Eukaryotic Cells and Microorganisms - PSAU · Fungi and most algae have a thick, rigid cell wall Protozoa and animal cells do not have this cell wall . The Main Themes of Microbiology

The Main Themes of Microbiology Microbiology: A Systems Approach

Chapter 1, pages 1 to 26 1

Eukaryotic

Cells and

Microorganisms

Chapter 5

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Cellular Acellular

Prokaryotes Eukaryotes Viruses

Bacteria and archaea

Fungi, protozoa, and helminths

Viruses and bacteriophages

Types of Microbes

Bacterial virus

AIDS virus

Envelope

Capsid

Nucleic

acid

Prokaryotic

Chromosome

Ribosomes

Cellwall Cell

membrane

Eukaryotic

Ribosomes

Cell membrane

Nucleus

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.



5.1 The History of Eukaryotes

First eukaryotic cells on earth approximately 2 billion years ago

Evidence points to these eukaryotic cells evolving from prokaryotic organisms through intracellular symbiosis

Eukaryotic organelles originated from prokaryotic cells trapped inside of them

First primitive eukaryotes- probably single-celled and independent

Eventually formed colonies

Cells within colonies became specialized

Evolved in to multicellular organisms

Eukaryotic vs. Prokaryotic Cell

Larger in size

Contains a nucleus

Division of labor

Organelles


Mitochondrion Cell wall*

Cell membrane

Golgi apparatus

Actin filaments

Ribosomes

Plasmid

Intermediate

filaments

Lysosome

Smooth

endoplasmic

reticulum

Microtubules

Chloroplast*

*Structure not present in all cell types

Rough endoplasmic

reticulum with

ribosomes

Flagellum*

Nuclear

membrane

with pores

Nucleus

Nucleolus

Glycocalyx*

Centrioles*

Fimbriae

Inclusion/

Granule

Cell wall

Outer

membrane

Cytoplasm

Endospore (not shown)

Glycocalyx

Bacterial

chromosome

or nucleoid

Pilus

Cell

(cytoplasmic)

membrane

Actin

cytoskeleton

Flagellum



Eukaryotic Organisms

5.2 Form and Function of the Eukaryotic

Cell: External Structures

Figure 5.2



Locomotion: Eukaryote Flagellum

Used for locomotion

Does not spin

Waves like an oar

Multi-protein complex

Microtubule core (9x2 + 2)

Dynein arms use ATP to slide the tubules which results in flexion.


a: © Scientifica/RMF/Visuals Unlimited, Inc.; b: © RMF/FDF/Visuals Unlimited

Microtubules

Cilia- similar to flagella but some differences

Shorter

More numerous

Can also function as feeding and filtering structures

Locomotion Appendages: Cilia



The Glycocalyx

Most eukaryotic cells have this outermost boundary

Usually composed of polysaccharides

Appears as a network of fibers, a slime layer, or a capsule

Slime layer- loosely organized

Capsule– greater organization, makes phagocytosis more difficult

Glycocalyx

Functions

Protection

Adhesion

Reception of signals

The layer beneath the glycocalyx varies among eukaryotes

Fungi and most algae have a thick, rigid cell wall

Protozoa and animal cells do not have this cell wall



Eukaryote Capsule

Present in some pathogens

Polymeric sugars

Important in avoiding immune clearance

Similar to prokaryotes

(a)

Cell Wall

Rigid

Provide support and shape

Different chemically from prokaryotic cell walls

Fungi

Thick, inner layer of chitin or cellulose

Thin outer layer of mixed glycans

Algae

Varied in chemical composition

May contain cellulose, pectin



Cytoplasmic Membrane

Bilayer of phospholipids with protein molecules embedded

Also contain sterols

Gives stability

Especially important in cells without a cell wall

Selectively permeable

5.3 Internal Structures - The Nucleus

Double lipid bilayer

Most of the genetic material of the cell

Nucleolus (rRNA synthesis)

