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18.4 Bacteria and Archaea KEY CONCEPT Bacteria and archaea are both single-celled prokaryotes.

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Presentation on theme: "18.4 Bacteria and Archaea KEY CONCEPT Bacteria and archaea are both single-celled prokaryotes."— Presentation transcript:

1 18.4 Bacteria and Archaea KEY CONCEPT Bacteria and archaea are both single-celled prokaryotes.

2 18.4 Bacteria and Archaea Prokaryotes are widespread on Earth. Prokaryotes can be grouped by their need for oxygen. –obligate anaerobes are poisoned by oxygen –obligate aerobes need oxygen –facultative aerobes can live with or without oxygen

3 18.4 Bacteria and Archaea Bacteria and archaea are structurally similar but have different molecular characteristics. Bacteria commonly come in three forms. –rod-shaped, called bacilli Lactobacilli: rod-shapedSpirochaeta: spiralEnterococci: spherical Archaea have many shapes. – spiral, called spirilla or spirochetes – spherical, called cocci

4 18.4 Bacteria and Archaea Bacteria and archaea have similar structures. flagellum pili plasmid cell wall chromosome plasma membrance This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences. –plasmid –flagellum –pili

5 18.4 Bacteria and Archaea Bacteria and archaea have molecular differences. GRAM NEGATIVEGRAM POSITIVE –Archaea have different lipids entirely –The amount of peptidoglycan within the cell wall can differ between bacteria

6 18.4 Bacteria and Archaea Gram staining identifies bacteria. Gram-negative bacteria have a thin layer of peptidoglycan and stain red. Gram-positive bacteria have a thicker peptidoglycan layer and stain purple. –stains polymer peptidoglycan –gram-positive stains purple, more peptidoglycan –gram-negative stains pink, less peptidoglycan

7 18.4 Bacteria and Archaea Bacteria have various strategies for survival. Prokaryotes exchange genes during conjugation. conjugation bridge TEM; magnification 6000x Bacteria may survive by forming endospores.

8 18.4 Bacteria and Archaea KEY CONCEPT Prokaryotes perform important functions for organisms and ecosystems.

9 18.4 Bacteria and Archaea Prokaryotes provide nutrients to humans and other animals. Prokaryotes live in digestive systems of animals. –make vitamins –break down food –fill niches

10 18.4 Bacteria and Archaea Bacteria help ferment many foods. –yogurt, cheese –pickles, sauerkraut –soy sauce, vinegar

11 18.4 Bacteria and Archaea Prokaryotes play important roles in ecosystems. Prokaryotes have many functions in ecosystems. –photosynthesize –recycle carbon, nitrogen, hydrogen, sulfur –fix nitrogen

12 18.4 Bacteria and Archaea Bioremediation uses prokaryotes to break down pollutants. –oil spills –biodegradable materials

13 18.4 Bacteria and Archaea KEY CONCEPT Understanding bacteria is necessary to prevent and treat disease.

14 18.4 Bacteria and Archaea Some bacteria cause disease. Bacteria cause disease by invading tissues or making toxins. A toxin is a poison released by an organism.

15 18.4 Bacteria and Archaea Normally harmless bacteria can become destructive. –may colonize new tissues

16 18.4 Bacteria and Archaea –immune system may be lowered Normally harmless bacteria can become destructive.

17 18.4 Bacteria and Archaea Antibiotics are used to fight bacterial disease. Antibiotics may stop bacterial cell wall formation. Antibiotics do not work on viruses. Prevention is best method to fight bacterial disease.

18 18.4 Bacteria and Archaea Bacteria can evolve resistance to antibiotics. A bacterium carries genes for antibiotic resistance on a plasmid. A copy of the plasmid is transferred through conjugation. Resistance is quickly spread through many bacteria. Bacteria are gaining resistance to antibiotics. –overuse –underuse –misuse Antibiotics must be used properly.


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