UNIT 10
MICROORGANISMS
READING:
Chapter 20
Chapter 21
Chapter 22
Viruses and Bacteria
Protists
Fungi
OBJECTIVES
At the end of this unit of study the student will be able to:
1.
Define virus.
2.
Describe the structure, composition, and classification of viruses.
3.
Describe the lytic and lysogenic cycles of viruses.
4.
List the characteristics of the Bacteria.
5.
List and describe the four phyla of the Bacteria.
6.
Describe the biological processes of the members of the Bacteria.
7.
Characterize the Kingdom Protista including Protozoa, Algae, and Fungus like Protists.
8.
List and describe the Phyla of Kingdom Protista.
a.
Protozoans.
b.
Algae.
c.
Fungus like Protists.
9.
List characteristics of the Kingdom Fungi.
10.
List and describe the five phyla of the Kingdom Fungi.
11.
Describe important symbiotic relationships involving microorganisms.
12.
Describe disease and its agents.
ASSIGNMENTS:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
MICROORGANISMS
I.
UNIT 10
Viruses
A. Biological particle composed of genetic material and protein.
1. Cause diseases
a. VIRULENT - causes a disease, usually immediately
b. TEMPERATE - does not cause a disease immediately.
2. OBLIGATE PARASITE - can only reproduce by invading a living host.
3. Comparison with cells
a. Constructed of compounds usually associated with cells
b. Have some characteristics of life but not all
1) No nucleus, cytoplasm, organelles, or cell membrane
2) Don't reproduce by either mitosis or meiosis.
3) Not capable of carrying out cellular functions
c. Contain nucleic acids
d. Can crystallize where cells cannot.
B. Viral Structure
1. Core of nucleic acid - either RNA or DNA
2. Core surrounded by protein layer called CAPSID.
a. Capsid made up of repeating protein units called CAPSOMERES.
b. Capsid gives virus its shape.
3. Function of viral nucleic acid
a. Used to code the production of new viral nucleic acid.
b. Also used to control manufacture protein coat.
4. Shape
a. Most common shape - Icosahedron - regular figure with 20 triangular faces - found in polio,
chicken pox, colds
b. Helix - subunits of protein coat form spiral chain - like coiled spring - found in rabies,
mumps
c. Strands surrounded by 2 protein layers - inner protein layer surrounded by lipid layer with
embedded glycoproteins - HIV.
C. Classification - doesn't follow usual rules of taxonomy.
1. Major division
a. RNA Viruses
b. DNA Viruses
2. Lower levels based on shape and size.
3. RETROVIRUSES - contain enzyme Reverse Transcriptase - directs host cell to make DNA using
RNA of virus as a template.
4. Disease causing particles - smaller and simpler than virus
a. VIROID - short, single strand of RNA with no capsid - believed interfere with normal cell
functions.
b. PRION - glycoprotein particle contains polypeptide of about 250 amino acids - no nucleic acid.
E. BACTERIOPHAGE (Phage) - virus that infects bacteria.
1. Have been used to gather complete information about viral replication.
2. Have round, oval, or many sided heads and hollow tails
a. Head contains nucleic acid.
b. Tail has fibers at tip - serve to anchor phage to bacteria.
F. LYTIC CYCLE - fundamental reproductive process of viruses.
1. Consists of 5 phases.
a. Attachment
1) Phage attaches to bacteria by its tail fiber.
2) Tail fibers recognize and attach to specific region - Receptor Sites.
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b. Entry
1) Enzymes breaks down bacterial cell wall.
2) Tail sheath contracts and drives DNA core into cell.
3) Empty protein coat remains outside - plays no further role.
c. Replication
1) Viral DNA takes complete control of cell activity - can be within minutes.
2) Bacterial genes turned off.
3) Phage DNA replicated many times.
4) Viral DNA transcribed to mRNA to make phage proteins.
d. Assembly
1) Host cell becomes factory for making viruses
2) Phage DNA and proteins assembled into 200 - 300 new phages
e. Release
1) Cell wall and membrane breaks down
2) Phages released to infect other cells.