Nuclear pores allow traffic into and out of the nucleus

Note that the DNA is partitioned from the cytoplasm and ribosomes

Nuclear pore

Nucleolus

(b Nuclear

envelope




Figure 5.6

Genetic Material

Multiple linear chromosomes are present

Haploid or diploid

DNA is condensed on proteins (histones)

Replicate using mitosis and/or meiosis

b: © Science VU/Visuals Unlimited




Figure 5.7

Cell Cycle

Endoplasmic Reticulum Phospholipid bilayer

Smooth ER

Lipid metabolism

Detox reactions

Rough ER

Ribosomes docked

Protein synthesis


(a)

(b)

(c)

RER membrane

Ribosome

Small subunit

Large subunit

Cistern

Polyribosomes

Cistern

Nuclear envelope

Nuclear pore

Protein being

synthesized

mRNA



Eukaryote Ribosome

Two subunits (40S and 60S)

Total size is 80S

Translate mRNA into proteins

Similar structure to prokaryotes but different shape

Antibiotic-resistant (selective toxicity)

Mitochondria

“Powerhouse”

Site of respiration

Bacterial endosymbiont


Own genetic material

Reproduce autonomously


Inner membrane

Matrix

Cristae

(a) Outer membrane

(b)

70S ribosomes

DNA strand

Cristae

(darker lines)

Matrix

(lighter spaces)

b: © Donald Fawcett/Visuals Unlimited



Chloroplasts Found in plants

and algae

Site of photosynthesis

Bacterial endosymbiont


Own genetic material

Reproduce autonomously


70S ribosomes

Granum Thylakoids

Stroma matrix

Chloroplast envelope

(double membrane)

DNA strand

Golgi Apparatus

Composed of a lipid bilayer

Protein trafficking centers

Import/Processing/ Export

“Stack of pancakes”

Vesicles bud off


Cell membrane

Golgi

apparatus

Condensing

vesicles

Transitional

vesicles

Rough

endoplasmic

reticulum Nucleus

Ribosome

parts

Nucleolus

Secretion by exocytosis

Secretory vesicle



Cytoskeleton

Intracellular protein matrix

Regulate cell shape

Involved in motility

Actin

polymerized into chains

Microtubules (green)

made of tubulin

Intermediate filaments

Microfilaments


(a)

Mitochondrion

Microtubule

(b)

Endoplasmic

reticulum

Intermediate

filaments

Actin

filaments

Plasma

membrane

b: © Albert Tousson/PhotoTake

Vacuoles

Lipid-enclosed space

Storage sites for water, food, enzymes, and waste

Vary greatly in size and function

Central vacuoles provide turgor pressure

Contractile vacuole eliminate water

Lysosomes contain digestive enzymes



5.4 The Kingdom of Fungi

Myceteae

Great variety and complexity

Approximately 100,000 species

Majority are unicellular or colonial

Hyphae

Some form a pseudohypha

The Fungi

Terrestrial, non-photosynthetic, and saprophytic

Single-celled forms are called yeast

Multicellular (Molds)

Hyphae form mycelium

Ergosterol in membrane

Chitin cell walls

Haploid and diploid cells occur

Sexual and asexual reproduction



Figure 5.17

Organization of Microscopic Fungi

Most grow in loose associations or colonies

Yeasts- soft, uniform texture and appearance

Filamentous fungal colonies- cottony, hairy, or velvety textures

Mycelium- the woven, intertwining mass of hyphae that makes up the body or colony of a mold



Mycelial Growth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a) Reproductive Hyphae

Hypha

Germ tube

Rhizoids

Spore

Substrate

Spores

Germination (d)

Vegetative Hyphae

Surface

hyphae

Submerged

hyphae

d: © Dr. George L. Barron

(b)

(c)

Organization of Fungi- Hyphae

Unique organizational features of hyphae Septa- divide the hyphae in to segments (most fungi-

septate hyphae)

