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.

flagellum

pili

plasmid

cell wall

chromosome

plasmamembrance

This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences.

– plasmid (circular DNA)

– flagellum – Pili (genetic

exchange)

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

• Eubacteria commonly come in three forms. – rod-shaped, called bacilli

Lactobacilli: rod-shaped Spirochaeta: spiral

– spiral, called spirilla or spirochetes

– spherical, called cocci

Enterococci: spherical

Domain Bacteria, Kingdom Eubacteria

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

GRAM NEGATIVE GRAM POSITIVE

– The amount of peptidoglycan within the cell wall can differ between Eubacteria: Gram negative has extra outer membrane, Gram positive cell wall just peptidoglycan

18.4 Bacteria and Archaea

• Gram staining identifies bacteria.

Gram-negative bacteria have a thin layer of peptidoglycan and stain red.

Gram-positive bacteria have a thicker peptidoglycan layer and stain purple.

– stains polymer peptidoglycan – gram-positive stains purple, more peptidoglycan – gram-negative stains pink, less peptidoglycan

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

– immune system may be lowered

• Normally harmless bacteria can become destructive.

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

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

• Kill the weak bacteria while stronger bacteria become resistant

Underuse of Antibiotics

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.