Lecture PowerPoint to accompany
Foundations in
Microbiology
Seventh Edition
Talaro
Chapter 5
Eukaryotic Cells and
Microorganisms
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
5.1 The History of Eukaryotes
• They first appeared approximately 2 billion
years ago
• Evidence suggests evolution from prokaryotic
organisms by symbiosis
• Organelles originated from prokaryotic cells
trapped inside them
2
3
4
5
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5.2 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 prokaryotic 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
7
8
Figure 5.4 Structure and locomotion in ciliates
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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
10
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
11
External Boundary Structures
• Cytoplasmic (cell) membrane
– Typical bilayer of phospholipids and proteins
– Sterols confer stability
– Serves as selectively permeable barrier in
transport
– Eukaryotic cells also contain membrane-bound
organelles that account for 60-80% of their
volume
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5.3 Internal Structures
• Nucleus
– Compact sphere, most prominent organelle of
eukaryotic 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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Figure 5.5 The nucleus
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Figure 5.6 Mitosis
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Internal Structures
• Endoplasmic reticulum – two types:
– Rough endoplasmic reticulum (RER) – originates
from the outer membrane of the nuclear envelope
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
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Figure 5.7 Rough endoplasmic reticulum
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Internal Structures
• Golgi apparatus
– Modifies, stores, and packages proteins
– Consists of a stack of flattened sacs called cisternae
– 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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Figure 5.8 Golgi apparatus
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Figure 5.9
nucleus  RER  Golgi  vesicles  secretion
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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
– Participate in digestion
• Vacuoles
– Membrane bound sacs containing particles to be
digested, excreted, or stored
• Phagosome – vacuole merged with a lysosome
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Figure 5.10
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Internal Structures
• Mitochondria
– Function in energy production
– Consist 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 prokaryotic ribosomes
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Figure 5.11 Structure of mitochondrion
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Internal Structures
• Chloroplast
– Convert the energy of sunlight into chemical
energy through photosynthesis
– Found in algae and plant cells
– Outer membrane covers inner membrane folded
into sacs, thylakoids, stacked into grana
– Larger than mitochondria
– Contain photosynthetic pigments
– Primary producers of organic nutrients for other
organisms
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Figure 5.12
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Internal Structures
• Ribosomes
–
–
–
–
Composed of rRNA and proteins
Scattered in cytoplasm or associated with RER
Larger than prokaryotic 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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Figure 5.13 A model of the
cytoskeleton
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Survey of Eukaryotic Microbes
•
•
•
•
Fungi
Algae
Protozoa
Parasitic worms
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5.4 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
33
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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Figure 5.15
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Figure 5.16c
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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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Figure 5.17 Nutritional sources for fungi
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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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Figure 5.18
40
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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Figure 5.19
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Fungal Reproduction
• Sexual reproduction – spores are formed
following fusion of two different strains and
formation of sexual structure
– Zygospores, ascospores, and basidiospores
• Sexual spores and spore-forming structures
are one basis for classification
43
Figure 5.20 Formation of zygospores
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Figure 5.21 Production of ascospores
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Figure 5.22 Formation of basidiospores in a mushroom
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Fungal Classification
Kingdom Eumycota is subdivided into several
phyla based upon the type of sexual
reproduction:
1. Zygomycota – zygospores; sporangiospores and some
conidia
2. Ascomycota – ascospores; conidia
3. Basidiomycota – basidiospores; conidia
4. Chytridomycota – flagellated spores
5. Fungi that produce only Asexual Spores (Imperfect)
47
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
48
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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5.5 Kingdom Protista
• Algae - eukaryotic organisms, usually
unicellular and colonial, that
photosynthesize with chlorophyll a
• Protozoa - unicellular eukaryotes that lack
tissues and share similarities in cell
structure, nutrition, life cycle, and
biochemistry
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Algae
• Photosynthetic organisms
• 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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54
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
•
•
•
•
•
Diverse group of 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 – lack chloroplasts
• Cytoplasm divided into ectoplasm and endoplasm
• 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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Figure 5.27
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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
Sarcodina – primarily amoeba; 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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Figure 5.28
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Figure 5.29
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Figure 5.30
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Figure 5.31
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Important Protozoan Pathogens
• Pathogenic flagellates
– Trypanosomes – Trypanosoma
• T. brucei – African sleeping sickness
• T. cruzi – Chaga’s disease; South America
• Infective amoebas
– Entamoeba histolytica – amebic dysentery;
worldwide
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Figure 5.32
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Figure 5.33
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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
• Acquired through 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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Figure 5.34 Parasitic Flatworms
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Figure 5.35
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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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