microbes and the immune system Flashcards
give and explain two examples of bacterial and fungal mutualism?
bacterial- colonic bacteria. synthesise vitamin k and folate, metabolised by host. e.g. ruminococcus spp. found in high numbers in gut and involved in cellulose breakdown (digestion)
fungal- mycorrhizae. associated with plant root. fungi attach to root and allow root extension, in exchange the plant provides sugars to the fungi
over 80% of plants are associated with mycorrhizae.
give and explain two examples of commensalism relationship in the gut microbes?
bacteroides benefits from e.coli (e.coli does not benefit).
they breakdown or generate metabolites we can synthesis.
staphylococcus epidermidi utilises dead skin cells without causing harm
pathogens are defined as primary and opportunistic. what are they?
primary pathogens=
microbes live or multiply within the host e.g. malaria
opportunistic pathogens=
does not cause disease until triggered by something e.g. toxoplasmosis or cold sores/
the difference between traditional koch postulates and modern
traditional- aims to tests whether a particular microorganism is a pathogen
modern- what genes attribute to a pathogens ability to cause disease
name some virulence factors?
pathogenicity- ability for organisms to cause disease
virulence- the degree of pathogenicity of an organism e.g infectivity/ intensity of virus
other virulence factors= phenotypic switching
what is the darwinian goal of a virus?
reproduction
how does quasispecies : viral genetic heterogeneity have high genetic diversity
(important for evolution)
from high mutation rates in RNA viruses, also with selection pressures within the host
diversity= insertions/deletions
how is viral evolution driven?
by selective pressures that favour mutants with enhanced fitness. e.g. invade immune detective/ replicate efficiently.
however most mutants are natural with no selective pressures which drives antigenic variation
the importance of antigenic drift in viruses e.g. influenza
gradual accumulation of mutations in viral genomes that alter structure of antigens, selective pressure.
importance of spike drift in RNA virus like SARS COv 2?
genetic change of spike protein is important for viral entry of host cell.
glycogen sheilding and biologically critical amino acids is important for this
how a virus can survive through viral mimicry?
evades host immune system by mimicking it to allow replication
3 mechanisms of horizontal gene transfer in organisms
-natural transformation
-conjugation
-tranduction
natural transformation- bacteria takes up free floating DNA from it’s environment
conjugation- genetic exchange between bacteria through physical connection
transduction- viruses (bacteriophages) carry genetic material from one bacterium to another
explain the mechanism TRANSFORMATION
of horizontal gene transfer (ssDNA)
not all bacteria are naturally competent (able to take up DNA). if genes are associated with antibiotic resistance, bacteria transfers
explain the mechanism
CONJUGATION (bacterial sex)
of horizontal gene transfer
occurs due to pilus (hair like structure). plasmids are genetic material transferred during connection e.g. F factor in e-coli
explain the mechanism TRANSDUCTION bacteriophages predate bacteria during horizontal gene transfer
- two lifecycles
-Difference between specialised transduction and generalised transduction
two lifecycles=
lytic: results in the replication of bacterial genome which destroys bacteria
lysogenic: integrates bacteriophage DNA into bacterial chromosome and becomes part of viral genome= specialised transduction
generalised= the bacteriophages pick up any portion of the hosts genome
specialisted= the bacteriophage picks up specific potions of the host genome