2. Steps similar to infection by all viruses - release in humans characterized by chills, aches, etc.
G. LYSOGENIC CYCLE
1. Involves temperate viruses
2. Viruses enter cell similarly to lytic cycle - consists of a small segment of DNA - PROPHAGE
3. Viral DNA becomes additional set of genes - incorporates into host's DNA - replicates with host DNA
4. External stimulus - radiation, chemicals - cause prophage to become virulent
H. Evolution 1. Believed to have evolved after cells
2. May have been simplification of some existing cells.
II. Kingdoms Eubacteria and Archaebacteria
A. Most common members - bacteria
B. Bacteria Characteristics
1. Prokaryotic - no nucleus and membrane bound organelles
2. Microscopic
3. May be heterotrophic or autotrophic.
C. Evolution
1. Fossil monerans found in Australian deposits - more than 3.5 billion years old.
2. Evolved into many forms - now live in many different environments.
3. Structural classification difficult; rely mostly on physiology
D. Classification - 2 Kingdoms
1. Kingdom Archaebacteria
a. Adapted to harsh environments - some species found around volcanic vents on ocean floor
b. Include methanogens, extreme halophiles, and thermoacidophiles.
1) Methanogens - Anaerobic; Use carbon dioxide and hydrogen to form methane; Live in bog
and lake bottoms, digestive tracts of livestock, and sewerage treatment plants.
2) Extreme Halophiles - live in high salt areas
3) Thermoacidophiles - live in very acidic and very hot areas (90o C)
2. Kingdom Eubacteria
a. All members of which we commonly call Bacteria
b. Identification
1) Classified on basis of shape
a) Coccus - spherical shaped cells.
c) Spirillum - Shaped like coiled rods or corkscrews
b) Bacillus - Rod shaped cells
2) Cells can cluster together or form chains or filaments
a) Staphylo - cluster
c) Diplo - pairs
b) Strepto -filament
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3) Classified on reaction to Gram stain - series of dyes - stains pink or purple
a) Gram-Negative Bacteria - outer covering of lipopolysaccharide - pink - difficult to
treat with antibiotics
b) Gram-Positive Bacteria - lacks covering - purple -treated with antibiotics
c. Two specialized Phyla
1) Phylum Cyanophyta
a) Called Blue-green bacteria (algae)
b) Similar to plants and plant-like protists
c) Photosynthetic - produce food and oxygen.
d) Clump together to form colonies surrounded by jellylike substance
e) Exhibit some division of labor within colony
2) Phylum Prochlorophyta
a) Photosynthetic
b) Live symbiotically with marine chordates called tunicates
c) Chlorophyll more similar to that found in eukaryotes.
III. Biology of Bacteria
A. Structure and Movement
1. DNA arranged in single circular chromosome
a. PLASMIDS - smaller circular strands of DNA capable of reproducing themselves
2. Cell walls differ from eukaryotes - some rigid, others flexible
3. Many produce CAPSULE - protective polysaccharide layer.
4. GLYCOCALYX - polysaccharide net that help many prokaryotes stick to surface of rocks, teeth,etc.
5. PILI - Protein strands by which some monerans attach themselves to objects
6. Under adverse conditions they may encase their DNA and some cytoplasm in tough envelope called
ENDOSPORE
a. Permits bacteria to lie dormant for years.
b. When favorable conditions return, endospore breaks open and cell becomes active.
7. Movement
a. Many move by rotating stiff flagellum bent into S-curve.
b. Spirochetes use filament that wraps around cell to move
B. Nutrition
1. May be heterotrophic or autotrophic.
a. Most are HETEROTROPHIC - use food produced by other organisms.
1) SAPROPHYTE - heterotroph that feeds on dead or decaying matter.
2) PARASITE - heterotroph that feeds on living materials
b. AUTOTROPHIC - produce own food from inorganic materials
1) PHOTOAUTOTROPHS - use sunlight as energy source.
