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Domain Bacteria Domain 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: 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 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 Cyanobacteria Clostridium—causes tetanus Some bacteria are photoautotrophs— capable of photosynthesis Some are chemoautotrophs Some are heterotrophs—these may be decomposers, parasites, or pathogens. 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 Endospores can lie dormant for of nutrients. centuries, perhaps even millions of years! Most bacteria are classified into one of three shapes: Cocci—spherical shaped Cocci Bacilli Spirilla Spirilla Bacilli—rod shaped 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: Photosynthetic Have 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 (6080oC) 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.