Bacteria. Bacteria and Archaea are both: unicelluar (single-celled) prokaryotes (lacking a nucleus and membrane bound organelles)

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1 Bacteria Bacteria and Archaea are both: unicelluar (single-celled) prokaryotes (lacking a nucleus and membrane bound organelles) 1

2 Grouped by their need for oxygen obligate anaerobes are poisoned by oxygen obligate aerobes need oxygen facultative aerobes can live with or without oxygen Shapes and Sizes Bacteria commonly come in three forms. rod-shaped, called bacilli spiral, called spirilla or spirochetes spherical, called cocci Spirochaeta: spiral Bacilli Cocci Spirilla 2

3 Bacteria and archaea have similar structures. Plasmid Chromosome Flagellum Pili Ribosomes Cytosol Cell membrane plasmid cell wall chromosome plasma membrance pili flagellum This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences. Bacteria and archaea have molecular differences. t4rrrrrrrrrrrrrrrrrrrr1. The amount of peptidoglycan within the cell wall can differ between bacteria 3

4 2. Archaea have different lipids entirely, they have different fatty acids (more branched) Gram + vs. Gram - Gram Positive Bacteria The bacteria remain colored with the Gram stain even after washing with alcohol or acetone Dark violet or purple Outer membrane is absent. Cell wall is nm thick, and multilayered pepidoglycan (polysaccharide and protein mesh) The cell wall is smooth Gram Negative Bacteria The bacteria do not retain the stain when washed with alcohol or acetone. Outer membrane is present Cell wall is 8-12 nm thick, thin single layer of peptidoglycan The cell wall is rough/ wavy comes into contact the plasma membrane at only a few places. The lipid content in the cell wall is very low The lipid content in the cell wall is % A few pathogenic bacteria belong to the Gram positive group Most of the pathogenic bacteria belong to the Gram negative group 4

5 Gram staining identifies bacteria. stains polymer peptidoglycan gram-positive stains purple, more peptidoglycan gram-negative stains pink, less peptidoglycan Gram-negative bacteria have a thin layer of peptidoglycan and stain red. Gram-positive bacteria have a thicker peptidoglycan layer and stain purple. Strategies for survival. Bacteria may survive inhospitable conditions by forming endospores. Because bacteria reproduce asexually they cannot increase genetic variability through reproduction, SO 5

6 Transformation Transformation pick up naked DNA from their environment Transduction Transfer of bacterial genes by virus. 6

7 Conjugation Prokaryotes can exchange genes. This process is not for reproduction so it is not sexual reproduction. Just sharing potentially useful genes. conjugation bridge sex pilli Value of Prokaryotes: 7

8 Prokaryotes provide nutrients to humans and other animals. Prokaryotes live in digestive systems of animals. make vitamins break down food fill niches Bacteria help ferment many foods. yogurt, cheese pickles, sauerkraut soy sauce, vinegar 8

9 Prokaryotes in ecosystems. Prokaryotes have many functions in ecosystems. photosynthesize (remember prokaryotes produced the first O2 in our atmosphere!) recycle carbon, nitrogen, hydrogen, sulfur (decomposer # 1 job!) fix nitrogen (without this plants wouldn t grow as well! Bioremediation uses prokaryotes to break down pollutants. oil spills biodegradable materials 9

10 Bacterial and Disease/illness Some bacteria cause disease. Bacteria cause disease by invading tissues or making toxins. A toxin is a poison released by an organism. 10

11 Normally harmless bacteria can become destructive. immune system may be lowered Antibiotics to fight bacterial disease. Antibiotics may stop bacterial cell wall formation. Penecillin Amoxicillin Antibiotics do not work on viruses. Prevention is best method to fight bacterial disease. Wash your hands with soap and water, avoid touching your eyes and mouth until hands are washed. 11

12 Antibiotic Resistance Bacteria are becoming resistance to antibiotics. overuse A bacterium carries genes for antibiotic antibiotic soaps resistance on a plasmid. and cleansers Underuse not completing antibiotic medications misuse prescribing unnecessary treatments Antibiotics must be used properly. A copy of the plasmid is transferred through conjugation. Resistance is quickly spread through many bacteria. 12