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CHAPTER 27 BACTERIA AND ARCHAEA
Transcript of CHAPTER 27 BACTERIA AND ARCHAEA
Rapid Reproduction, Mutation, and Genetic Recombination
Two domains: Bacteria and Arachea
1/20th the size of eukaryotes
Collective biomass = 10x of all eukaryotes
Adapt easily, genetically diverse
CHAPTER 27 BACTERIA AND ARCHAEA
the three ways prokaryotes reproduce -- transformation, transduction, and conjugation
A change in genotype and phenotype due to the assimilation of external DNA by a cell -- in English, this translates to prokaryotes change because they absorb their surroundings
A type of horizontal gene transfer in which phages (viruses) carry bacterial DNA from one host cell to another
In prokaryotes, the direct transfer of DNA between two cells (of the same or different species) that are temporarily joined.
three factors ---> high genetic diversity (a prereq for natural selection)
bacon bits -- mm, tasty
PLASMIDS: R is for resistance!
- occasional mutation causes antibiotic resistance (e.g. a mutation in one gene makes it less likely that a pathogen will transport a particular antibiotic into the cell)
- bacteria may have "resistance genes", which code for enzymes that hinder certain antibtiotics
- resistance genes are carried by R PLASMIDS.
- by natural selection, resistance to antibiotics has risen.
- problem is compounded by the fact that R plasmids code for sex pili and and enable plasmid transferal,
- R plasmids may carry as many as 10 genes for resistance.
Oxygen in Metabolism
-need oxygen for
-poisoned by oxygen
-energy through other mechanisms
e.g. use nitrate or sulfate
-can metabolize with or without oxygen
3 still water samples
Can you guess which tubes
have which type of bacteria?
-converting nitrogen into forms usable by plants
-some cyanobacteria/methanogens make N2 into NH3
-need light, CO2, N2, water, some minerals (simple)
-essential to Nitrogen Cycle
-most cells: photosynthesis
specialize in nitrogen fixation
e.g. Anabaena (filamentous colonies)
surface-coating bacterial colonies
secrete chemicals to recruit
damaging to health and medical equipment, etc.
-sulfate-consuming bacteria + methane-
consuming archaea = consume products
in the use of
They can withstand just about anything.
- not a problem. Ranges from 113 degrees Celsius in oceans vents to -10 degrees on ice cream. Surface hot springs have prokaryotes that live at 85 degrees C and on the sea floor the temperature is on average -2 degrees C.
- In springs in Iceland, conditions are such so that a certain type of bacteria can live at 11 pH. In the hot Springs of Beppu, Japan a different type, namely
, lives at an acidic pH of 3.
Salinity - prokaryotes survive in both double distilled water and Dead Sea saltwater.
Pressure - From 0.1 atm to 1,000 atm
Radiation - Certain types can rebuild themselves after thousands of breakages in DNA.
Not only this, but compared to prokaryotes we're latecomers. The first prokaryotes appeared around 3 BILLION years ago!
Prokaryotes provide the essential ecological service of liberating nutrients needed for photosynthesis and thus are sustainers of life. For example, in oceans, bacteria liberate nitrogen and phosphorous from organic compounds through oxidation, transforming them to their inorganic form.
Decomposers on a Food Chain
Restoration of other essential elements, like iron and silicon
use carbon dioxide to form organic compounds, and pass these through the food chain
make atmospheric oxygen
Mitochondria are acknowledged today to be descendants of bacteria that were engulfed in a primitive eukaryote and passed down through generations and generations for the past billion years.
Why? Besides the fact that the
mitochondria carry bacterial DNA separate from the rest of the cell,
each one has a double cell membrane, exactly what one would expect if it were engulfed. Similar tests reveal that
chloroplasts are descended from cyanobacteria.
Prokaryotes are key in recycling. Without them, the whole world would quickly starve to death.
Delving into the Nitrogen Cycle
Certain prokaryotes are instrumental in
, the process by which nitrogen gas (N2) is transformed to ammonia via the following reaction:
This process requires 8 electrons and at least 16 ATP molecules, which is why only a select few prokaryotes can reliably undergo this energy intensive process (Nitrogen is very, very stable in its gaseous form).
Of course, nitrogen can be fixed in other, abiotic ways. Another common possibility is through combustion. The next most common, though, is through lightning strikes.
Other processes like nitrification take place exclusively through prokaryotes. Ammonification, denitrification, and and anammox all utilize prokaryotes to some degree. Each chemical reaction is driven by different types of prokaryotes.
