Lecture 3: Bacteria and Archaea Flashcards
How can Prokaryotic tolerate extreme conditions?
- High Salinity
- Radiation
- Low pH
- Extreme temp (hot/cold)
- In rocks below earth’s surface
Who developed Gram Staining?
Hans Christian Gram
What is the purpose of Gram Staining?
Determines the type of bacteria
Color posses in Gram +
purple
Color posses in Gram -
pink
What do cell wall contains in Prokaryotes and what purpose does it serve?
Maintains cell shape and contains peptidoglycan
Prevents cell from lysing (cell bursting)
Gram + vs Gram -
Gram (+) => - high peptidoglycan
- Stain Purple
- use antibiotics that inhibit peptidoglycan cross- linking
Gram (-) => - thin layer of peptidoglycan
- Outer membrane containing lipopolysaccharides (lipoprotein)
Capsule def
Cell wall surround by sticky layer of polysaccharide (protein)
Functions of Capsule
- Adhere to substrate
- Protects against dehydration
- Shield pathogenic prokaryotes from attack by their hosts immune system
Endospores def
Bacteria develop resistance cells to withstand harsh conditions
Function of Fimbriae
Allow prokaryotes to stick to their substrate or to one another
Function of Pili
Appendages that pull two cells together prior to DNA transfer from one cell to the other
Also called Sex Pilus (exchange in genetic info)
Motility (moving)
How do prokaryotes move?
Half are moved by taxis
Taxis- directed movement toward or away from a stimulus
Stimulus= Chemotaxis (+ or -)
(+) Effect of Chemoattractants => towards
(-) Effect of Chemoattranctants => away
Function of Flagella
Common structure that enable prokaryotes to move
- Arose independently
- Analogous structures
Internal Organization and DNA (prokaryotes)
- simple
- circular chromosomes (dsDNA)
- Plasmids (smaller rings of independently replicating DNA molecules)
- Replication is similar but ribosomes are different
Reproduction of Prokaryotes
Reproduce by Binary Fission (asexual)
- very short generation times
Would you expect low or high levels of genetic diversity within prokaryotes?
High levels
3 High levels of genetic diversity are due to…
Rapid Reproduction
Mutations
Genetic Recombination
The significance of and mechanisms (3) by which recombinant bacteria form
Three mechanisms:
- Transformation
- Transduction
- Conjugation
Significance:
= Transformation- Cell is recombinant; cell surface proteins recognize foreign DNA from a closely related species & transport it to cell
= Transduction- bacteriophages carry prokaryotic genes from one host cell to another
= Conjugation- DNA is transferred b/w 2 prokaryotic cells (usually of the SAME SPECIES) that are temporarily joined; forms temporary “mating bridge” by sex pilus
Compare and contrast the mechanisms (3) [great short ans/ essay question]
Transformation deals with taking in foreign DNA (genetic material) through the cell membrane and into its genome.
Transduction is a bacteriophage injecting the foreign DNA into the hosts cell.
Conjugation is DNA being joined by 2 prokaryotic cells (same species) by a temporary “mating bridge” (sex pilus)
Compare: mechanisms that allow DNA to be transfered from one cell to another.
F plasmid (F+ cell) vs. Hfr cell (donor)
F plasmid (+) = fertility factor in plasmid
- part of chromosome transferred
Hfr cell= [High Freq recombination] fertility factor is located bacterial chromosome (whole transferred)
Nutritional & Metabolic Adaptations
Phototrophs
derive energy from light
Chemotrophs
obtain energy from chemicals
Autotrophs
need only CO2 or related inorganic compounds as a carbon source (photosynthetic)
Heterotrophs
require @ least one organic nutrient (ex: glucose)
Role of Oxygen in Metabolism
Obligate aerobes
MUST use O2 for cellular respiration and CANNOT grow without it
Obligate anaearobes
Poisoned by O2 and some live by fermentation, other extract chemical for anaerobic respiration
Facultative anaerobes
use O2 if its present BUT can also carry fermentation or anaerobic respiration
Nitrogen Metabolism
- production of AA and nucleic acids
- Prokaryotes can metabolize nitrogen in many forms
Nitrogen Fixation
- some cyanobacteria can convert to atmospheric nitrogen to AMMONIA
- incorporated into AA and other organic molecules
Two Domains in Prokaryotes
Domain Archaea
Domain Bacteria
What plays a key role in the evolution of prokaryotes?
Horizontal gene transfer
- genetic diversity is immense
Alpha Proteobacteria
Mitochondria may have evolved from aerobic alpha proteobacteria
Beta Proteobacteria
Aquatic and soil bacteria as well as the species that causes gonorrhea
- Recycling Nitrogen
Gamma Proteobacteria
Include Legionnaires’ disease, Salmonella,
cholera, & E. coli
Delta Proteobacteria
slime- secreting myxobacteria
Epsilon Proteobacteria
Most are pathogenic to human or other animals
- Blood poisoning, stomach ulcers (Helicobacter pylori)
Archaea
- Extremophiles (known as loving extreme conditions)
halophiles - live in high saline environ
Thermophiles- live in very hot environ
Importance of Prokaryotes in biosphere
Chemical Recycling
- Function as decomposers
- Convert molecules to forms that can be taken up by other organisms
Symbiosis
Two species live in close contact w/ each other
Mutualism
Both species benefit
- E. coli in your intestines helps absorb vitamin K
Commensalism
One species benefits while other is neither harmed nor helped
Parasitism
Eat cell contents, tissues, or body fluids of host
- harm but usually don’t kill their host
Pathogens
disease causing bacteria
Cyanobacteria
- Photoautotrophs
- Gram (-)
- ONLY prokaryotes that perform PLANT-LIKE, O2 producing photosynthesis
- ancestral species form which chloroplasts evolved
