The Basics of Bacteria

What are bacteria? Bacteria are single-celled prokaryotes Bacteria are single-celled prokaryotes DNA is not located in a nucleus DNA is not located in a nucleus Bacteria appeared on Earth at least 3.5 billion years ago Bacteria appeared on Earth at least 3.5 billion years ago

Bacterial Shapes Most bacteria have one of the following shapes: Most bacteria have one of the following shapes: Bacilli Bacilli Cocci Cocci Spirilla Spirilla

Bacterial Structures Most bacteria have the following structures: Most bacteria have the following structures: Cell wall (contains peptidoglycan, a compound composed of amino acids and carbohydrates) Cell wall (contains peptidoglycan, a compound composed of amino acids and carbohydrates) Cell membrane Cell membrane Cytoplasm Cytoplasm Chromosome (Single-loop of DNA) Chromosome (Single-loop of DNA)

Additional Bacterial Structures Some bacteria may have the following structures: Some bacteria may have the following structures: Capsule (covering outside of cell wall that protects bacterial cell) Capsule (covering outside of cell wall that protects bacterial cell) Pili (hair-like structures used to transfer genetic material from one bacterium to another) Pili (hair-like structures used to transfer genetic material from one bacterium to another) Endospore (Thick covering around DNA; developed under harsh conditions) Endospore (Thick covering around DNA; developed under harsh conditions) Plasmid (small, additional loop of DNA) Plasmid (small, additional loop of DNA) Flagella (Used for motion) Flagella (Used for motion)

Nutrition and Growth Bacteria obtain their energy in one of two ways: Bacteria obtain their energy in one of two ways: Heterotrophs (must obtain “food” for energy) Heterotrophs (must obtain “food” for energy) Autotrophs (obtain energy from sunlight or minerals) Autotrophs (obtain energy from sunlight or minerals)

Nutrition and Growth continued Oxygen requirements Oxygen requirements Obligate anaerobes (can’t survive in presence of oxygen) Obligate anaerobes (can’t survive in presence of oxygen) Facultative anaerobes (don’t require oxygen, but can survive around it) Facultative anaerobes (don’t require oxygen, but can survive around it) Obligate aerobes (require oxygen) Obligate aerobes (require oxygen)

Bacterial Reproduction Bacteria reproduce by binary fission: Bacteria reproduce by binary fission: One cell divides to form two identical cells One cell divides to form two identical cells

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Genetic Recombination If bacteria reproduce “clones” by binary fission, why aren’t all bacteria identical? If bacteria reproduce “clones” by binary fission, why aren’t all bacteria identical? Transformation: cell takes in DNA from environment and replaces a portion of its own DNA with this new DNA Transformation: cell takes in DNA from environment and replaces a portion of its own DNA with this new DNA Conjugation: A bacterium attaches its pilus to another cell and transfers a copy of its plasmid to this cell Conjugation: A bacterium attaches its pilus to another cell and transfers a copy of its plasmid to this cell Transduction: Virus “infects” a bacterium with a piece of bacterial DNA it is carrying from a different bacterial cell Transduction: Virus “infects” a bacterium with a piece of bacterial DNA it is carrying from a different bacterial cell

Transformation transformation and conjugation video hill.com/sites/ /student_view0/chapter13/animation_quiz_ 1.html

Conjugation s/conjugation/conj_frames.htm

Transduction ulty/tfischer/images/speci alized%20transduction.jpg

Bacterial Defenses Bacteria have numerous defenses against the threats in their environment: Bacteria have numerous defenses against the threats in their environment: Exotoxins: Poisonous proteins secreted by bacteria Exotoxins: Poisonous proteins secreted by bacteria Endotoxins: Toxin in bacterial cell wall; released when bacteria die Endotoxins: Toxin in bacterial cell wall; released when bacteria die

Naturally-Occurring Antibiotics

Antibiotics Chemicals that interfere with cell functions; inhibit bacteria growth. Chemicals that interfere with cell functions; inhibit bacteria growth. Bacteria are sensitive if they don’t grow in the presence of the antibiotic. Bacteria are sensitive if they don’t grow in the presence of the antibiotic. Bacteria are resistant if they do grow in the presence of the antibiotic. Bacteria are resistant if they do grow in the presence of the antibiotic.

Bacteria Growth and Antibiotics