Marconi 2007

Marconi 2007

Bacteria consist of only a single cell, but don't let their small size and seeming simplicity fool you. They're an amazingly complex and fascinating group of creatures.

Marconi 2007

Builders of Modern Life Bacteria are among the

earliest forms of life that appeared on Earth billions of years ago.

Bacteria helped shape and change the young planet's environment, eventually creating atmospheric oxygen that enabled other, more complex life forms to develop.

Marconi 2007

What are bacteria? Bacteria are unicellular, living things.

Prokaryotic cells (without a nucleus).

Obtain nutrients is different ways: Photosynthetic autotrophs- convert inorganic

molecules into sugar using sunlight Heterotrophs- consume food by growing on it Saprophytes- obtain food by decomposing dead

material Chemotrophs- manufacture organic compounds

from inorganic compounds such as hydrogen sulfides

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Cyanobacteria in a lake

Bacteria feeding on saguaro

Chemotrophs at hydrothermal Vent

Bacteria used in wastewater treatment

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Marconi 2007

Marconi 2007

Classification of Prokaryotes

All prokaryotes belong to the kingdoms:Archaea Eubacteria

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Archaea First discovered in 1970’s Discovery made the term “Moneran” obsolete Biochemically different from eubacteria May have evolved in the harsh conditions of

early Earth They are abundant in, but not restricted to,

extreme environments because of their ability to withstand the harshest of environments

May be the early ancestors of eubacteria

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Characteristics of Archaea Archaea (Formerly Archaebacteria)

Lack an important carbohydrate (peptidoglycan) found in the cell wall of nearly all Eubacteria.

Live in harsh environments Oxygen-free environments

Methanogens (ex. Thick mud & digestive tracts)Produce methane gas

Salty environmentsExtreme HalophilesGreat Salt Lake/Dead Sea

Hot SpringsThermoacidophiles

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Characteristics of EubacteriaEubacteria = Modern Bacteria

Unicellular Cell walls contain peptidoglycan Genes lack introns Reproduce asexually by binary fission Either autotrophic or heterotrophic Extremely diversified groups Certain types may be ancestors of

mitochondria

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Identifying Prokaryotes

Bacterial ShapesBacillus = Rod Coccus = RoundSprillium = Spiral

Colony growthCells arranged in

particular ways Form long chains Grow in clusters

Bacterial movementFlagellaSome do not moveSome glide

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Shape #1 is rod shape, also known as bacillus.

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Shape #2 is sphere shaped, also known as coccus.

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Shape #3 is spiral shape, also known as sprillum

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Micrococcus luteus tetrad Bacillus cereus

Vibrio Rhodospirillum

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Bacterial Structures

Cell Wall- support and protection No nucleus- Bacterial DNA is usually coil-

shaped and not enclosed in a nuclear membrane. Most bacteria also have small ring-shaped pieces of

DNA called plasmids Capsule- protective layer that surrounds the cell Some have flagellum to aide with movement Pilus aides in adhesion to other cells

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Marconi 2007

Bacterial growth and reproduction

Grow and reproduce at an incredible rate when conditions are favorable

Bacterial growth stays under control due to limiting factors such as nutrient availability and production of waste products.

Reproduction methodsBinary fissionConjugation

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Binary fission

Asexual reproduction

When a bacterium is almost double in size, it replicates it’s DNA and divides in half.Example: E. coli

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Conjugation Sexual reproduction Long bridge of protein in

between 2 bacterial cells connecting them.

Genetic material from donor cell is transferred to the other cell.

Recipient cell ends up with different combo of genes. Leads to genetic

variation, evolution, antibiotic resistance Example

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Spore formation

Spores form when conditions become unfavorable.

Endospore is a type of spore that forms a thick internal wall that protects the DNA and cytoplasm.

Endospores can remain dormant for months to years while waiting for favorable conditions to arise.

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Food production Yogurt, cheese, buttermilk, sour cream, pickles

Used in industry Digest petroleum; clean up oil spills Used in mining Used in sewage treatment plants

Symbiosis Digestion Nitrogen-fixation and plants

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PathogensDisease causing agentsSmall number of bacteria are pathogens

Examples of pathogenic bacterial infections:Syphilis, cholera, tuberculosis, bubonic plague,

botulism, tetanus, gingivitis, strep throat Pathogens cause disease by:

Damaging cells and tissues for use of nutrientsRelease toxins

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Marconi 2007

Antibiotics destroy bacteria by disrupting the structure of the cell wall

Over prescribing of antibiotics is causing antibiotic resistance because bacteria mutate readily

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Bacterial respiration Energy is supplied by respiration and

fermentation Respiration involves oxygen and breaks down food

molecules to release energy Fermentation is energy production without oxygen

Obligate aerobes Bacteria that require a constant supply of oxygen

Obligate anaerobes Must live in the absence of oxygen Example: Clostridium botulinum

If subjected to air and allowed to grow on food, it will produce toxins that cause severe food poisoning.

Facultative anaerobes Can survive with or without oxygen Allow facultative anaerobes to live almost anywhere.

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The End