Transcript Chapter 1: The Microbial World and You

Lecturer Mr. Zivuku .M
Classification of
Microorganisms
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Phylogeny: The Study of Evolutionary
Relationships of Living Organisms
 Over 1.5 million different organisms have been
identified to date.
 Many similarities among living organisms:
 Made up of cells surrounded by a plasma membrane.
 Use ATP as energy source.
 Store genetic information as DNA.
 Ribosomes are the site of protein synthesis.
 Both differences and similarities among organisms
are caused by natural selection (Darwin, 1858).
 Organisms can be classified into taxonomic
categories (taxa), Lecturer:
basedMr on
the differences and
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similarities among them.
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Phylogeny: The Study of Evolutionary
Relationships of Living Organisms
 Ancient Greeks classified all living organisms
into two groups
 Kingdom Plantae
 Kingdom Animalia
 In 1850s bacteria and fungi were incorrectly
placed in the Plant Kingdom.
 In 1860s Kingdom Protista was proposed to
include bacteria, fungi, algae, and protozoa, but
many scientists still classified bacteria and fungi
as plants.
Intense disagreement over classification of
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bacteria and fungi persisted over 100 years.
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Phylogeny: The Study of Evolutionary
Relationships of Living Organisms
 In 1930s electron microscopy made it clear that
bacterial cells lacked a nucleus. The term
procaryote was introduced in 1937.
 In 1959 Kingdom Fungi was established.
 In 1961 the current definition of the term
procaryote was established.
 In 1968 the Kingdom Procaryotae was accepted
by biologists.
 In 1969 Robert Whitaker proposed a fivekingdom system of biological classification for
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all living organisms.
Differences Between Eucaryotic and
Procaryotic Cells
Procaryotes
Cell size
0.2-2 um in diameter
Nucleus
Absent
Membranous
Organelles Absent
Cell Wall
Chemically complex
Ribosomes Smaller (70S)
DNA
Single circular
chromosome
Cell Division Binary fission
Eucaryotes
10-100 um in diameter
Present
Present
When present, simple
Larger (80S) in cell
70S in organelles
Multiple linear
chromosomes (histones)
Mitosis
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Procaryotes: Lack Nucleus and
Membrane-Bound Organelles
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Prokaryotes: Bacteria and Archaea
 Unicellular and lack nuclei
 Much smaller than eukaryotes
 Found everywhere there is sufficient
moisture; some found in extreme
environments
 Reproduce asexually
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Prokaryotes: Bacteria and
Archaea
 Two kinds
– Bacteria – cell walls contain
peptidoglycan; some lack cell walls; most
do not cause disease and some are
beneficial
– Archaea – cell walls composed of
polymers other than peptidoglycan
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The Six Kingdom Classification
of organism
 Taxonomy is the branch of biology that
names and groups organisms according to
their characteristics and history.
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Kingdoms
 Archaebacteria
 Eubacteria
 Protista
 Fungi
 Plantae
 Animalia
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Kingdom Archaebacteria
 The members of the kingdom
Archaebacteria (AHR-KEE-bak-TIR-eeuh) are unicellular prokaryotes.
 They differ from other forms of life by
having distinctive cell membranes and
different genetic and chemical properties.
 Autotrophic species of archaebacteria
produce food by chemosynthesis
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Kingdom Archaebacteria
 Some members produce flammable gases,
such as methane, as waste products.
 Archaebacteria are known to live in harsh
environments such as sulfurous hot springs,
very salty lakes, and oxygen deprived
environments such as the intestines of
animals.
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Kingdom Eubacteria
 Eubacteria (YOO-bac-TEER-ee-uh) are
one-celled prokaryotes.
 You are in constant contact with these types
of bacteria for they are responsible for such
things as tooth decay, changing milk into
yogurt, and some types of food poisoning.
Most species of eubacteria use oxygen but
there are a few species that are anaerobic.
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Kingdom Eubacteria
 They both reproduce primarily by binary
fission.
 However, some have ways to recombine
genes, allowing organisms with different
characteristics to develop.
 It is this recombination of genes that
accounts for the remarkably fast
development of antibiotic-resistant bacteria.
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Kingdom Protista
 The kingdom Protista (pro-TIS-tuh) has a
variety of eukaryotic organisms.
 Most are single-celled organisms but there
are a few multicellular types such as giant
kelp.
 Because protists are eukaryotic, they have a
membrane-bound nucleus and membranebound organelles.
