Bacteria and Archaea

Page
4

F factor

Hfr cell

A+

A+

A+

A+

A+

A–

A–

A–

A–

A+

Recombinant

F– bacterium

Slide 25

R Plasmids and Antibiotic Resistance

R plasmids carry genes for antibiotic resistance.

Antibiotics select for bacteria with genes that are resistant to the antibiotics.

Antibiotic resistant strains of bacteria are becoming more common.

Slide 26

Concept 27.3: Diverse nutritional and metabolic adaptations have evolved in prokaryotes

Phototrophs obtain energy from light.

Chemotrophs obtain energy from chemicals.

Autotrophs require CO2 as a carbon source.

Heterotrophs require an organic nutrient to make organic compounds.

These factors can be combined to give the four major modes of nutrition: photoautotrophy, chemoautotrophy, photoheterotrophy, and chemoheterotrophy.

Slide 27

Prokaryotic Nutritional Diversity

Slide 28

The Role of Oxygen in Metabolism

Prokaryotic metabolism varies with respect to O2:

Obligate aerobes require O2 for cellular respiration.

Obligate anaerobes are poisoned by O2 and use fermentation or anaerobic respiration.

Facultative anaerobes can survive with or without O2.

Slide 29

Nitrogen Metabolism

In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3).

Metabolic Cooperation between prokaryotes allows them to use environmental resources they could not use as individual cells.

In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocytes exchange metabolic products.

Slide 30

Metabolic Cooperation between Bacteria Cells

Photosynthetic

cells

Heterocyte

20 µm

Slide 31

Lessons from Molecular Systematics

Molecular systematics is leading to a phylogenetic classification of prokaryotes.

It allows systematists to identify major new clades.

The use of polymerase chain reaction (PCR) has allowed for more rapid sequencing of prokaryote genomes.

A handful of soil many contain 10,000 prokaryotic species.

Horizontal gene transfer between prokaryotes obscures the root of the tree of life.

Slide 32

Molecular Systematics: Classification

UNIVERSAL

ANCESTOR

Eukaryotes