The Antisocial Microbe - Introduction To Pathogens Flashcards
Cellular types of pathogen
Single celled (fungi/protists) Multicellular eukaryotes (tapeworm etc) Bacteria 🦠
Acellular types of pathogen
Viruses (including bacteriophage)
Prions
What is a prion pathogen
An infectious particle made up of misfolded proteins
Example of a prion disease
Kuru
What is a bacteriophage
A virus that infects and replicates within bacteria and archaea
Explain lytic bacteriophage life cycle (4)
- Phage from environment infects bacterial host
- They replicate inside the host at its expense
- Bacterial lysis (death) and phage particles are released back into environment
- New phage particles infect another bacterial host
Main difference between lytic and lysogenic cycle
Lytic cycle destroys host cell but lysogenic cycle does not
Lytic phage
Bacterial cell lysed and viral progeny leaves host to find new hosts to infect
Lysogenic phage
Bacterial host not lysed. Viral genome integrates within host DNA and replicates alongside it
Most abundant biological entity on the planet?
10^30 bacteriophages
What do many pathogens require?
Host to host transmission because they don’t reside in an environmental reservoir
Example of a pathogen that reside permanently in a host without an environmental reservoir
Chlamydia trachomatis
Vertical transmission
Passing of infections from parent to offspring
Horizontal transmission
Passing of infections among different individuals
Example of vertical transmission of pathogens in humans
Transfer of a pathogen from a pregnant woman to her foetus
Transfer of pathogen from mother to infant while breastfeeding
Three types of complications that vertical transmission of pathogens in humans can cause
Congenital - infection during pregnancy and can be transferred to foetus
Neonatal - serious complications shortly after birth
Maternal - severe disease during pregnancy but not transmitted
Example of a virus that hosts can become immune to
Measles virus
Once infected with measles …
A single infection of measles provides long term immunity
Acute infections
Occur in short period of time, in this time they pas in to new host
Chronic infection
Pathogen remains dormant in host but can be reactivated to become infectious
What’s a disadvantage of acute infections
The pathogen is vulnerable because the host might die or gain immunity
But in chronic infection the pathogen can live there for a while
i think slide 9
What causes chicken pox and shingles?
Varicella zoster virus
Before shingles occurs where is the virus dormant
In the sensory ganglia
Then it’s reactivated
How does varicella zoster virus spread
Local replication, lymphoid tissues, T cells
What are dead end hosts
Species which have received pathogen for one host but are not able to pass on transmission of this pathogen
Pathogen that evolved in one host species can occasionally do what
Infect another host species (this host species may be able to continue to transmit the pathogen or may not - in that case it’s a dead end host)
When might a novel infectious cycle emerge
If a pathogen in one host infects another host (different species) and this second host is able to transmit the pathogen
How does rabies spread long hosts
Biting
Grows in the salivary glands
How does the rabies virus move within the host
Intracellularly in the nervous system
What would a complex life cycle of a pathogen involve
Multiple species (host isn’t just a single species)
Why are complex life cycles of pathogens involving multiple species costly?
Pathogen have to survive in a variety of different environments and evade a variety of different immune responses
Transmission cycle of schistosomiasis
Humans infected by contact with contaminated water
Pathogen penetrates skin of host
Migrates through tissues and resides in veins
Eggs deposited in intestine and released into environment through urine/faeces
Eggs hatch into miracida which infect snails (intermediate host)
Growth of sporocysts in snail and then release of pathogen completing life cycle
Pathogen that causes cervical cancer
Human papillomaviruses
How can microbes cause cancer
Indirect
Direct
Indirect - production of toxic products
Direct - alteration of host cells
A few cancers are what
Infectious
Eg. Devil facial tumour disease
Devil facial tumour disease
Aggressive nonviral clonally transmissible cancer which affects Tasmanian devils
Autocatalytic
One product of a reaction is a catalyse for the same reaction or a coupled reaction
How is prion protein produced
By normal host cells
How can prions be transmitted
Orally
Why are prions unusual
Infection is a particular part of the protein and high is naturally present in mammalian brains
Key point summary
Microbial diseases major source of global morbidity
Microbial pathogens evolved multiple times on tree of life
Predominantly infectious
Many elaborations of infectious and pathogenic lifestyle
Pathogens can have diverse effects on hosts - some necessary for survival and some incidental
