ch 16 prokaryotes thrive in moderate & extreme environments found everywhere (ubiquitous) some...

Ch 16 Prokaryotes • Thrive in moderate & extreme environments • Found everywhere (ubiquitous) • Some are beneficial (good) • Some are harmful • Earliest forms of life on Earth

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Ch 16 Prokaryotes• Thrive in moderate & extreme environments

• Found everywhere (ubiquitous)

• Some are beneficial (good)

• Some are harmful

• Earliest forms of life on Earth

Steps to Life Steps to Life

• Earth’s atmosphere contained CO, CO2, N2, and H2O, but little or no O2

• Energy sources like volcanoes, lightning, and UV radiation from the sun were all very intense

• “Early Earth” experiments produce SIMPLE organic compounds including all 20 amino acids, several sugars, lipids, the nitrogenous bases found in DNA and RNA, and even ATP.

Steps to Life

• To imitate early Earth, organic molecules in lab were placed in extreme places (volcanic rock, sand, dirt, heat vents)

• They polypeptides and polysaccharides – formed without living cells or enzymes being present.

• Other experiments have shown that polypeptides can come together and form microscopic, fluid-filled spheres called pre-cells.

All of these experiments together support a hypothetical four-stage sequence for how life could have first developed on Earth.

• First, small organic molecules, such as amino acids and nucleotides, formed from simpler molecules present in the environment.

• Second, these small molecules joined together into larger ones such as proteins and nucleic acids.

• Third, molecules that could copy themselves provided a basis for the inheritance of molecular information.

• In the last stage, these various organic molecules became packaged within membranes and separated from their surroundings forming pre-cells.

2 domains of prokaryotes(Archaea and Bacteria)

Archaea – Greek = meaning "ancient." – prokaryotes, many live in extreme environments on Earth.– extremophiles, meaning "lovers of the extreme."

• thermophiles (heat lovers) live in hot water such as the hot springs of Yellowstone National Park or deep-sea vents

• Halophiles (salt lovers) thrive in such environments as Utah's Great Salt Lake, or in seawater evaporating ponds.

• Some archaea live in oxygen-free environments such as the mud at the bottom of lakes and swamps where they produce bubbles of "swamp gas" (methane).

• Bacteria – Prokaryotic organisms classified as bacteria

differ from archaea in cell structure and chemical makeup

– Scientists place the two groups of prokaryotes in separate domains partly because of key differences in the information contained in their nucleic acids (DNA and RNA).

2 domains of prokaryotes(Archaea and Bacteria)

Structure of Bacteria





Characteristics of Bacteria 1. Unicellular- only one cell 2. Prokaryotic- lacks a nucleus and membrane bound organelles.


A)Bacillus- rod shaped

B)Spirilla- spiral shaped

C)Cocci- spherical


Bacilli Cocci Spirilla

Bacteria is identified based partly on three characteristics:

• Cell Shape– Bacteria come in three basic

shapes:– Spherical – cocci (berries)– rod-shaped -- bacilli– spiral-shaped -- spirochetes

• Cell Wall Structure

• Motility – About half of all prokaryotes are motile, meaning

that they can move. – flagellum (plural, flagella) or slime threads


A)gliding on slime B)twisting in acorkscrew fashion C) FlagellaD) some don't move


• Most prokaryotes reproduce at a very fast rate under the right conditions.

• Prokaryotic cells copy their DNA almost continuously and divide repeatedly.

• called binary fission

Modes of Nutrition• "mode of nutrition" describes how

organisms obtain energy and carbon atoms.– energy by photosynthesis = photo-– Energy from chemical sources = chemo-

– Autotrophs obtain carbon atoms from CO2

– Heterotrophs obtain carbon from existing organic molecules (such as those in food).

• Adding a prefix, photo- or chemo-to either autotroph or heterotroph fully describes the mode of nutrition

Chemical Recycling

• Life depends on the cycling of chemical elements between the biological and nonliving parts of ecosystems. Prokaryotes play a vital role in chemical recycling.

• Many prokaryotes perform an essential function by breaking down, or decomposing, organic waste products and dead organisms in the environment.

Human Uses of Prokaryotes

• bioremediation -- the use of organisms to remove pollutants from water, air, and soil

• Pseudomonas is used to clean up oil spills on beaches

• Other prokaryotes are used to clean up old mining sites where the water is acidic and laced with chemicals such as arsenic, copper, zinc, lead, and mercury.

• In another example of the usefulness of prokaryotes, pharmaceutical companies raise bacteria that make vitamins and antibiotics.

Helpful Bacteria

A) Bacteria in the intestine help digest food

B) Bacteria help in production of cheese, yogurt, sour cream, pickles, and sauerkraut.

C) Bacteria decompose dead organisms

D) Some bacteria help plants by Nitrogen Fixation

How Bacteria Cause Illness• You are constantly exposed to bacteria -- they are in

the air you breathe, in the water and food you ingest, and on the surfaces you touch.

• most bacteria are neither harmless or helpful to you, BUT some bacteria can make you ill.

• Bacteria and other microorganisms that cause disease are called pathogens.

• Some bacteria cause disease by invading tissues and destroying cells.

• Most pathogenic bacteria cause disease by producing bacterial poisons.

Harmful Bacteria

A) 1 - 5% of bacteria are Pathogens - disease causing organisms

B) Disease is caused by attacking cells directly or the production of toxins- poisons

Defense Against Bacterial Diseases

• Since the discovery that bacteria cause many diseases, cases of such diseases have declined dramatically.

• the major reasons for this decline are better hygiene and public health measures. – washing hands– careful preparation of food– attention to water quality help minimize the

risk of pathogen infection.

Defense Against Bacterial Diseases

• The human body protects itself against infection– Your skin and the mucous lining of your mouth,

nose, and digestive system provide a physical barrier to bacteria.

– Those bacteria that do manage to enter (through a cut, for example) meet chemical and cellular defenses that make up the immune system.

• Doctors and medicines also play a role in fighting bacterial diseases. – Antibiotics = chemicals that slow or prevent the

growth of microorganisms.– Many antibiotics act by damaging or preventing

the formation of the bacterial cell wall.

Protection against bacteria

A) Antibiotics- chemicals produced by fungus that inhibit bacterial growth or kill the bacteria.

B) Penicillin- first antibiotic discovered by Alexander Flemming in 1929.

Lab Conclusion:

1. Where did you expose your petri dish?

2. Why did you think there would be bacteria present there?

3. Was bacteria present?

4. What are the conditions most favorable for bacteria growth.

5. Where can we conclude bacteria lives?