Transcript Microorganisms

Biological particle composed of genetic material
and protein
Cause diseases
Virulent –immediate
Temperate - not immediately
Obligate Parasite - only reproduces in a
living host
Comparison with cells
Constructed of compounds usually associated with
cells
Have some characteristics of life but not all
No nucleus, cytoplasm, organelles, or cell
membrane
Don't reproduce by either mitosis or meiosis.
Not capable of carrying out cellular functions
Contain nucleic acids
Can crystallize where cells cannot.
Viral Structure

Core of nucleic acid - either RNA or DNA

Core surrounded by protein layer called Capsid
Made of repeating protein units called Capsomeres
Gives virus its shape.

Function of viral nucleic acid
Codes for production of viral nucleic acid.
Control manufacture protein coat.

Shape
Icosahedron - 20 triangular faces; Most common shape
Polio, chicken pox, colds
Helix - subunits of coat form spiral chain - like coiled spring
Rabies, mumps
Strands surrounded by 2 protein layers - inner protein layer
surrounded by lipid layer with embedded glycoproteins
HIV.
Classification




Major division
RNA Viruses
DNA Viruses
Lower levels based on shape and size.
Retroviruses - contains enzyme Reverse Transcriptase
Directs host cell to make DNA using viral RNA of virus
as a template.
Disease causing particles - smaller and simpler than virus
Viroid - short, single strand of RNA with no capsid
interferes with normal cell functions
Prion - glycoprotein particle contains polypeptide of
about 250 amino acids - no nucleic acid.
Bacteriophage(Phage) - virus that infects bacteria
Have been used to gather information about
viral replication.
Have round, oval, or many sided heads and
hollow tails
Head contains nucleic acid.
Tail has fibers at tip
Anchors phage to bacteria
Lytic Cycle - fundamental reproductive process of
viruses
Consists of 5 phases.
Attachment
Entry
Replication
Assembly
Release
Lysogenic Cycle
 Involves temperate viruses
 Viruses enter cell similar to lytic cycle
Consists of a small segment of DNA
Prophage
 Viral DNA becomes additional set of genes
Incorporates into host's DNA
Replicates with host DNA
 External stimulus - radiation, chemicals - cause
prophage to become virulent
Evolution

Believed to have evolved after cells

May be simplification of some existing cells.



Most common members - bacteria
Bacteria Characteristics
Prokaryotic - no nucleus
Microscopic
Heterotrophs or autotrophs
Evolution
Fossil monerans - 3.5 billion years old.
Evolved into many forms - live in different
environments.
Classification difficult; rely on physiology
Classification - 2 Kingdoms

Kingdom Archaebacteria

Kingdom Eubacteria


Adapted to harsh environments
Include methanogens, extreme halophiles, and
thermoacidophiles.
Methanogens
Anaerobic
Use carbon dioxide and hydrogen to form
methane
Live in bog and lake bottoms, digestive tracts
of livestock, and sewerage treatment plants.
Halophiles - live in high salt areas
Thermoacidophiles - live in very acidic and hot
areas
All members of which we commonly call Bacteria
Identification
Classified on basis of shape
Coccus - spherical shaped cells
Bacillus - Rod shaped cells
Spirillum - Shaped like coiled rods or corkscrews
Cells can cluster together or form chains or filaments
Staphylo - cluster
Strepto -filament
Diplo - pairs
Classified on reaction to Gram stain - stains pink or purple
Gram-Negative - pink - difficult to treat with antibiotics
Gram-Positive - purple -treated with antibiotics
Two specialized Phyla
 Phylum Cyanophyta
Blue-green bacteria (algae)
Similar to plants and plant-like protists
Photosynthetic - produce food and oxygen.
Clump to form colonies
Exhibit some division of labor
 Phylum Prochlorophyta
Photosynthetic
Live symbiotically with tunicates
Chlorophyll similar to eukaryotes.
Structure and Movement







