Domain BacteriaDomain Archaea

Domain Archaea Prokaryotes Single-celled Most live in extreme

environments (different species may live in extreme cold, hot, salty, acidic or other extreme conditions)

Domain Bacteria Prokaryotes Single-celled Live everywhere

(except extreme environments)

Kingdom: BacteriaProkaryoticCell Walls made of

peptidoglycanBacterial DNA is not

associated with histone proteins (“naked DNA”)

Ribosome activity is inhibited by the antibiotics streptomycin & chloramphenicol

By their mode of nutrition, or how they metabolize resources (what they eat)

By their ability (or not) to produce endospores

By their means of motility

By their shape By their cell walls

Some bacteria are photoautotrophs—capable of photosynthesis

Some are chemoautotrophs

Some are heterotrophs—these may be decomposers, parasites, or pathogens.

Cyanobacteria

Clostridium—causes tetanus

Some bacteria (mostly Gram+) have the ability to produce endospores.

These are resistant bodies that contain the genetic material and a small amount of cytoplasm surrounded by a cell wall.

Endospore formation usually starts with a lack of nutrients.

Endospores can lie dormant for centuries, perhaps even millions of years!

Most bacteria are classified into one of three shapes:

Cocci Bacilli Spirilla

Cocci—spherical shaped

Bacilli—rod shaped

Spirilla

Gram-positive cell walls have a layer of peptidoglycan outside of the cell membrane.

Gram-negative cell walls have a layer of peptidoglycan in between two layers of cell membranes. (The outer layer is made of lipopolysaccharides—LPS)

Peptidoglycan is a combination of a monosaccharide and amino acid chains.

Cyanobacteria:PhotosyntheticHave chlorophyll to

capture light energy

Split H2O and release O2

They may also contain accessory pigments called phycobilins

Chemosynthetic Bacteria

Autotrophs (chemoautotrophs)

Make their own food from inorganic compounds such as nitrogen, sulfur, or hydrogen.

Some are called nitrifying bacteria—these convert nitrite (NO2

-) to nitrate (NO3

-)

Nitrogen-fixing Bacteria: Heterotrophs that fix

nitrogen. They can convert N2 gas into nitrate (NO3

- ).This form of Nitrogen can be taken up by plants and other organisms.

Many of these have mutualistic relationships with plants—both the plant and the bacteria benefit from an interdependent relationship.

The bacteria live in nodules, specialized structures in plant roots.

Nitrogen-fixing bacteria live in the roots of Legumes such as soybeans and alfalfa.

Spirochetes Coiled bacteria that

move with a corkscrew motion.

Their flagella are internal, positioned within the layers of the cell wall.

A spirochete bacteria causes Lyme Disease

These differ from other bacteria in several important ways:

Archaea cell walls contain various polysaccharides, but not peptidoglycan (as in bacteria)

Archaea cell membranes contain different types of phospholipids—(the hydrocarbon chains are branched)

The DNA of both archaea and eukaryotes are associated with histone proteins.

Bacterial DNA is “naked”—it does not have histones.

Ribosomal activity in both archaea and eukaryotes are not inhibited by the antibiotics streptomycin and chloramphenicol.

Methanogens These are obligate

anaerobes (cannot survive in O2)

They produce methane (CH4) as a by-product of obtaining energy

They live in mud, swamps, and the guts of cows, humans, termites, and other animals.

Extremophiles: Halophiles (“salt

lovers”) live in environments with high salt contents, such as the Great Salt Lake and the Dead Sea

Thermophiles (“heat lovers”) live in hot (60-80oC) environments such as hot springs or geysers. Most are sulfur-bases chemoautotrophs.

In the deepest parts of the ocean, where it is extremely cold and dark, there is an entire ecosystem based on chemosynthetic archaea bacteria.

These thrive on the H2S gases from hydrothermal vents. Other organisms feed on the bacteria.

Yeti Crab feed on bacteria by filtering them with their feathery gills.