Ch 16 Prokaryotes

1. Ch 16 Prokaryotes • Thrive in moderate & extreme environments • Found everywhere (ubiquitous) • Some are beneficial (good) • Some are harmful • Earliest forms of life on Earth

2. Steps to Life • Earth’s atmosphere contained CO, CO2, N2, and H2O, but little or no O2 • Energy sources like volcanoes, lightning, and UV radiation from the sun were all very intense • “Early Earth” experiments produce SIMPLE organic compounds including all 20 amino acids, several sugars, lipids, the nitrogenous bases found in DNA and RNA, and even ATP.

3. Steps to Life • To imitate early Earth, organic molecules in lab were placed in extreme places (volcanic rock, sand, dirt, heat vents) • They polypeptides and polysaccharides – formed without living cells or enzymes being present. • Other experiments have shown that polypeptides can come together and form microscopic, fluid-filled spheres called pre-cells.

4. All of these experiments together support a hypothetical four-stage sequence for how life could have first developed on Earth. • First, small organic molecules, such as amino acids and nucleotides, formed from simpler molecules present in the environment. • Second, these small molecules joined together into larger ones such as proteins and nucleic acids. • Third, molecules that could copy themselves provided a basis for the inheritance of molecular information. • In the last stage, these various organic molecules became packaged within membranes and separated from their surroundings forming pre-cells.

5. 2 domains of prokaryotes(Archaea and Bacteria) Archaea • Greek = meaning "ancient." • prokaryotes, many live in extreme environments on Earth. • extremophiles, meaning "lovers of the extreme." • thermophiles (heat lovers) live in hot water such as the hot springs of Yellowstone National Park or deep-sea vents • Halophiles (salt lovers) thrive in such environments as Utah's Great Salt Lake, or in seawater evaporating ponds. • Some archaea live in oxygen-free environments such as the mud at the bottom of lakes and swamps where they produce bubbles of "swamp gas" (methane).

6. 2 domains of prokaryotes(Archaea and Bacteria) • Bacteria • Prokaryotic organisms classified as bacteria differ from archaea in cell structure and chemical makeup • Scientists place the two groups of prokaryotes in separate domains partly because of key differences in the information contained in their nucleic acids (DNA and RNA).

7. Structure of Bacteria * * * *

8. Characteristics of Bacteria • Unicellular- only one cell • Prokaryotic- lacks a nucleus and membrane bound organelles.

9. Form • Bacillus- rod shaped • Spirilla- spiral shaped • Cocci- spherical

10. Bacteria Bacilli Cocci Spirilla

11. Bacteria is identified based partly on three characteristics: • Cell Shape • Bacteria come in three basic shapes: • Spherical – cocci (berries) • rod-shaped -- bacilli • spiral-shaped -- spirochetes • Cell Wall Structure • Motility • About half of all prokaryotes are motile, meaning that they can move. • flagellum (plural, flagella) or slime threads

12. Movement • gliding on slime • twisting in a corkscrew fashion C) Flagella D) some don't move

13. Reproduction • Most prokaryotes reproduce at a very fast rate under the right conditions. • Prokaryotic cells copy their DNA almost continuously and divide repeatedly. • called binary fission

14. Modes of Nutrition • "mode of nutrition" describes how organisms obtain energy and carbon atoms. • energy by photosynthesis = photo- • Energy from chemical sources = chemo- • Autotrophs obtain carbon atoms from CO2 • Heterotrophs obtain carbon from existing organic molecules (such as those in food). • Adding a prefix, photo- or chemo-to either autotroph or heterotroph fully describes the mode of nutrition

16. Chemical Recycling • Life depends on the cycling of chemical elements between the biological and nonliving parts of ecosystems. Prokaryotes play a vital role in chemical recycling. • Many prokaryotes perform an essential function by breaking down, or decomposing, organic waste products and dead organisms in the environment.

17. Human Uses of Prokaryotes • bioremediation -- the use of organisms to remove pollutants from water, air, and soil • Pseudomonas is used to clean up oil spills on beaches • Other prokaryotes are used to clean up old mining sites where the water is acidic and laced with chemicals such as arsenic, copper, zinc, lead, and mercury. • In another example of the usefulness of prokaryotes, pharmaceutical companies raise bacteria that make vitamins and antibiotics.

18. Helpful Bacteria • Bacteria in the intestine help digest food • Bacteria help in production of cheese, yogurt, sour cream, pickles, and sauerkraut. • Bacteria decompose dead organisms • Some bacteria help plants by Nitrogen Fixation

19. How Bacteria Cause Illness • You are constantly exposed to bacteria -- they are in the air you breathe, in the water and food you ingest, and on the surfaces you touch. • most bacteria are neither harmless or helpful to you, BUT some bacteria can make you ill. • Bacteria and other microorganisms that cause disease are called pathogens. • Some bacteria cause disease by invading tissues and destroying cells. • Most pathogenic bacteria cause disease by producing bacterial poisons.

20. Harmful Bacteria • 1 - 5% of bacteria are Pathogens - disease causing organisms • Disease is caused by attacking cells directly or the production of toxins- poisons

21. Defense Against Bacterial Diseases • Since the discovery that bacteria cause many diseases, cases of such diseases have declined dramatically. • the major reasons for this decline are better hygiene and public health measures. • washing hands • careful preparation of food • attention to water quality help minimize the risk of pathogen infection.

22. Defense Against Bacterial Diseases • The human body protects itself against infection • Your skin and the mucous lining of your mouth, nose, and digestive system provide a physical barrier to bacteria. • Those bacteria that do manage to enter (through a cut, for example) meet chemical and cellular defenses that make up the immune system. • Doctors and medicines also play a role in fighting bacterial diseases. • Antibiotics = chemicals that slow or prevent the growth of microorganisms. • Many antibiotics act by damaging or preventing the formation of the bacterial cell wall.

23. Protection against bacteria • Antibiotics- chemicals produced by fungus that inhibit bacterial growth or kill the bacteria. • Penicillin- first antibiotic discovered by Alexander Flemming in 1929.

24. Lab Conclusion: • Where did you expose your petri dish? • Why did you think there would be bacteria present there? • Was bacteria present? • What are the conditions most favorable for bacteria growth. • Where can we conclude bacteria lives?