microbes lecture 1- fundamentals in microbiology Flashcards
what are symbiotic relationships?
the association of 2 or more partners in micro organisms, animals and surfaces
what are types of symbiosis?
mutualism- may rely on each other for survival
commensalism- one organism benefits while the other remains unchanged
parasitism- one species benefits at the expense of the other
what population exceeds us in terms of abundance and diversity?
the microbial population. a lot remains unknown about these relationships, specifically in relation to health and disease
what are examples of human-microbe relationships?
These interactions are not new!
Egyptian mummies and TB (600 BC)
Black Death – up to 200 million deaths (mid 1300s)
Irish potato famine - Phytophthora infestans (1840s)
Our relationship continues to change
HIV pandemic
- First cases early 1980s
Zika epidemic in the Americas
2015-2016
Mosquito-borne viral infection
Ebola in West Africa
- First recognised 1976
- First case of 2014 outbreak; 2 yr old died in 2013 in Guinea
what is the mutualism between mycorrhizae and other organisms?
Over >80% of plants are associated with mycorrhizae e.g. trees, crops, plants, highlighting how important they are, but there are other advantages to plants
-Obtain immobilised nutrients e.g. phosphate, iron
-Speed up decomposition of organic matter
-Increased resistance to disease
-Remove heavy metal toxicity
Mycorrhizae (myco = fungi, rhiza = root)
Fungal mycelium associated with plant roots
Fungi attach to the roots and allow root extension
In exchange, the plant provides sugars to the fungi
what are other types of commensalism?
Colonic bacteria provided with a niche in the host
Organisms synthesise vitamin K and folate, metabolised by host
Ruminococcus spp. can be found in high numbers in the gut and involved in cellulose breakdown.
A product produced by one organism can be beneficial to the other organism
-Bacteroides (and other obligate anaerobes) benefit from Escherichia coli
-Staphylococcus epidermidis utilises dead skin cells without causing harm
-We’re reliant on many gut microbes e.g. Bifidobacterium, Bacteroides
- breakdown or generation of metabolites
what happens in parasitism?
Parasitic microbe live or multiply within/on the host, causing damage in the process
such as mosquitos, anthrax virus, histoplasmosis and ebola virus
what are opportunistic pathogens?
Do not normally cause disease
-Candida albicans (candidiasis)
-Pseudomonas aeruginosa (burn-related infection)
-Toxoplasma gondii (toxoplasmosis)
-Herpes simplex virus (cold sores)
what is zoonosis?
an infectious disease transmitted to humans from animals
what is kochs postulates?
1) the suspected pathogen must be absent in all healthy individuals but present in all diseased hosts
2) the pathogen must be isolated and grown in pure culture from all diseased patients
3) the pathogen must cause the same disease if sued to inoculate the healthy host
4) the same organism must be reisolated from the inoculated diseased host
what did Stanley falkow say in 1988?
Stanley Falkow (1988) – ‘father of molecular microbial pathogenesis’
Isolation of genetic material enables pathogen identification
Specific genes correlate with disease
Knockouts linked with disease reduction
what is pathogenicity?
the ability to cause disease
what is virulence?
the degree of pathogenicity of an organism e.g. infectivity/ intensity
what is a microbiome?
Large and mixed population of microorganisms coexisting together under many circumstances.
what is phenotypic switching?
- increased adherence
- biofilm development
- invasion
