Genetics of Human Pathogens Flashcards
Define pathogenicity
the ability of a pathogen to cause disease in a host.
Define virulence
the severity of the disease a pathogen causes.
In a growing population…
…new diseases are inevitably going to emerge.
Innate immune response is the…
…skin
What must a pathogen do for success?
Colonise the host
Locate a nutritionally compatible niche (in order to grow and reproduce, moves towards the nutritents)
Evade host immune response (innate and adaptive)
Replicate (using host resources)
Exit and spread to new host ( coughs, sneezes, other symptoms like diarrhea).
Types of Human Pathogens
Bacteria (Vibrio cholerae – cholera, 1.3 to 4.0 million cases)
Viruses (varicella-zoster virus – chicken pox)
Protists (protozoa - Plasmodium falciparum – malaria)
Fungi (Aspergillus species – lung infections)
Parasitic worms (flatworms, roundworms)
Prions (proteinaceous infectious particle - Creutzfeldt-Jakob disease )
Function of cell wall in prokaryotes?
maintains shape of bacteria cell
Cell capsule function in prokaryotes?
protects cell from immune response – acts as a shield
Prokaryotes contain dna in the form of a…
…circular chromosome.
Describe endotoxins
They are part of the bacterias cell wall
They are released from a bacteria once the cell wall is compromised and the bacteria dies.
This triggers the immune system
Endotoxins can also be released during spore formation
Describe exotoxins.
Released by bacteria into the environment
Polypeptide proteins
Deliberately released
Mostly released by gram +ve bacteria.
Define Lysis
when a bacteria cell dies/breaks down. This causes the release of more pathogenic agents.
How can viruses hide from cells?
Viruses can hide from cells by putting their dna into the chromosomes of a cell.
What is the name of the pathogen which causes malaria?
Plasmodium falciparum
In what temps do fungi thrive in?
Fungi thrive in lower temperatures, not higher temperatures.
Whats the name of the fungi pathogen?
Aspergillus fumigatus
How do u get Aspergillus fumigatus
(fungi)?
from breathing in aspergillus fumigatus fungus which is found in soil
How common is Aspergillus fumigatus ?
Rare
Who most likely to get Aspergillus fumigatus?
immunocompromised individuals are most likely to get this. For example, someone who already has aids.
Where do parasitic worms survive in the body?
Worms are able to survive the conditions of the stomach.
How does someone get parasitic worms?
You can get this from undercooked food eg burgers.
How do worms increase in number?
The worm secretes lots of eggs in the stomach. They have these in sacs – proglottid.
Whats CJD caused by?
prions
WHats a prion?
abnormal, pathogenic agents that are transmissible and induce abnormal
folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain.
Endo/exo toxins are critical to…
…the growth and replication of cholera. Key to its pathogenicity.
Whats TCP?
a spike protein sticking out of the surface of the bacteria. ( type 4 in cholera ). Important for colonisation.
Main symptoms of cholera?
watery diarrhoea due to increase of water secretion from lumen into the gut.
Why is diarrhoea effective for spread of bacteria?
This is there exit route which is their way of spreading, making them an effective and fit bacteria.
Whats a plasmid?
A plasmid is a small DNA molecule which is extra to the chromosome. Contains very few genes but can give the bacteria and evolutionary advantage.
What do virulence genes encode for?
virulence factors (proteins)
What are virulence factors?
molecules that assist the bacterium with host colonisation
These factors are either secretory, membrane associated or cytosolic
Describe pathogenicity islands?
Compact and distinct genomic islands which contain many virulence genes.
How are pathogenicity islands acquired?
Horizontal gene transfer
What does horizontal gene transfer lie behind?
lies behind the spread of antibiotic resistance.
Natural populations of many pathogens have a…
…clonal structure.
In some cases, single clones are responsible for …
…geographically widespread disease.
HGR - important contributions to…
…bacterial evolution
Horizontal Gene transfer is a process in which …
…an organism incorporates genetic material from another organism without being its offspring
Horizontal gene transfer involves the transfer of…
…genes between cells of the same generation in two different species
Groups of virulence genes are …
…transferred together
Horizontal gene transfer (HGR) alows bacteria to…
…inhabit new hosts and cause disease
Horizontal Gene Transfer is common in…
…bacteria, rare in eukaryotic cells
WHat are the mechanisms of bacteria gene transfer?
- Transformation
- Conjugation
- Transduction
Define transformation in bacterial gene transfer.
when bacteria break down, their components are released into the environment such as dna. Some bacteria have the ability to be naturally transformed. A bacteria cell takes up the dna from a dead cell.
Define conjugation in bacterial gene transfer.
due to F plasmids. F = fertility. Like bacterial sex. Two cells come together and a pillar forms between them. One cell then donates a plasmid to the other. Also donates some of the bacterial dna. The bacteria aims to replicate itself.
Why do viruses hijack other cells in order to replicate?
Viruses do not have their own machinery for dna replication so hijack other cells in order to replicate.
Bacterial, fungal and parasitic pathogens are living cells which have their own…
…machinery for DNA replication, transcription & translation, and have their own source of metabolic energy.
Viruses carry little more than…
…nucleic information
Size of virus genomes?
viruses have small genomes
Viruses consist of…
…double-stranded DNA or single-stranded RNA
How many and what proteins do viral genomes encode?
- proteins for replicating the genome
- proteins for packaging the genome & delivering it to more hosts
- proteins for modifying the structure or function of the host cell to enhance the replication of the virus
Whats a virion?
viral particle
Describe steps of viral replication [DO NOT MEMORISE FOR EVO GEN EXAM JUST READ THROUGH]
Entry into host cell
Disassembly of the
infectious virus particle
Viral genome replication
Transcription of viral genes
Synthesis of viral proteins
Assembly of viral components into
progeny virus particles
Release of progeny virions
Virion interacts with…
…receptors on the plasma membrane of the cell.
The virus can change…
…its structure to match the shape of the receptor.
Virus enters host cell via…
…endocytosis
Hypothesis about where viruses originated from?
Hypothesis - viruses originated from sections of cellular nucleic acids that moved from one cell to another - injured cell surfaces
Viruses cannot…
…replicate their own genes.
Original sources of viral genomes include …
…plasmids and transposons
plasmids and transposons are…
… mobile genetic elements.
Antigenic variation as a result of …
…error prone replciation
Mutation improves …
…infection efficiency
Viruses evolve faster than …
…their hosts.
Viruses swap DNA and RNA in a process called…
…recombination
What happens in recombination?
Viruses swap DNA and RNA in a process
What causes evolution and genetic variation in influenza?
Randommutation
What happens in random mutation?
a change occurs in the DNA or RNA sequence of a virus.
What are zoonoses ?
- infectious diseases that spread from non-human animals to humans
Whats a zoonotic virus?
originate from animal populations.
Examples of zoonotic viruses?
Ebola, MERS-CoV, SARS-CoV-2
Mutation may provide …
…resistance to a drug
Reverse transcriptase inhibitor?
nevirapine
Fungal and Protozoan Parasites are…
…eukaryotes
Difficult to find drugs that will kill Fungal and Protozoan Parasites without…
…killing the host.
Why are Fungal and Protozoan Parasites diificult to treat?
different forms during their life cycles
Malaria caused by…
…4 species of Plasmodium
How is malaria transmitted to humans?
Transmitted to humans by female Anopheles mosquito
Plasmodium falciparum - most serious form of malaria
- requires human and mosquito hosts to complete sexual cycle
