Week 4: Viral Replication & Microbial Classification Flashcards
steps of viral replication
- Attachment
- Penetration
- Uncoating
- Synthesis
- Assembly
- Release
attachment step
marks initial contact bw the virion and host cell
viral specificity
specific interaction between virus and host cell
viral glycoproteins located in
evelope & capsid
penetration step
virion enters the host cell by endocytosis or fusion
uncoating step
shedding of viral capsid
synthesis step
genetic material is replicated and capsomeres are produced
assembly step
characterized by the reassembly of complete virions after replication of capsomeres and genetic material
release step
release of virion from the host cell by either cell lysis or budding
synthesis of DNA viruses
• Viral DNA is used to make viral RNA. RNA are usually short segments of
template instructions used to synthesize proteins
• Proteins in the host cell read the RNA templates and synthesize viral proteins
• Newly synthesized viral proteins are used to copy hundreds, or thousands of
copies of Viral DNA
• Newly synthesized DNA and capsid proteins reassemble in the assembly stage prior to release from the cell
synthesis of RNA viruses
RNA is used as a template to both synthesize new capsid proteins as
well replicated many times to create newly synthesized RNA molecules for viral
assembly & release
synthesis of retroviruses
RNA is the genetic material, but use a unique replication process
• RNA is converted into DNA by reverse transcription
• Requires a unique enzyme to do this: reverse transcriptase
• DNA is then transcribed into RNA:
• RNA copies for the new viral particle genomes,
• Or, are translated into new capsid proteins
taxonomy
the categorization of living things based on a hierarchy of relatedness
as you move down a taxonomy hierarchy, grouping becomes
more related
binomial nomenclature was introduced by
linnaeus
species are assigned two names in the following format
Genus species
phylogenetics
classify organisms based on genetic relatedness and shared ancestry
3 domains of life
archaea, bacteria, eukarya
bacteria
Prokaryotes; generally includes the bacteria that we’re most familiar with
archaea
Prokaryotes that are structurally and functionally unique from Bacteria
eukarya
Animals, plants, protozoa and fungi
domain bacteria - aquifex/hydrogenobacter
Thermophiles – grow at extremely high temperatures (~95°C)
domain bacteria - green nonsulpher bacteria
Also composed entirely of thermophiles, but don’t tolerate the extreme heats of the
Aquifex/Hydrogenobacter lineage
• Photosynthetic
domain bacteria - radioresistant cocci
Resistant to very high doses of radiation
• Multi-layered cell wall combined with an outer membrane and excellent DNA repair functions
make this group highly resistant to radiation
domain bacteria - spirochetes
Flexible helical shape
• Known to infect humans ex. Treponema pallidum the causative agent of syphilis
domain bacteria - green sulpher bacteria
photosynthetic
domain bacteria - flavobacteria
• Ex. Bacteroides gingivalis a strict anaerobe (cannot grow in the presence of oxygen)
thrives below the gumline causing gingivitis
domain bacteria - clamydiae
Obligate intracellular parasites – cannot grow unless inside the cytoplasm of an
appropriate host cell
domain bacteria - gram positive
Contains the Staphylococcus and Streptococcus sp.
• Significant category for human health
domain bacteria - cyanobacteria
- Photosynthetic
- Important players in a variety of ecosystems
- Release large amounts of oxygen into the environment/ air
- Nitrogen fixation supporting plant growth
domain bacteria - proteobacteria
Contains the Gram-negative species
• Highly variable in shape, metabolism and motility
• Significant category for human health
domain archea - extremophiles
- Prokaryotes living in extreme environmental conditions
- Thermophile (heat)
- Halophile (salt)
- Acidophile (acid)
archea characteristics
Usually have cell walls, but no peptidoglycan
• Unique lipids in the plasma membrane
• Protein synthesis more closely mimics the eukaryotic process
• Methanogens are an important lineage
domain eukarya consists of
protozoa, fungi
protozoa
• Unicellular eukaryotes • No cell wall • Found in aquatic and moist environments • Complex life cyles
protozoan life cycle
- Trophozoite – feeding and reproducing stage
- Under favourable environmental conditions, the protozoa exists in this stage
- Cyst – metabolically inactive
- When environmental conditions are not ideal, the protozoa exists in this stage
parasitic protozoans
Generally exist in the environment as cysts, when they enter a new host they
develop into trophozoites where they feed and reproduce. New cysts are
released back into the environment
4 main types of protozoa
flagellates, amoebae, ciliates, apicomplexa
fungi
Play an important ecological role by recycling nutrients in the environment
• Many fungi have mutualistic symbiotic relationships with plant species; whereby the
plant and the fungi benefit from living together, both receiving the nutrients they
require to thrive
2 types of fungal bodies
- Single celled (ex. yeast)
* Filamentous fungi
4 main phyla of kingdom fungi
- chytridiomycota
- zygomycota
- basidiomycota
- ascomycota
myocoses
fungal infections in animals