2) CHEMOAUTOTROPHS - use energy of chemical reactions to synthesize food.
a) Some fix nitrogen - NITROGEN FIXATION - process by which gaseous nitrogen
converted into ammonia compounds.
C. Respiration
1. OBLIGATE ANAEROBES - cannot survive in presence of oxygen.
2. FACULTATIVE ANAEROBES - can live with or without oxygen.
3. OBLIGATE AEROBES - cannot live without oxygen.
D. Reproduction
1. Some reproduce rapidly - may divided every 15-20 minutes
a. Can produce millions of cells in short time
b. Rate of reproduction affected by heat, cold, predation and lack of food
2. BINARY FISSION - cell reproduces by splitting in two
a. Asexual
b. DNA replicates first
c. Plasma membrane and cell wall grows inward form 2 identical daughter cells.
3. CONJUGATION - type of sexual reproduction, genetic material exchanged.
a. Recombination of genetic material by 2 bacteria
b. Portion of DNA from one cell passes across bridge formed by pili.
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c. DNA piece aligns with homologous piece in recipient cell - recipient DNA destroyed and new DNA
is substituted
E. Toxin Production
1. PATHOGEN - any organism that causes disease.
2. Most bacterial diseases caused by toxins produced by bacteria.
a. TOXIN - poisonous substance that disrupts metabolism of infected organism.
1) ENDOTOXIN - come from pieces of cell wall of Gram-negative bacteria; symptoms - fever,
weakness, and damage to circulatory system; example - Typhoid Fever.
2) EXOTOXIN - products of bacterial metabolism - secreted into area around bacteria - most
potent poisons known; examples - Diphtheria and Botulism (food poisoning)
F. ANTIBIOTICS
1. Chemicals capable of inhibiting growth of some bacteria.
2. First Antibiotic - Penicillin - discovered by Alexander Fleming -1929
a. Produced by fungus Penicillium
3. When bacterial population is treated by antibiotics, most members die - mutation may permit
survival of some - produce resistant colonies
a. Reason doctor tells you to take all of an antibiotic
4. Antibiotic don't work on viruses only on bacteria.
IV. Protists - Kingdom Protista
A. Characteristics
1. Eukaryotic - have true nucleus.
2. Most are unicellular but some live in colonies.
3. Does include some simple multicellular organisms - lack specialized tissues.
4. Some are autotrophic while others are heterotrophic.
5. Generally live in aquatic or moist environments.
6. Reproduce sexually and asexually.
B. Organisms are generally placed in this kingdom because they don't have characteristics of organisms in
other kingdoms.
C. Separated into 3 broad groups.
1. PROTOZOA - heterotrophic protists; "first animals"
2. ALGAE - autotrophic protists.
3. Unusual Protists - fungus like protists
V. Protozoa
A. General Characteristics
1. Heterotrophic
2. Most are unicellular, some form colonies - most are microscopic.
3. Live freely or as parasites (in the intestines is common)
a. Many free living protozoans makeup ZOOPLANKTON
1) Unicellular, heterotrophic organisms that drift in water.
b. Parasitic forms cause disease
4. Most lack a protective outer covering - semipermeable cell membrane serves as boundary.
5. Most have physiological mechanism for monitoring and responding to environment.
a. Sense touch and chemical changes - will bypass noxious chemicals.
b. EYESPOT (in some) - Localized region of pigment that detects changes in quality and quantity
of light.
6. Classified into 4 phyla - based on mode of movement.
a. Phylum Sarcodina - move by pseudopodia
b. Phylum Ciliophora - move by cilia
c. Phylum Zoomastigina - move by flagella.
d. Phylum Sporozoa - immobile; parasites
B. Protozoan Phyla and Representatives
1. Phylum Sarcodina - Amoeba
a. Most have flexible cell membrane; Some marine forms have calcium carbonate shells.
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b. Move by means of pseudopodia - Ameboid Movement
1) PSEUDOPODIUM - "False Foot" - cytoplasmic extension that functions in movement.