DNA arranged in single circular chromosome called plasmids
Cell walls differ from eukaryotes - some rigid, others flexible
Many produce Capsule - protective polysaccharide layer.
Glycocalyx - polysaccharide that helps many stick to surfaces
Pili - Protein strands to attach themselves to objects
May form endospores under adverse conditions
Permits bacteria to lie dormant for years.
Favorable conditions, endospore breaks; cell becomes active.
Movement
Many move by rotating stiff flagellum bent into S-curve.
Spirochetes use filament that wraps around cell to move
Nutrition
May be heterotrophic or autotrophic
Most are Heterotrophic
Saprophyte feeds on dead or decaying matter.
Parasite feeds on living materials
Some Autotrophic
Photoautotrophs - use sunlight as energy source.
Chemoautotrophs - use energy of chemical
reactions to synthesize food.
Nitrogen Fixation - gaseous nitrogen
converted into ammonia compounds
Respiration



Obligate Anaerobes - cannot survive in presence of
oxygen.
Facultative Anaerobes - can live with or without
oxygen.
Obligate Aerobes - cannot live without oxygen.
Reproduction



Some reproduce rapidly - divide every 15-20 minutes
Binary Fission - cell reproduces by splitting in two
Asexual
DNA replicates first
Plasma membrane and cell wall grows inward form 2
identical daughter cells.
Conjugation - type of sexual reproduction, genetic material
exchanged.
Recombination of genetic material by 2 bacteria
Portion of DNA from one cell passes across bridge
formed by pili.
Recipient DNA destroyed and new DNA is substituted
Toxin Production


Pathogen - any organism that causes disease.
Most bacterial diseases caused by toxins produced by bacteria.
Toxin - poisonous substance that disrupts metabolism of
infected organism.
Endotoxin - pieces of cell wall of Gram-negative bacteria
Symptoms - fever, weakness, and damage to
circulatory system
Example - Typhoid Fever.
Exotoxin - products of bacterial metabolism
Secreted into area around bacteria
Most potent poisons known
Examples - Diphtheria and Botulism (food poisoning)
Characteristics






Eukaryotic - have true nucleus.
Most are unicellular but some live in colonies.
Does include some simple multicellular
organisms - lack specialized tissues.
Some autotrophic; others heterotrophic.
Live in aquatic or moist environments.
Reproduce sexually and asexually.


Organisms placed in this kingdom because
they don't have characteristics of organisms in
other kingdoms.
Separated into 3 broad groups.
Prototozoa - heterotrophic protists; "first
animals"
Algae - autotrophic protists.
Unusual Protists - fungus like protists
General Characteristics



Heterotrophic
Most are unicellular, some form colonies - most are
microscopic.
Live freely or as parasites (in the intestines is common)
Many free living protozoans makeup zooplankton
Unicellular, heterotrophic organisms that
drift in water.
Parasitic forms cause disease



Most lack a protective outer covering - semipermeable cell
membrane serves as boundary.
Most have physiological mechanism for monitoring and
responding to environment.
Sense touch and chemical changes - will bypass noxious
chemicals.
Eyespots (in some) - Localized region of pigment that
detects changes in quality and quantity of light.
Classified into 4 phyla - based on mode of movement.
Phylum Sarcodina - move by pseudopodia
Phylum Ciliophora - move by cilia
Phylum Zoomastigina - move by flagella.
Phylum Sporozoa - immobile; parasites







Most have flexible cell membrane; Some marine forms have
calcium carbonate shells.
Move by means of pseudopodia - Ameboid Movement
Pseudopodium - "False Foot" - cytoplasmic extension that
functions in
movement.
Cytoplasm has 2 regions
Ectoplasm
Endoplasm
Ameboid Movement - internal flow of cell contents.
Excess water excreted by Contractile Vacuole
Ingest nutrients (food) by phagocytosis
Undigested food and water excreted by Exocytosis
Reproduce by Binary Fission - identical offspring.
Form Cysts - protective outer wall - when conditions are bad






