Chapter 1: Evolution of Microorganims and Microbiology

Microorganisms - organisms too small to be clearly seen by the unaided eye

Divisions of Microbes

• Cellular

  • Fungi

  • Protists

  • Bacteria

  • Archea

• Acellular

  • Viruses

    • Protein and nucleic acid

  • Viroid

    • Rna

  • Satellites

    • Nucleic acid enclosed in a protein shell

  • Prion

    • Proteins

Diversity of microorganisms

• More microbes on earth than stars in the known universe

• Found in gut and sediments deep beneath the sea floor

Five kingdoms by Robert Whittaker 1969

1. Monetary

2. Protista

3. Fungi

4. Plants

5. Animals

Three domains by Carl Woese 1960

• Based on comparing ribosomal RNA genes

1. Bacteria (true bacteria)

2. Archaea

3. Eukarya (eukaryotes)

Types of Microbial Cells

Two Types:

• Prokaryotic Cells

  • No nucleus

• Eukaryotic Cells

  • Have nucleus

  • Have other organelles

Domain Bacteria

• Usually single-celled

• Most have cell wall with peptidoglycan

  • Think of cell wall like egg shell

• Most lack membrane bound nucleus

• Some are pathogenic - the bacteria is pathogenic

  • Microbiome - group of bacteria in our outside of our body (pathogenic or non-pathogenic)

    • Long time ago they would use antibodies to cure sickness and then inject someone else's gut microbiome into the anus

Domain Archaea

• Distinguished from bacteria by unique rRNA sequences

• Have unique membrane lipids

• Some have unusual metabolic characteristics

• Extreme environments

  • High temp

  • Gas

  • High pressure

• Non-pathogenic

Domain Eukarya

• Protists

  • Unicellular but generally larger than other two

    • Protozoa - animal like metabolisms

    • Algae - photosynthetic

• Fungi

  • Unicellular or multicellular

    • Yeast - unicellular

    • Molds and mushrooms - multicellular

Microbial Evolution

• Defintion of life:

  • Orderly structure

  • Metabolism

  • Reproduction

  • Growth

  • Responsiveness

• Origins of Life

  • Life was present on Earth 3.5-3.8 bil years ago

• Relationships of DNA/RNA/Protein in Cells  picture 2

  • Proteins

    • Catalytic (enzymes)

    • Structural

  • DNA

    • Stores herditary information that's replicated passed on to next generation

  • RNA

    • Acts as messenger taking info from DNA and synthesizing proteins

  • Which came first?

    • Proteins need RNA and other proteins to be made

    • DNA is only storage

    • RNA required both DNA as a template and proteins as enzyme

• Earliest Molecules - RNA: According to "RNA World Hypothesis"

  • Original moleucle must be able to store, copy and express genetic info

  • Ribozymes

    • Catalytic RNA molecules

    • RNA molecules that form peptide bonds.

    • Early cells may have been RNA surrounded by liposomes

  • RNA World

    • Precellular state in the evolution of life

      • Lipid membrane formed around RNA

        • Lipids spontaneous form vesicles

  • Evidence of RNA World Hypothesis

    • Most cell. RNA in modern cells exists in and is associated with the ribosome

    • rRNA catalyzes peptide bond formation in protein synthesis

    • Energy source of current cells is a ribonucleotide: ATP

    • RNA can regulate gene expression

• Evolution of the Three Domains of Life

  • Last Universal Common Ancestor (LUCA)

    • Most recent organisms from which all 3 types of life arose

  • Endosymbiotic Hypothesis

    • Origin of mitochondria, chloroplasts, and hydrogenosomes

      • Endosymbiosis - interaction between two organisms in which one lives inside of the other

    • Mitochondria and chloroplasts

      • DNA and ribosomes have similar sequences to bacteria

        • Mitochondria - proteobacteria

        • Chloroplast - prochloron or cyanobacteria

          • Both are still able to produce ATP

          • They both have DNA

    • Hydrogenosome - anaerobic endosymbiont that makes ATP via fermentation

• Evolution of Cellular Microbes

  • Mutation of genetic material led to selected traits

  • New genes and genotypes evolved

  • Bacteria + Archaea increase gene pool through horizontal gene transfer

  • Eukaryotes sexual reproduction

• Phyletic Classification Systems

  • Compare organisms on basis of evolutionary relationships

  • Microbial Phylogeny- comparison of cell wall structure, biomolecules, and nucleotide sequences rRNA

  • Phylogentic Tree

    • Display evolutionary relationship between organisms

    • Building a Phylogenetic Tree - Distance-Based Approach

      • Differ ce in sequences made k to statistic

    • Phylogenetic Tree Topologies

      • Unrooted

        • Defines phylogenetic relationships rather than primitive relationship

        • Doesn’t indicate age

      • Rooted

        • Includes a node - taxonomic unit - that serves as a common ancestor

  • Microbial Taxonomy

    • Taxonomy - Science of classifying living things

      • Classification

      • Nomenclature -  binomial  nomenclature

      • Genus species

      • • Carl Linnaeus 1753are

        • Strain - descendants of a pure microbial culture

          • Can differ biochemically morphologically and pathogenicslly

          • Recent research uses meta genomic analysis (gut microbiome) to define hierarchy

        Microbiology - Origins

        • Study of microorganisms

        • Tools used for the study

          • Microscopes

          • Culture techniques

            • Pure culture - isolated strain

          • Molecular genetics

          • Genomics

          • Proteomomcs

• Discovery of Microorganisms

  • Earliest microscopic observations

    • Robert Hook:

