Lecture PowerPoint to accompany
Foundations in
Microbiology
Sixth Edition
Talaro
Chapter 5
Eucaryotic Cells and
Microorganisms
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
The History of Eucaryotes
• They first appeared approximately 2 billion
years ago.
• Evidence suggests evolution from procaryotic
organisms by symbiosis.
• Organelles originated from procaryotic cells
trapped inside them.
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External Structures
• Locomotor appendages
– flagella
• long, sheathed cylinder containing microtubules in a 9+2
arrangement
• covered by an extension of the cell membrane
• 10X thicker than procaryotic flagella
• function in motility
– cilia
• similar in overall structure to flagella, but shorter and
more numerous
• found only on a single group of protozoa and certain
animal cells
• function in motility, feeding and filtering
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External Structures
• Glycocalyx
– an outermost boundary that comes into direct contact
with environment
– usually composed of polysaccharides
– appears as a network of fibers, a slime layer or a
capsule
– functions in adherence, protection, and signal
reception
– beneath the glycocalyx
• Fungi and most algae have a thick, rigid cell wall.
• Protozoa, a few algae, and all animal cells lack a
cell wall and have only a membrane.
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External Boundary Structures
• Cell wall
– rigid, provides structural support and shape
– Fungi have thick inner layer of polysaccharide
fibers composed of chitin or cellulose and a thin
layer of mixed glycans.
– algae – varies in chemical composition;
substances commonly found include cellulose,
pectin, mannans, silicon dioxide, and calcium
carbonate
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External Boundary Structures
• Cytoplasmic (cell) membrane
– typical bilayer of phospholipids and proteins
– sterols confer stability
– serves as selectively permeable barrier in
transport
– Eucaryotic cells also contain membrane-bound
organelles that account for 60-80% of their
volume.
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Internal Structures
• Nucleus
– compact sphere, most prominent organelle of
eucaryotic cell
– nuclear envelope composed of two parallel
membranes separated by a narrow space and is
perforated with pores
– contains chromosomes
– nucleolus – dark area for rRNA synthesis and
ribosome assembly
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Internal Structures
• Endoplasmic reticulum – two types:
– Rough endoplasmic reticulum (RER)– originates
from the outer membrane of the nuclear envelop
and extends in a continuous network through
cytoplasm; rough due to ribosomes; proteins
synthesized and shunted into the ER for packaging
and transport; first step in secretory pathway
– Smooth endoplasmic reticulum (SER)– closed
tubular network without ribosomes; functions in
nutrient processing, synthesis and storage of
lipids, etc.
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Internal Structures
• Golgi apparatus
– consists of a stack of flattened sacs called cisternae
– closely associated with ER
– Transitional vesicles from the ER containing
proteins go to the Golgi apparatus for modification
and maturation.
– Condensing vesicles transport proteins to
organelles or secretory proteins to the outside.
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Internal Structures
• Lysosomes
– vesicles containing enzymes that originate from
Golgi apparatus
– involved in intracellular digestion of food particles
and in protection against invading microbes
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Internal Structures
• Mitochondria
– consists of an outer membrane and an inner
membrane with folds called cristae
– Cristae hold the enzymes and electron carriers of
aerobic respiration.
– divide independently of cell
– contain DNA and procaryotic ribosomes
– function in energy production
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Internal Structures
• Chloroplast
– found in algae and plant cells
– outer membrane covers inner membrane folded
into sacs, thylakoids, stacked into grana
– larger than mitochondria
– contain photosynthetic pigments
– convert the energy of sunlight into chemical
energy through photosynthesis
– primary producers of organic nutrients for other
organisms
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Internal Structures
• Ribosomes
–
–
–
–
composed of rRNA and proteins
40S and 60S subunits form 80S ribosomes
larger than procaryotic ribosomes
function in protein synthesis
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Internal Structures
• Cytoskeleton
– flexible framework of proteins, microfilaments
and microtubules form network throughout
cytoplasm
– involved in movement of cytoplasm, amoeboid
movement, transport, and structural support
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Survey of Eucaryotic Microbes
•
•
•
•
Fungi
Algae
Protozoa
Parasitic worms
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Kingdom Fungi
• 100,000 species divided into 2 groups:
– macroscopic fungi (mushrooms, puffballs, gill
fungi)
– microscopic fungi (molds, yeasts)
• Majority are unicellular or colonial; a few
have cellular specialization
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Microscopic Fungi
• Exist in two morphologies:
– yeast – round ovoid shape, asexual reproduction
– hyphae – long filamentous fungi or molds
• Some exist in either form – dimorphic –
characteristic of some pathogenic molds
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Fungal Nutrition
• All are heterotrophic
• Majority are harmless saprobes living off dead
plants and animals
• Some are parasites, living on the tissues of other
organisms, but none are obligate; mycoses –
fungal infections
• Growth temperature 20o-40oC
• Extremely widespread distribution in many
habitats
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Fungal Organization
• Most grow in loose associations or colonies
• Yeast – soft, uniform texture and appearance
• Filamentous fungi – mass of hyphae called
mycelium; cottony, hairy, or velvety texture
– hyphae may be divided by cross walls – septate
– vegetative hyphae – digest and absorb nutrients
– reproductive hyphae – produce spores for
reproduction
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Fungal Reproduction
• Primarily through spores formed on reproductive
hyphae
• Asexual reproduction – spores are formed
through budding or mitosis; conidia or
sporangiospores
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Fungal Reproduction
• Sexual reproduction – spores are formed
following fusion of male and female strains
and formation of sexual structure
• Sexual spores and spore-forming structures
are one basis for classification.
