BIOL1105 Lecture 11 Prokaryotes PDF

BIOL1019 Module 3 Lecture A Bacteria and Archaea (Prokaryotes) Readings: Chapter 1 ( section 1.2) Chapter 25 (all sections) Reading: Chapter 27  Define prokaryotes. List the structural and functional attributes of Learning...

BIOL1019 Module 3 Lecture A Bacteria and Archaea (Prokaryotes) Readings: Chapter 1 ( section 1.2) Chapter 25 (all sections) Reading: Chapter 27  Define prokaryotes. List the structural and functional attributes of Learning prokaryotes. Objectives Explain what happens during prokaryote reproduction. State the roles of prokaryotes in the biosphere and in human health.  Two of the three domains for the Tree of Life are prokaryotic. Prokaryotes  Bacteria & Archaea Dominate planet by numbers and biomass Prokaryotes Relatively simple morphology and anatomy Circular chromosomes and plasmids Rapid reproduction, mutation and genetic recombination = high genetic variation  Masters of Adaptation Prokaryotes have been found living in: Hot springs Environments that are too toxic/hostile (high salinity, pH, polluted) for other forms of life Substrate 2 km below Earth's surface!  Prokaryotes play crucial roles in the biosphere Decomposition & nutrient cycling Some fix atmospheric N2 Symbiotic and parasitic relationships Essential for eukaryotic survival!  Prokaryotes have both beneficial and harmful impacts on humans Responsible for ~ 50% of human diseases 500-1000 species of prokaryotes in the human microbiome  An Overview of Prokaryotic Diversity  Diverse nutritional and metabolic adaptations have evolved in prokaryotes Photoautotroph = Chemoautotroph = Photoheterotroph = Chemoheterotroph =  Structural and functional adaptations contribute to prokaryotic success Forms: Individual cells (coccus, bacillus, spiral)​ Temporary or permanent aggregates/colonies​ Simple multicellular forms Division of labour (e.g. heterocyst) Structure and Function Cell wall Maintains shape Protects cell Prevents bursting in hypotonic environment Structure and Function Capsule Outside cell wall​ Polysaccharides or proteins Protection from host Attachment​ Substrate​ Colony formation​ Fimbriae & pili Hair-like appendages​ Attachment​ Structure and Function Endospore formation Waiting for environment to change Chromosome duplicated Encased with essential cellular components (enzymes, etc.) Water removed (halting metabolism) Lysis releases endospore Structure and Function Motility Directed motion (=taxis) Mechanisms: Gliding Flagella - over surface or concentrated at one or both ends Structure and Function Internal organization No membrane-bound organelles Plasma membrane Some have internal membranes to increase surface area for metabolic activity & exchange with the environment  Prokaryote DNA Small & circular No nucleus; nucleoid region Some have plasmids Three factors contribute to diversity: Rapid reproduction Mutation Genetic recombination  Reproduction Binary fission Rapid!  Mutation is the source of most generation-to-generation variation 1 mutation in each gene every 10 million cell divisions One human = 20 billion new E. coli per day 2000 mutations per gene every day in a single human E. coli has 4300 genes, so 8.6 million mutant E. coli per Prokaryote person per day! Reproduction Other sources of genetic variation: Transformation Uptake of naked foreign DNA from environment Transduction Viruses that infect bacteria transfer DNA from one host to another Conjugation Direct transfer of DNA from one bacterium to another  (modified) Requires F factor (plasmid or chromosomal) Pilus Conjugation F+ = donor; F- = recipient Sex pili attach F+ to F- F+ condition is heritable (modified)  Hfr (high frequency of recombination) transfer DNA transferred from Hfr to F- cell, recombination Conjugation occurs Non-circularized DNA degraded (modified)  In summary Prokaryotes include bacteria and Archaea. Bacteria and Archaea are both lineages comprised of unicellular organisms with circular chromosomes and no membrane-bound organelles (other features we discussed are common). Bacteria are distinct from Archaea in that they have peptidoglycan in their cell walls. Reproduce via binary fission. Sources of genetic variation include transformation, transduction, and conjugation. Reading for Next Class Chapter 28: Protists