Domain Bacteria Domain Archaea

Two Domains of Prokaryotic Cells: 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)

Domain Bacteria Kingdom: Bacteria Prokaryotic Cell Walls made of peptidoglycan Bacterial DNA is not associated with histone proteins (“naked DNA”) Ribosome activity is inhibited by the antibiotics streptomycin & chloramphenicol

How to classify Bacteria: 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

Mode of Nutrition Some bacteria are photoautotrophs—capable of photosynthesis Some are chemoautotrophs Some are heterotrophs—these may be decomposers, parasites, or pathogens. Cyanobacteria Clostridium—causes tetanus

Endospores 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!

Bacteria Shapes Most bacteria are classified into one of three shapes: Cocci Bacilli Spirilla Cocci—spherical shaped Spirilla Bacilli—rod shaped

Bacterial Cell Walls 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.

Common Groups of Bacteria: Cyanobacteria: Photosynthetic Have chlorophyll to capture light energy Split H2O and release O2 They may also contain accessory pigments called phycobilins

Common Groups of Bacteria: 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-)

Common Groups of Bacteria: 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.

The Nitrogen Cycle requires several types of bacteria:

Common Groups of Bacteria: 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

Domain Archaea 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)

Archae Bacteria are similar to Eukaryotes in some ways: 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.

Major Groups of Archaea: 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.

Major Groups of Archaea: 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.

Deep Sea Hydrothermal Vent Archaea: 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.

Photosynthesis vs. Chemosynthesis: