..., chance favors only prepared minds. - Louis Pasteur Father of Microbiology

Transcription

1 BIOL 3702: Chapter 1..., chance favors only prepared minds. - Louis Pasteur Father of Microbiology The Evolution of Microorganisms and Microbiology Slide No. 1 Slide No. 2 What is Microbiology? u The term microbiology is defined as: v The study of organisms and acellular biological agents too small to be seen clearly with the unaided eye. Such organisms and agents are termed microorganisms (or microbes) v The use of techniques necessary to isolate, grow, and study microbes Members of the Microbial World u Microorganisms v Most populous and diverse group of organisms v Found everywhere on the planet v Play a major role in recycling essential elements v Source of nutrients and some carry out photosynthesis v Benefit society by their production of food, beverages, antibiotics, and vitamins v Some cause disease in plants and animals Slide No. 3 Slide No. 4 Figure 1.1 u Microorganisms v Organisms and acellular entities too small to be clearly seen by the unaided eye Ø Some are microscopic (< 1 mm in diameter) Ø Some are macroscopic, e.g., mushrooms v Relatively simple in construction, generally lacking highly differentiated cells and distinct tissues v Different basic types of microbes can be distinguished based upon cellular structure (or its absence) Slide No. 5 Slide No. 6 Dr. Cooper 1

2 u Types of cells v Prokaryotic - lack a true membrane-delimited nucleus (this is not absolute) v Eukaryotic Ø Have a membrane-enclosed nucleus Ø More complex morphologically Ø Usually larger than prokaryotic cells u Carl Woese (1970) developed a new microbial classification scheme v Based on a comparison of ribosomal RNA sequences v Divides microorganisms into three domains Ø Bacteria (true bacteria; prokaryotic) Ø Archaea ( ancient bacteria; prokaryotic) Ø Eukarya (eukaryotic) [Source: en.wikipedia.org/wiki/carl_woese] Slide No. 7 Slide No. 8 u Domain Bacteria v Prokaryotic v Usually single-celled v Majority have cell walls containing peptidoglycan v Most lack a membrane-bound nucleus v Ubiquitous and some live in extreme environments u Domain Archaea v Prokaryotic v Distinguished from Bacteria by unique rrna sequences v Lack peptidoglycan in cell walls v Possess unique membrane lipids v Some exhibit unusual metabolic characteristics v Many live in extreme environments Slide No. 9 Slide No. 10 Figure 1.2 u Domain Eukarya v Eukaryotic v Two major groups Ø Protists generally larger than Bacteria and Archaea Algae photosynthetic Protozoa may be motile, hunters, grazers Slime molds two life cycle stages Water molds devastating disease in plants Ø Fungi two morphological forms: Yeast (unicellular) and mold (multicellular) Slide No. 11 Slide No. 12 Dr. Cooper 2

3 Figure 1.1 u Acellular infectious agents v Viruses Ø Smallest of all microbes Ø Requires host cell to replicate Ø Cause range of diseases, some cancers v Viroids and Virusoids Ø Infectious agents composed of RNA v Prions infectious proteins Slide No. 13 Slide No. 14 Microbial Evolution u Conditions of early earth amenable to the origin of the first life forms u Definition of life v Cells and organization v Response to environmental changes v Growth and development v Biological evolution v Energy use and metabolism v Regulation and homeostasis v Reproduction [Question: does the above apply to viruses?] Slide No. 15 Slide No. 16 u Microbial fossils v Swartkoppie chert granular silica v 3.5 billion years old u Fossil record sparse need to rely on indirect evidence u How did early cells arise? u In Earth s prebiotic soup, chemicals reacted with one another v Energy release v Catalyst v Aggregation v Replication Figure 1.3 Slide No. 17 Slide No. 18 Dr. Cooper 3

4 u Three types of candidate molecules v Proteins catalyst v Deoxyribonucleic acid (DNA) replication and heredity v Ribonucleic acid (RNA) conversion of information in DNA into proteins u With regard to evolution, one of these molecules must be able to do cellular work and replicate How did life on Earth begin? Science Na7on [h#p://youtu.be/tmx8ukgmex8] Slide No. 19 Slide No. 20 Figure 1.5 u Cech s discovery of ribozymes (catalytic RNA) in 1981 led to the RNA World Hypothesis for the Origin of Life (1986) Figure 1.6 Slide No. 21 Slide No. 22 Opening Chapter Figure u Another consideration: early Earth lacked oxygen v Presumably, first microbes were anaerobic and used inorganic material as a source of energy v Photosynthesis likely arose 2.5 billion years ago with the evolution of the cyanobacteria Ø Oxygen is a by-product of photosynthesis Ø Fossil evidence of cyanobacteria exists in the form of stromatolites mats of mineralized bacteria Figure 1.7 Slide No. 23 Slide No. 24 Dr. Cooper 4

