Association of bacteria with other organisms: commensals, symbionts & pathogens I Flashcards
What is infection
Colonisation of the host
What is transmissbility
The ability to spread from host to host
Carriage
The establishment of harmless long term relationship
Disease
Infections that damage the host
Pathogenicity
Ability to cause disease
Virulence
Severity of disease caused
Commensal
Shares its food (parasites feed on body of host)
Symbiosis
Association of two different organisms and contribute to each other’s support
How does syntrophy explain a possible mechanism for the origin of eukaryotes and multicellularity
Highly nutritionally interdependent communities of eubacteria and archaea exist in anoxic environments
Patterns of gene exchange –> may not be wholly independent organisms
What are the stages of host adaptation
- Free living and extra cellular
- Facultative intracellular
- Obligate intracellular
- Obligate intracellular mutualist
- Organelle
What are diatoms and what are they predominantly associated with
- Abundant microscopic algae - contribute about 20% photosynthesis
- Associated with proteobacteria and bacteriodetes
How have bacteria contributed to diatom genomes
Via HGT
Metabolic interactions between diatom and bacteria include:
Parasitism
Synergism
Competition
Important in biogeochemical cycles
Bacterial and fungal associations : lichens
- Mycobiont: protection of photobiont and absorb mineral nutrients
roles of prokaryotic photobiont
Legumes and rhizobium
Important biological symbiosis and species specific
What is the role of the plant
Provide nutrition
Role of bacterium
nitrogen fixation
How are rhizobium root nodules formed
- Recognition and attachment
- Signalling
- Invasion
- Travel through infection thread
- Bacteriod formation
- Bacterial and plant growth to form the nodule
Outline verminephrobacter symbiosis in earthworms
Almost all earth worms have species-specific endosymbionts
- Vertically transmitted
- Bacteria live on host waste products - beneficial for host reproduction because of nutritional advantage conferred to host
- Reductive evolution of bacterial genome results in streamlining
Insect endosymbionts
Please outline the extent of aphids’ dependence on buchnera
Buchnera are obligate intracellular endosymbionts of aphids
Aphids die without bacteria (eg can be killed by antibiotics)
Bacteria are maternally transmitted
Most buchnera genes have close homologues in the enteric bacteria - ancestor like e.coli that has undergone reductive evolution
Please outline the host and symbiont roles in the metabolic interdependence of aphids and buchnera
The host supplies energy, carbon, nitrogen in the form of glutamine from the phloem (aphids feed on trees)
Symbiont role: production of amino acids especially tryptophan (12 -16 copierss of trpEG genes)
What is the evidence of long term co-speciation between endosymbionts and insect hosts
Mutualistic symbiosis
150-250 million years ago
Vertical transmission of symbionts (from parent to offspring)
Coevolution of bacteria and host.- similar aphid and symbiont phylogenetic trees
What is the evidence of long term co-speciation between endosymbionts and insect hosts
Mutualistic symbiosis
150-250 million years ago
Vertical transmission of symbionts (from parent to offspring)
Coevolution of bacteria and host.- similar aphid and symbiont phylogenetic trees
What happens in wolbachia infection
Wolbachia induced cytoplasmic incompatibility
Causes a modification in the sperm that can be rescued by eggs of infected females - uninfected embryos die
