KingdomsArchaebacteria and Eubacteria

KEY CONCEPT

Kingdoms Eubacteria and Archaeabacteria are composed of single-celled prokaryotes.

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

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.

ARCHAEA BACTERIA• Archaea are single celled organisms, classified as prokaryotes along with bacteria.

• they are among the earliest forms of life that appeared on earth.

• Archaea and Bacteria diverged from a common ancestor about 4 billion years ago.

• Millions of years later, the ancestors of Eukaryotes split off from the Archaea.

• Some (but not all) archaeans live in extremely adverse conditions and are often called extremophiles.

• Thermophiles - live in extremely hot temperatures (some can survive 100 Celsius - like in a hydrothermal vent).

• Halophiles - live in very salty, called hypersaline, environments

Halobacteria

Classifying Archaebacteria

• Psycrophiles - live at unusually cold temperatures (some are found in Antarctic lakes). Most will die above 20 Celsius.

• Acidophiles - many can exist at a pH of 0, all live in acidic environments.

Mud-Pool at Rotorua, NZ

• Not all archaea are extremophiles, many live in normal temperatures and environments.

• Most are methanogens which means they absorb CO2, N2, or H2S and gives off methane gas as a waste product the same way humans breathe in oxygen and breathe out carbon dioxide.

• Archaea was originally thought to be just like bacteria, but are actually a much different and simpler form of life.

• Archaea requires neither sunlight for photosynthesis as do plants, nor oxygen for respiration.

Archaebacteria

• Archaebacteria are typically obligate anaerobes (cannot live in oxygen).

• 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.

• 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.

Typical Eubacteria

• 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

Eubacteria groups (prefixes describe bacteria)

• Diplo: two• Staphlo: cluster• Strepto: chain

• Ex. Diplococcus• Ex. Staphlospirlli• Ex. Streptobacillus

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

• 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 (large amounts)

peptidoglycan – gram-negative stains pink, less (very little)

peptidoglycan

ASEXUAL REPRODUCTION:

• Since bacteria lack a nucleus, true mitosis and meiosis cannot occur.

• Reproduction of bacteria in this case must occur through binary fission (splitting in two).

• Bacteria contain a single chromosome which holds its genetic information

• This single chromosome replicates, the bacteria grows, elongates and separates the 2 chromosomes.

• The cell then builds a partition between the two chromosomes and the original cell splits into 2 smaller identical cells.

• This method is very fast and a bacteria cell can divide in 20 minutes.

• The two new bacteria both multiply again and so on, and so on. A single cell can become 30,000 cells in only 5 hours.

Bacterial Reproduction

Sexual Reproduction - Bacteria have various strategies for survival.

• Form of genetic recombination is conjugation.– transfer of genetic

material (exchanging of genes) between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells

conjugation bridge

TEM; magnification 6000x

Other forms of genetic exchange• Transduction:

exchange of genes using a virus, does not require cell-to-cell contact like conjugation.

• Transformation: endocytosis of free-floating DNA outside the cell.

Transduction

Transformation

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

Prokaryotes provide nutrients to humans and other animals.

• Prokaryotes live in digestive systems of animals. – make vitamins– break down food – fill niches

• Bacteria help ferment many foods.– yogurt, cheese– pickles, sauerkraut – soy sauce, vinegar

Prokaryotes play important roles in ecosystems.

• Prokaryotes have many functions in ecosystems. – photosynthesize – recycle carbon, nitrogen,

hydrogen, sulfur – fix nitrogen

• Bioremediation uses prokaryotes to break down pollutants.

– oil spills

– biodegradable materials

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.

– immune system may be lowered

• Normally harmless bacteria can become destructive.

Ex. Tuberulosis (Mycobacterium tuberculosis)

• Bacteria multiply in the lungs, killing WBCs• Host releases histamines which cause swelling

Ex. Staph poisoining (Staphylococcus aureus)

• Food poisoning caused by mishandling of food• Infection of the skin

Ex. Botulism (Clostridium botulinum)• Improperly canned foods contaminated with endospores

Ex. Flesh eating bacteria (Streptococci) • Colonize tissue through cut or scrape

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.

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

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.