Nonseptate hyphae- one long, continuous cell

Functions of hyphae Vegetative hyphae (mycelia)- visible mass of growth

on the substrate surface; penetrates the substrate to digest and absorb nutrients

Reproductive (fertile) hyphae- from vegetative hyphae; responsible for the production of spores



Figure 5.16

Microscopic morphology of Yeast

Yeasts

Single-cell fungi

Budding

Blastospores

Useful yeasts

Saccharomyces

Pathogens

Cryptococcus

Candida


(a)

Ribosomes

Mitochondrion

Nucleus

Nucleolus

Cell membrane

Golgi apparatus

Cell wall

Storage vacuole

Bud scar

(b)

(c)

Bud

Nucleus Bud scars

Pseudohypha

Bud

Endoplasmic

reticulum

Fungal (Yeast) Cell

b: © David M. Phillips/Visuals Unlimited



Reproductive Strategies and Spore

Formation

Most can propagate by growth of hyphae or fragmentation

Primary reproductive mode- the production of spores

Function of spores

Multiplication

Survival

Producing genetic variation

Dissemination

Large diversity in spores among the fungi

General grouping of spores- asexual and sexual

Why are sexual spores favorable?

The Roles of Fungi in Nature and

Industry

Nearly all fungi are free-living and don’t need a host

Human infection by pathogenic fungi usually occurs through accidental contact

Humans are generally resistant to fungal infection, except for two main types

Primary pathogens

Opportunistic pathogens

Mycoses vary in the way the agent enters the body and the degree of tissue involvement

Also involved in allergies, poisonings, agricultural damage



Benefits of

Fungi

Decomposing organic matter and returning essential minerals to the soil

Mycorrhizae increase the ability of plant roots to absorb water and nutrients

Production of

Antibiotics

Alcohol

Organic acids

Vitamins

Food flavorings

Fungal Infections



5.5 The Protists

Traditionally contains the algae and protozoa

Two major taxonomic categories

Subkingdom Algae

Subkingdom Protozoa

Algae: Photosynthetic Protists

Eukaryotic

Photosynthetic, free-living

Single-celled forms

Filamentous forms

Colonial forms

Classified by pigments

Cell walls vary in composition

Red tide



Classes of Algae

Phaeophyta - Brown: Macroscopic (kelp)

Rhodophyta - Red: Macroscopic (agar source)

Chlorophyta - Green: Macro- and Microscopic

Euglenophyta - Euglenoids: Motile and green

Dinophyta - Dinoflagellates: “Red Tide” Karenia brevis – Florida red tide

Prototheca: rare parasitic, non-photosynthetic algae.

Biology of the Protozoa

About 65,000 species

Most are harmless, free-living inhabitants of water and soil

Few are parasites



Protists

Eukaryotes

Single-cell

Free-living and pathogens

Grouped by locomotion

Cell wall absent

Two cell forms

Trophozoite

Cyst

Protozoan Form and Function

Most are single cells

Contain major eukaryotic organelles except chloroplasts

Cytoplasm usually divided Ectoplasm: clear outer layer involved in locomotion,

feeding, and protection

Endoplasm: granular inner region housing the nucleus, mitochondria, and food and contractile vacuoles

No cell wall- so some flexibility

Cell shape can remain constant or can change constantly (amoebas)

Size between 3 to 300 µm



Protist Life Cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Trophozoite

(active, feeding stage)

Trophozoite

is reactivated

Mature cyst

(dormant, resting stage)

Early cyst wall

formation

Cell rounds up,

loses motility

Cyst wall

breaks open

Life Cycle and Reproduction

Vary from simple to complex

Some exist only in trophozoite stage

Others alternate between trophozoite and cyst

Life cycle of a parasitic protozoan determines the mode of transmission to hosts

All reproduce by asexual methods

Sexual reproduction occurs during the life cycle of most protozoa



Classification of Selected Medically

Important Protozoa

Four groups

Based on:

