Topic 6: Evolution and You: Bacteria and Viruses Flashcards
Parascitism
One organism benefits
One suffers
Commensalism
One organism benefits, the other is not affected
Mutualism
Both organisms benifit
Microbiome
The totality of microbes in an environment (can be a human)
3 enterotypes in human microbiome
What do bacteria do for us? (6 things)
How many kcals do mice need if they are in a sterile environment?
help
metabolism physiology maturation of immune system energy balance susceptibility to disease behavior
Mice living in a sterile environment need 30% more kcals
Where do bacteria come from (in microbiome)
Babies get some in utero and continue to get some over the first few years
The appendix - function
and when did we evolve it/why?
Darwin thought this had been evolved and was a left over, no longer useful
Actually, likely evolved to repopulate the gut with good bacteria.
In primate evolution
Individuals lived in low density populations
Occasionally alone
Useful to have a reserve of bacteria in case of illness
The appendix evolution
Evolved in two independent times
for marsupials and for ancestors of mammals and rodents (lost in the lineages of tree shrews and lemurs)
Urbanization
Big increase in urbanization globally
Increased pop density and sanitation issues
Possible that appendixes are less useful today
Cholera
Drink infected water
Moves into small intestine
Grow flagella and go into intestinal walls
Reproduce
Illness - watery diarrhea
Lots of spread into place there has historically not been any. Due to human movement.
Haiti - free since the 1800s Earthquake Aid workers from Nepal Not much infrastructure cos of hurricane Sandy Big outbreaks
Problems with urbanization
Unfamiliar bacteria
Bacteria in the wrong place
Strep pneumoniae
Usually colonises human skin
In other places, skin abcesses, and other serious health conditions
Staph
Skin
MRSA exists
What has helped cut down infections (2 things)
Sanitation development
Antibiotics
Penicillin
Alexander Fleming observed agar plate around blue-green mold was clear of bacteria
Found that the mold produced a substance that killed bacteria and called it penicillin
Florey and Chain researched how to make larger quantities. A woman in Peoria, Illinois brought in a moldy cantaloupe.
Very fast to produce. By 1942 was enough to use on ww2. By 1943 was an antibiotic resistant strain
Natural selection and antibiotic resistence
Population mutates as normal
Introduce antibiotics
Some have resistant characteristics
The antibiotics create a selection pressure in favor of these genes
The frequency of these alleles will be greater in the next generation
3 ways antibiotics can work
Attack cell wall synthesis
Attack nucleic acid synthesis
Attack protein synthesis
Ways bacteria target antibiotics (3)
Drug modification - change the drug so it does not work
Drug degradation - break down the drug
Reduce accumulation -0 prevents bacteria getting inside or the build up of it
Bacterial plamids
Contain DNA, often of stuff that is important for survival
Can replicate independently of the bacterial chromatid
Horizontal gene transfer - bacteria
Donor makes a Philus and connects to recipient
Plasmid duplicates
Basses between the two cells
Both not have plasmid
5 ways bacteria gain antibiotic resistence
From other bacteria (horizontal transmission)
From viruses - gets infected but gains DNA
From dead bacteria
From the environment
From reproduction (fission)
Bacterial fission
Very fast (hours)
Asexual, all offspring would have resistant alleles
The generation time is also really fast so there is plenty of opportunity for mutation
Microbiome and antibiotics
Take antibiotics for an infection
Selection pressure, only bacteria with genes for resistance survive
In the process, good bacteria can also be depleted
These dead bacteria can be replaced by another species, altering the local ecology in your environment
There is lots of resistence
Bacteria find new methods of resistance quicker than we develop antibiotics.
