Prokaryotes

Taxis and Chemotaxis Taxis: movement towards or away from a stimulus (signal) in the environment Positive Chemotaxis  move TOWARDS nutrients or oxygen Negative Chemotaxis  move AWAY from toxic chemicals

Cooperation in Colonies Specialized cells within a colony (ex. Anabaena… some photosynthesize; others undergo nitrogen fixation) Biofilms  individuals in colony secrete molecules to attract nearby cells = allows colony to grow

Molecular systematics Emergence of “Archaea” domain Diversity in prokaryotes is HUGE! Horizontal gene transfer is prokaryote evolution (conjugation)

Impact of bacteria on Earth and Life Bacteria are decomposers (break down dead/decaying material) Cyanobacteria produce oxygen Various symbiotic relationships (mutualism, commensalism, parasitism)

B. thetaiotaomicron In our digestive tract Genes in bacteria help synthesize carbs, vitamins, and other nutrients (these are used by our bodies) Help stimulate vascular network in intestinal lining (nutrient absorption) In return, human cells induced to produce antimicrobial compounds to keep other bacteria out of our systems

Endo and Exotoxins EXOTOXINS ENDOTOXINS Both exo and endotoxins produce toxic substances! Exo: secreted by bacteria while alive (ex. cholera, botulism) Endo: released once bacteria die Toxins in cell wall (ex. salmonella)

Bacterial Benefits! Used in production of some cheeses and yogurt Bioremediation  removing pollutants from soil, air and water Metal extraction from ores Genetic engineering  production of important vitamins, antibiotics, and hormones

Bacterial Reproduction… Quick Facts Reproduction happens FAST Can reproduce within 20 minutes Binary Fission Asexual form of reproduction Most bacteria reproduce this way Let’s check out the diagram…

Let’s check out this diagram… Conjugation A sexual “form” of reproduction Protein “bridge” forms between 2 bacteria… allows for transfer of a SMALL piece of genetic info Bacteria get new genetic info = increased DIVERSITY within the bacterial population! Let’s check out this diagram…

Endospore Formation Promotes bacterial survival in difficult environmental conditions Unfavourable Conditions: lack of food; pH not optimal; too hot/cold Endospore forms to protect genome Bacteria remains dormant until… Favourable conditions return One last diagram…

Interesting Bacterial Groups… Bacteria- diverse group Archaea Extreme thermophiles: live in hot environments (thermal vents in ocean, volcanic springs) Extreme halophiles: live in very salty environments (Dead Sea, salt flats) Methanogens: anaerobes (poisoned by oxygen)- use CO2 to oxidize H2 & release methane in the process * All other organisms fall into the Domain Eukarya (Eukaryotes)