Taxonomy : microorganisms and viruses

1. Taxonomy : microorganisms and viruses Chapter 9

2. Taxonomy • Aristotle (384 – 322 BCE) described the dominance of humans over all living things as the scala natural or “ladder of nature” • The science of classifying organisms • Used to identify organisms and to represent the relationships among them • Usually uses a hierarchical system to classify where organisms are arranged in a series

3. Taxonomic Classification • Carl Linnaeus (1707 – 1778) developed our present system of classification, based on physical and structural features • Binomial Nomenclature is a method of naming organisms by using a two-part scientific Latin / Greek name: • The genus name • The species name • Ex: North American Black Bear – Ursusamericanus • The scientific name is always italicized • and only the genus name has the first • letter capitalized

4. Binomial Nomenclature • The two name system provides an added advantage by indicating similarities in anatomy, embryology and evolutionary ancestry. • Example: • Tamiasciurus hudsonicus • Mustela erminea • Marmota monax • Mustela vison

5. Levels of Classification • There are currently 8 main taxa • Categories used to classify organisms • Did • King • Philip • Cry • Out • “For • Goodness • Sakes!?”

6. Domains • Some genes in Archaea are most closely related to human genes than to similar genes in bacteria

7. Kingdoms • There are 6 Kingdom systems of Classification: • Eubacteria • Lacks nuclei, cell wall is often present and can reproduce asexually • Archaebacteria • Lives in extreme environments, cell wall is present • Protists • Live in aquatic / moist habitats, not cell wall • Fungi • Most are multicellular, cell wall present and mostly terrestrial • Plantae • All autotrophs, cell wall present, can reproduce sexually or asexually • Animalia • All heterotrophs, no cell wall, most reproduce sexually

8. Viruses • Viruses do not it into the 6 kingdom classification system because they don’t display the most of the characteristics of living cells. • Outside of a cell, a virus is lifeless • Once the virus enters cell, it will replicate • Because of the unique characteristics of a virus, it occupies a position between living and non-living

9. Viruses Cont’d. • Viruses are so small that they were not discovered until the invention of the electron microscope in 1934 and are measured in nanometers. • Ex: Human RBC = 7500 nm vs. influenza virus = 115 nm

10. Viruses Cont’d. • Two life cycles: • Lytic • At the end of this cycle, the host cell is destroyed upon release of the virus • Bacteriophages that cause lysis (destruction)is referred to as a virulent phage. • Lysogenic • A virus does not kill the host cell, but may coexist with the cell and be replicated through many generations

11. Viruses Cont’d. • Most bacteriophages have a fairly restricted host range • The limited number of host species, tissues or cells that a virus or parasite can infect • Ex: AIDS virus can only attach to a specific site on certain types of WBC (white blood cells) • In humans, many diseases are caused by viruses • The virus destruction of cells by the virus cause symptoms of disease • Some viruses can be prevented with vaccines by causing the body to produce antibodies • Example: polio or smallpox

12. Viral Replication • Attachment • The virus recognizes the host through chemical signals and inserts its DNA / RNA into the cell • Synthesis • The viral DNA / RNA directs the host cell in replicating its viral components • Assembly • The viral nucleic acids, enzymes and proteins are assembled into new viruses • Release • The newly formed virus particles are released from the infected host cell

14. Eubacteria • Come in many different shapes including: • Spherical - cocci [plural] or coccus [singular] • Rod-shaped – bacilli (plural) or bacillus (singular) • Spiral – spirilla (plural) or spirillum (singular)

15. Eubacteria Cont’D. • Eubacteria can also be classified by respiration and modes of nutrition: • Obligate Aerobes: bacteria that require oxygen for respiration • Obligate Anaerobes: bacteria that conduct respiration processes in the absence of oxygen • Facultative Anaerobes: bacteria that prefer environments with oxygen but can live without it

16. Beneficial Bacteria • Bacteria constitute most of the decomposers of plant and animal waste and are essential for recycling biological materials • Examples: • Nitrogen fixing bacteria • Intestinal bacteria • Food digestion and synthesizing vitamins in humans • Streptomyces • Source of antibiotics

17. Harmful Bacteria • Bacteria are probably best known for causing disease. • Bacteria can cause disease symptoms by the amount of cells burdening the host tissues, destroying host cells or by producing poisons. • Ex: Streptococcus Necrotizing Faciitis

18. Reproduction • Sexual reproduction is uncommon in bacteria, however it can occur in some intestinal bacteria • Conjugation can occur when a donor cell inserts a plasmid of DNA into the recipient cell through a pili • Ex: E. coli • Endospores are dormant cells that contain genetic material encapsulated by a thick wall • Develops when conditions are unfavourable • Can lay dormant for thousands of years! • When environmental conditions improve the wall will break down and the cell will become active again

19. Reproduction • Asexual Reproduction • Main method is binary fission

20. Archaebacteria • Extremophiles – meaning they inhabit environments that are extreme in comparison to a normal bacterial environment • Examples: • Very hot environments  geysers • Very cold environments  artic waters • High salt content environments  salt lakes • Extremely acidic or alkaline environments

21. Protists • First appeared about 1.5 billion years ago • Contain organelles such as ribosomes and mitochondria to carry out metabolic processes more efficiently • Mostly microscopic and unicellular, and found in fresh or salt water • Ex: Plankton • Made up of 3 distinct groups: • Plant-like protists (autotrophs) • Animal-like protists (heterotrophs) • Fungi-like protists (heterotrophs)

22. Plant-like Protists • The group is considered plant like because the organism contains chlorophyll, which is the pigment found in plants that traps sunlight energy for photosynthesis • Traditionally called algae, however now algae is grouped into two kingdoms: • Eubacteria • Ex: Cyanobacteria (blue – green algae) • Protista • Ex: Green, Brown and Red algae

23. Plant-like Protists • The plant-like protists are broken down into 6 phyla: • Euglenophyta • Euglena, particularly abundant in stagnant water • Chrysophyta • Diatoms • Pyrrophyta • Dinoflagellates (posses two flagella) • Chlorophyta • Green algae • Phaeophyta • Brown algae • Rhodophyta • Red algae

24. Animal-like protists • Protozoa • All heterotrophs • Must move to consume food • Referred to as holozoic because they engulf their food • The major criteria used for classifying is locomotion: • Sarcodina • Move using pseudopods • Mastigophora (Zooflagellates) • Move by flagella • Ciliophora • Uses synchronized cilia to move • Sporozoa • Parasitic movement

25. Animal-like protists cont’d • Large variation in size, can vary from 2 µm to 5 cm. • Can be free living or parasitic • Reproduction is usually asexual by binary fission, however they can produce sexually under certain conditions • Some engulf food, while others can absorb nutrients directly through the cell membrane.

26. Fungi-like Protists • Referred to as slime moulds • Placed in the phylum Gymnomycota • Their name comes from the slimy trail left behind the mould as it moves • Moves very slowly, sometimes only a few millimeters a day • Inhabit cool, shady, moist places • May resemble protozoans during some life stages and become amoeba-like or have flagella • Does not always remain a single-celled organism