbioses Flashcards
define and describe symbiosis
describe the 3 types of symbiotic relationships
describe the 2 classes of symbiosis in terms of the location of the symbiont
- when two species liver together in a community and form an exclusive close relationship. the organisms gain a new structure or ,metabolic capability
- often the net benefit isn’t to the individual but to the population as a whole
- both partners are so intimate that often coevolution occurs
- acquisition of partner may be ancient or may occur every lifetime
i) mutualistic; both species benefit
ii) commensal; one species benefits while the other has no benefit/detremental effect
iii) parasitic; one species benefits which the other suffers harm
I)ectosymbiont; symbiont remains outside of the host; vertebrate gut
ii)endosymbiont; the symbiont is inside the symbiont
intracellular; inside cells; chorella
extracellular; enclosed within a host cavity or in intercellular space; ectomycorrhizae
name the 11 examples of symbiosis
vertebrate gut biome
rumen biome
paramecium eukaryote and chorella algae
ancient symbiotic event when archaea engulfed a bacteria
coral reef and dinoflagellate algae
legume root nodules and rhizobia bacteria
plant roots and mycorrhizae fungi
squid and bioluminescent bacteria
aphids and bacreria
giant tube worms and chemosynthetic bacteria
discuss the vertebrate gut microbiome; which type of symbiosis is it and what function does it serve
disucss mammalian microbiome function and cell density
discuss ruminants and state which 3 novel metabolisms are acquired
vertebrates
- ectosymbiosis
- many novel metabolisms aquired
mammals
- very high cell density (10^12 cells/ml)
- function is resistance to invasion from harmful microbes.
ruminants
- have a specific organ to house bacteria
- novel metabolism;
a) cellulose digestion into Acetly CoA via anaerobic fermention provides 70% of rumens energy needs. cellulose is the most abundant carbohydrate so many niches can be exploited
b) nitrogen breakdown
c) vitamin B synthesis - sterile at birth; microbes aquired each generation
- partly digested food from the rumen is passed back to the mouth for more chewing
- microbes are later digested in abomuasum
why are not all vertebrates ruminants
-very costly to be a ruminant; fermention vat needs alkaline salivam mixing movements, elimination of methane
describe the parmecium-chorella relaitonship
- paramecium is a single celled eukaryote
- chorella is an algae
- up to 1000 chorella can be found in a paramecium
- bidirectional tranfer of food and nutrients
- symbiosis only occurs when food supply is scarce; its a burden in normal conditions especially low light
discuss the origin or human genes
37% are from bacteria 28% from eukaryotes 16% from animals 13% from vertebrates 6% from primates; 6% unique to primates
describe the three symbioses plants have with microbes
1) legume-rhizobia bacteria
- rhizobia have nitrogenase complex which fixes nitrogen gas into ammonia
2) many angisperms (200)-frankia bacteria
- nix nitrgoen gas into ammonia
3) most plants-mycorrhizae
- increase nutrient gathering ability
discuss the symbiois a squid has
-bioliminescent bacteria exist which help the squid hunt at night by causing it to have no shadow
which symbiois to aphis have
- they have bacteria is special type of adipocyte cells (contain fatty acids) called bacteriocyte cells
- the bacteria produce essetnial enzymes needed
name the latin binomial for giant tube worms
where do these animals live
descibe a symbiosis with giant tube worms
Riftia pachyptila
deep sea hydrothermal vents
chemosynthetic bacteria which convert vent chemicals to food for the worm
the worm has no mouth of gut
describe the ancestral ensosymbiotic event
an early eukaryote from within the archaea domain developed the abilityto perform phagocytosis (ingest bacteira in membrane bound vesicles)
many prokaryotes were ingested which led to peroxisomes, mitochondria, chloroplasts
which family of archaea is thought to of led to Eukaryotas and why
lokiarchaeota
has many similar characteristics to eukaryotes
discuss in detail the coral reef symbiosis
names of host and symbiont:2
where does the symbiosis exist:4
decribe cnideria anatomy; 4 marks
whats the role and structure of mucus
what is the concentration of algae; 1 mark
how do both parts of the superorganism gain energy; 2
discuss energy statistics of the relationship: 4
dicsuss the diversity of the microbiome; 3 marks
- Coral (Cnideria animal)- dinoflagellate (Zooxanthellae algae)
- high light intensity, moderate wave action, low nutrients, warm tropical sea. this symbiosis involves tight recycling of nutrients so the symbiosis can exist in very low nutrient areas
- each poly has a ring of tentacles which move food to the gut (many polyps have a connected gut)
- thin ectoderm with many mucus glands>acellular mesoglea>endoderm packed with algae>inner mass of calcium carbonate cytoskeleton
- first layer of defence against invading pathogens
- made of mucins (glycoproteins)
-1-10 milion cells per cm^2 of tissue
- the cnideria is heterotrophic and uses nematocyst cells in a harpoon like way to catch prey
- zooxanthellae uses photosynthesis
-1% of algal energy is used for growth; tightly regulated
-21% of algal energy is used by algae and is released as heat energy etc
-78% of algal energy goes to animal cell;
a)45% used for mucus release
b)25% used for respiration
other uses are tissue growth and reproduction
- the presence of the mucus surface means cnideria can be very selective of the symbionts
- no/very few bacteria; if they are present they usually have a very important function such as nitrogen fixation
- some species are very specific to the cnideria species, some algae appear in many species
discuss coral diseases
discuss 4 flaws with Koch’s postulates
discuss 6 diseases
state why coral disease is difficult to investigate;1
discuss the 4 possible explanations for coral disease
- many coral diseases exist
- all theories of disease are highly flawed which suggests coral disease is very unique
i) assumes only a single pathogen causes disease
ii) 99% of microbes cant be cultured
iii) many microbes exist in an organism; its hard to known which one to publish
iiii) if large amounts of culture are given to a host, disease will likely occur even if the microbe isint the causal agent
1) bleaching (loss of symbiotic algae); Mediterranean; vibrio shiloi infects ocilina patagonica; papers ecist to disprove this for example the bacteria doesnt exist in diseased organisms
2) bleaching/lysis; indian ocean/red sea; vibrio coralliilyticus; shown to cause bleaching at 25 degrees however these results cant be generalised to real coral bceause bleaching only occurs above 27 degrees. the pathogen also is commonly found in healthy indiviuals
3) aspergillosis; caribbean; aspergillus sydowii fungus; microbe found in healthy individuals and not diseased ones
4) white band disease; caribbean; vibrio charcharia; kochs postulates werent tested for
5) white plague; caribbean; aurantimonas coralicida; not been detected in diseased corals
6) yellow band disease; caribbean; 4 vibrio species named; to do kcohs postulates you need to name one species
healthy corals and diseased coral are connected b seawater in their guts; isolating pathogens is difficult
1)multiple different pathogens can cause the same disease symtoms. for example a stressor such as climate change reduces corals defence and disturbs healthy probiotics meaning pathogens can invade
LIKELY; this is how the human gut works
2)many unique different diseases exist with very similar disease symptoms POSSIBLE
3)there is indeed a single pathogen which causes a single disease, but the pathogen hasnt been identified; those microbes identified are secondary invadors
POSSIBLE
4)polymicrobial explanation; multiple pathogens are needed to cause a disease
UNLIKELY; rarely observed in nature and hard to explain in terms of evolution