Move by Cilia - short, hairlike projections
Paramecium has rigid protein covering called Pellicle - shaped like shoe
sole.
Has 2 kinds of nuclei
Macronucleus - large; control cell activities
Micronucleus - small; involved in sexual reproduction
Foodgetting and Digestion
Food enters through funnel-like Oral Groove -.
Cilia sweeps food to Mouth Pore .
Mouth pore opens into a Gullet, forms food vacuoles
Contents of vacuole digested and absorbed.
Indigestible matter in vacuole moves to the Anal Pore -eliminated.
Exhibit Avoidance Behavior - move away from harmful conditions
Reproduction
Asexual - Binary Fission - macronucleus splits– one part to each
daughter cell.
Sexual – Conjugation - involves 2 mating strains; (+) or (-)

Move by 1 or more long, whiplike Flagella

Many freeliving.

Some are parasitic
Best known - Trypanosoma - African
Sleeping Sickness
Transmitted by tsetse fly - live in Africa




All parasitic.
No means of locomotion - in body fluids of hosts.
Reproduce by spores.
Example - Plasmodium
Causes Malaria
Complex Life Cycle - in female Anophiles sp. - mosquito
Spores enter blood stream thru mosquito saliva
Spores reproduce asexually - infect red blood cells rupture releasing toxin and more spores - causes chills
and fever.
Mosquito bites infected person some of cells ingested become gametes - combine and divide - migrate to
mosquito's salivary glands to begin cycle again.
General Characteristics

Eukaryotic, plantlike protists

Autotrophic protists - produce food by photosynthesis.

Most aquatic - terrestrial forms in moist situations.

Unicellular and multicellular forms (large forms discussed with plants)
Thallus - Body of an alga - unicellular, colonial, filamentous, or thalloid.
Phytoplankton - photosynthetic plankton
Provide food for numerous aquatic organisms
Generates great amounts of oxygen.

Were classified in past as plants
Gametes formed in unicellular gametangia, plant multicellular gametangia.

Classified into 4 phyla - based on color, food storage substances, and cell wall
composition.
All contain chlorophyll a; usually have other forms of chlorophyll
Contain accessory pigments.






Unicellular, colonial, filamentous, or thalloid
Most aquatic or moist terrestrial environments
Photosynthetic Pigments - Chlorophylls a and
b; xanthophylls, carotenes
Food stored as starch.
Cell wall composition - Polysaccharide,
sometimes cellulose
Importance - Believed to be ancestors of
plants





Mostly unicellular
Photosynthetic pigments - Chlorophylls a and c; Carotenes - fucoxanthin
Food stored as Chrysolaminarin - oily carbohydrate
Cell wall if present of cellulose, some contain silica
Most members are Diatoms
Marine and freshwater specimens
Have silica containing shells - highly ornamented, double walls.
Halves fit together like a box - half called Valve
Types
Centric Diatoms - circular or triangular valves - marine waters.
Pennate Diatoms - rectangular valves - freshwater ponds and lakes
Responsible for bulk of worldwide photosynthesis.
Diatom shells don't decompose - forms Diatomaceous Earth - abrasive ingredient in detergents, paint removers, fertilizers, insulators,
scouring powders.






