Prokaryotes: BACTERIA small, lack membrane bound organelles must have cell walls simpler genomes most numerous organisms important as decomposers small percentage cause disease many have symbiotic relationships

Taxis: movement towards or away from a stimulus light = phototatic chemical = chemotactic magnetic field = magnetotactic

G. Metabolic Diversity: Photoautotrophs: use light to synthesize organic compounds from CO 2 Photoheterotrophs: must obtain organic carbon, but use light to form ATP Chemoautotrophs: need only CO 2 as carbon source; obtain E by oxidizing H 2 S, NH 3, and Fe +2 Chemoheterotrops: must obtain organic molecules for E and carbon (*most bacteria)

Chemoheterotrophs: Saprobes: decomposers that absorb nutrients from dead organic matter Parasites: bacteria that absorb nutrients from body fluids of living hosts Can differ in their response to oxygen. Obligate aerobes, facultative anaerobes, and obligate anaerobes

Bacteria are important to the cycling of N through ecosystems Nitrogen fixation (N 2  NH 3 ): makes N available to organisms some convert NH 3  NO 2 - some denitrify NO 2 - or NO 3 -  N 2

Miller and Urey – created life in a flask, using the components of the early Earth – proved that inorganic molecules could result in basic organic molecules

I. Origins of Glycolysis: * First prokaryotes were probably chemoheterotrophs that used free organic compounds made by abiotic synthesis. * As ATP supplies decreased, natural selection favored prokaryotes that could generate ATP from ADP. (O 2 was not abundant on the early Earth)

II. Origin of ETC and Chemiosmosis: * Early prokaryotes used transmembrane pumps to help regulate internal pH by expelling H + ions. * ATP would have been necessary to drive the pumps. * ATP was conserved by ETC by coupling oxidation of organic acids to transport H + out of the cell.

III. Origin of Photosynthesis: * As supply of ATP and abiotically produced organic molecules was depleted, natural selection would have favored organisms that could make their own molecules from inorganic ones. * Light absorbing pigments probably originated as protection from absorbing excess light energy, especially UV light (probably coupled with ETC to power ATP synthesis)

IV. Origins of Cellular Respiration: * Oxygen released by photosynthesis probably reacted with dissolved iron to make iron oxide, preventing the accumulation of free O 2 * the iron and O 2 would have become concentrated in the oceans where eventually the O 2 would be released as a gas

* as O 2 accumulates, strict anaerobes (some archaebacteria) would become extinct * aerobic respiration originates as a modification of ETC’s use in photosynthesis

A. Prokaryotes in Chemical Cycles: Decomposers: break down dead organisms and waste of live organisms in order to return elements such as C and N to the environment Autotrophic Bacteria: fix CO 2, to help support the food chains (other bacteria support the cycling of N, S, Fe, and H)

B. Symbiotic Bacteria: Symbiosis = ecological relationship between two organisms * usually smaller symbiont, lives within or on the larger host

Categories of Symbiosis: Mutalism: (+,+) both partners benefit ex. N-fixing bacteria in root nodules of certain plants

Commensalism: (+,0) symbiont benefits while neither helping nor harming the host ex. Remora on sharks

Parasitism: (+,-) symbiont (parasite) benefits at the expense of the host ex. liver fluke, many fungi

C. Bacteria and Disease: Opportunistic = normal inhabitants of the body that become pathogenic only when defenses are weakened by other factors such as poor nutrition or other infections (ex. streptococcus pneumonia)

Koch’s Postulates: criteria used to determine if a specific pathogen is the cause of a disease 1.The agent must be present in every case of the disease. 2.The agent must be isolated from the host and grown in vitro (in a test tube). 3.The disease must result when a pure culture of the agent is introduced into a healthy susceptible host. 4.The same agent must be recovered once again from the experimentally infected host.

Some pathogens cause disease by the production of TOXINS. Endotoxins= proteins secreted by bacterial cells most potent poisons known to cause disease, organism doesn’t need to be present; the toxin is enough elicits specific symptoms ex. botulism

Endotoxins= toxic component of the outer membranes of some Gram - bacteria include general symptoms of fever and aches ex. Salmonella typhi (typhoid fever) Salmonella induced food poisoning

Using Bacteria: used to digest organic wastes at sewage treatment plants use to decompose pesticides and other synthetic compounds used to produce products such as acetone, vitamins, antibiotics, and insulin used to convert milk into yogurt and cheese