Chapter 28

ADVANCED BIOLOGYPROKARYOTES

The Earth formed approximately 4.5 billion years ago

The first fossil formations found on Earth are dated to 3.5 billion years ago Microfossils

Fossil form of microscopic organisms

Isotopic Data Carbon-12 is found in

microfossilsThis is used for carbon

dating of organisms and carbon fixation Pathways include:

Calvin Cycle (photosynthesis)

Krebs Cycle (cellular respiration)

Hydrocarbons biomarkers

THE FIRST CELLS (28.1)

Abundant amounts of prokaryotes – ~10% identified

New techniques to identify w/o culturing

Two groups: Archae and

Eubacteria

Prokaryotes are the oldest form of life.

They have a simple structure and

They are also the most abundant form of life on Earth Cyanobacteria

(photosynthetic) changed Earth’s atmosphere to be able to produce oxygen

PROKARYOTIC DIVERSITY (28.2)

Found in deep sea caves, volcano rims and inside glacier formations

Some Archae are extremophiles – extreme environments such as hot springs, geysers, toxic gases and extreme cold (Anartica)

Extremes may indicate earth’s conditions 3.5 bya

PROKARYOTES CAN LIVE ANYWHERE

Prokaryotes Unicellular Cell size – vary

≤1ųm up to 750 ųm Single circular chromosome Plasmids Binary Fission – asexual Horizontal gene transfer No internal compartments –

ribosomes differ Flagella – single fiber – spin Oxygenic and anoxygenic chemolithitrophic

Eukaryotes Unicellular and

multicellular Cell size – normally

≥10ųm Membrane bound nucleus Mitosis – sexual Genetic Diversity via

Mutations Membrane bound

organelles Flagella and cilia

w/microtubules – whiplike Photosynthesis release

oxygen

PROKARYOTE VS. EUKARYOTE

Prokaryotes Eukaryotes

Plasma membrane in both but differs in glycerol link to hydrocarbon chains

Cell Wall– Peptiglycan in Eubacteria but not in Archae

DNA Replication differs by place of origin and proteins

Gene Expression – Archae may have more than one RNA polymerase

ARCHAE VS. EUBACTERIA

CLASSIFICATION

Classification of prokaryotes were gram staining and observations such as: Can photosynthesize Mobility Unicellular or colonies Spores or binary fission Whether it is pathogenic

Now classified by evolutionary means using DNA analysis

Three basic forms:Rod shaped (bacillus)

Sperical shaped (coccus)

Spiral shaped (spirillum or spirochetes)

PROKARYOTE CELL STRUCTURE (28.3)

Cell wall determines cell shapeLack cell wall, no particular cell shape

FlagellaChainsColoniesBranching

filaments

CELL STRUCTURE

Cell wall basically contains peptidoglycan with a polymer that forms a strand of crosslinked polysaccharides with peptide chains

Archae may have pseudomurein or pseudopeptidoglycan

CELL WALL

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Gram + will stain purple

Thick Peptioglycan so traps crystal violet

Gram – will stain pink

Multiple layers does not trap crystal violet but will show the red dye

GRAM STAINING

CapsuleGel type outer layer

Allows for adherance and evasion from immune system

Flagella Structure that allows movement connected at cell wall and spins – made of protein flagellin

OTHER STUCTURES

Pili Hairlike structure that allows movement (gram-), attachment and exchange of genetic information

EndosporesDormant stage in prokaryotes

Thick wall formed when environmental stress

Stay dormant for days to centuries Examples: Tetanus or

anthrax

Internal membranesRespiratory membranes – photosynthesis

Nucleoid Double stranded circular DNA (nucleoid region)

Plasmid – replicating circular DNA (small)

RibosomesSmaller than Eukaryote ribosomes

Different proteins and RNA

Antibiotics will bind to these ribosomes blocking protein synthesis

INTERNAL STRUCTURES

Prokaryotes reproduce asexually

Exchange DNA throughConjugation - transfer plasmids (F+/F- )

Transduction transformation

CONJUGATION

PROKARYOTIC GENETICS (28.4)

TransductionDNA transfer from one bacterium to another via a virus

Transformation (Griffith) – Cell death causes lysis that releases fragments of DNA into the environment where another bacteria incorporates it into its genetic material

Plasmids can have resistant genes incorporated E.coli found in digestive tract of humans vulnerable

Due to its rapid reproduction a mutation in a bacterium can spread rapidlyMedia growth (Nutrient Agar) Auxotroph – need

supplement MRSA and VRSA

ANTIBIOTIC RESISTANCE AND MUTATIONS

Intake of energy and carbon – 4 Ways: Photoautotrophs Chemolithoautotro

phs Photoheterotrophs Chemoheterotroph

s

Photoautotrophs – sunlight to build from carbon dioxide

Chemolithoautotrophs – oxidize inorganic substances such as ammonia to nitrite

Photoheterotrophs – Sunlight for energy and other molecules for carbon

Chemohetertrophs – carbon and energy from other molecules

PROKARYOTIC METABOLISM (28.5)

Infective diseases by bacteria killed over 20% of US children before age 5 before the discovery of antibiotics by Pasteur and Koch

Bacteria can infect by various methods such as droplets in air, feces or pests

See Table 28.1 on page 561.

HUMAN BACTERIAL DISEASE

Prokaryotes can cause harm but there are some that are beneficialBacterial decomposers along with fungi put C, N,P, S back into the soil

Fixation during nutrient cycling of carbon and nitrogen

Symbiotic relationshipsMutualism – nitrogen fixation or digestion

Commensalism - live outside of organism without harming

Parasitism - infection

BENEFICIAL PROKARYOTES

Genetic EngineeringHuman genes can be inserted into bacterium to produce human proteins such as insulin

Biofactories for enzymes, vitamins, antibiotics and industrial compounds

BioremediationRemoving pollutants from water, air and/or soil

Bacterium used in wastewater treatment plants to breakdown raw sewage.

Future development in removing toxic waste