Prokaryotes Structure Function Reproduction Diversity Ecological Impact

Prokaryotes Dominate the biosphere Collective biomass outweighs all eukaryotes Found wherever there is life About 5,000 species known, but an estimated 400,000 – 4 million species

Prokaryotes Make up two kingdoms and domains –Domain Bacteria kingdom Eubacteria –Domain Archaea kingdom Archaebacteria

Domain Bacteria Most diverse and widespread Prokaryotes Have cell walls that contain peptidoglycan Include everyday common bacteria such as E. coli, streptococcus, and staphylococcus

Domain Archaea Extreme prokaryotes –Live in extreme locations like hydrothermal vents, high salinity areas, and in anaerobic conditions –Extremophiles such as methanogens, halophiles, and thermophiles Cell walls do not contain peptidoglycan Have unique lipids in membrane Have as much in common with Eukarya as they do Bacteria

Structure Most unicellular –May colonize Three most common shapes –Cocci – spheres –Bacilli – rods –Spirilla – spiral, helices

Structure Almost all have cell walls –Differ in composition and construction from eukaryotic cell walls –Most have peptidoglycan – polymers of sugars and short polypeptides (Eubacteria) Can be identified by gram stain –Gram-positive – simpler and large amount of pep. (trap violet dye) –Gram –negative – more complex and less pep. (retain red dye)

Gram Stain PositiveNegative

Structure May secrete sticky substance to form a capsule Some have surface appendages called pili used for adherence

Motility Flagella (tail-like) most common movement mechanism –May have one or several –May be scattered or concentrated –Differ from euk. Flagella; one-tenth the width and not covered by plasma membrane

Motility May have helical filaments that rotate –Corkscrew like movement May secrete slimy threads that allows it to glide along May wander randomly

Taxis Movement toward or away from stimulus –Chemotaxis – response to chemicals Toward food or oxygen (+) Away from toxins (-) –Phototaxis – response to light Move toward light (+)

Prokaryotic Genome Have smaller, simpler genomes –About 1/1000 DNA of euk. Concentrated in nucleoid region (since they lack nuclei) One double-stranded, ring shaped chromosome May have smaller DNA plasmids with additional genes

Reproduction Mostly asexual by binary fission (split in half) –Creates identical cells –Can occur very rapidly May transfer genes between two individuals –Transformation – takes up genes from surroundings –Conjugation – direct transfer with the help of pili –Transduction – transfer of genes by viruses

Nutrition and Metabolism Nutrition – how the organism get energy and carbon to build organic compounds Four major modes of nutrition: –Photoautotrophs – use light energy to drive synthesis of org. cmpds from CO 2 –Chemoautotrophs – use chemicals to get energy and use CO 2 as carbon source –Photoheterotrophs – use light to generate energy and consume organic compounds –Chemoheterotrophs – consume organic compounds for energy and carbon

Metabolism and Oxygen Variation among metabolism of prok. –Obligate aerobes – use O 2 for cellular respiration –Facultative anaerobes – will use O 2 if present but can grow by fermentation in anaerobic environments –Obligate anaerobes – poisoned by O 2 ; live exclusively by fermentation or perform anaerobic respiration

Ecological Impact Many serve as decomposers or producers Major role in nutrient cycles –Nitrogen fixation and denitrification –Use and production of CO 2 Symbiotic relationships –Mutualists or parasites Pathogens – disease causing –May invade tissues or produce endotoxins or exotoxins

Other uses Research Genetic engineering Bioremediation – removal of pollutants –Sewage treatment –Oil spill clean up Production of commercial products Food industry

Major Groups/Clades Proteobacteria – large, diverse, gram negative bacteria Chlamydias – gram negative parasites Spirochetes – spiral-shaped; free – living or pathogens (syphilil and Lyme disease) Gram-Positive Bacteria – very diverse; includes strep and staph Cyanobacteria – photoautotrophic producers; chloroplast ancestor