Prokaryotes

Prokaryotes• Microscopic, unicellular cells that may form

colonies• The three most common of which are spheres

(cocci), rods (bacilli), and spirals

Cell Surface Structure

• The cell wall of many prokaryotes is covered by a capsule, a sticky layer of polysaccharide or protein

• Adhere to molecules– fimbriae and pili

• Protection

Cell Surface Structure

Gram + bacteria contain large amounts of peptidoglycanGram – bacteria contain greater amounts of lipopolysaccharides

Motility• propel themselves by flagella• exhibit taxis– ability to move toward or away from certain

stimuli

Genome

• a ring of DNA that is not surrounded by a membrane and that is located in a nucleoid region

• Some have smaller rings of DNA called plasmids

Variation

• Nutrition types– Photoautotrophy– Chemoautotrophy– Photoheterotrophy– Chemoheterotrophy

• Metabolism– varies with respect to oxygen

Archaea

• Some archaea live in extreme environments– very hot environments– high saline environments

Gene Transfer and Genetic Recombination

• Transformation– alteration of a bacterial

cell’s genotype and phenotype by the uptake of naked, foreign DNA from the surrounding environment

Gene Transfer and Genetic Recombination

• Transduction– phages carry bacterial genes from one host cell to

another

Gene Transfer and Genetic Recombination

• Conjugation – direct transfer of genetic material between

bacterial cells that are temporarily joined• The transfer is one-way: One cell (“male”)

donates DNA, and its “mate” (“female”) receives the genes– ability to form a sex pilus and donate DNA, results

from an F (for fertility) factor