Prokaryotes Chapter 27 Outline Prevalence of Prokaryotes Prokaryotic

Prokaryotes Chapter 27

Outline • • Prevalence of Prokaryotes Prokaryotic Diversity Prokaryotic Complexity Prokaryotic Variation Prokaryotic Metabolism Human Bacterial Diseases Benefits of Prokaryotes 2 2

Prevalence of Prokaryotes • Prokaryotes are the oldest, structurally simplest, and most abundant forms of life on earth. – abundant for over 2 billion years before the appearance of eukaryotes – 5, 000 different kinds currently recognized 3 3

Prokaryotic Cell 4 4

Prevalence of Prokaryotes • • Prokaryotic form – bacillus (bacilli) straight and rod-shaped – coccus (cocci) spherical shaped – spirillum (spirilla) long and helical shaped Some bacterial colonies form spore producing structures. 5 5

Prevalence of Prokaryotes • Prokaryotes versus Eukaryotes – unicellularity – cell size – chromosomes – cell division and recombination – internal compartmentalization – flagella – metabolic diversity 6 6

Prokaryotic Diversity • Key classification characteristics – photosynthetic or nonphotosynthetic – motile or nonmotile – unicellular or colony-forming or filamentous – spore formation by division or transverse binary fission 7 7

Kinds of Prokaryotes • Very early, prokaryotes split into two lines – Archaea and bacteria are as different in structure and metabolism from each other as either is from eukarya. § Domain Archaea 8 8

Prokaryotic Diversity • Comparing archaebacteria and bacteria – plasma membranes § composed of different lipids – cell wall § archaebacteria lack peptidoglycan – gene translation machinery § archaebacteria similar to eukaryotes – gene architecture § bacteria not interrupted by introns 9 9

Prokaryotic Complexity • Prokaryotic cell surface – cell wall maintains shape and protects the cell from swelling and rupturing § usually consist of peptidoglycan v Gram-positive - thicker peptidoglycan v Gram-negative - thinner peptidoglycan – flagella – slender protein - locomotion – pili - hairlike structures - attachment – endospores - resistant to environment 10 10

Gram Stain 11 11

Flagellar Motor 12 12

The Cell Interior • • • Internal membranes – invaginated plasma membrane Nucleoid region – lack nucleus - genes encoded with single double-stranded DNA Ribosomes – Prokaryotic ribosomes are smaller than eukaryotic ribosomes, and differ in protein and RNA content. 13 13

Prokaryotic Variation • Two process create bacterial variation: – mutation § spontaneous errors in DNA replication v prokaryotic ability to mutate rapidly often has adverse effect on humans – genetic recombination § occurs by gene transfer from one cell to another by viruses or conjugation 14 14

Prokaryotic Metabolism • • Autotrophs – obtain carbon from inorganic CO 2 § photoautotrophs - sunlight § chemoautotrophs - inorganic chemicals Heterotrophs – obtain carbon from organic molecules § photoheterotrophs - sunlight § chemoheterotrophs - organic molecules 15 15

Prokaryotic Metabolism • How heterotrophs infect host organisms – proteins secreted by type III system § may be used to transfer other virulence proteins into nearby eukaryotic cells 16 16

Human Bacterial Diseases • • Tuberculosis – afflicts respiratory system and easily transmitted from person to person through the air Dental caries – tooth decay caused by bacteria present in plaque § high sugar diets increase tooth decay v lactic acid bacteria ferment sugars and reduce p. H, thus degenerating tooth enamel 17 17

Human Bacterial Diseases • Sexually transmitted diseases – Gonorrhea (Neisseria gonorrhoeae) – Syphilis (Treponema pallidum) – Chlamydia (Chlamydia trachomatis) 18 18

Benefits of Prokaryotes • • Environment – chemical cycling – decomposition – nitrogen fixation § reduces N 2 to NH 3 Symbiotic properties – nitrogen-fixation – digestive tract of animals 19 19

Benefits of Prokaryotes • • Genetic engineering – nonpolluting insect control – bioremediation § pollutant removal – biofactories § commercial production of antibiotics Bioweapons – anthrax – smallpox 20 20

Bioremediation 21 21

Summary • • Prevalence of Prokaryotes Prokaryotic Diversity Prokaryotic Complexity Prokaryotic Variation Prokaryotic Metabolism Human Bacterial Diseases Benefits of Prokaryotes 22 22

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