Ch 23: Bacteria

• Are prokaryotes:– Unicellular– No membrane-bound organelles

(nucleus, ER, lysosomes)

• Live nearly everywhere… in/on other organisms, in ice, in hot springs,

at the bottom of the ocean, in rocks, soil, air

• 2 main kinds: Eubacteria and Archaea

Archaea

• Live in extreme environments (temperature, pressure, chemicals (methane, salt))

• Different:– Cell walls (more peptiodglycen (protein+

sugars))– Lipids in cell membranes– DNA and RNA

Classifying Bacteria

• Shape: Colonies:– Round (coccus) Strepto (chains)– Rod (bacillus) Staphylo– Spiral (spirillum) (clusters)

Classifying Bacteria

• Gram stain– Stains outer wall, depending on structure– Gram +: purple, simple cell wall– Gram - : red, complex cell walls

Impact on humans:

• Proteobacteria: live in soil and make nitrogen usable by living things

• Gram +: cause disease (botulism, anthrax), make food (yogurt, sour cream), make antibiotics

• Cyanobacteria: makes oxygen, food for aquatic food chains

• Spirochetes: cause Lyme Disease andsyphilis

• Chlamydia: STD

Structures and functions

• Outside:– Up to 3 layers:• Cell membrane: lets things in and out• Cell wall (different makeup than plants):

structure• Capsule (maybe): helps stick together

–Movement:• Flagella: long whip like tail, may have many• Cilia: small hairs-like structures

– Pili: small structures for reproduction

Structures and functions

• Inside– Cytoplasm: where most cell functions take

place, since no organelles– Ribsomes: make proteins– DNA: in a loop

• Plasmid, small separate piece of DNA

• Getting oxygen:– Some bacteria have to have: (obligate

aerobes)– Some have to not have (obligate anaerobes)– Some can live with or without (facultative

anaerobes)

Reproduction• Asexually: Binary fission– DNA ring copies (2 only replication forks)

and cell splits in two

• Sexually:– Conjugation: exchange DNA with

another bacterium through pili– Transformation: take in DNA in

environment (usu. from dead bacteria)

– Transduction: get new DNA from a virus

Reproduction

Bacteria and Health

• Sometimes it releases chemicals while it’s alive (exotoxins), sometimes after it’s dead (endotoxins)

• Antibiotics: medicines that fight bacterial diseases. Make cell wall stop growing so bacterium “pops”

• Population can become resistance to antibiotics by mutation or by not finishing whole course of medications

Antibacterial Resistance

Good or bad?

• Bad:– Anthrax Botulism Cholera– Tooth decay Gonorrhea Tetanus– Lyme disease Salmonella E. coli– Staph infectionStrep throat

• Good:– Food: sour cream, cheese, yogurt, pickles, – Copy DNA for medicines– Fight pests (Bt)– Decompose– Nitrogen cycle

Ch 24: Viruses• Not considered alive:– Don’t reproduce on own– don’t metabolize– don’t grow/develop– don’t perform homeostasis– don’t respond to environment

Structure/classification

• Vary greatly in structure/shape– DNA or RNA – Surrounded by capsid (protein coat)– Some surrounded by bilipid envelope

• Classified by:– DNA or RNA– Single or double strand– Linear or circular– Shape of capsid

Replication

• Viruses injects DNA/RNA, takes over the cell, makes the cell make

more viruses, Kills cell when new viruses released infects more cells

• 2 cycles:– Lytic: happens fast, virus kills cells,

virulent phages– Lysogenic: happens slow…days, weeks,

months, years. Virus “hides” in the cell as part of cell’s genome, then enters lytic

cycle, temperate phages

Lytic cycle• Virulent phage: happens quickly

– Viruses injects DNA/RNA– takes over the cell, makes the cell make more viruses– Kills the cell when viruses released to infect more cells

Lysogenic cycle• Temperate phage: happens slowly…days, weeks,

months, years. – Virus “hides” in the cell as part of cell’s genome– then enters lytic cycle and kills cells

Diseases & treatments

• Diseases:– Chicken pox/shingles AIDS– Hepatitis Warts– Flu Meningitis– Ebola SARS– Bird Flu

• Treatments:– Vaccines: give inactive virus or parts of virus,

helps immune system recognize and respond faster

– Control vector: if spread by animal, kill animal– Antiviral drugs (few available)