Chapter 5:

Question 1

What is symbiosis?

Answer 1

Relationships that have evolved between individuals

Question 2

What is parasitism?

Answer 2

-A relationship between individuals where one individual (parasite) benefits to the harm of the others (host)
-for example parasite in snails that hypnotises them

Question 3

What is commensalism ?

Answer 3

-A relationship between individuals where one individual benefits and the other is unaffected
-Arctic fox that eats the leftovers of the polar bear

Question 4

What is mutualism?

Answer 4

-A relationship between individuals (usually from different species) where both individuals benefits
-ex: bees and flowers

Question 5

What is the microbiome?

Answer 5

The totality of microbes in an environment

Question 6

How many different species are there on human skin?

Answer 6

-Close to 200 different species per person
-44 on the forearm
-19 behind the ear
-even more in the gut/intestines.

Question 7

How many different enterotypes is there in the microbiome of humans and apes?

Answer 7

-3 enterotypes
-defined by the dominant bacterial type

Question 8

How does evolution vary within each person?

Answer 8

-Different evolution within each person
-Essentially each person is their own ecosystem.
-Each person is their own island

Question 9

Why is the the microbiome mutualism and not parasitism?

Answer 9

Bacteria are incredibly useful: It influences hosts:
-metabolism
-physiology
-maturation of the immune system
-energy balance
-susceptibility to disease
-behavior

Question 10

What is an example of why the microbiome is useful?

Answer 10

Mice living in a sterile environment need to consume 30% more food in order to et sufficient calories

Question 11

Where do the bacteria come from?

Answer 11

-begin acquiring bacteria in utero, continue to gain bacteria over first few years
-The gut can be repopulated (ex: after an illness) by the appendix

Question 12

What did Darwin describe the appendix as?

Answer 12

Something not selected for or against but acquired by common descent

Question 13

Why does the appendix turn out to be still part of human species?

Answer 13

-Likely evolved to repopulate the gut with good bacteria
-During primate evolution, individuals were in small social groups and occasionally alone, could be useful to have a reservoir of bacteria in case of illness.

Question 14

How does appendix seem to have evolved ?

Answer 14

-At least two independent times:
-Once in marsupials
-Once in the ancestor to rodents and primates
-Then lost in the tree shrews and lemurs

Question 15

What did urbanisation result in?

Answer 15

Greater probability of encountering bacteria

Question 16

Why do we have greater probability of encountering bacteria with urbanisation?

Answer 16

-increased population density
-sanitation/hygiene issues

Question 17

What influence did urbanisation play on the role of appendix ?

Answer 17

-May be less necessary because there are other to repopulate the gut
-But if everyone is an “island, repopulation could change your ecosystem

Question 18

Why has urbanisation lead to other problems regarding bacteria exposure?

Answer 18

1)Unfamiliar bacteria
2) Bacteria in the wrong place

Question 19

How is cholera transmitted?

Answer 19

-contaminated water
-cholera bacteria can survive in the acids in your stomach
-moves into the small intestine
-then grows a flagella
-propels them into the intestinal walls
-start to reproduce
-watery diarrhoea which can infect the water someone else drinks

Question 20

Where has cholera erupted?

Answer 20

-In a number of parts of the world
-It can be imported into regions where it was previously absent, and spread if the new region has poor sanitation.

Question 21

What is an example of cholera eruption in a previously “free” country?

Answer 21

-Haiti free since the mid-1800’s
-Cholera epidemic started after 2010 earthquake
-Cholera strain was from Southeast Asia
-Arrived via some aid worker from Nepal
-subsequent storms destroyed already poor sanitation and infrastructure

Question 22

What is the situation in Haiti today?

Answer 22

-18 months without a case
-Between 2010 and 2019
820 000 cases and 9800 deaths

Question 23

How did we combat medical infectious with urbanisation?

Answer 23

-improved sanitation and hygiene
-antibiotics

Question 24

How did bacteriologist Alexander Fleming discover Penicillin?

Answer 24

-Observed a plate culture of Staphylococcus had been contained by a blue-green mold
-The colonies of bacteria adjacent to the mold were being dissolved
-He grew the mold in pure culture and found that is produced a substance that killed a number of disease-causing bacteria.

Question 25

Who wanted to produce bigger quantities of penicillin?

Answer 25

-Andrew Florey and Ernst Chain -woman brought a moody cantaloup -Enough was produced for allied troops in WW1

Question 26

When did the first antibiotic resistant strains start to appear ?

Answer 26

-1943

Question 27

What is resistance bacteria ?

Answer 27

Those bacteria with genes that enable them to survive and reproduce in the presence of an antibiotic

Question 28

How do you en dup with antibiotic resistant bacteria?