Most are marine; oceanic phytoplankton - called
Dinoflagellates - all unicellular
Photosynthetic pigments - chlorophylls a and c;
Carotene
Food stored as starch
Cell wall of cellulose - looks like armor.
responsible for Bioluminescence - light produced
by living things.
Produce "Red Tides" - discoloration of ocean ;
population explosion of dinoflagellates - produce
toxins may cause respiratory paralysis in
vertebrates





Have characteristics of green algae and protozoa.
Contain chlorophylls a and b, carotenes in some.
Food stored as a starch - Paramylon
Have no cell wall, surrounded by pellicle
Not completely autotrophic, heterotrophic - in
the dark.
Mostly freshwater species.
Contractile vacuole gets rid of excess water.
Moves by whipping flagellum.
Red-orange eyespot functions as light detector
Members of group traditionally classified as fungi
- actually are protists

Life cycles look fungus like

Store food as glycogen

Morphological differences considered
superficial
Phylum Acrasiomycota - Slime Molds
 Live mostly on land or in freshwater.
 Feeding stage - Myxameba - uninucleate cell
Live on forest floor or on decaying plants
Move and feed like amoeba
 During environmental stress myxameba come
together to form a Pseudoplasmodium
Group of individual cells that act as one unit
Moves together.
Unit forms sporangia that produce spores
Spores develop into individual myxameba
Phylum Myxomycota - Plasmodial Slime Molds
 Feeding stage - Plasmosium - multinucleate cytoplasm
surrounded by a membrane that moves as a mass,
feeds on organic matter
 Stressful periods - plasmodium becomes stationary produces sporangia on stalks
 Sporangia produce spores - may be dormant for years.
 Spore releases myxameba or flagellate swarm cells
Cells fuse; nucleus for zygote divides repeatedly
Doesn't undergo cytokinesis
Multinucleate plasmodium
Diverse group living in many different habitats.
Characteristics
 Eukaryotic
 Many microscopic; some easy to see.
 Important as decomposers - breakdown organic materials
Release inorganic materials to environment to be reused.
Most are either parasitic or saprophytic; a few predatory.
Parasite - organism that lives off of living
organisms.
Saprophyte - organism that lives off of dead
organisms or waste products.
 Generally grow in moist environments.
Characteristics


Composed of vegetative filament called a Hypha - may
or may not be divided by cross walls.
Coenocytic - filaments without crosswalls.
Hypha may be have perforated crosswall - Septum.
Hypha grows at tip.
Mycelium - a mat of interwoven hyphae.
Made of Chitin - complex polysaccharide, also in
exoskeleton of arthropods and insects.
Food stored as glycogen.
Characteristics

Reproduce both sexually and asexually.
Asexual Reproduction
Produce spores on special branches of hypha
Spores often carried by wind.
Finds suitable food source germinates; new hyphae grows
May reproduce asexually by fragmentation
Sexual Reproduction
Gametes from 2 mating strains undergo cytoplasmic fusion.
Nuclei don't fuse immediately - divide independently.
Heterokaryotic - different nuclei
Homokaryotic - similar nuclei.
Classification
 Basis
Structure of hyphae
Coenocytic Hyphae – No crosswalls
Septate Hyphae - With crosswalls
Unicellular Hyphae - single cell
Type of Reproduction - particularly spore type.
 Five Phyla
Phylum Oomycota
Phylum Zygomycota
Phylum Basidiomycota
Phylum Ascomycota
Phylum Deuteromycota






Aquatic and terrestrial species - water molds, white rusts, and downy
mildews
Both parasitic and saprophytic
Coenocytic with branched hyphae
Cell walls have cellulose not chitin
Reproduction
Male gametangium, antheridium, release sperm
Female gametangium, oogonium, forms egg
Fusion of egg and sperm develops thick-walled
diploid
Oospore
Oospore germinates into coenocytic hyphae
Asexual reproduction - flagellated zoospores produce hyphae
Example - Phytophthora infestans - Late Blight of Potatoes
Irish Potato Famine of 1845-47
Result - mass migration of Irish to United States.




terrestrial organisms
Coenocytic - hyphae lack septa
Reproductive structures are separated from other hyphae by
unperforated cross walls
Rhizopus consists of 3 types of hyphae
Rhizoids - anchoring hyphae – absorb nutrients
Stolons - hyphae that grow across surface of bread
Sporangiophore - upright hyphae - sporangia at their tips
Reproduction
Asexual - spores from a sporangium on sporangiophore.
Sexual - Conjugation - two strains unite to form a Zygospore
Favorable conditions -asexual reproduction
Unfavorable conditions - sexual reproduction





