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2 Kingdoms Archaebacteria and Eubacteria (P5).notebook THE LIFE OF A PROKARYOTE Prokaryotes are single-celled organisms. They are the smallest, simplest • organisms. The group includes: • Archaebacteria are found in anaerobic and extreme conditions (high o [salt], high temperature, and low pH), similar to what are believed to be the conditions on the early Earth. Earth's early atmosphere did not contain oxygen, therefore the § Early Atmosphere earliest organisms were anaerobic. Eubacteria includes the traditional bacteria and is the larger of the o two. They are found in nearly every habitat • studied, including some that no other organism is able to withstand. Bacteria have a cell wall and cell • membrane, but no membrane-bound organelles such as a nucleus, mitochondria, chloroplasts, Golgi apparatus, or ER. Some are covered by a layer of “slime” called a capsule. November 02, 2010 Early Atmosphere of Primitive Earth • Probably H2 and He -Possibly lost to space because Earth's gravity is not strong enough to hold lighter gases • Gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, Cl2, N2, H2) and NH3 and CH4. -No free O2 at this time (not found in volcanic gases). Back Characteristics Primitive Earth • . Some bacteria are able to move using special cell structures called cilia and flagella. Hair-like cilia (singular, cilium) and tail-like flagella (singular, o flagellum) are projections from the cell. By repetitive beating (like a bending motion), they cause the cell to o move. Think of oars in a boat. Flagella can propel the cell by waving back and forth. If a cell is fixed in place, they can also cause water to move § across the surface. Shapes Cilia and Flagella RESPIRATION Obligate aerobes must have oxygen. • Obligate anaerobes can not survive in the presence of oxygen. • Facultative anaerobes will use oxygen if it is present but do not need it. • NUTRITION Most are heterotrophic… • Some are parasites which live off a living host. o Some are decomposers, feeding on dead organisms and waste. o Some are autotrophic… • Either use chemicals as a source of energy (chemoautotrophs) or are o photosynthetic (photoautotrophs). REPRODUCTION Prokaryotes have a single circular chromosome attached to the inside of the • Single Chromosome plasma membrane. Asexual reproduction • Prokaryotes reproduce by simply splitting in two in a process called o Binary Fission binary fission. The DNA is copied and the cell divides into two identical cells. o Sexual reproduction • Sexual reproduction combines genes from two different individuals and o increases variation. Prokaryotes do not technically reproduce sexually but can mix genes with one another. Conjugation Conjugation - Two cells join briefly and one cell donates some DNA o (called a plasmid) to the other one. Sometimes part of the cell‛s chromosome is donated as well. Transformation - Bacteria can also pick up pieces of DNA from the o environment. Transduction - Sometimes viruses transfer pieces of DNA from one cell o to another. Endospores • Some bacteria form endospores when environmental conditions become o unfavorable. Endospores Endospores are DNA and a small amount of cytoplasm enclosed in a tough cell wall. They are resistant to extremes in temperature, drying, and harsh chemicals. Mutation is a large source of genetic diversity in bacteria. o • Early symptomatic HIV infection: Mycobacterium marinum infection on the hand Resp/Nutr Bacterial Pericarditis Reproduction 1 2 Kingdoms Archaebacteria and Eubacteria (P5).notebook November 02, 2010 E. coli Chromosome Reproduction The Eyes of Nye (Antibiotics) Cell Phones The Eyes of Nye (Antibiotics) 2