Ch 22: Prokaryotes

background

• first organisms on Eart ~3.5-3.8 BYA

• millions of species (named or not), found everywhere

• live on and in every other living organism

• most benign & many essential to all life

ancient atmosphere

• anoxic

• only anaerobic organisms were able to live

• autotrophic organisms that convert solar energy into chemical energy are phototrophs

• photoprophs appeared within 1 billion years of the formation of Earth

• cyanobacteria, evolved from these simple phototrophs at least 1 billions years later

• ancestral cyanobacteria began “oxygenation” of the atmosphere

• increase in O2 concentrations allowed the evolution of other life forms

anoxic

no molecular oxygen

what is cyanobacteria also known as?

blue-green algae

what did ancestral cyanobacteria begin of the atmosphere?

oxygenation

what is the most abundant photosynthetic organism on Earth?

marine cyanobacteria Prochlorococcus

extremophiles

bacteria and archaea that are adapted to grow under extreme conditions

acidophiles

pH 3 or below

alkaliphiles

pH 9 or above

thermophiles

temperature 60-80C (140-176F)

hyperthermophiles

temperature 80-122C (176-250F)

psychrophiles

temperature of -15-10C (5-50F) or lower

halophiles

salt concentration of at least 0.2 M

osmophiles

high sugar concentration

Deinococcus radiodurans

a prokaryote that can tolerate very high doses of ionizing radiation

prokaryotes in the dead sea

• it is a hypersaline basin that is 10x saltier w/ 40x more magnesium than sea water

• in addition, they have divalent cations (Ca2+), are acidic, and have intense solar radiation (not an easy place to survive) - halophiles

2 mediums for growing prokaryotes in the lab

culture medium and pure culture

what is German phys

culture medium

contains all the nutrients needed by the target microorganism, can be liquid(broth) or solid

• after an incubation time at the right temperature, there should be evidence of microbial growth in the culture medium

• solid: agar - a solidifying agent extracted from seaweed

pure culture

a laboratory culture containing a single species of microorganism

blood agar plates

used to diagnose Streptococcus infections

incubation

to maintain the controlled environmental conditions necessary for supporting growth

blood agar plates: destroyed red blood cells so surrounding media turns clear

left: non-hemolytic streptococcus

right: hemolytic streptococcus

inoculation

process of introducing microorganisms into a culture media

• 1: highest concentration, 4: most diluted

what are prokaryotes growth limited to when growing in the lab?

food, moisture, crowding

how long does it take for one E. coli cell to divide?

20 minutes

how long does it take one E. coli cell to become 1 million?

6.7 hours, 20 divisions

colony

a visible mass of microorganisms originating from a single mother cell

prokaryotic cell size and structure

• prokarytoic cells (0.1-5.0 um in diameter) are significantly smaller than eukaryotic cells (10-100 um in diameter)

• the predominantly single-celled organisms of the domains Bacteria and Archaea are classified are prokaryotes

all cells have four common structures

1. the plasma membrane: functions as a barrier for the cell and separates the cell from its environment

2. the cytoplasm: a complex solution of organic molecules and salts inside the cell

3. a double-stranded DNA genome: the information archive of the cell

4. ribosomes: sties of protein synthesis

3 main shapes of prokaryotes

1. cocci

2. bacilli

3. spirilli

cocci

spherical or round

bacilli

rod-shaped

spirilli

spiral-shaped

diplococci

exist in pairs

tetrad

4 paired together

true or false. prokaryotes often occur in characteristic aggregates (pairs, chains, tetrads, clusters, etc.)

true

prokaryote structures

• no membrane-bound organelles

  • no nucleus: DNA in nucleoid

  • ribosomes “free”

• no microtubules

microtubules function

aid eukaryotes in cell division, movement, and mechanical support

capsule function

protective layer

pili function

attachment

flagellum function

movement

what 3 structures are not find in all prokaryotes

• capsule

• pili

• flagellum

5 categories of proteobacteria

1. alpha

2. beta

3. gamma

4. delta

5. epsilon

what types of bacteria are gram -?

1. proteobacteria

2. chlamydias

3. spirochetes

4. cyanobacteria

proteobacteria

gram neg, diverse metabolism/nutrition

• includes many N-fixing bacteria

• includes common gastrointestinal pathogens (“food-poisoning”)

true or false. proteobacteria w N-fixing bacteria converts N2 to NH3, which becomes useful for plants

true

proteobacteria examples

• escherichia coli - E. coli: normally beneficial, some strains cause disease

• salmonella

• Vibrio cholerae: causes cholera → severe diarrhea

what eukaryotic membrane is derived from proteobacteria?

mitochondria

chlamydias

gram neg, all are endoparasites (live w/ in animal cells)

chlamydias example

chlamydia in humans causes STD

chalmydia trachomatis

• causes eye infection (conjunctivitis) or pneumonia in children of infected women

• causes pelvic inflammatory disease → infertility

• preventable and curable

• antibiotics are safe to use during pregnancy

spirochetes

• spiral shape (spirrili)

• many are free-living but include disease-causing pathogens

• gram neg

spriochetes examples

Treponema pallidum → syphilis (STD)

• later stages: nerve and brain damage

Borrelia burgdorferi → Lyme disease

• fever, rash, headache, fatigue

• vector: tiny deer ticks which gets it from mice

cyanobacteria

• gram neg

• plant-like, O2-generating photosynthesis (take in Co2)

• some are also N-fixers

• created living conditions

• “blooms” can make toxins → make so much O2

  • hepatotoxins, neurotxins

heterocysts

cells on cyanobacteria that are specialized N2 fixing cells

a filamentous cyanobacterium

Oscillatoria

gram-positive bacteria

• include many decomposers in soils

• include many pathogens

gram-positive bacteria examples

• Bacillus anthracis → anthrax

• Clostridium tetani → tetanus

• streptococcus → strep throat

• staph and MRSA infections

Domain Archaea

• includes extremophiles and methanogens

  • but also many live in “normal” conditions

• no human-disease causing archaeans!

what did chloroplasts derive from?

cyanobacteria

methanogenic archaea (methanogens)

produce methane (CH₄) as a byproduct of anaerobic respiration.

prokaryote structure

almost all have a cell well

• lies outside plasma membrane

• protects and prevents cell lysis

• peptidoglycan?

