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Download II. Pathways of Discovery in Microbiology 1.6 The
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II. Pathways of Discovery in Microbiology 1.6 The Historical Roots of Microbiology The Historical Roots of Microbiology 1.6 The Historical Roots of Microbiology Robert Hooke (1635-1703) was the first to describe 1.7 Pasteur and the Defeat of Spontaneous Generation microbes Illustrated the fruiting structures of molds (Figure 1.9b) 1.8 Koch, Infectious Disease, and the Rise of Pure Anton A t van Leeuwenhoek L h k (1632-1723) (1632 1723) was th the fi firstt tto Culture Microbiology describe bacteria (Figure 1.10b) 1.9 Microbial Diversity and the Rise of General Further progess required development of more powerful Microbiology microscopes 1.10 The Modern Era of Microbiology Ferdinand Cohn (1828-1898) founded the field of bacteriology and discovered bacterial endospores Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Robert Hooke and Early Microscopy Robert Hooke and Early Microscopy Figure 1.9a Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 1.9b Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 1.7 Pasteur and the Defeat of Spontaneous Generation The van Leeuwenhoek Microscope Louis Pasteur (1822-1895) Discovered that living organisms discriminate between optical isomers Discovered that alcoholic fermentation was a biologically mediated process (originally thought to be purely chemical) Disproved theory of spontaneous generation (Figure 1.13) Led to the development of methods for controlling the growth of microorganisms Developed vaccines for anthrax, fowl cholera, and rabies Figure 1.10 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Pasteur’s Experiment Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 1 The Defeat of Spontaneous Generation: Pasteur’s Experiment The Defeat of Spontaneous Generation: Pasteur’s Experiment ~1860: Where do microorganisms come from? Spontaneous generation? Heat was used to kill the microbes in liquid Figure 1.13a Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings When dust was prevented from reaching the sterilized liquid, no microbes grew in the liquid Figure 1.13b Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Defeat of Spontaneous Generation: Pasteur’s Experiment 1.8 Koch, Infectious Disease, and the Rise of Pure Cultures Robert Koch (1843-1910) Definitively demonstrated the link between microbes and infectious diseases Identified causative agents of anthrax and tuberculosis Koch Koch’ss postulates (Figure 1 1.15) 15) Developed techniques (solid media) for obtaining pure cultures of microbes, some still in existence today Awarded Nobel Prize for Physiology and Medicine in 1905 Contact with dust resulted in growth of microbes in the liquid Æ disproved spontaneous generation Figure 1.13c Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Koch’s Postulates Anthrax, caused by Bacillus anthracis Organism present in blood of all diseased animals Æ cause or result of the disease? Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Koch’s Postulates Conclusion – specific organisms cause specific diseases Koch’s postulates can be extended beyond disease-causing organisms Figure 1.15 Figure 1.15 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 2 1.9 Microbial Diversity and the Rise of General Microbiology 1.9 Microbial Diversity and the Rise of General Microbiology General Microbiology Field that focuses on non-medical aspects of microbiology Sergei Winogradsky (1856-1953) and the Concept of Chemolithotrophy Roots in 20th century Demonstrated that specific bacteria are linked to specific Martinus Beijerinck (1851-1931) biogeochemical transformations (e (e.g., g S & N cycles) Developed Enrichment Culture Technique Microbes isolated from natural samples in a highly selective Proposed concept of chemolithotrophy Oxidation of inorganic compounds linked to energy fashion by manipulating nutrient and incubation conditions e.g., Nitrogen-fixing bacteria conservation (Figure 1.19) Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Major Concepts Conceived by Sergei Winogradsky Major Concepts Conceived by Sergei Winogradsky Figure 1.19a Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Figure 1.19b Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Some Landmarks in Molecular Microbiology since 1985 Brock Biology of Microorganisms Ch hapter 2 Twelfth Edition Madigan / Martinko Dunlap / Clark A Brief Journey to the Microbial World Figure 1.20 Lectures by Buchan & LeCleir Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 3 II. Cell Structure and Evolutionary History 2.5 Elements of Cell and Viral Structure 2.5 Elements of Cell and Viral Structure All microbial cells have the following in common: 2.6 Arrangement of DNA in Microbial Cells Cytoplasmic membrane 2.7 The Evolutionary Tree of Life Cytoplasm Ribosomes Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Internal Structure of Prokaryotic Cell Internal Structure of Eukaryote Cell No organelles Figure 2.11a Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 2.5 Elements of Cell and Viral Structure Figure 2.11b Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Electron Micrographs of Sectioned Cells Eukaryotic vs. Prokaryotic Cells Eukaryotes DNA enclosed in a membrane-bound nucleus Cells are generally larger and more complex Contain organelles Prokaryotes No membrane-enclosed organelles No nucleus Generally smaller than eukaryotic cells Figure 2.12a and b Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 4 Electron Micrographs of Sectioned Cells 2.5 Elements of Cell and Viral Structure Viruses Not considered cells No metabolic abilities of their own Rely completely on biosynthetic machinery of infected cellll Infect all types of cells Smallest virus is 10 nm in diameter Viruses of bacteria = bacteriophages Yeast cell, 8 μm diameter Figure 2.12c Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Virus Structure and Size Comparison of Viruses and Cells 2.6 Arrangement of DNA in Microbial Cells Genome A cell’s full complement of genes Prokaryotic cells generally have a single, circular DNA molecule called a chromosome DNA aggregates to form the nucleoid region Prokaryotes also may have small amounts of extrachromosomal DNA called plasmids that confer special properties ( i.e., antibiotic resistance) Figure 2.13 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 2.6 Arrangement of DNA in Microbial Cells Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Nucleoid Eukaryotic DNA is linear and found within the nucleus Associated with proteins that help in folding of the DNA Usuallyy have a e more o e than a one o e chromosome c o oso e Usua Typically have two copies of each chromosome [Insert Fig. 2.14] Figure 2.14 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 5 2.6 Arrangement of DNA in Microbial Cells The Tree of Life Defined by rRNA Sequencing Escherichia coli Genome 4.68 million base pairs 4,300 genes , different kinds of protein p 1,900 2.4 million protein molecules Human Cell 1,000X more DNA per cell than E. coli 7X more genes than E. coli Figure 2.17 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 2.7 The Evolutionary Tree of Life Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Ribosomal RNA (rRNA) Gene Sequencing and Phylogeny Evolution The process of change in a line of descent over time that results in new varieties and species of organisms Phylogeny Evolutionary relationships between organisms Relationships can be deduced by comparing genetic information (nucleic acid or amino acid sequences) in the different specimens Ribosomal RNA (rRNA) are excellent molecules for determining phylogeny Can visualize relationships on a phylogenetic tree Figure 2.16 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 2.7 The Evolutionary Tree of Life 2.7 The Evolutionary Tree of Life Comparative rRNA sequencing has defined three distinct lineages of cells called domains. Eukaryotic microorganisms were the ancestors of multicellular organisms Bacteria (prokaryotic) Mitochondria and chloroplasts also contain their own Archaea (prokaryotic) genomes (circular, like prokaryotes) and ribosomes Eukarya (eukaryotic) These organelles are ancestors of specific lineages of Archaea and Bacteria are NOT closely related. Archaea are more closely related to Eukarya than Bacteria. Bacteria Mitochondria and chloroplasts took up residence in Eukarya eons ago This arrangement is known as endosymbiosis Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 6 The Tree of Life Defined by rRNA Sequencing Figure 2.17 Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 7
