The Eukaryotic Members
of the Microbial World
Chapter 12
Algae
Diverse group of eukaryotic
organisms
Use light to convert carbon
dioxide and water to
carbohydrates
Includes both microscopic
unicellular and macroscopic
multicellular organisms
Algae
Classification of algae
Algae not a distinct classification term
Grouped for identification based on numerous
properties
Photosynthetic pigments
Cell wall structure
Type of storage products
Mechanism of motility
Mode of replication
Names are derived from major color displayed by
group
Algae
Algal habitats
Found in both fresh and salt water and soil
Aquatic algae major producers of oxygen
Also important users of carbon dioxide
Algae often grow where other life forms can’t
Often first to become established in barren
environments
Algae
Structure of algae
Can be both micro and macroscopic
Can float free or be propelled by flagella or
filaments
Macroscopic algae are multicellular
Contain numerous structures for specific
functions
Holdfast anchors organism to firm substrate
Stapes hold blades which are the major
photosynthetic portion of algae
Gas-containing bladders to help maintain blades in
proper position for maximum sunlight
Algae
Structure of algae
Cell wall
Rigid structure made mostly of
cellulose
Diatoms have silicon dioxide
incorporated in cell wall
Cell structures
Have membrane bound nucleus
containing DNA
Have both chloroplast and
mitochondria
Chloroplast for photosynthesis
Mitochondria for respiration
Algae
Algae reproduction
Most single cell algae
reproduce through binary
fission
Chromosome goes
through mitosis
Some algae reproduce
through fragmentation
Portion of parent
organism breaks off to
form new organism
Sexual reproduction
through meiosis also
occurs
Algae
Algae do not cause disease
directly
Numerous algae produce toxin
Toxins are poisonous to
humans
Some species such as
dinoflagellates produce
neurotoxins
Dinoflagellates eaten by
shellfish and produce toxin
Toxin accumulates in
shellfish tissues
Human eat shellfish and
suffer paralytic shellfish
poisoning
Protozoa
Microscopic unicellular
organisms
Lack photosynthetic
capability
Usually motile
Reproduce by asexual
fission
Protozoa
Classification of protozoa
Not a unified group
Lumped together as unicellular organism lacking
chlorophyll
Traditionally divided into groups based on mode
of locomotion
Some belong to phylum Sarcomastigophora
Includes two subphyla
Mastigophora
Sarcodina
Protozoa
Classification of protozoa
Mastigophora
Includes flagellated protozoa
Most significant include
Giardia lamblia, Leshmania species Trichomonas
vaginalis and Trypanosoma species
Sarcodina
Move by means of pseudopodia
Entamoeba hystolytica produces disease in
humans
Protozoa
Classification of protozoa
Other phylum include
Ciliophora
Organism have cilia
Balantidium coli only pathogenic ciliate
Apicomplexa
Cause most serious protozoan disease
Plasmodium species causes malaria
Microspora
Cause sever infection in immunocompromised
Protozoa
Protozoan habitats
Majority are free-living
Found in marine, fresh water and terrestrial habitats
Essential decomposers
Require large amounts of moisture
Important part of food chain
Protozoa eat bacteria and serve as food for larger
species
Help maintain ecological balance in soil
Important in sewage disposal
Results in decrease of sewage solids
Protozoa
Structure of protozoa
Cell wall
Lack cell wall
Shape determined by material beneath plasma
membrane
Cell structures
Have membrane bound nucleus and organelles
Lack photosynthetic chloroplasts
Have specialized structures for movement
Cilia, flagella or pseudopodia
Protozoa grouped by mode of locomotion
Protozoa
Protozoan reproduction
Life cycles complex
Often require more than one
habitat or host
Polymorphic
Can exist as trophozoite or as
cyst
Both sexual and sexual
reproduction common
Many replicate via binary fission
Many replicate by schizogony
Many fissions
Nucleus divides numerous times
then cell produces numerous
single celled organisms
Fungi
Describes a taxonomic classification of
organisms
No longer includes slime molds and water molds
Fungi require organic compounds for energy
and as a carbon source
Most are aerobic or facultative anaerobe
