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

• 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

A filamentous actinomycete Streptomyces scabiesBacterium found in soil causes potato scab disease

Prokaryotes cause disease• Both animal and plants

• Humans (TB, cholera, anthrax, gonorrhea, botulism, syphilis, tetanus, ulcers)

Bacterial effects on Plants

Flagella on Pseudomonas marginalis- soil bacteriumCauses soft rot disease found in fleshy vegetables

Bacillus-Clostridium botulinum- deadly food poisoning

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

Cocci- Micrococcus luteus- and others that causeMilk to sour and oxidizes ammonia to nitrites

Fruiting body of myxobacterium (Chrondomyces crocatus)A gliding bacterium produces fruitingBodies, each containing 1 million Cells (Slime Bacteria).

Another form of Bacteria-Slime Bacteria

Slime bacteria - Psuedonomonas

• Pseudomonas corrugata

• Pith Necrosis of Tomato

Binary fissionCell division in a bacterium

Mutation does occur and are responsible for evolutionary adaptability

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

Spiroplasmas- motile bacteria that cause corn stunt diseaseAnd stubborn disease

Mycoplasmiclike organism devestated a grove ofCoconut palms

Mycoplasmalike Organisms- slow weakening

General life cycle of a virusTwo stages1. Replication inside host2. Spread to new host

Tobacco Mosaic Virus

Streaked flowers of Rembrandt tulipsViral infection eventually weakens plant

Wound tumor virusTumor produced in sweet clover

Electron MicroscopeTumor virus particles

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

Cyanobacteria electron micrograph

CyanobacteriaGenera Oscillatoria

Cyanobacteria Genera Nostoc commune

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

Filament of anabaena

Heterocyst

Filament of Anabaena with heterocyst

Rice Planting Malaysia- Anabaena allow for continuousGrowing w/o fertilizer