  • bacteria: w / peptidoglycan (polysaccharides, sugars, and amino acids)

  • archaea: 2/ other structural polysaccharides (do not have peptidoglycan)

• many have a capsule or slime layer

• some have hair-like protein fimbriae

what is the difference between the bacteria and archaea cell wall

bacteria cell wall has peptidoglycan, archaea does not

prokaryotic plasma membrane

• thin lipid bilayer (6-8 nm)

• selectively permeable

• phospholipid bilayer composed of 2 layers of lipids molecules

bacterial membrane

fatty acids linked to glycerol (like eukarya)

archaeal membrane

branched isoprene (phytanyl) chains linked to glycerol

true or false. a gram-stain reflects cell wall type

true

what color does a gram pos bacteria stain?

purple

who invented staining procedure?

Han Christian Grams in 1882

staining procedure

1. crystal violet stain: the primary stain in a gram stain is crystal violet, which binds to all bacterial cells. both gram pos and neg bacteria initially take up the crystal violet

2. iodine treatment: after, iodine is used as a mordant, which forms a complex w the dye. the complex is larger and harder to wash out the cell

3. decolorization w ethanol: ethanol is used as a decolorizer and causes the cell wall of gram neg bacteria to become more porous → crystal violet - iodine complex leaks out.

4. counterstaining w safranin: a counterstain (safranin) is applied, which stains any bacteria that were decolorized in the gram neg bacteria red or pink. b/c the gram pos bacteria retains the violet dye, they remain purple

in staining, why does crystal violet - iodine complex leak out of the gram neg bacteria but not the gram pos bacteria?

b/c gram pos bacteria have a thick layer of peptidoglycan in their cell walls, the wall retains the complex, unlike in gram neg bacteria

staining: gram positive bacteria

bacteria w/ thick peptidoglycan layer → stains purple in Gram stain

staining: gram negative bacteria

bactera w/ thinner peptidoglycan layer plus outer lipid bilayer membrane → stains pink in gram stain

• outer lipopolysaccharide (LPS) layer often toxic, resists drugs and immune system

how much percentage does peptidoglycan make of the cell wall of a gram negative bacteria?

10%

how is a slime layer different from a capsule?

a slime layer is similar to a capsule but is loosely associated and easily washed off

many prokaryotes have a capsule or slime layer

• sticky carbs and proteins secreted outside cell wall

• adheres (glues) cells together or to surface

• resists attack from immune system

• holds in moisture

  • hydrophilic

  • prevents bacteria from dehydrating

_______ filaments held together by slime make an easily visible mass

Nostoc (cyanobacteria)

true or false. flagellum, plural flagella, are hairlike structures that acts primarily as an organelle of the immune system.

false. these structures act primarily as an organelle of locomotion (motility)

some prokaryotes have hair-like protein fimbriae

• some also have short pili

• help cells stick to surfaces and each other

• many can form sex pilus (pl. pili) pulls two bacteria cells together for DNA transfer (conjugation)

• forms mating bridge

short pili

• originate in the plasma membrane

• large and fewer in # than fimbriae

• mainly in gram neg but sometimes in gram pos

plasmids

many prokaryotes have plasmids:

• extra tiny DNA rings w/ few genes

• replicate independently

• not “essential” for life, but add diversity

  • ex. drug resistance genes

true or false. plasmids cannot replicate independently.

false. plasmids can replicate independently

prokaryote reproduction

• reproduction in prokaryotes is asexual

• usually takes place by binary fission

• binary fusion does not provide an opportunity for gentic recombination or genetic diversity

true or false. binary fission provides an opportunity for genetic recombination or genetic diversity.

false

prokaryotes can share genes by 3 mechanism

1. transformation

2. transduction

3. conjugation

prokaryote reproduction and genetic diversity

using transformation, transduction, and conjugation

• high rate of cell division → many mutations

• one mutation can change phenotype

• mutations (except lethal ones) are passed on in clones

• selection favors best clones

• short generation times → rapid evolution

endospores

• under stress, some bacteria produce endospores (dormant, non-reproductive)

• endospores survive heat, drought for years

what are names of gram pos bacteria capable of producing endospores?

• Bacillus anthracis → anthrax

• Clostridium tetani → tetanus

photoautotrophs

use energy from sunlight, and carbon from carbon dioxide

chemoheterotrophs

obtain both energy and carbon from an organic chemical source

chemolithoautotrophs

obtain their energy from inorganic compounds, and they build their complex molecules from carbon dioxide

photoheterotrophs

obtain their energy from light, but their carbon from organic compounds

how to describe humans based on their use of carbon and energy sources?

chemo-organotrophs

phototrophs

use light as an energy source

chemotrophs

use chemical as their energy source

chemo-organotrophs

use organic chemicals as energy source

chemlithotrophs

use inorganic chemicals as energy source

autotrophs

use carbon dioxide as carbon source