Chapter 27: The Prokaryotes

1. Chapter 27: The Prokaryotes • Objectives • Learn about the prokaryotic adaptations that make them successful, including the diverse metabolic pathways. • Learn how rapid reproduction promotes genetic diversity. • The important role of molecular biology in the classification of prokaryotic organisms. • Role of prokaryotic organisms. • The impacts of prokaryotic organisms on humans.

2. Shapes and Size • Three basic Shapes • Unicellular • Small • Some grow and thrive in colonies

3. Cell Surface Structures -All have cell wall (Protection and keep from bursting in hypotonic solution) -All cell walled organisms have trouble reproducing in hypertonic solutions (Salt can be used in preservation of food) -Bacterial Cell walls are made up of peptidoglycan not cellulose or chitin (plants) -Archaeal prokaryote walls don’t have either peptidoglycan or cellulose but other polysaccharides. -Antibiotics work on the peptidoglycan of bacteria --- Eukaryotic cells don’t have peptidoglycan Two main categories of bacteria Mostly Peptidoglycan Much more complex

4. Motility or Movement -Flagella are the most common means of movement -Most movement is random -Some bacteria have been found to exhibit taxis or movement in response to stimulus ex. Movement towards other organisms of the same species forming colonies

5. Internal Structure -Lack membrane bound organelles including nucleus -Have extensions of plasma membrane that performs metabolic functions -Chromosomes are located in a nucleoid region and have less nucleic acid then Eukaryotic Cells Prokaryotic cells also may have a plasmid which is a ring of DNA with only a few genes.

6. Key Features of Prokaryotic Reproduction • Small in size • Binary Fission • Short Generations • Endospores may develop to ensure transfer of genetic material • -Dormancy • -Hard Shell • -Dehydrated • -Stores nucleic acid • Can evolve quickly • Population sizes can be in the trillions

7. Reproduction promotes Genetic Diversity • Rapid Reproduction + Mutations = Much Diversity • E Coli Example • E coli reproduce by binary fission yielding offspring of identical genomes. Mutations occur one in 10 million cell divisions. There are approximately 200 billion new E coli cells in the human intestine daily. The total amount of mutations per day equal 9 million. • Genetic Recombination results from combining DNA from two different sources. Conjugation – When two bacteria are linked by a mating bridge – Donor cell extends Sex pilli. ***Note – Not all cells are donors (p. 563) -Sex Pilli are formed by a fertility gene or F – factor - F – factors can be found either in the plasmid (F+) or in the chromosomes (Hfr) R – plasmid strain Antibiotic resistance Transduction -Use of viral phage -Part of Bacterial DNA is incorporated into viral DNA -New viral DNA inserts DNA into new host

8. Role of Oxygen • Obligate Aerobes – need and use O2 • Obligate anaerobes – are poisoned by O2 • Anaerobic Respiration – use NO3-1 or SO4-2 instead of O2 as an electron receptor • Facultative Anaerobic Respiration will use O2 if present Bacteria use a variety of ways to gain energy and carbon needed to make necessary organic molecules. Bacteria also cooperate in colonies -Some form biofilms

9. Archaea • Methanogens – Anaerobes that produce methane gas. • Extremophiles – lovers of extreme environments • Thermophiles – heat loving • Halophiles – salt loving Eukarya (p. 569) -Gram + -Gram – -Cyanobacteria – only photosynthesis process that resembles plants.

10. Bacteria form ecological interactions like… • Mutualism • Commensalism – most bacteria on/in your body • Parasitism/pathogens – disease causing • -Exotoxins – produced and excreted by bacteria • -Endotoxins – produced by breakdown of dead bacteria’s cell walls • Bacteria are essential in … • Bioremediation • Industry • Genetic Engineering • Making of synthetic species • Bacteria are….. • Decomposers