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Protozoa
 Single-celled eukaryotes
 Similar to animals in their nutritional needs
and cellular structure
 Typically live freely in water; some live
inside animal hosts
 Most reproduce asexually; some reproduce
sexually
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Protozoa
Most are capable of locomotion by
-Pseudopodia – cell extensions that flow in
direction of travel
-Cilia – numerous, short, hairlike
protrusions that propel organisms through
environment
-Flagella – extensions of a cell that are
fewer, longer, and more whiplike than cilia
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Examples of Protozoa
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Examples of Protozoa
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Examples of Protozoa
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Algae
Unicellular or multicellular
Photosythetic
Simple reproductive structures
Categorised on the basis of pigmentation,
storage products and composition of cell
walls
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Examples of algae
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Examples of algae
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Fungi
Eukaryotic (have membrane-bound
nucleus)
 Obtain food from other organisms
 Possess cell walls
 Composed of:

– Molds – multicellular; have hyphae; reproduce
by sexual and asexual spores
– Yeasts – unicellular; reproduce asexually by
budding; some produce
sexual
spores
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Mycology, Fungi
 Widely distributed, found where moisture is
present
 Exist in the form of filamentous hyphae
 Fungi digest insoluble organic matter by
secreting exoenzymes, then absorbing the
soluble nutrients
 2 reproductive structure occur
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Fungi
 1 . sporangia form asexual spores
 2. gametangia form sexual gametes
 The zygospores have resting structures
called zygospores (cells in which zygotes
are formed)
 The ascomycetes form zygote within the
club shaped structure and results in the
production of ascospores
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Nutrition and Metabolism
 Grow best in dark moist habitat
 Are saprophytic
 Chemoheterophs + use organic material as
source of carbon, electrons and energy
 Optimum pH5.5 some can grow at pH 2-9
 Optimum temperature 20-35 deg C,
pathogenic spp have a higher temp range
 Usually aerobic, some yeasts are facultative
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anaerobic
Reproduction of Fungi
 Either sexual or asexual
 Asexual reproduction, no union or nuclei,
sex cell or sex organs can be accomplished
in several ways
 1. A parent cell can divide into two
daughter cells by central constriction and
formation of new cell wall
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Reproduction of fungi
 2. A hyphae can fragment to form cells that
behaves as spores, called athrophores. If the
cells are surrounded by thick wall before
separation, they are called chlamydospores
 3. Somatic vegetative cells or spores may
bud to produce new organism (common in
yeast)
 4. Fungi can directly produce spores
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Examples of Fungi
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Examples of Fungi
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Kingdom Plantae
 The kingdom Plantae (PLAN-tee) is made
up of multicellular plants.
 Most forms are Autotrophic and use
photosynthesis as their source of energy.
However, a few parasitic forms exist.
 Over 350,000 species of plants have been
identified, most of whom live on land.
Included in the kingdom Plantae are
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mosses, ferns, conifers,
and
flowering
plants.
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Kingdom Animalia
 Eukaryotic, multicellular heterotrophic
organisms make up the kingdom Animalia.
 Most animals have a symmetrical body
organization and are mobile. Almost all
animals reproduce through meiosis.
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VIROLOGY
 Virus means toxins
 This word came about before people
actually found the causative agent of viral
disease
 They presumed poisonous substance caused
the disease present
 Viruses constitute the largest heterogeneous
group of infecting agents
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Properties of Viruses
 They are obligate intracellular parasites for
the cells of their specific hosts,.
 Viruses are the smallest infectious agents
and are 20-30nm in size, These can only be
seen by an electron microscope.
 Viruses contain either DNA or RNA as their
genetic material, never both
 Viruses are not sensitive to antibiotics
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Morphology, Contains DNA or
RNA coated by a protein coat
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BACTERIOPHAGES
 These are bacteria viruses which can only
multiply inside a specific bacteria which
they eventually lyses.
 A typical phage T4 can attack a bacteria
where it exact its effect on the chromosome
 Adsorption, leading to either integration
into the chromosome (lysogenic pathway)
or replication of phage DNA(lytic pathway)
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Structure of phage, T4
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Phagetyping
 Bacteriophages can be used in
epidemiology to type microorganisms e.g.
Salmonella spp and Staphylococcus spp in
order to trace the source of infection.
 PHAGETYPING; is performed by growing
the unknown bacterial culture, isolated from
a patient on agar plate.
 Known phages are systematically spotted
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Phagetyping
 Spotted onto the confluent growth of
bacteria
 After a suitable incubation period the zones
or areas of lyses clearing called plaques
appear if the particular bacteria is present
 From the phages that produce plaques, the
bacteria host can be identified
 Used identification Salmonella typhi and
Staphylococcus Lecturer:
aureus
(food
poisoning)
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Classification of Organisms
Scientific Nomenclature
 Scientific nomenclature: Universal system for naming
and classifying living organisms. Initially developed in the
18th century by Carl Linnaeus.
 Binomial nomenclature: Each organism (species) has a
two part name. Names are either italicized or underlined.
 Genus name: Always capitalized, always a noun. May use initial.
 species name: Always lower case, usually an adjective.
 Names are usually derived from Latin (or Greek) or may
have latinized endings. Examples:
 Homo sapiens (H. sapiens): Human
 Penicillium notatum (P. notatum): Mold that produces penicillin
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 Canis familiaris (C. familiaris): Domestic dog
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Taxonomic Categories
Division
(Bacteria)
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Classification of Organisms
Hierarchy of Taxonomic Categories
DOMAIN
Kingdom
 Phylum or Division (Bacteria)
 Class
 Order
 Family
 Genus
species
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Examples
 Streptococcus (strep throat)
 Staphylococci aureus(responsible for
"staph" infections and gangrene)
 Escherichia coli or E.coli (found in the
intestines of mammals)
 Salmonella typhi (causes typhoid fever
 and food poisoning)
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