2) Cytoplasm has 2 regions
a) ECTOPLASM - thin slippery colloidal sol directly inside the cell membrane.
b) ENDOPLASM - colloidal sol and gel found in interior of cell.
3) Endoplasm pushes outward aided by slippery ectoplasm - pseudopodium forms; previously
formed pseudopodia retracted.
4) AMEBOID MOVEMENT - form of cytoplasmic streaming - internal flow of cell contents.
c. Excess water excreted by CONTRACTILE VACUOLE.
d. Ingest nutrients (food) by PHAGOCYTOSIS - surround food by forming pseudopodia - portion
of cell membrane pinches off to form a food vacuole.
e. Undigested food and water excreted by EXOCYTOSIS
f. Reproduce by BINARY FISSION - mitotic division; identical offspring.
g. Form CYST - protective outer wall - when conditions unfavorable.
2. Phylum Ciliophora - Paramecium
a. Move by CILIA - short, hairlike projections that line cell membrane and beat in synchronized
strokes.
b. Paramecium surrounded by rigid protein covering called PELLICLE - shaped like shoe sole.
c. Has 2 kinds of nuclei
1) MACRONUCLEUS - large; control cell activities - respiration, protein synthesis,
digestion, and asexual reproduction.
2) MICRONUCLEUS - small; involved in sexual reproduction and heredity.
d. Foodgetting and Digestion
1) Food taken in through funnel-like ORAL GROOVE - lined with cilia.
2) Beating cilia create currents that sweep food down to MOUTH PORE.
3) Mouth pore opens into a GULLET, which forms food vacuoles that circulate in cytoplasm.
4) Contents of vacuole digested and absorbed.
5) Indigestible matter in vacuole moves to the ANAL PORE where it is eliminated.
e. Exhibit AVOIDANCE BEHAVIOR - reaction away from potentially harmful conditions - backs
up and moves away.
f. Reproduction
1) Asexual - Binary Fission - macronucleus elongates and splits into 2 parts - each part goes
to daughter cell.
2) Sexual - CONJUGATION - involves 2 mating strains; (+) or (-)
3. Phylum Zoomastigina (Mastigophora)
a. Move by 1 or more long, whiplike FLAGELLA
b. Many freeliving.
c. Some are parasitic - best known - Trypanosoma - African Sleeping Sickness - transmitted by
tsetse fly - live only in Africa
4. Phylum Sporozoa
a. All parasitic.
b. Adults have no means of locomotion - carried in body fluids of hosts.
c. Reproduce by means of spores.
d. Example - Plasmodium
1) Causes Malaria
2) Complex Life Cycle - in female Anophiles mosquito
a) Spores enter person's blood stream when mosquito bites - in mosquito's saliva
b) Spores reproduce asexually - infect red blood cells - every 3 to 4 days red blood cells
rupture releasing toxin and more spores - causes chills and fever.
c) When mosquito bites infected person some of cells are ingested - become gametes - that
combine and then divide - migrate to mosquito's salivary glands to begin cycle again.
VI. Algae (Plant like Protists)
A. General Characteristics
1. Diverse group of eukaryotic, plantlike protists
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2. Autotrophic protists - have chloroplasts and produce their own food by photosynthesis.
3. Most are aquatic - terrestrial forms live in moist situations.
4. Unicellular and multicellular forms (large forms discussed with plants)
a. THALLUS - Body of an alga - may be unicellular, colonial, filamentous, or thalloid.
b. PHYTOPLANKTON - photosynthetic plankton
1) Provide food for numerous aquatic organisms
2) Generates great amounts of oxygen.
5. Were classified in past as plants
a. Algae have gametes formed in and protected by unicellular gametangia, plant gametes in
multicellular gametangia.
6. Classified into 4 phyla - based on color, food storage substances, and cell wall composition.
a. All contain chlorophyll a; usually have other forms of chlorophyll
b. Contain accessory pigments.