Large number of fungi cause disease in plants
Only a few cause disease in humans
Fungi
Classification of fungi
Can be both micro and macroscopic
Cell wall consist of chitin
No flagellated cells
Four groups of true fungi
Zygomycetes
Basidiomycetes
Ascomycetes
Deuteroomycetes
A.k.a fungi imperfecta
Classification in groups based on sexual reproduction
Except d where sexual reproduction is not seen
Fungi
Classification of fungi
Zygomycetes
Includes common bread mold Rhizopus
Ascomycetes
Includes the fungi of Dutch elm disease
Basidiomycetes
Includes common mushroom and puffballs
Deuteromycetes
Includes medically and commercially important
species including the penicillium
Fungi
Classification of fungi
Grouping of fungal forms
Yeasts
Single celled fungi
Spherical, oval or cylindrical
Reproduction through binary fission or budding
Molds
Filamentous fungi contain hyphae collection of hyphae called mycelium
Reproductive spore is single celled germinates to develop hyphae cells
divide into new form
Dimorphic fungi
Can grow as yeast or mold depending on environment
Many pathogenic fungi are dimorphic
Fungi
Fungal habitats Growth requirements of
Found in virtually every fungi
habitat Slightly moist environment
Mainly terrestrial with high humidity
Fungal spores found 70% or higher
throughout the earth pH range varies
Uncountable Most grow well in
numbers found in air slightly acidic
Major cause of environment
asthma
Most are aerobic
Some yeast facultative
Some fungi obligate
anaerobes
Fungi
Fungal diseases in humans
Cause disease in one of four ways
Allergic reaction
Result from inhaling fungal spores
React to fungal toxin
Many have hallucinogenic properties
Certain species produces alflatoxin implicated in cancer
Mycoses
Fungi grows on or in the body
Economic impact
Destroy human food supply causing starvation
Fungi
Symbiotic relationships of fungi
Form several symbiotic
relationships with other organisms
Lichens result from relationship
between fungi and photosynthetic
organism
Relationships are very close
Fungus provides protection and
growing platform
Other organism supplies nutrient
Mycorrhizae symbiosis with roots of
plants
Increases absorptive property of
roots
Allow plant partners to grow in
dryer climates
Fungi
Economic importance of fungi
Many are important commercially
Saccharomyces used in production of beer, wine and
bread
Many important for cheese production
Penicillin, griseofulvin as well as other antimicrobials
are made from fungi
Elimination of disease causing fungi from
commercial crops vitally important
Fungi used in genetic and biochemical studies
Yeast genetically engineered to produce human
insulin
Slime Molds and Water Molds
Used to be considered types of fungi
They are completely unrelated
Good example of convergent evolution
Two organisms develop similar characteristics
and adaptations but not related on molecular
level
Slime Molds and Water Molds
Acellular slime molds
Terrestrial organisms
Non motile
Reproduction depends of formation of
dispersible spores
Acellular slime molds readily visible in
environment
Plasmodium formed from nucleus
spreads over surface of decaying
matter
Cellular slime molds
Has vegetative form made of ameba-
like cells
Single cells congregate into form
called slug
Slug forms fruiting body and spores
Slime Molds and Water Molds
Water molds
A.k.a Oomycetes
Members of heterokonts
Do not have chlorophyll
Once considered fungi
Due to morphology
Form masses of white thread on decaying
matter
Zoospores cause serious disease of food
crops
Multicellular Parasites:
Arthropods and Helminths
Arthropods include Helminths include nematodes,
Insects such as cestodes and tremetodes
mosquitoes responsible Cause disease by
for transmission of invading host tissues
malaria and fleas which and robbing nutrients
transmits plague Nematodes invade
Ticks responsible for gastrointestinal tract and
transmission of Rocky blood stream
Mountain Spotted Fever Cestodes associated
and Lyme disease with meats especially
Lice responsible for pork
transmission of typhus Transmission results
and other fevers from consumption of
uncooked meat
Mites transmit scabies
Trematodes
Can be found discharged
in waters such as lakes
and ponds