Module 1; Lecture 5, evolution and you Flashcards
Symbiosis
Relationships that have evolved between individuals
There are how many categories of symbiosis? name them
3 ( that we will talk about)
1. Parasitism
2.Commensalism
3.Mutualism and Co-evolution
What is parasitism?
A relationship between individuals where one individual benefits (parasite) to the harm of the other ( host) Examples:
1. Parasitic wasps who lay their eggs inside of caterpillars, caterpillar dies but it serves as a nice home for the offspring of the wasps
2. Particular parasites that live inside the mouth of fish
3. tics
4. bedbugs
5. mosquitos
6. a crazy example ( video example) are snails who eat a parasite turning them into a zombie, parasite take over brain and all components, snails become possessed. Now snails look like maggots the favourite food of birds, the bird attacks and the parasite attacks. life cycle of parasite in snails never end because the other snails feed on bird poop which is full of parasites.
Examples of Parasitism?
- Parasitic wasps who lay their eggs inside of caterpillars, caterpillar dies but it serves as a nice home for the offspring of the wasps
- Particular parasites that live inside the mouth of fish
- tics
- bedbugs
- mosquitos
6.
What is commensalism
A relationship between individuals where one individual benefits and the other is unaffected.
Examples of commensalism?
- Sharks are often surrounded by other fish that will eat what the shark doesn’t finish but the shark isn’t bothered by them necessarily.
- Similarly, Polar bears might be followed by Arctic foxes eating the left overs
Mutualism and Co-evolution
A relationship between individuals ( usually from different species) where both individuals benefit.
Examples mutualism and co-evolution
1.Hummingbird and flowers / bees and flowers
2.The relationship between humans and bacteria.
Microbiome
The totality of microbes in an environment ( us humans can be included as the environment)
How many different species per person? Forearm/behind the ear?
- On human skin, close to 200 different species per person
- 44 on forearm
- 19 behind the ear
- even more species in the gut/intestines
How many enterotypes are in humans and apes ?
3 enterotypes in humans and apes ( don’t need to remember the group names)
How are the enterotypes defined?
These are defined by the dominant bacteria type
Why mutualism and not parasitism ?
turns out that bacteria is super useful for us humans
Bacteria has an influence on what?
1.Metabolism
2.Physiology
3.Maturation of the immune system
4.Energy balance
5.Susceptibility to disease
6. Behavior
How much more food do mice living in sterile environments need to consume?
They will need to consume 30% more food in order to get sufficient calories.
Why do mice eat less in the wild?
Because they would contract gut bacteria, those bacterias help with digestion (pulling out more nutrients out of the food), so the mice don’t have to eat as much because they can get the same out of less.
When do we start acquiring bacteria?
Babies begin acquiring bacteria in the Utero, continuing to gain bacteria over the first few years of life.
TRUE OR FALSE; THE GUT CAN BE REPOPULATED
TRUE, The gut can be repopulated ( For example, after an illness, stomach flu for example) by the appendix.
How did darwin explain the appendix
Darwin described as something not selected for or against but acquired by common descent ; just kept getting passed down from generation to generation for reasons that he couldn’t explain.
What does the appendix do?
Likely evolved to repopulate the gut with “Good” bacteria.
How many times does the appendix like structure seem to have evolved?
2 independent times; An appendix-like structure seems to have evolved at least two independent times**
1.Once in marsupials Tree shrews Lemurs
2. Once in the ancestor to rodents and primates (then lost in tree shrews and lemurs
Primate evolution and appendix
During primate evolution:
–Individuals lived in low density social groups
–Individuals occasionally alone
–Could be useful to have a reservoir of bacteria in case of illness because not always guaranteed that you could get more
What has Urbanization resulted in?
-Urbanization has resulted in greater probability of encountering bacteria.
-sanitation/hygiene issues
- ex; increased population density ( like montreal before and now)
Is the appendix important now?
yes, but less, appendix may be less necessary now then it was before in the course of human evolution because there are other ways to repopulate the gut because you wont go long without running into more bacteria since the area is dense in population.
What if everyone is an island repopulation?
Everyone would have a changed ecosystem
Why is it an issue to have greater probability to encounter more bacteria ( due to urbanization)?
1.Unfamiliar bacteria (while you might interact well with certain bacterias it might not be the case for all bacteria)
2.Right bug wrong place
What is an example of unfamiliar bacteria?
Cholora
How is Cholora transmitted?
Transmitted through contaminated water
Explain Cholora;
- Gives really bad watery diarrhea and thats how it gets put back into the water system and given to other people if sanitation is poor.
- Over the years, its spread around the world like more and more regions have had outbreaks.
How is Cholera spread through countries, what is the given example of this and the outcome today?
Poor sanitation = Can be imported into regions where it previously was absent & spreads because of poor sanitation…
Thats what happened in haiti, following the 2010 earthquake, people from around the world came to help out, some peopel from Nepal particularly were contaminated and since all their infrastructures were destroyed.