B. Algal Phyla and Representatives
1. Phylum Chlorophyta - "Green" algae
a. Can be unicellular, colonial, filamentous, or thalloid
b. Most are aquatic - may inhabit moist terrestrial environments
c. Photosynthetic Pigments - Chlorophylls a and b; xanthophylls, carotenes
d. Food stored as starch.
e. Cell wall composition - Polysaccharide, sometimes cellulose
f. Importance - Believed to be ancestors of plants
2. Phylum Chrysophyta - "Golden Brown" Algae
a. Mostly unicellular
b. Photosynthetic pigments - Chlorophylls a and c; Carotenes - fucoxanthin
c. Food stored as Chrysolaminarin - oily carbohydrate
d. Cell wall if present of cellulose, some contain silica
e. Most members are DIATOMS
1) Both marine and freshwater specimens
2) Have silica (silicon dioxide) impregnated shells - highly ornamented, double walls.
a) Two halves fit together like 2 parts of box - each half called a VALVE
3) Types
a) CENTRIC DIATOMS - circular or triangular valves - abundant in marine waters.
b) PENNATE DIATOMS - rectangular valves - abundant in freshwater ponds and lakes
4) So abundant they are responsible for bulk of worldwide photosynthesis.
5) Diatom shells don't decompose - forms material called DIATOMACEOUS EARTH - abrasive
- ingredient in detergents, paint removers, fertilizers, insulators, scouring powders.
3. Phylum Pyrrophyta - "Fire" Algae
a. Most are marine; important component of oceanic phytoplankton - also called
DINOFLAGELLATES - all unicellular
b. Photosynthetic pigments - chlorophylls a and c; Carotene
c. Food stored as starch
d. Cell wall of cellulose - forms plates that look like armor.
e. Many are responsible for BIOLUMINESCENCE - light produced by living things.
f. Responsible for "Red Tides" - discoloration of section of ocean caused by population explosion by
some dinoflagellates - produce toxins that can cause respiratory paralysis in vertebrates
4. Phylum Euglenophyta - "True Eye" Algae - Euglena
a. Have characteristics of green algae and protozoa.
1) Contain chlorophylls a and b, carotenes in some.
2) Food stored as a starch - Paramylon
3) Have no cell wall, surrounded by thick, protein rich pellicle
4) Not completely autotrophic, become heterotrophic when in the dark.
b. Mostly freshwater species.
c. Use contractile vacuole to get rid of excess water.
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d. Moves by whipping flagellum.
e. Red-orange eyespot functions as light detector; guides to bright areas.
VII.Fungus like Protist
A. Members of group traditionally classified as fungi - actually are protists
1. Life cycles look fungus like
2. Store food as glycogen
3. Morphological differences considered superficial
B. Phylum Acrasiomycota - Slime Molds
1. Live mostly on land or in freshwater.
2. Feeding stage is MYXAMEBA - uninucleate cell
a. Live on forest floor or on decaying plants
b. Move and feed like amoeba
3. During times of environmental stress myxameba come together to form a PSEUDOPLASMODIUM
a. PSEUDOPLASMODIUM - group of individual cells that act together as a unit.
b. Moves together.
c. Unit forms sporangia that produce spores
d. Spores develop into individual myxameba
C. Phylum Myxomycota - Plasmodial Slime Molds
1. Feeding stage called PLASMODIUM - multinucleate cytoplasm surrounded by a membrane that
moves as a mass, feeding on organic matter
2. During stressful periods - plasmodium becomes stationary - produces sporangia on stalks
3. Sporangia produce spores that may stay dormant for years.
4. Under proper conditions spore releases myxameba or flagellate swarm cells
a. Cells fuse and nucleus for resulting zygote divides repeatedly
b. Cell doesn't undergo cytokinesis - results in multinucleate cytoplasm or plasmodium
VIII.Kingdom Fungi
A. Diverse group living in many different habitats.
B. Characteristics
1. Eukaryotic
2. Many are microscopic but some are easy to see.
3. Important as decomposers - breakdown organic materials
a. Release inorganic materials to environment to be reused.
b. Most are either parasitic or saprophytic; a few are predatory.
1) PARASITE - organism that lives off of living organisms.
