Chapter 27: Prokaryotes II

Obligate aerobe

MUST have O₂ for cellular respiration and can’t grow without oxygen

Obligate anaerobe

O₂ is LETHAL

• live exclusively by fermentation

Facultative anaerobe

Can use O₂ if present, but can also carry out anaerobic respiration with no O₂

• prefer to use O₂

• most dangerous because these organisms can adapt to several environments

Microaerophile

Only likes a small amount of O₂

Aerotolerant anaerobes

Don’t use oxygen for metabolism, but can survive in its presence

• tolerant of O₂

Lungs

have a high amount of oxygen

Blood

have a moderate amount of oxygen

Muscles during exercise

have a low amount of oxygen (gets used during exercise)

Intestines and wounds

have a very low amount of oxygen

E.coli, Staphylococcus, Salmonella, Streptococcus are some of the most common human pathogens. Why?

They are examples of facultative anaerobes and can adapt to environments inside and outside the body

Nitrogen fixation

N₂ (atmospheric nitrogen) -→ ammonia

• transformation is conducted by bacteria

How to prokaryotes drive global cycles?

• Recycle carbon

• Fix and cycle nitrogen

• Metabolize sulfur to fuel ecosystem

Why are prokaryotes considered a mosaic?

Because significant portions of their genes are imported from other species

• makes it difficult to determine phylogenetic relationships

Proteobacteria

• Gram-negative (pink)

• includes photoautotrophs, chemoautrotrophs, and heterotrophs

E. Coli is what kind of bacteria?

Proteobacteria

Neisseria gonorrhoeae

Proteobacteria

• causes gonorrhea

Vibrio cholerae

Proteobacteria

• Causes cholera → bacterial disease causing severe diarrhea and dehydration

• spread in water

Helicobacter pylori

Proteobacteria

• Causes stomach ulcers

• Barry Marshall proved this by drinking the pathogen

Streptococcus

• Gram positive

• strep throat, scarlet fever, rheumatic fever

• spread by respiratory droplets

• common in schools/dorms

Staphylococcus aureus

• Gram positive

• skin infections, pneumonia (very dangerous in hospitals and gyms )

• MRSA: antibiotic resistant strain due to mutations

Bacillus anthracis

• Gram positive

• Causes anthrax (disease of livestock and humans)

• Forms resistant spores in soil

• Bioterrorism case: 2001 anthrax letters

Spirochetes

• Helical gram-negative heterotrophs

• spiral through their environments by rotating internal, flagellum-like filaments

Treponema pallidum

Syphilis

• Pathogenic spirochete

• Sexually transmitted

Borrelia burgdorferi

Lyme disease

• Pathogenic spirochete

Archaea

Prokaryotes that can thrive in environments that are too extreme for other organisms

• Can live in ‘moderate’ environments too

Extremophiles

Lovers of extreme conditions

• subdivided into halophiles and thermophiles

Extreme halophiles

Live and thrive in highly saline environments

• some require environments saltier than seawater

Halobacterium

Halophile

• functions improve in extreme salty environments, but cant function if salinity drops below 9%

Extreme thermophiles

Thrive in very hot environments

Methanogens

• Archaea

• release methane

• obligate anaerobes (poisoned by oxygen)

• live where oxygen has been consumed by other organisms

Decomposers

Chemoheterotrophic prokaryotes that break down dead organisms and waste products

• unlock supplies of carbon, nitrogen, and other elements

• cycle starts again

Symbiosis

“Living together”

• Two species live close contact with each other

Mutualism

Both species (host and symbiont) benefit

Commensalism

One benefits while the other is not harmed or helped

Ex: Fish protected by the shark

Parasitism

One (parasite) harms their host

• pathogens

• parasites don’t want to kill their host because they want their nutrients