      • Micrographia

        • 1665

      • Drew fungus Mucor

      • Coined term cell

    • Anthony van Leeuwenhoek

      • First person to observe microorganisms accurately

  • The Conflict Over Spontaneous Generation

    • Spontaneous Generation

      • Idea that living organisms can develop from nonliving/decomposing matter

        • Discredited by Francesco Redi

          • Showed maggots on decaying meat came from fly eggs

    • John Needham

      • Based on observation that heated gravy gave rise to microorganisms

    • Lazzaro Spallanzani

      • Proved that the gravy itself didn't make microorganisms if in sealed environment

    • Scientists who disproved:

      • Redi

      • Spallanzani

    • Scientists who supported

• Louis Pasteur

  • Swan-neck flask expierment

    • Created flasks with long, curved necks

    • Boiled the solutions

    • Left flasks exposed to air

  • Result

    • No growth of microorganisms in swan-neck flask

• Final Blow to Theory of Spontaneous Generation

  • John Tyndall (1820-1893)

    • Dust carries microorganisms

      • No dust aka filtered air --> nutrient broths remain sterile, even if directly exposed to air

      • Provided evidence for the existence of exceptionally heat-resistant forms of bact.

  • Ferdinand Cohn 1828-1898

    • Heat-resistant bact. Could product endospores

• Early Evidence for the Relationship Between Microorganisms and Disease

  • Agostino Bassi 1773-1856

    • Showed a disease of silkworms was caused by a fungus

  • M . J. Berkely 1803-1889

    • Demonstrated the potato blight of Ireland was caused by a protozoa

  • Heinrich de Bary 1831-1888

    • Showed fungi caused crop diseases

  • Louis Pasteur 1822-1895

    • Demonstrated microorganisms carried out fermentation

    • Helped french wine industry by developing pasteurization to avoid wine spoilage by microbes

  • Joseph Lister 1827-1912

    • Provided indirect evidence that microorganisms were the causal agents of diseases

    • Developed an antiseptic surgery system to prevent microorganisms from entering wounds

    • His patients had fewer postoperative infections

  • Final Proof

    • Robert Koch 1843-1910

      • Established the relationship between bacillus anthracis and anthrax

      • Mycobacterium tuberculosis  causes TB

      •  

• Koch's Postulates

  • The microorganism must be present in every case of the disease but absent from healthy organisms

    • Staining technique developed to examine human tissue.

    • Mycobacterium tub. Could be identified in diseased cell

  • The suspected microorganisms must be isolated and grown in a pure culture

    • Grew M. tuberculosis in pure culture on coagulated blood serum

  • The same disease must result when the isolated microorganisms is inoculated into a healthy host

    • Injected cells from the pure culture of M. tuberculosis into guinea pigs

      • Guinea pigs subsequently died of TB

  • The same microorganism must be isolated again from the diseased host

    • Isolated M. TB in pure culture on coagulated blood serum from dead guinea pigs

  • Limitations of Koch's Postulates

    • Some cant be grown in pure cult bc they rely on host cells

    • Using humans in completing the postulates is bad

    • Molec and genetic evidence may replace and overcome these limits

• The Development of Techniques for Studying Microbial Pathogens

  • Koch's work --> discovery/development of:

    • Nutrient broth + nutrient agar

    • Methods for isolating microorganisms

  • Martinus Beijerinick 1851-1931

    • Studied tobacco mosaic disease using porcelain bacterial filters

      • Extracts from diseased plants were pased through this filter

      • Extracts are still infections, therfore, must have something smaller than bacterium (viruses)

• Development of Vaccines

  • Pasteur and Roux

    • Discovered that incubation of cultures for long intervals between transfers = pathogens unable to cause disease --> attenuated cultures

      • Could be used to develop vaccines for chicken cholera, anthrax and rabies

• Immunological Studies

  • Led to immunology --> study of host defenses

  • Edward Jenner 1749-1823

    • Used vaccination procedure to protect against smallpox

  • Emil von Behring 1854-1917 + Shibasaburo Kitasato 1852-1931

    • Developed antitoxins (antibodies) for diphtheria

  • Elie Metchnikoff 1845-1916: Father of Natural Immunity

    • Discovered 1st immune system cells from starfish

    • Made phagocyte term

• Microbiology Encompasses Many Subdisciplines

  • Basic aspects

    • Concerned w individual groups of microbes, microbial physiology, genetics, molecular biology + taxonomy

  • Applied Aspects

    • Concerned w practical problems - disease, water, food, and industrial microbiology

  • Major Fields in Microbiology

    • Medical microbiology

      • Diseases of humans and animals

      • John Snow first identified cholera outbreak in london

    • Public health microbio

      • Control and spread of communicable diseases

    • Immunology

      • How the immune system protects a host from pathogens

    • Microbial ecology

      • The relationship of organisms with their environment

    • Agricultural microbio

      • The impact of microorganisms on food production

    • Food microbio

      • Microbes used to make food and beverages

      • Spoilage microbes

    • Industrial Microbio

      • Uses microbed to make products useful to humans

        • Antibiotics, vaccines, steroids, alcohols, vitamins, amino acids, enzymes, biofuels

    • Microbial physiology

      • Studied metabolic pathways of microorganisms

    • Microbial genetics, molecular biology, bioinformatics

      • Studies the nature of genetic information + how it regulates the development and function of cells and organisms