2) SAPROPHYTE - organism that lives off of dead organisms or waste products.
4. Generally grow in moist environments.
5. Composed of vegetative filament called a HYPHA - may or may not be divided by cross walls.
a. COENOCYTIC - filaments without crosswalls.
b. Hypha may be divided by perforated crosswall called SEPTUM.
c. Hypha grows at tip.
d. MYCELIUM - a mat of interwoven hyphae.
e. Made of CHITIN - complex polysaccharide, also found in exoskeleton of arthropods and insects.
6. Food stored as glycogen.
7. Reproduce both sexually and asexually.
a. Asexual Reproduction
1) Produce spores - usually on special branches or modified cells of hypha
2) Small, lightweight spores often carried by wind.
3) If spore lands on suitable food source it will germinate and grow into a new hyphae.
4) May also reproduce asexually by fragmentation, or breaking apart.
b. Sexual Reproduction
1) Gametes from 2 mating strains undergo cytoplasmic fusion.
2) Nuclei don't fuse immediately - will divide independently.
a) HETEROKARYOTIC - Hypha that contains genetically different nuclei.
b) HOMOKARYOTIC - Hypha with genetically similar nuclei.
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C. Classification
1. Basis
a. Structure of hyphae
1) Coenocytic Hyphae - filament without crosswalls
2) Septate Hyphae - filament with crosswalls
3) Unicellular Hyphae - single cell
b. Type of Reproduction - particularly spore type.
2. Five Phyla (Division sometimes used because they were classified as plants at one time)
a. Phylum Oomycota
b. Phylum Zygomycota
c. Phylum Basidiomycota
d. Phylum Ascomycota
e. Phylum Deuteromycota
IX. Fungal Phyla - Descriptions
A. Phylum Oomycota
1. Includes aquatic and terrestrial species - water molds, white rusts, and downy mildews
2. Both parasitic and saprophytic
3. Coenocytic with branched hyphae
4. Cell walls have cellulose not chitin
5. Reproduction
a. Male gametangium, antheridium, release sperm
b. Female gametangium, oogonium, forms egg
c. Zygote forms from fusion of egg and sperm develops thick-walled diploid OOSPORE.
d. Oospore germinates into coenocytic hyphae
e. In asexual reproduction - oomycete produce flagellated zoospores that produce hyphae
6. Example - Phytophthora infestans
a. Late Blight of Potatoes
b. Causative agent that lead to Irish Potato Famine of 1845-47
c. Resulted in mass migration of Irish to United States.
B. Phylum Zygomycota - Rhizopus - bread mold
1. Mostly terrestrial organisms
2. Coenocytic - hyphae lack septa
a. Reproductive structures are blocked off from other hyphae by unperforated cross walls
3. Rhizopus consists of 3 types of hyphae
a. RHIZOIDS - anchoring hyphae - penetrate bread, produce digestive enzymes; absorb nutrients
b. STOLONS - hyphae that grow across surface of bread
c. SPORANGIOPHORE - upright hyphae - sporangia at their tips
4. Reproduction
a. Asexual - spores produced in a sporangium on sporangiophore.
b. Sexual - Conjugation - two strains unite to form a ZYGOSPORE.
c. During favorable conditions asexual reproduction usually occurs, while sexual reproduction
occurs during unfavorable times - ensures genetic recombination.
C. Phylum Basidiomycota - Club Fungi
1. Includes mushrooms, toadstools, puffballs, rusts, and smuts - mostly terrestrial
2. Have septate hyphae
3. Under proper conditions, underground hyphae grow together, intertwine, and produce
BASIDIOCARP - reproductive body of a basidiomycete.
a. Mushroom is a basidiocarp.
1) STALK - stem-like portion
2) CAP - flattened top portion
a) GILLS - radiating rows under cap - site of basidia; thousands are found here
b) BASIDIUM - specialized club-shaped reproductive cell; produces BASIDIOSPORES.
b. Homokaryotic hyphae grows - septa form - each cell has one nucleus - called PRIMARY
MYCELIUM.
