Prokaryotes; Campbell textbook

What characteristics enable prokaryotes to reach large population sizes and thrive in diverse environments

• Small size

• Rapid reproduction

• Mutations

• Diverse adaptations

• Rapid evolution

What domains do prokaryotes make up

Bacteria and archaea

Common shapes of prokaryotes

1. Spherical (e.g. cocci)

2. Rod shaped (e.g. bacilli)

3. Spiral (e.g. spirochetes)

Role of the cell wall

Maintains cell shape, protects the cell and prevents it from bursting in a hypotonic environment

Peptidoglycan

A polymer composed of modified sugars cross linked by short polypeptides

What is the capsule

A sticky layer of polysaccharide or protein which surrounds the cell wall and enables the prokaryote to adhere to their substrate or other individuals in a colony.

Endospores

Resistant cells which develop when certain bacteria lack water or essential nutrients. It is formed when the original cell produces a copy of its chromosome and surrounds that copy with a multilayered structure

Fimbriae

Hairlike appendages that allow some prokaryotes to attach to surfaces or to other cells

Taxis

A directed movement toward or away from a stimulus for example moving towards nutrients and oxygen or moving away from toxic substances

3 main parts of bacterium flagella

Motor, hook and filament

Where are chromosomes in prokaryotes

Nucleoid- a region of cytoplasm that is not enclosed by a membrane

What are plasmids

Small rings of independently replicating DNA

Genetic recombination

The combining of DNA from two sources

What processes bring together DNA from different prokaryotic individuals

1. Transformation; the genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA

2. Transduction; phage carry prokaryotic genes from one host cell to another

3. Conjugation; DNA transferred between two prokaryotic cells that are temporarily joined this is always in one way in bacteria

F factor

Particular piece of DNA (F for Fertility) which exists either as a plasmid or segment of DNA

What must use oxygen for cellular respiration and cannot grow without it

Obligate aerobes

What are poisoned by oxygen

Obligate anaerobes

Do facultative anaerobes use oxygen

If it is present but can carry out fermentation in an anaerobic environmen

Nitrogen fixation

Conversion of nitrogen to ammonia carried out by heterocysts

Biofilms

Surface coating colonies which secrete signalling molecules that recruit nearby cells to cause the colony to grow

Key groups of bacteria

• Spirochetes

• Proteobacteria

• Cyanobacteria

• Chlamydias

• Gram positive

Extremophiles

Live in environments so extreme that only few can survive

Where do extreme halophiles live

Highly saline environments

Where do extreme thermophiles live

Very hot environments

What are methane gens

Archaea which release methane as a byproduct of how they obtain energy