Further potential uses from genetic engineering
Tuberculosis, cholera, Lyme Disease, botulism, salmonella, E. Coli, anthrax
Resistance building = perpetual war on disease
Common Shapes of Prokaryotes
Plant - Cellulose
Fungi - Chitin
Bacteria - Peptidoglycan
Archaea - Polysaccharides
Classifying Bacterial Species with the Gram Stain:
- Based on cell wall composition
- GRAM POSITIVE: simpler walls, large amount of peptidoglycan
- GRAM NEGATIVE: less peptidoglycan, structually more complex with outer membranes containing lipopolysaccharides
- Importance in medicine
- Sticky layer of polysaccharide/protein covering
the cell wall
- Enables prokaryotes to adhere to
- Protect against dehydration
- Shield from immune system attacks
Fimbriae: hair-like appendages
The flagella helps makes taxis in bacteria possible
Features that allow for large prokaryotic populations:
1) small size 2) binary fission 3) short generation times
Conditions that check prokaryotic reproduction:
- Exhausting nutrient supply
- Poisoning by metabolic waste
- Being consumed by other organisms
RAPID REPRODUCTION/ MUTATION
: mutations happen rarely. But then how can a whole colony/group/pride/gaggle/ community of bacteria mutate so quickly? The answer is simple.
= more chances for mutations
genetic variation also arises from genetic recombination: the combining of genes from two sources
factor: F is for fertility!
- particular piece of DNA that allows for the formation of sex pili and ability to donate DNA during conjugation
- comes in two forms: chromosomal and plasmid.
Nucleoid: Where a prokaryote's chromosome is located in. Appears lighter than surrounding cytoplasm in electron micrographs.
Plasmids: Smaller rings of separately replicating DNA
Prokaryotes and Antibiotics
Under optimal conditions, many prokaryotes can divide every 1-3 hours. A whole generation can be produced in 20 minutes.
James Wang, Jiying Zou, Jared Nagro, Rebekah Tang, Rebecca Liu
Some bacteria develop resistant cells called endosperms when an essential nutrient is lacking.
Short generation times allow for substantial evolution in short periods of time and rapid adaptation.
1) Gram-negative bacteria have _____ peptidoglycan than gram-positive cells, and their cell walls are _____ complex structurally.
A) more; more
B) more; less
C) less; less
D) less; more
E) none of the above
2. Photoautotrophs are different from chemoautotrophs in that...
A) they don't need carbon
B) they use light rather than inorganic chemicals for energy
C) their carbon source is organic molecules
D) they all have a modified Calvin cycle
E) they are more photogenic
Molecular systematics has shown that prokaryotes have a large amount of genetic differences.
Another thing shown is the importance of horizontal gene transfer in prokaryotes evolution.
Prokaryotes acquire genes from distantly related species over millions of years and still continue to do this.
Illuminates Prokaryote Phylogeny
This phylogenetic tree is based off of molecular data found and its relationships with other prokaryotes.
Archaea have many unique traits that differ from bacteria and eukaryotes.
-"extremophiles" : love extreme conditions.
-extreme halophiles : those that live in extremely high salinity
-methanogens : live in more moderate conditions and use CO2 to oxidize H2, releasing methane as waste
Chrenarchaeotes contain most of the extreme thermophiles, which are those that live in very hot temperatures.
There are 5 major types of bacteria; Proteobacteria, Chlamydias, Spirochetes, Cyanobacteria, and Gram-positive bacteria.
A large and diverse clade of gram-negative bacteria.
Some are anaerobic while others are aerobic.
5 subgroups of Proteobacteria; Alpha, Beta, Gamma, Delta, and Epsilon.
Parasites that can only survive inside animal cells.
They depend on the host for basic materials like ATP.
Helical heterotrophs that move through the environment by rotating internal flagella like filaments.
Many are free living but others are pathogenic parasites.
Have a lot of differences from other bacteria.
Has a diverse structure from gram-negative bacteria.
Photoautotrophs that are the only prokaryotes that have plantlike oxygen-generating photosynthesis.
Present wherever there is water and it provides plenty of food for freshwater and marine ecosystems.
Some have cells that are specialized for nitrogen fixation to make organic molecules from atmospheric N2.
What exactly are
good for? (27.5-27.6)
We know that they're small and numerous
..but how many individuals are there?
In one gram of soil?
In a human's colon?
In the entire world?
How quick reproduction and short life span factor in.
Prokaryotes in Nutrient Cycling
Most prokaryotes form symbiotic associations with
much larger organisms. They form a symbiont-host
3. Plantlike photosynthesis that releases oxygen occurs in:
E) Chemoautotrophic Bacteria
4. Which of the following statements about
prokaryotes is true?
A) Prokaryotes have no industrial uses.
B) The vast majority of prokaryotes are pathogenic.
C) Prokaryotes are widely used for bioremediation.
D) Prokaryotes are not useful in genetic engineering
because their DNA is too different from eukaryotes.
E) It is important to try and rid your body of all
Which of the following is NOT a method of
E) All of the above are methods of prokaryotic