Prokaryotes Chapter 27

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

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

Prokaryotic Cell

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.

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

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

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

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

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

Gram Stain

Flagellar Motor

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.

Prokaryotic Variation Two process create bacterial variation: mutation spontaneous errors in DNA replication 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

Prokaryotic Metabolism Autotrophs obtain carbon from inorganic CO2 photoautotrophs - sunlight chemoautotrophs - inorganic chemicals Heterotrophs obtain carbon from organic molecules photoheterotrophs - sunlight chemoheterotrophs - organic molecules

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

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 lactic acid bacteria ferment sugars and reduce pH, thus degenerating tooth enamel

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

Benefits of Prokaryotes Environment chemical cycling decomposition nitrogen fixation reduces N2 to NH3 Symbiotic properties nitrogen-fixation digestive tract of animals

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

Bioremediation

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