Method of motility

Mode of reproduction

Stages in the lifecycle

Protozoa Styles of Locomotion

Some unusual species move by gliding or twisting

Pseudopods : Amoeboid motion

Can serve as feeding structures

Flagella : From one to several

Some attached along the length of the cell by the undulating membrane

Cilia: Mostly distributed over the entire surface of the cell

Form characteristic patterns



Move using flagella (Whip)

Complex life cycles

Many parasitic species

Trypanosoma cruzi

Giardia lamblia

Trichomonas vaginalis

Mastigophora

Flagellum Undulating membrane

a: © David M. Phillips/Visuals Unlimited;


Sarcodina

Move using pseudopodia

Phagocytosis

Includes amoeba

Entamoeba histolytica

Naegleria fowleri

Nucleus

Pseudo pod

Water-

expelling

vacuole

Food

vacuole

(b)


(b): © Stephen Durr



Ciliophora

Move using cilia “eyelashes”

Most are free living

Paramecium

Macronucleus and

Micronucleus

Conjugation

Balantinium coli

Cilia


c: © BioMEDIA ASSOCIATES

Apicocomplexa (Sporozoa)

Non-motile protozoa

Obligate parasites

Apicomplexans

Plasmodium vivax

Toxoplasma gondii

Cytostome Nucleus Food vacuoles

d: © Yuuji Tsukii, Protist Information Server, http://protist.i.hosei.ac.jp/protist_menuE.html




Important Protozoan Pathogens

5.6 Parasitic Helminths

Worms are not microorganisms

Multicellular organisms

Two main groups:

Aschelminthes or nematodes (round worms)

Platyhelminthes (flat worms)

Cestodes (tapeworms)

Tremetodes (flukes)



Flatworms

Phylum Platyhelminthes

Thin

Often segmented

Subdivisions

Cestodes (tapeworms)

Trematodes (flukes)

Parasitic Flatworms

A cestode A tremetode

1 cm

1 mm


b: © Carol Geake/Animals Animals; d: © Arthur Siegel man/Visuals Unlimited



Roundworms

Phylum Aschelminthes

Aka nematodes

Elongate

Cylindrical

Unsegmented

Pathogenic Flagellates: Trypanosomes

Genus Trypanosoma

T. brucei causes sleeping sickness

T. cruzi causes Chagas disease



Figure 5.24

Infective Amoebas: Entamoeba

Amoebiasis caused by Entamoeba histolytica

Fourth most common protozoan infection in the world

Aka amoebic dysentery



Life Cycles and Reproduction

Fertilized egg (embryo), larval, and adult stages

In most, adults derive nutrients and reproduce sexually in a host’s body

Must complete the life cycle by transmitting an infective form to the body of another host

Larval development- intermediate (secondary) host

Adulthood and mating- definitive (final) host



A Helminth Cycle: The Pinworm

Person swallows microscopic eggs Picked up from another infected person by direct contact

Or by touching articles an infected person has touched

Eggs hatch in the intestine

Release larvae that mature in to adult worms (about 1 month)

Male and female worms mate

Female migrates out of the anus to deposit eggs Causes intense itchiness

Relieved by scratching

Scratching contaminates the fingers which transfer the eggs

Eggs spread to others or the original host reinfects him or herself

Typical Helminth Lifecycle

Pinworm

Worm eggs are shed

Fecal-oral route

Difficult to irradicate

Female Anus

Male Eggs

Mouth

Cuticle Mouth

Autoinoculation

Copulatory

spicule

Fertile

egg

Cross-

infection

Self-

infection



Distribution and Importance of Parasitic

Worms

About 50 species parasitize humans

Distributed in all areas of the world

Yearly estimate of worldwide infections- in the billions

Documents

Eukaryotic Cells and Microorganisms - PSAU · Fungi and most algae have a thick, rigid cell wall Protozoa and animal cells do not have this cell wall . The Main Themes of Microbiology