BIOL 1108 Edition 1nd Lecture 6 Outline of Last Lecture I Learning Objectives II Phylogenetic terminology III Homologies and Analogies IV Reading phylogenetic trees Outline of Current Lecture I Learning Objectives II Prokaryote vs Eukaryote III Archaea IV Bacteria V Phylogenetic Tree of Life Current Lecture I II Learning Objectives Know the defining features that distinguish eukaryotes and prokaryotes Be able to define the Archaea and know how to distinguish them from bacteria What role s do bacteria play in human biology ignore we did not get to this today What are the advantages and disadvantages of having a bacterial cell wall What is meant by antibiotic resistance and by what mechanisms can bacteria become resistant to antibiotics Prokaryote vs Eukaryote These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Prokaryotes These are typically organisms with no nucleus or major organelles within their cell Although they appear simple they can be biochemically and structurally very complex Includes Bacteria and Archaea Eukaryotes These are organisms with nuclei and cellular organelles sub cellular components with specialized functions such as mitochondria chloroplasts and cilia They include all animals plants fungi and protists III Both are considered to be single cells but the organization of bacteria and archaea is significantly less complex than in eukaryotes protists plants animals fungi In general the genomes of Bacteria and Archaea are smaller fewer genes less complexity and less DNA than those of Eukaryotes Archaea Bacteria and Archaea replicate by way of binary fission splitting into two The entire genome on a single chromosome duplicates and one copy is distributed to each of the daughter cells Cell membranes are chemically different from all other living things including a backwards glycerol molecule and isoprene derivatives in place of fatty acids Chemically the cell membranes of Bacteria and Eukaryotes are very similar to each other whereas the membranes of Archaea are quite different The cell walls of Archaea may be made of glycoprotein S layers or polysaccharides are but are not made of peptidoglycans IV Bacteria A Cell wall The bacterial cell wall differs from that of all other organisms by the presence of a peptidoglycan wall which is located immediately outside of the plasma membrane Peptidoglycan is polymer made of carbohydrates and amino acids and is responsible for the rigidity Relatively porous and is not considered to be a permeability barrier for small molecules B Gene Transfer Pilli needed to exchange genes because the bacterial cell wall prevents two bacterial cells from fusing their membranes and exchanging genes conjunction o When this occurs a physical connection conjugation tube is made between two cells The DNA on a plasmid is duplicated and the copied DNA is transferred Bacteria and Archaea replicate by way of binary fission splitting into two The entire genome on a single chromosome duplicates and one copy is distributed to each of the daughter cells o Bacteria typically have a single large circular chromosome and multiple smaller DNA plasmids Both chromosomes and plasmids can contain genes but only the chromosome is distributed with high fidelity to the daughter cells Transduction bacteriophages have evolved mechanisms to overcome bacterial defenses and insert their genome into a host cell ultimately killing it phage therapy a possible form of antibiotic treatment C Antibiotics In 1928 Scottish scientist Alexander Fleming noted that bacterial cultures accidentally contaminated with the fungus Penicillium chrysogenum secreted something that actively killed bacteria V Antibiotics such as penicillin block the formation of the peptidoglycan wall The increasing number of antibiotic resistant bacteria is one of the greatest threats facing modern medicine The antibiotic may be destroyed by an enzyme sequestered or inactivated by a different enzyme or actively pumped out of the cell by a third enzyme Phylogenetic Tree of Life Based on the sequences of the genes that code for ribosomal RNA in 1977 Carl Woese proposed that the Archaea were significantly different from the bacteria and were closer to eukaryotes