1. Prokaryotes Prokaryotes are microscopic single-celled organisms. Although you cannot see them without the aid of a microscope, their combined biomass is more than ten times that of the eukaryotes.

2. Prokaryotic Structure size1-5mm (resolution of the human eye ~750mm) Cell wall – main component is peptidoglycan (modified sugar polymers) can be further differentiated performing a gram stain – positive – More peptidoglycan – negative – Less peptidoglycan » more often pathogenic » liposaccharides of the cell surface are often toxic to the host » more resistant to antibiotics – Bacteria from Achaea lack peptidoglycan but have other polysaccharides

3. Prokaryotic Structure May contain a capsule – protects against the hosts defenses – helps it adhere to substances or to others in the colony – may also adhere to surfaces using fimbriae (tiny hair-like structures) or pili (cytoplasmic extension used to attach during conjugation)

4. Motility flagella – hair-like structure – Most common mode of locomotion – Movement by a whip-like motion cilia – many shorthair-like structures covering entire organism – Movement by oar-like motion taxis -movement toward a particular stimuli – chemotaxis- toward a substrate – phototaxis- toward light – thermotaxis- toward heat

5. Internal organization of genome – lack compartmentalization – DNA located in nucleoid region single stranded ring of DNA may have a smaller ring called a plasmid – contains specialized genes that help it survive under other than normal conditions » example: antibiotic resistance, digestion of a special substrate,... – Replicate independently of the DNA – can be transferred between bacteria Ribosomes are slightly smaller that in eukaryotes – Free floating and not attached to an ER – certain antibiotics bind to them and render them useless » erythromycin & tetracyclin

6. Reproduction and Adaptation Reproduction via binary fission – can pass characteristics via conjugation – rapidly reproduce aiding in adaptation increases mutation rate for adaptation slowed by lack of nutrients, poisoning by waste, competition by other microorganisms and defenses of host – presence of endospores helps them survive in harsh conditions copy of DNA surrounded by a thick wall Contents are dehydrated can last centuries Rehydration activates the endospore to become bacteria

7. Nutritional requirements Photoautotrophs- use the sun's energy to produce energy. need CO 2 as a substrate cyanobacteria – Chemoautotrophs- make own energy from other chemicals may use NH 3, H 2 S, or Fe 2+ as energy source methanogens – Photoheterotrophs - use light for the production of energy but must obtain carbon from an organic source – Chemoheterotrophs - must consume organic molecules for both energy and carbon Most prokaryotes

8. Metabolism aerobes -use oxygen for cellular respiration – Facultative - make energy best in the presence of oxygen but can do fermentation if oxygen is not present anaerobes- use fermentation for the production of energy – Obligate anaerobes - poisoned be oxygen and grow exclusively be fermentation – May extract energy anaerobically by the reduction of other molecules (NO 3, SO 4 ) Nitrogen is incorporated into the organism through the process of nitrogen fixation Some colonies may work under metabolic cooperation where organisms produce products that are in turn used by a neighboring colony – Nitrogen fixaton