5 BIOL 3702: Chapter 1 AY Figure 1.2 u Evolution of the Three Domains of Life v Universal phylogenetic tree is based upon small subunit ribosomal RNA sequences (SSU rrna) v Differences between the SSU rrna sequences of two organisms measures their evolutionary distance or relatedness v Distances can be represented by a tree v The various trees that resulted eventually led to the designation of Three Domains of Life Slide No. 25 Slide No. 26 u Last Universal Common Ancestor (LUCA) v The root or origin of modern life is on bacterial branch, but its nature is still controversial v Archaea and Eukarya evolved independently of Bacteria v Archaea and Eukarya diverged from common ancestry v LUCA is still unkown u So, how did eukaryotic cells evolve? u Endosymbiotic Hypothesis is generally Slide No. 27 accepted as the origin of three organelles: mitochondrion, chloroplast, hydrogenosome v Mitochondria and chloroplasts Ø SSU rrna show bacterial lineage Ø Genome sequences closely related to Rickettsia and Prochloron, respectively v Hydrogenosomes from anaerobic endosymbiont Slide No. 28 u Evolution of cellular microbes v Mutation of genetic material led to selected traits v Bacteria and Archaea increased their genetic pool by horizontal gene transfer To view this video, go to Chapter 1 Animations of Prescott's Microbiology Companion Site (8th ed.) located at the following URL: Dr. Cooper Slide No. 29 [Source: animations/stills/as_compev7.html] Slide No. 30 5

6 u Microbial species v Bacteria and Archaea tend not to reproduce sexually v Referred to as strains - descendants of a single, pure microbial culture v Binomial nomenclature - genus and species epithet (e.g., Yersinia pestis) Microbiology and Its Origins u Before they were visibly observed, microbes were suspected not only to exist, but also to cause disease v Lucretius, a Roman philosopher v Fracastoro, a 16th century physician u Hans Jansen developed the first useful apparatus with compound lenses (Telescope? Microscope?) Slide No. 31 Slide No. 32 u Francesco Stelluti used a microscope to observe bees and weevils u Credit for the first person to observe and describe microbes is often given to Antony van Leeuwenhoek. u However, a history clearly shows that Robert Hooke first observed and described microbes. u Robert Hooke - great scientist/inventor of the 17th century v Coined the term cells to describe the little boxes he observed in examining cork slices with a compound microscope v In 1665, published the book Micrographia documenting his various observations v In 1678, he was asked to confirm van Leeuwenhoek s observations (For details, go to Slide No. 33 Slide No. 34 Hooke s drawing in Micrographia compared to a photomicrograph of the fungus Mucor Hooke s drawings, as published in Micrographia of a flea (above) and cells from a cork slice (right) (Source: (Source: ASM News 70: , 2004) (Source: Slide No. 35 Slide No. 36 Dr. Cooper 6

7 Figure 1.11a u Leeuwenhoek v Developed single lens microscopes v 1673 to publishes his discovery of animalcules Ø Bacteria Ø Protozoa Ø Vinegar eels Leeuwenhoek s microscope and drawings Figure 1.11b-c Slide No. 37 Slide No. 38 Vinegar eels (Source: I have had several gentlewomen in my house, who were keen on seeing my little eels in vinegar; but some of em were so disgusted at the spectacle that they vowed they d never use vinegar again. But what if one should tell such people in the future that there are more animals living in the scum on the teeth in a man s mouth, than there are men in a whole kingdom?... - Leeuwenhoek (Source: Steven Lehrer, Explorers of the Body [1979]) Slide No. 39 Slide No. 40 Spontaneous Generation u From before the time of Aristotle ( B.C.), people believed that life could arise from non-living matter, i.e., spontaneous generation u Evidence includes: v Mice from grain v Beetles from dust v Worms and frogs from mud v Maggots from rotting meat u In the late 1600s, Francesco Redi challenged this view through a series of experiments involving rotting meat (Source: Pommerville 2004) Slide No. 41 Slide No. 42 Dr. Cooper 7

