Prokaryotic life Characteristics, Classification, Evolution

E. coli, a Typical Eubacterium Peptidoglycan Cell Membrane Ribosomes Pili DNA Flagellum Cell Wall

Characteristics Small –few micrometers in length Unicellular No nucleus May have flagella for movement

Characteristics Have a cell wall –May contain peptidoglycan (a sugar & protein polymer) Found Everywhere Many Cause Disease Many are Useful Very diverse

Prokayotes can be autotrophs or heterotrophs -Autotrophs: -Self producers, by sunlight or organic chemicals -Heterotrophs: - Consumes energy from other organisms Energy can be released by: cellular respiration if there is oxygen available fermentation if there is no oxygen. Characteristics

Classification Divided into 2 Domains: –Archaea –Bacteria

Hot Spring Yellowstone Deep Ocean Vent Compost Food Cavities

Archaebacteria vs. Eubacteria Archaebacteria Are ancient. Lack peptidoglycan. Live mostly in harsh environments –Salty lakes –Thick mud –Deep ocean vents –Guts of animals Eubacteria Considered “true bacteria” Have peptidoglycan. Live almost everywhere.

Classification Can be classified by shape: –Cocci- round –Bacilli- rod shaped –Spirilla- spiral

3 Possible Shapes of Bacteria Bacilli Cocci Spirilla

Prefixes Used to Describe & Identify Bacteria: Diplo = 2 –Neisseria meningitidis (aka diplococcus meningitidis) Strepto =chain –Streptococcus pneumonia Staphylo =clumps –Ex: Staphylococcus aureus

Gram Staining - used to identify bacteria with extra membranes –Extra membrane helps them to better resist damage and means they are usually more pathogenic (disease causing). –Gram + stain purple (have peptidoglycan) –Gram – (extra membrane) stain red Classification

Their success depends on the selective pressures that are applied. If they can survive their environment they will survive to reproduce and spread. Obstacles that bacteria have to overcome: –Temperature –Food –Chemical balance –Antibiotics –Antimicrobials Evolution

Why so successful in evolving? Recall: All living organisms have evolved from a common ancestor. Short, rapid reproduction time Diversity of bacteria: Bacteria can be found virtually everywhere. They are in the air, soil, water, and in and on plants and animals, including us.

Examples of bacterial evolution: Bacterial resistance to anti-biotics Bacterial resistance to anti-microbials (hand sanitizer/soap)

Bacteria can share genetic content. This is why bacteria are so successful: the sharing of advantageous traits may enable evolving species to become even more successful. Evolution of antibiotic resistant bacteria

Prokaryotic Reproduction Binary fission and Conjugation

Bacterial Reproduction They can reproduce in 2 main ways: –Binary Fission (asexual): splitting in half –Conjugation (sexual): sharing genetic info

Binary Fission Video

-Conjugation (sexual) : swapping genes over a bridge between two bacteria

Successful Evolution Bacteria can reproduce very rapidly! –E.coli can reproduce in just 20 minutes! Environments exert natural selection on populations causing them to change.