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Fungal Classification
Subkingdom Amastigomycota – terrestrial
inhabitants including those of medical importance:
1. Zygomycota – zygospores; sporangiospores and some
conidia
2. Ascomycota – ascospores; conidia
3. Basidiomycota – basidiospores; conidia
4. Deuteromycota – majority are yeasts and molds; no
sexual spores known; conidia
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Fungal Identification
• Isolation on specific media
• Macroscopic and microscopic observation
of:
–
–
–
–
–
asexual spore-forming structures and spores
hyphal type
colony texture and pigmentation
physiological characteristics
genetic makeup
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Roles of Fungi
• Adverse impact
– mycoses, allergies, toxin production
– destruction of crops and food storages
• Beneficial impact
– decomposers of dead plants and animals
– sources of antibiotics, alcohol, organic acids,
vitamins
– used in making foods and in genetic studies
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Kingdom Protista
• Algae
• Protozoa
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Algae
• Photosynthetic organisms
• Kelps, seaweeds, euglenids, green algae, diatoms,
dinoflagellates, brown algae, and red seaweeds
• Microscopic forms are unicellular, colonial,
filamentous.
• Macroscopic forms are colonial and multicellular.
• Contain chloroplasts with chlorophyll and other
pigments
• Cell wall
• May or may not have flagella
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Algae
• Most are free-living in fresh and marine water –
plankton.
• Provide basis of food web in most aquatic habitats
• Produce large proportion of atmospheric O2
• Dinoflagellates can cause red tides and give off
toxins that cause food poisoning with neurological
symptoms.
• Classified according to types of pigments and cell
wall
• Used for cosmetics, food, and medical products
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Protozoa
•
•
•
•
•
65,000 species
Vary in shape, lack a cell wall
Most are unicellular; colonies are rare
Most are harmless, free-living in a moist habitat
Some are animal parasites and can be spread by insect
vectors.
• All are heterotrophic.
• Feed by engulfing other microbes and organic matter
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Protozoa
• Most have locomotor structures – flagella, cilia, or
pseudopods.
• Exist as trophozoite - motile feeding stage
• Many can enter into a dormant resting stage when
conditions are unfavorable for growth and feeding –
cyst.
• All reproduce asexually, mitosis or multiple fission;
many also reproduce sexually – conjugation.
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Protozoan Identification
•
•
Classification is difficult because of diversity.
Simple grouping is based on method of motility,
reproduction, and life cycle.
1.
2.
3.
4.
Mastigophora – primarily flagellar motility, some flagellar
and amoeboid; sexual reproduction; cyst and trophozoite
Sarcodina – primarily ameba; asexual by fission; most are
free-living
Ciliophora – cilia; trophozoites and cysts; most are freeliving, harmless
Apicomplexa – motility is absent except male gametes;
sexual and asexual reproduction; complex life cycle – all
parasitic
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Important Protozoan Pathogens
• Pathogenic flagellates
– Trypanosomes – Trypanosoma
• T. brucei – African sleeping sickness
• T. cruzi – Chaga’s disease; South America
• Infective amebas
– Entameba histolytica – amebic dysentery;
worldwide
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Parasitic Helminths
• Multicellular animals, organs for reproduction,
digestion, movement, protection
• Parasitize host tissues
• Have mouthparts for attachment to or digestion of
host tissues
• Most have well-developed sex organs that produce
eggs and sperm.
• Fertilized eggs go through larval period in or out
of host body.
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Major Groups of Parasitic Helminths
1. Flatworms – flat, no definite body cavity;
digestive tract a blind pouch; simple
excretory and nervous systems
• cestodes (tapeworms)
• Trematodes or flukes, are flattened ,
nonsegmented worms with sucking mouthparts.
2. Roundworms (nematodes)- round, a complete
digestive tract, a protective surface cuticle,
spines and hooks on mouth; excretory and
nervous systems poorly developed
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Helminths
• 50 species parasitize humans.
• Acquired though ingestion of larvae or eggs
in food; from soil or water; some are carried
by insect vectors
• Afflict billions of humans
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Helminth Classification and Identification
• Classify according to shape, size, organ
development, presence of hooks, suckers, or
other special structures, mode of reproduction,
hosts, and appearance of eggs and larvae
• Identify by microscopic detection of adult
worm, larvae, or eggs
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Distribution and Importance of
Parasitic Worms
• Approximately 50 species parasitize humans.
• Distributed worldwide; some restricted to
certain geographic regions with higher
incidence in tropics
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