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c. Hyphae grow and fuse with hyphae of another mating strain - SECONDARY MYCELIUM forms.
1) Hyphae are heterokaryotic - one nucleus from each strain in each cell.
2) Secondary mycelium forms basidiocarp.
4. Asexual reproduction by fragmentation.
5. Importance
a. Rusts - parasites of many cereal crops
b. Smuts - plant pathogens - particularly corn
c. Mushrooms - some food value
D. Phylum Ascomycota - Sac Fungi
1. Includes yeasts, molds, mildews, and morels - terrestrial and aquatic species.
2. Have septate or unicellular hyphae
3. Reproduction
a. Asexual
1) Production of spore called CONIDIUM - forms at ends of specialized branches called
CONIDIOPHORES
2) Yeast asexual reproduction is by BUDDING - mitosis with unequal cytokinesis
b. Sexual
1) Two mating strains form male or female gametangia
a) Female gametangium - ASCOGONIUM
b) Male gametangium - ANTHERIDIUM
2) Gametangia fuse - male and female nuclei pair but don't fuse
3) Cells divide to produce hyphae that intertwine forming an ASCOCARP - reproductive body
of ascomycete; contains sacs called ASCI (ascus) that produce ascospores.
4. Yeast important because of their ability to breakdown carbohydrates
a. Bread/Baking Industry - use carbon dioxide from anaerobic respiration
b. Brewing Industry - fermentation of juices/liquids
E. Phylum Deuteromycota - Fungi Imperfecti - Imperfect fungi
1. Taxonomic holding tank - composed of species of fungi that no sexual reproductive phase has been
discovered.
a. Many have characteristics similar to ascomycetes
b. Classified on basis of asexual reproduction.
c. Aspergillis and Penicillium - former deuteromycetes now classified as ascomycetes
1) Aspergillis - ferments soy beans and to make soy sauce
2) Penicillium - produce antibiotic penicillin; gives flavor to Roquefort and Camembert
cheeses
2. Have septate hyphae
3. Terrestrial species
4. Reproduce asexually by conidia.
F. Symbiotic Relationships
1. MUTUALISM - type of symbiosis in which both organisms benefit
2. Mycorrhizae
a. Symbiotic association between fungi and plant roots
b. Help plants absorb water and nutrients - phosphorous and potassium
c. Fungus forms extensive network of hyphae in soil - increases surface area.
d. Digestive action of fungal enzymes provides nutrients that can be readily absorbed by the plant.
e. Fungi absorb some of sugar produced by plant in photosynthesis
3. Lichens
a. Symbiotic association between a fungus (usually an ascomycete and a green algae or
cyanobacteria
b. Considered symbiotic but may actually be a controlled parasitism
c. Fungal hyphae penetrate photosynthetic cells and absorb food
d. Fungal member provides some protection against drying of algae.
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e. Lichens classified according to nature of their thallus
1) Crustose - grow as layer on surface of rocks and trees
2) Foliose - loosely attached to substrate and have leafy thallus
3) Shrubby - upright growth; also called 2-fold lichens
X. DISEASE
A. Any change, other than injury, that interferes in normal functioning of a body.
1. PATHOGEN - Disease causing microorganism.
2. INFECTION - Invasion of a body by a pathogen.
B. Germ Theory of Infectious Disease
1. Idea that disease is caused by microorganisms.
2. Earlier belief was that disease was caused by evil spirits, magic, or miasmas (vapors of marshes or
decaying organic matter.
3. Based on work of Louis Pasteur (French) and Robert Koch (German)
4. Koch’s Postulates
a. Microorganism should always be found in host but not in a healthy organism.
b. Microorganism must be isolated and grown in pure culture away from host.
c. When microorganisms of pure culture are injected into new host, they should cause disease.
d. Microorganisms should be reisolated from second host and grown in pure culture and identified
as the same as the original pure culture.
C. Agents of Disease
1. Viruses
2. Bacteria
3. Fungi
4. Protozoa
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