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Prokaryotes• Oldest organisms on Earth
• The most dominant and successful forms of life
• Great metabolic diversity and rapid rate of growth
• Escherichia coli double in size every 20 min.
Prokaryotes
• Occur in icy areas of Antarctica
• Dark depths of the ocean
• Near-boiling waters of hot springs
• Can survive without free oxygen
What is the basic structure of a prokaryotic cell?
• Lack an organized nucleus • Plasma membrane and cell wall • Nucleiod region- Singular circular
or continuous DNA molecule (non-histone protien)
• May contain smaller extrachromosomal pies of circular DNA – plasmids
• Ribosomes and inclusions• Cynobacteria is an exception
contains many thylakoids (structure found in chloroplast responsible for photosynthesis)
Three major forms of prokaryotes
Bacilli- rod shaped bacterium
Cocci- sphere shape
Spirilla- long curved or spiral rods
Prokaryotes cause disease• Both animal and plants
• Humans (TB, cholera, anthrax, gonorrhea, botulism, syphilis, tetanus, ulcers)
Flagella on Pseudomonas marginalis- soil bacteriumCauses soft rot disease found in fleshy vegetables
Bacillus can form Endospores
• Certain species of Bacteria (Bacillus and Clostridium) can form endospores
• Endospores- dormant bacterial cells when food supply is low, resist heat, radiation, chemicals,
• Protoplast is dehydrated• Can remain viable for many years• Viable endospore obtained from a
25-40 million year old Extinct Bee gut
Mature Endospore- Bacillus Megaterium
Fruiting body of myxobacterium (Chrondomyces crocatus)A gliding bacterium produces fruitingBodies, each containing 1 million Cells (Slime Bacteria).
Another form of Bacteria-Slime Bacteria
Binary fissionCell division in a bacterium
Mutation does occur and are responsible for evolutionary adaptability
Metabolic Diversity
• Some Prokaryotes are autotrophs- self feeding– Photosythetic
Sunlight (Energy)+ 6CO2 + 6H2O C6H12O6 + 6O2
– Chemosythetic (chemolithotroph)
6{CO2}+6{H2O}+3{H2S} C6H12O6+3{H2SO4}
Prokaryotes world ecosystem
• Fixing nitrogen- incorporating nitrogen gas into nitrogen compounds
• Autotrophic bacteria major contributor to global carbon balance (more than 90% other than that associated with human activity comes from bacteria and fungi)
• Decomposers (natural and toxins)- patroleum, pesticides, mercury, and dyes-
Cyanobacteria
• Important in Carbon and nitrogen cycles• Photosynthetic cyanobacteria have chlorophyll
a, carotenoids and phycobilins.• Important lineage of bacteria and eukaryotic
cells
Limestone
Plankton
• Cells of cyanobacteria living in freshwater or marine habitats
• Plankton commonly contain bright irregularly shaped structures – gas vesicles
• Gas vesicles provide bouancy• When not able to regulate they float and
form mass “blooms”• Red sea- Trichodesmium
Nitrogen fixation
• Some cyanobacteria can fix nitrogen converting nitrogen gas to ammonium
• A form which the nitrogen is available for biological reactions
• Occurs in Heterocyst-specialized enlarged cells