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


Ascomycetes


Includes the fungi of Dutch elm disease
Basidiomycetes


Includes common bread mold Rhizopus
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
fungi
 Found in virtually every
habitat
 Slightly moist environment
with high humidity
 Mainly terrestrial
 70% or higher
 Fungal spores found
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


Relationships are very close



Lichens result from relationship
between fungi and photosynthetic
organism
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 amebalike 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



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Insects such as
mosquitoes responsible
for transmission of
malaria and fleas which
transmits plague
Ticks responsible for
transmission of Rocky
Mountain Spotted Fever
and Lyme disease
Lice responsible for
transmission of typhus
and other fevers
Mites transmit scabies
 Helminths include nematodes,
cestodes and tremetodes



Cause disease by
invading host tissues
and robbing nutrients
Nematodes invade
gastrointestinal tract and
blood stream
Cestodes associated
with meats especially
pork


Transmission results
from consumption of
uncooked meat
Trematodes

Can be found discharged
in waters such as lakes
and ponds