Bio 112 Exam 2: Bacteria and Archaea

Prokaryotes

1st organisms, millions, live on and in other organisms

Anoxic

meaning that there was no molecular oxygen

anaerobic

no oxegen, able to live in ancient atmosphere

phototrophs

Autotrophic organisms that convert solar energy into chemical energy

Cyanobacteria

“blue-green algae,” evolved from these simple phototrophs at least one billion years later

Ancestral cyanobacteria

began “oxygenation” of the atmosphere

Increase in O2 concentrations allowed the evolution of other life forms

Extremophiles

Bacteria and archaea that are adapted to grow under extreme conditions (e.g. deep see vent, heat, dry, cold, radiation, etc.)

Ex. Deinococcus radiodurans - a prokaryote that can tolerate very high doses of ionizing radiation

Robert Koch: discoveries in lab

discovering the techniques for pure culture, including staining and using growth media

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

Pure culture

a laboratory culture containing a single species of microorganism

Blood agar plates

used to diagnose Streptococcus infections

Growing prokaryotes in the lab

growth limited by food, moisture, crowding

Prokaryotic cell size

(0.1–5.0 μm), Bacteria and Archaea are classified as prokaryotes

4 Structures of all cells:

The plasma membrane, The cytoplasm, A double-stranded DNA genome, A double-stranded DNA genome:

Prokaryotes name

before nucleus

3 Types of Bacteria

Cocci, Bacilli, Spirilli

Prokaryote Structure

No membrane-bound organelles

• no nucleus: DNA in nucleoid

•ribosomes “free”

•No microtubules

e features of a typical prokaryotic cell

Flagella, capsules, and pili are not found in all prokaryotes

Domain Bacteria : Proteobacteria

• Gram-neg; diverse metabolism/nutrition

• includes many N-fixing bacteria •

includes common gastrointestinal pathogens (“food poisoning’)

Domain Bacteria : Chlamydias

endoparasites (live w/in animal cells)

• Ex: Chlamydia in humans causes STD

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

• causes Pelvic Inflammatory Disease, leading to infertility

Domain Bacteria : Spirochetes

characteristic spiral shape • many free-living but include disease-causing pathogens: •

Ex: syphilis (STD)

Domain Bacteria : Spirochetes: Lyme Disease

Borrelia burgdorferi

Domain Bacteria : Cyanobacteria

• plant-like, O2-generating photosynthesis

•some are also N-fixers

cyanobacteria “blooms” can make toxins

Domain Bacteria : Gram-Positive Bacteria

•include many decomposers in soils

•include many pathogens

: • Ex: Bacillus anthracis (anthrax),

Clostridium tetani (tetanus)

• Ex: “staph” & MRSA infections

Ex: “strep” throat

Domain: Archaea

extremophiles & methanogens

• but also many live in “normal” conditions

•No human-disease-causing archaeans!

Methanogens

produce methane (CH4) as by-product of anaerobic respiration

Prokaryote Structure

• Almost all have cell wall

• lies outside plasma membrane

• protects & prevents cell lysis (rupture)

• bacteria: w/ peptidoglycan (PG)

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

Prokaryotic Plasma Membrane

Thin lipid bilayer (6 – 8 nm)

Selectively permeable:

keeps ions, proteins, and other molecules within the cell and prevents them from diffusing into the extracellular environment

Structure of membrane

phospholipid bilayer composed of two layers of lipid molecules

Bacterial membrane

fatty acids linked to glycerol

Archaeal membrane:

branched isoprene (phytanyl) chains linked to glycerol

Gram positive bacteria

•Gram-stain reflects cell wall type

•Gram + (pos.): bacteria w/ thick PG layer

•stains purple in Gram stain

Gram negative bacteria

• Gram – (neg.): bacteria w/ thinner PG layer plus outer lipid bilayer membrane

• Pink in Gram stain; outer lipopolysaccharide layer often toxic, resists drugs & immune system

Prokaryote Structure

capsule or slime layer

• sticky carbs & proteins secreted outside cell wall

• adheres (glues) cells together or to surface

• resists attack from immune system

• holds in moisture

fimbriae

e hair-like protein, • help cells stick to surfaces & each other

Flagellum

are hairlike structures that acts primarily as an organelle of locomotion (motility)

form sex pilus

pulls two bacteria cells together for DNA transfer (conjugation), mating bridge

Plasmids

• extra tiny DNA rings w/ few genes •replicate independently

• not “essential” for life, but add diversity

• e.g. drug resistance genes

Prokaryote Reproduction

Reproduction in prokaryotes is asexual

 Usually takes place by binary fission

 Binary fission does not provide an opportunity for genetic recombination or genetic diversity

Endospores

survive heat, drought for years

• Ex: Bacillus anthracis (causes anthrax), Clostridium tetani (causes 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

Prokaryotes and the carbon cycle

primary producers

Symbiosis

two species living in close relationship (free-living = not living in symbiosis)

Parasitism

smaller parasite benefits at expense of other species (host)

•incl. pathogens (cause disease)

Commensalism

one sp. benefits without any impact (good or bad) on other species

Mutualism

both species benefit from each other • Ex: Rhizobium in legume roots get sugar & water; provide fixed N for plant

Pathogenic Bacteria

• exotoxins are secreted •

Produced by both gram-negative and gram-positive bacteria

• Ex: tetanus, botulism

endotoxins

are toxic outer membranes of some gram-negative bacteria • generalized toxic effect • Ex: Salmonella food poisoning

Antibiotics

kill bacteria cells but not eukaryotic cells • Ex: penicillin affects peptidoglycan cell wall •some antibiotics come from other bacteria!

bacteria becomes resistant

Due to many factors, HGT as one, the bacteria are gaining resistance faster than we can create new drugs

Prokaryotes everyday use

food products: yogurt, cheese, etc.

DNA technology & genetic engineering

• Commercial chemical & drug production