Download 18.4 Bacteria and Archaea

18.4 Bacteria and Archaea
KEY CONCEPT
Kingdoms Eubacteria and Archaeabacteria are
composed of single-celled prokaryotes.
18.4 Bacteria and Archaea
Prokaryotes are widespread on Earth.
• Prokaryotes can be grouped by their need for oxygen.
– obligate aerobes
are need oxygen
– facultative aerobes
can live with or
without oxygen
– obligate
anaerobes are
poisoned by
oxygen
18.4 Bacteria and Archaea
• Eubacteria and Archaebacteria are structurally similar but
have different molecular characteristics.
– plasmid (circular
DNA)
– flagellum
– Pili (genetic
exchange)
pili
plasma
membrance
chromosome
cell wall
plasmid
This diagram shows the typical structure
of a prokaryote. Archaea and bacteria
look very similar, although they have
important molecular differences.
flagellum
18.4 Bacteria and Archaea
Domain Archaea, Kingdom Archaebacteria
• Archaebacteria are typically obligate anaerobes.
• Live in extremely harsh environments, ex.stomachs of
cows, high salt concentrated areas such as the Dead
Sea and in sulfur springs or deep sea vents.
• Divided into 3 groups: methanogens (methane
producers, halophiles (salt loving) and thermophiles (heat
loving)
• Come in a variety of shapes, similar to Eubacteria.
• There is no peptidoglycan in their cell walls, contain
entirely different lipids than Eubacteria.
• ***Eubacteria is actually evolutionary older than
Archeabacteria
18.4 Bacteria and Archaea
Domain Bacteria, Kingdom Eubacteria
•
Eubacteria commonly come in three forms.
– rod-shaped, called bacilli
– spiral, called spirilla or spirochetes
– spherical, called cocci
Lactobacilli: rod-shaped
Enterococci: spherical
Spirochaeta: spiral
18.4 Bacteria and Archaea
Eubacteria groups (prefixes describe bacteria)
• Diplo: two
• Staphlo: cluster
• Strepto: chain
• Ex. Diplococcus
• Ex. Staphlospirlli
• Ex. Streptobacillus
18.4 Bacteria and Archaea
Eubacteria
– The amount of peptidoglycan within the cell wall can
differ between Eubacteria: Gram negative has extra
outer membrane, Gram positive cell wall just
peptidoglycan
GRAM NEGATIVE
GRAM POSITIVE
18.4 Bacteria and Archaea
• Gram staining identifies bacteria.
– stains polymer peptidoglycan
– gram-positive stains purple, more peptidoglycan
– gram-negative stains pink, less peptidoglycan
Gram-negative bacteria have a thin layer of
peptidoglycan and stain red.
Gram-positive bacteria have a thicker
peptidoglycan layer and stain purple.
18.4 Bacteria and Archaea
Bacteria have various strategies for survival.
• Form of genetic
recombination is
conjugation.
– Prokaryotes
exchange genes
using pili
conjugation bridge
TEM; magnification 6000x
18.4 Bacteria and Archaea
Other forms of genetic exchange
• Transduction: exchange of genes using a virus
• Transformation: endocytosis of DNA
18.4 Bacteria and Archaea
Bacteria survival
• Bacteria may survive by
forming endospores.
– Resistant to most
cleaning agents and
temperature changes
– Creates double
membrane around
DNA to survive harsh
conditions
– Sterilize versus
disinfect?
18.4 Bacteria and Archaea
Prokaryotes provide nutrients to humans and other
animals.
• Prokaryotes live in digestive systems of animals.
– make vitamins and medicines
– break down food
– fill niches (role in ecosystem)
18.4 Bacteria and Archaea
• Bacteria help ferment many foods.
– yogurt, cheese
– pickles, sauerkraut
– soy sauce, vinegar
18.4 Bacteria and Archaea
Prokaryotes play important roles in ecosystems.
• Prokaryotes have many functions in ecosystems.
– photosynthesize
– recycle carbon, nitrogen,
hydrogen, sulfur
– fix nitrogen (make it useable)
18.4 Bacteria and Archaea
• Bioremediation uses prokaryotes to break down
pollutants.
– oil spills
– biodegradable materials
18.4 Bacteria and Archaea
Some bacteria cause disease.
• Bacteria cause disease by one of two methods:
– invading tissues
– making toxins (poison released by an organism)
18.4 Bacteria and Archaea
• Normally harmless bacteria can become destructive.
– immune system may be lowered
18.4 Bacteria and Archaea
Ex. Tuberculoses (Mycobacterium tuberculosis)
• Bacteria multiply in the lungs, killing WBCs
• Host releases histamines which cause swelling
18.4 Bacteria and Archaea
Ex. Staph poisoining (Staphylococcus aureus)
• Food poisoning caused by mishandling of food
• Infection of the skin
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Ex. Botulism (Clostridium botulinum)
• Improperly canned foods contaminated with endospores
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Ex. Flesh eating bacteria (Streptococci)
• Colonize tissue through cut or scrape
18.4 Bacteria and Archaea
Antibiotics are used to fight bacterial disease.
• Antibiotics may stop bacterial cell wall formation.
• Their role is to interfere with the ability of the bacteria’s
reproduction process.
18.4 Bacteria and Archaea
Overuse of Antibiotics
• Bacteria become resistant due to exposure
Underuse of Antibiotics
• Kill the weak bacteria while stronger bacteria become
resistant
Misuse of Antibiotics
• Viruses cannot be treated with antibiotics, allowing
normal bacteria to become resistant or killing them
18.4 Bacteria and Archaea
Bacteria can evolve resistance to antibiotics.
1. Bacterium carries genes
for antibiotic resistance on
a plasmid (circular DNA).
2. Copy of the plasmid is
transferred through
conjugation (using pili).
3. Resistance is quickly
spread through many
bacteria.