Answer 28

-By natural selection -Some indiv have mutations that protect them against antibiotics (resistance level) -Change in the environment introduces selection pressure on the bacteria that are not resistant ex: bacteria is inside the pressure and selection pressure starts happening when the person starts taking antibiotics -the frequency of the alleles for resistance will be higher in the next generation

Question 29

What are the 3 classes of antibiotics ?

Answer 29

-Based on what the antibiotics interfere with -Cell wall synthesis -Nucleic acid synthesis -Protein synthesis

Question 30

Cell wall synthesis?

Answer 30

Bacteria build protective cell walls around themselves for protection

Question 31

Nucleic acid synthesis?

Answer 31

Bacteria must copy DNA to reproduce, if bacteria can't make DNA, they can't reproduce

Question 32

Protein synthesis?

Answer 32

Bacteria need proteins to do things (build cell walls, copy DNA, etc...)

Question 33

How do antibiotics work?

Answer 33

-Many ways for antibiotics to target a bacteria -Many ways for a bacteria to be antibiotic resistant -Some bacteria have multiple defences against antibiotics -For some multi-antibiotic resistant strains there are no antibiotics that can kill them

Question 34

What are the different adaptations that make bacteria antibiotic resistant?

Answer 34

Bacteria use these different adaptations to defend themselves against antibiotics: -drug modification: bacteria alter the antibiotic so they don't work properly -drug degradation: bacteria break down antibiotic -reduced drug accumulation within the bacteria: bacteria prevent antibiotic from getting inside or pushes it outside.

Question 35

How specific is the bacteria with the class of antibiotics they counter?

Answer 35

They have evolved ways to counter EACH class of antibiotics

Question 36

What are the multiple ways in which bacteria can gain antibiotic resistance ?

Answer 36

1) From other bacteria: horizontal transfer 2)From viruses 3)From dead bacteria 4)From the environment 5)Bacteria pass on resistance genes when they reproduce (by fission)

Question 37

What are the two ways bacteria store DNA?

Answer 37

Chromosomal DNA:usual form of DNA Plasmid DNA

Question 38

How does plasmid DNA work?

Answer 38

-replicate independently of chromosomal DNA -contain genes important for survival including those for antibiotic resistance or for producing toxins -can be passed by horizontal gene transfer

Question 39

How does horizontal gene transfer work?

Answer 39

plasmids are copied an transferred to other bacteria

Question 40

What can we say about the speed of the spread of genes for antibiotic resistance?

Answer 40

-Spread in the absence of reproduction: through horizontal transfer without needing to reproduce -Reproduction is asexual: ALL offspring will have the resistance allele -Reproduction is fast -The generation time for bacteria is quick: multiple generations produced in hours

Question 41

What happens when you have a bacterial infection and take antibiotics?

Answer 41

-selection pressure: only bacteria with genes for antibiotic resistance will survive -selection bacteria also on other kinds of bacteria in the microbiome -good bacteria can be depleted -can be filled with other bacteria, alters the local ecology of your microbiome

Question 42

What is the current status of antibiotic resistance in bacteria?

Answer 42

-For penicillin, resistant bacteria developed within a year -So created semisynthetic antibiotic that have a ring bacteria can't break -But same thing happened. Bacteria didn't break the ring but resisted in another way

Question 43

Why can't we just keep making new antibiotics to counter antibiotic resistance?

Answer 43

-They're not used for very long -We should use them less frequently overall especially the most effective antibiotics to try to prevent resistance to them because the more you use the more resistance there will be. -Lifestyle drugs have better payback for pharmaceutical companies -Because of this, alot of major pharmaceutical companies have stopped doing programs to develop new antibiotics.

Question 44

When and where is selection acting? (Use of antibiotics)

Answer 44

-Agriculture -Higher levels of resistance in people who live near to large livestock compared to people who live further away -European Union and Scandinavian countries have tighter regulations on the use of antibiotics in agriculture, it has been effective in reducing resistance in some cases. -Also selection in humans

Question 45

How do we counter antibiotic resistance in humans?

Answer 45

-Treating each infection sufficiently but only when necessary -Immune system can deal with some infections, so we should treat only the infections that the immune system can't deal with. -Avoid treating the wrong disease: antibiotics are effective against bacteria but not viruses

Question 46

What is the problem if you treat the wrong disease with antibiotics?

Answer 46

-If you have a virus and are given antibiotics because your symptoms suggest that selection pressure will still act on the microbiome, so some good bacteria might be destroyed.

Question 47

Are vaccines an alternative to antibiotics?

Answer 47

-Yes when we have them -Vaccines trait the immune system to recognize bacteria and infections -Bacteria are less likely to develop resistance to them