Blue Green Algae Diagram of Bacteria

BACTERIA

Biology 20 Salmonella Bacteria

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Common Bacteria

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 Belong to the Domain Bacteria and Kingdom Eubacteria  They are microscopic prokaryotes. Organisms are classified as bacteria by one characteristic: the lack of a cell nucleus.

 They are the most numerous organisms on Earth. There are more bacteria on or in your body than there are people in the world!

Bacteria

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 Relatively few species of bacteria cause infection.  Hundreds of species of bacteria live on the human body and within the gastrointestinal tract (critical to human well-being).

Bacteria

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 • They have evolved into many different forms and are part of every environment on Earth. For example, there are: Aerobic organisms that need oxygen to survive.

• • • Anaerobic organisms that die in the presence of oxygen.

Autotrophic organisms that produce their own food.

Heterotrophic organisms that get their nutrition from other organisms.

Kinds of Bacteria

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 Currently identified using DNA but historically the shape and arrangement of bacteria identified them Shape Spherical (coccus) Rod-shaped (bacillus) Spiral (spirillum)  Three basic shapes: round, rod-shaped, or spiral

Kinds of Bacteria

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 Spirillum only live as single cells.

 Some coccus form pairs and chains while others grow in grape like bunches. Arrangement

Diplo – paired Staph – in clusters Strep – in chains

 Some bacilli also form pairs or chains but they do not grow in bunches.

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Characteristics

 Prokaryotic cell  Singular circular chromosome  Cell wall containing peptidoglycan  Lacking nuclear envelope  Lacking organelles and cytoskeleton

Structure

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Structures that help bacteria survive in hostile environments

 Capsules (slime layers) – protects the cell from drying out, helps evade immune system and adhere to surfaces  Pilli – hair-like projections that help cells attach to surfaces  Endospores – bacteria become dormant until conditions become favourable

Structure

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Structures that help bacteria move

 Flagella – one or more tail like structures

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Reproduction

 Occurs most often by an asexual process called binary fission  One cell splits into two cells; offspring are genetically identical to parents  Can occur in under 20 minutes; producing 1 billion bacteria in under 10 hours

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Reproduction

 Can also occur through bacterial conjugation  Two cells attach to each other and exchange genetic information; offspring have new genes and new traits  Only between bacteria in the same or closely related species

Photosynthetic Bacteria

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Cyanobacteria

 commonly called blue green algae  the oldest known fossil (>3.5 billion years old!)  responsible for many Proterozoic oil deposits  cyanobacterial blooms common on prairie sloughs – can harm livestock, pets, and humans

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Gram-negative bacteria

 Few organisms have the ability to utilize atmospheric nitrogen.  Nitrogen-fixing bacteria within the root nodules of certain plants provide a usable source of nitrogen to plants. E.g. Rhizobium,

Pseudomonas

Bacteria & Health

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 Only a small percentage of bacteria cause disease in humans.  Bacterial diseases include: gonorrhea, chlamydia, strep throat, pneumonia, acne, botulism, food poisoning, Lyme disease.

 Bacteria can also cause disease in plants and animals.

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Eubacteria & Archaebacteria

Archaebacteria

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 Classified in Domain and Kingdom Archaea  Thought to be more ancient than bacteria and yet more closely relate to eukaryotes  Their cell walls do not contain peptidoglycan and they have some of the same proteins as eukaryotes.

Archaebacteria

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 There are diverse in shape and nutrition. Some are autrophic, but most are heterotrophic.  They are referred to as “extremophiles” because they can live in extreme environments: boiling hot springs, salty lakes, thermal vents on the ocean floor, and marsh mud where there is no oxygen.

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Characteristics

      Prokaryotic cell Singular circular chromosome Cell wall without peptidoglycan Membrane lipids Lacking nuclear envelope With organelles and cytoskeleton

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Methanogens

 Typically found in swamps and marshes  Produce methane gas as a by-product of metabolism

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Thermoacidophiles

 Resistant to hot temperatures and high acid conditions  Found in acid hot springs, acidic soil, and deep ocean volcanic vents