Mushrooms, toadstools, puffballs, rusts, and smuts - mostly terrestrial
Septate hyphae
Underground hyphae produce Basidiocarp - reproductive body
Mushroom is a basidiocarp.
Stalk - stem-like portion
Cap - flattened top portion
Gills - radiating rows under cap - site of basidia;
Basidium - club-shaped reproductive cell; produces
Basidiospores
Hyphae grows - septa form - called Primary Mycelium
Hyphae grow,fuse with another mating strain – Secondary mycelium forms.
Hyphae heterokaryotic - one nucleus in each cell.
Secondary mycelium forms basidiocarp.
Asexual reproduction by fragmentation.
Importance
Rusts - parasites of many cereal crops
Smuts - plant pathogens - particularly corn
Mushrooms - some food value




Includes yeasts, molds, mildews, and morels - terrestrial and aquatic species.
Have septate or unicellular hyphae
Reproduction
Asexual
Spores called Conidium – on Conidiophores
Yeast asexual reproduction is by Budding
Sexual
Two mating strains form male or female gametangia
Female gametangium – Ascogonium
Male gametangium – Antheridium
Gametangia fuse - nuclei pair but don't fuse
Hyphae intertwine form an Ascocarp - reproductive body of
ascomycete; contains sacs -Asci (ascus) that produce ascospores.
Yeast important – able to breakdown carbohydrates
Bread/Baking Industry - use carbon dioxide from anaerobic respiration
Brewing Industry - fermentation of juices/liquids




Taxonomic holding tank - fungi that where no sexual
reproductive phase has been discovered.
Have characteristics similar to ascomycetes
Classified on basis of asexual reproduction.
Aspergillis and Penicillium - former deuteromycetes now
classified as ascomycetes
Aspergillis - ferments soy beans makes soy sauce
Penicillium - produce antibiotic penicillin; gives
flavor to Roquefort and Camembert cheeses
Septate hyphae
Terrestrial species
Asexually Reproduce by conidia.
MUTUALISM - type of symbiosis in which both
organisms benefit
Examples
Mycorrhizae
Symbiotic association between fungi and plant
roots
Lichens
Symbiotic association between a fungus (usually
an ascomycete and a green algae or
cyanobacteria





Symbiosis between fungi and plant roots
Help plants absorb water and nutrients
Fungus forms extensive network of hyphae in
soil - increases surface area.
Action of fungal enzymes provide nutrients
that can be readily absorbed by the plant.
Fungi absorbs of sugar produced by plant





Symbiosis between a fungus (usually an ascomycete
and a green algae or cyanobacteria
Considered symbiotic-may be a controlled parasitism
Fungal hyphae penetrate algal cells and absorb food
Fungal member provides some protection against
drying of algae.
Lichens classified according to thallus
Crustose - grow surface of rocks and trees
Foliose - have leafy thallus
Shrubby - upright growth; also called 2-fold lichens
Any change, other than injury, that interferes in
normal functioning of a body.

Pathogen - Disease causing microorganism

Infection - Invasion of a body by a pathogen.




Idea that disease is caused by microorganisms.
Earlier belief was that disease was caused by evil spirits, magic, or
miasmas (vapors of marshes or decaying organic matter.)
Based on work of Louis Pasteur (French) and Robert Koch
(German)
Koch’s Postulates
 Microorganism should always be found in host but not in a
healthy organism.
 Microorganism must be isolated and grown in pure culture
away from host.
 When microorganisms of pure culture are injected into new
host, they should cause disease.
 Microorganisms should be reisolated from second host and
grown in pure culture and identified as the same as the original
pure culture.
Agents of Disease




Viruses
Bacteria
Fungi
Protozoa