1 Prokaryotes Chapter 27

2 Prevalence of Prokaryotes Prokaryotes are the oldest, abundant for over 2 billion years before the appearance of eukaryotes structurally simplest, most abundant forms of life on earth. – 5,000 different kinds currently recognized bacillus coccus spirillum pili - hairlike structures - attachment endospores - resistant to environment

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

4 Prokaryotic Diversity 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. 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

5 Gram Stain for Bacterial classification Gram-positive - thicker peptidoglycan Gram-negative - thinner peptidoglycan

6 Flagellar Motor flagella – slender protein - locomotion

7 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.

8 Prokaryotic Variation Two process create bacterial variation: – mutation  spontaneous errors in DNA replication  prokaryotic ability to mutate rapidly – genetic recombination  occurs by gene transfer from one cell to another by viruses or conjugation

9 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

10 Benefits of Prokaryotes decomposition nitrogen fixation digestive tract of animals nonpolluting insect control pollutant removal commercial production of antibiotics