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
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.
pili
– plasmid
– flagellum
– 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, and they
contain entirely different lipids than Eubacteria.
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-negative stains pink, less (very little)
peptidoglycan
– gram-positive stains purple, more (large amounts)
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.
– transfer of genetic
conjugation
material (exchanging
bridge
of genes) between
bacterial cells by
direct cell-to-cell
contact or by a
bridge-like
connection between
TEM; magnification
6000x
two cells
18.4 Bacteria and Archaea
Other forms of genetic exchange Transduction
• Transduction:
exchange of genes
using a virus, does
not require cell-tocell contact like
conjugation.
• Transformation:
endocytosis of free- Transformation
floating DNA
outside the cell.
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
18.4 Bacteria and Archaea
Prokaryotes provide nutrients to humans and other
animals.
• Prokaryotes live in digestive systems of animals.
– make vitamins
– break down food
– fill niches
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
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.
- A toxin is a 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. Tuberulosis (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
18.4 Bacteria and Archaea
Ex. Botulism (Clostridium botulinum)
• Improperly canned foods contaminated with endospores
18.4 Bacteria and Archaea
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.
2. Copy of the plasmid is
transferred through
conjugation.
3. Resistance is quickly
spread through many
bacteria.