Today haiti has gone 18 months without a case but between 2010 and 2019, estimated total of 820 000 cases and almost 10 000 deaths…
what does right bug wrong place stand for?
Some bacteria might do well in areas but be dangerous in others…
What happens when this right bug gets in the wrong places?
Infections
How do we cure infections
antibiotics
Can antibiotics help viruses
NO, antibiotic are useless for viruses
What is one of the biggest discoveries of the 20th century?
Antibiotics: One of the biggest discovery of the 20th century were antibiotics to protect us against these sorts of bacterial infections
Penicillin ? ( founder & year)
Penicillin, 1928, Alexander Fleming
Alexander flemming parcour
- 1930s how to make larger substances of penicillin; asked people worldwide to send over all moldy subjects.
- 1942, they were able to produce enough penicillin to use on troops in world war 2
- 1943, the first antibiotic resistant strains started to appear
Resistant bacteria
Those bacteria with genes that enable them to survive and reproduce in the presence of an antibiotic.
How is there Rise of antibiotic resistance?
- Natural selection; Some individuals have mutations that protect them against antibiotics ( resistance level)
- Then, there is a change in the environment that introduces selection pressure on the bacteria that are not resistant
- Frequency of alleles for resistance will be higher in the next generation.
NATURAL SELECTION—>CHANGE IN ENVIRONMENT= SELECTION PRESSURE–>FREQUENCY OF ALLELES GOES UP
How many classes of antibiotics?
3 classes of antibiotics based on what the antibiotics interfere with within the bacteria.
How do antibiotics work?
Some bacteria have developed multiple defenses against certain antibiotics.
True or false, for some multi-antibiotic resistant bacteria strains there are no antibiotics that can kill them
True
What are the adaptations that make a drug resistant ?
- drug modification; Bacteria alter the antibiotics so that they don’t work properly
- drug degradation: Bacteria produce substances to break down the antibiotics.
- reduced drug accumulation within the bacteria; Bacteria prevent antibiotics from getting inside.
Bacterias gaining antibiotic resistance in multiple ways
1.From other bacteria ( horizontal transfer)
Bacteria store DNA in two ways
2. Horizontal Gene transfer : Plasmids are copied and transferred to other bacteria.
3. From viruses
4. From dead bacteria
5. From the environment
6. Bacterias pass on resistance genes when they reproduce ( by fission)
what are the two ways bacteria stores DNA?
Chromosomal DNA and plasmid DNA ( replicate independently of chromosomal DNA, can contain genes important for survival including those for antibiotic resistance, can be passed by horizontal gene transfer)
TRUE OR FALSE; Genes for antibiotics resistance can spread rapidly
TRUE
Reproduction of genes
- Spread in the absence of reproduction : Horizontal transfer
- Reproduction is asexual; All offspring will have resistance alleles
- Reproduction is fast
- Generation time is quick: Bacteria produce multiple generations in hours( not years)
== Plenty of opportunity for mutation
How quick is the generation time of bacteria , this being the reason for what?
Bacteria produce multiple generations in hours( not years) = Plenty of opportunity for mutation
What does this mean for the microbiome? what does antibiotics provide ?
Antibiotics provide selection pressure: Only bacteria with genes for antibiotic resistance survive
- In the process of taking the antibiotic, good bacteria can by depleted
What can we do about antibiotic resistance?
Make new antibiotics ; drug development
Issues with making new antibiotics( drug development)
- Not cost effective to create new antibiotics
- Relying on creating new antibiotics is not a long term solution
What kind of drugs promise the best pay back?
Lifestyle drugs; antidepressants, diabetes drug, those promise much better pay back because people need those and use those all the time vs antibiotics we need to reduce use.
Agriculture
Operations often vent air from inside the buildings then pump in clean air, the air that is vented is often full of stuff, including bacteria. Samples from the air finds strains of bacteria that are the same as those found inside. This aerosol of bacteria can spread to nearby communities. = Higher level of MRSA in people who live near to large livestock operations vs people who live in communities farther from the operations.
Who has tighter regulations on the use of antibiotics in agriculture?
The European and all the Scandinavian countries = tighter regulations on the use of antibiotics in agriculture
When and where is selection acting?
Treating each infection sufficiently, but only when necessary.
How do you treat infections sufficiently?
- Taking the full course of antibiotics can reduce the number of bacteria that survive
- The immune system is capable of dealing with bacterial infections ; treat only those infections not clearing up naturally
- Avoid treating the wrong disease; antibiotics only effective for bacteria but not for viruses.
Why is it a problem to treat wrong disease?
Because that increases potential for antibiotic resistance
Vaccines as an alternative
Vaccines train the immune system to recognize bacteria and infections, so that bacterias are less likely to develop resistance to them, making them an alternative to antibiotics
