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Chapter 13:
Prokaryotes and Viruses
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
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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
A filamentous actinomycete Streptomyces scabies
Bacterium found in soil causes potato scab disease
Thermophilic prokaryotesaerial view of a Hot spring
Yellowstone National Park
Wyoming
Halophiles- salt loving Archaea
Extreme thermophiles- archaea YNP HS rich
Flagella on Pseudomonas marginalis- soil bacterium
Causes soft rot disease found in fleshy vegetables
Three major forms of prokaryotes
Bacilli- rod shaped bacterium
Cocci- sphere shape
Spirilla- long curved or spiral rods
Bacillus-Clostridium botulinum- deadly food poisoning
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
Peptidoglycan in bacteria
Mature Endospore- Bacillus Megaterium
Cocci- Micrococcus luteus- and others that cause
Milk to sour and oxidizes ammonia to nitrites
Spirilla- Magnetospirillum magnetotacticum
Fruiting body of myxobacterium
(Chrondomyces crocatus)
A gliding bacterium produces fruiting
Bodies, each containing 1 million
Cells (Slime Bacteria).
Reproduction and Gene Exchange
• Most prokaryotes reproduce by simple cell
division called Binary Fission
• Produce ‘clones’
Binary fission
Cell division in a bacterium
Mutation does occur and
are responsible for
evolutionary adaptability
Adaptability of Bacteria
• Provided by the genetic recombinations that
take place in conjugation, transformation,
and transduction
Conjugation
• The prokaryotic version of sex
• Donor cell produces a ‘pilus’ and comes in
contact with the recipient cell
Pilus
Donor cell
Recipient cell
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}
Beggiatoa gigantea sewage Filamentous sulfur oxidizing bacteria
Heterotrophs
• Most are Heterotrophs- require organic
compounds
• Vast majority are the saprophytes (saprosrotten) obtain from dead material
• Saprophytic bacteria and fungi responsible
for decomposition
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-
Prokaryotes cause disease
• Both animal and plants
• Humans (TB, cholera,
anthrax, gonorrhea, botulism,
syphilis, tetanus, ulcers)
Prokaryotes used commercially
Antibiotics
Amino acids
Dairy products
Cyanobacteria
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Important in Carbon and nitrogen cycles
Photosynthetic cyanobacteria have chlorophyll
a, carotenoids and phycobilins.
Important lineage of bacteria and eukaryotic
cells
Hotsprings Yellowstone
Limestone
Cyanobacteria
Cyanobacteria electron micrograph
Cyanobacteria
Genera Oscillatoria
Cyanobacteria
Genera Calothrix
Cyanobacteria
Genera Nostoc commune
Stromatolites- flourishing colonies of cyanobacteria
Bind calcium carbonate into domed structures
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
Heterocyst
Filament of anabaena
Filament of Anabaena with heterocyst
Rice Planting Malaysia- Anabaena allow for continuous
Growing w/o fertilizer
Spiroplasmas- motile bacteria that cause corn stunt disease
And stubborn disease
Mycoplasmiclike organism devestated a grove of
Coconut palms
Mycoplasmalike Organisms- slow weakening
Bacterial effects on Plants
General life cycle of a virus
Two stages
1. Replication inside host
2. Spread to new host
Tobacco Mosaic Virus
Streaked flowers of Rembrant tulips
Viral infection eventually weakens plant
Wound tumor virus
Tumor produced in
sweet clover
Electron Microscope
Tumor virus particles