8 BIOL 3702: Chapter 1 AY u Redi s experiments, and those by others, u For the next 150 years, proponents for and refuted the spontaneous generation theory for larger organisms u These experiments did not, however, dispel speculation that the theory still held true for microorganisms u Proponents cited evidence of microbial growth in boiled extracts of hay or meat opponents against spontaneous generation provided numerous proofs u Proponents linked their proof to the a vital force that existed in the air and was sensitive to extreme heat u By the late 1800s, Pasteur and Tyndall conclusively disproved the theory of spontaneous generation Slide No. 43 u Louis Pasteur v Father of Microbiology v Contributions include: Slide No. 44 u In 1861, Pasteur provided definitive proof against spontaneous generation using swan-necked flasks Ø Wine fermentation Ø Microbial diseases of grapes and silkworms Ø Pasteurization Ø Rabies vaccine Slide No. 45 (Source: Pommerville [2004]) Slide No. 46 u Debate Positions: v Pasteur: Because no living thing is able to reach the broth, there is no growth v Critics: If accessible and given enough time, the vital force will reach the broth (Source: Pommerville [2004]) Dr. Cooper Slide No. 47 Slide No. 48 8

9 Microbes and Disease (Source: Black [2002]) u Claims by Pasteur s critics seem to be unfounded since a number of the swan-necked flasks still exist today with no growth yet to be observed in the nutrient broth u Despite the discovery of microbes, their role in causing disease was not recognized until the early 1800s u Prior to this, it was commonly thought that most diseases were due to supernatural forces, poisonous vapors (miasmas), or an imbalance of the four humors - blood, phlegm, yellow bile, and black bile Slide No. 49 Slide No. 50 Microbes and Disease (cont.) Microbes and Disease (cont.) u Support for a Germ Theory of disease: v Bassi discovers that a fungus causes a form of silkworm disease v Berkeley proves that the Great Potato Blight of Ireland is due to a fungus v de Bary demonstrates fungal causes for certain cereal crop diseases v Late 1800s - Pasteur demonstrates a protozoan disease of silkworms Spraying carbolic acid over the field of surgery (Source: surgeons/lister.htm) u Indirect evidence for microbial disease in human comes from Joseph Lister v Implemented the use of sterile surgical instruments v Used carbolic acid (phenol) during surgery and on wound dressings Slide No. 51 Slide No. 52 Microbes and Disease (cont.) Microbes and Disease (cont.) Koch peering through a microscope u Robert Koch - first to directly prove a role for microbes in human disease v used a set of criteria to establish the cause of anthrax v Criteria first proposed by Koch s mentor, Jacob Henle u Criteria known as Koch s Postulates: 1. The microbe must be present in each disease case, but absent from healthy individuals 2. The suspected microbe must be isolated from the disease case and grown in pure culture 3. The same disease must result when a healthy host is inoculated with the isolated microbe 4. The same microbe must be isolated again in pure culture from the diseased host Slide No. 53 Slide No. 54 Dr. Cooper 9

10 Figure 1.15 Microbes and Disease (cont.) u Using these principles, Koch demonstrated the causes of anthrax (1876), tuberculosis (1882), and cholera (1883) u Koch published his postulates in 1884 u Today, Molecular Koch s Postulates have been established in light of advances in the molecular biology of pathogenic microbes Slide No. 55 Slide No. 56 Microbiology Today (Source: riseaboveplastics.blogspot.com/2010/06/la-times-hates-plastic-bags.html) u Steven Jay Gould has stated that we live in the Age of Bacteria u Microbes influence human society in countless ways Microbiology Today (cont.) u One indicator of the importance of microbiology is reflected by the number of Nobel Prize winners - one-third of all awardees are microbiologists or investigators using a microbial model (Source: bytesizebio.net/index.php/tag/nobel-prize) Slide No. 57 Slide No. 58 Microbiology Today (cont.) Microbiology Today (cont.) u Areas impacted by microbes include: v Medicine v Agriculture v Industry v Ecology v Genetics v Biochemistry v Molecular Biology u Presently, and for the foreseeable future, microbiologists will face many challenges to solve many of society s problems including combating disease, reducing environmental pollution, and maintaining/improving the world s food supply Portions Copyright The McGraw-Hill Companies, Inc. and Copyright C. R. Cooper, Jr. Slide No. 59 Slide No. 60 Dr. Cooper 10