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Foundations in Microbiology

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					Chapter 5

Microbiology
 Fall 2010
   Beatty
   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



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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
    Flagella & Cilia Animation
• http://www.northland.cc.mn.us/biology/Biol
  ogy1111/animations/flagellum.html




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9
Figure 5.4 Structure and locomotion in ciliates




                                          10
             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
                                                       11
    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


                                                        12
   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


                                                    13
        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


                                                   14
Figure 5.5 The nucleus




                         15
Figure 5.6 Mitosis




                     16
            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

                                                   17
Figure 5.7 Rough endoplasmic reticulum




                                     18
              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


                                                       19
Figure 5.8 Golgi apparatus




                             20
Figure 5.9




      nucleus  RER  Golgi  vesicles  secretion   21
              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
                                                       22
Figure 5.10




              23
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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


                                                        25
Figure 5.11 Structure of mitochondrion




                                         26
  Mitochondria
ATP Synthase Movie
http://vcell.ndsu.nodak.edu/animations/a
tpgradient/movie-flash.htm


http://www.youtube.com/watch?v=3y1
dO4nNaKY



                                       27
             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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       Photosynthesis Video
http://www.youtube.com/watch?v=hj_WKgn
  L6MI




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Figure 5.12




              30
             Internal Structures
• Ribosomes
  –   Composed of rRNA and proteins
  –   Scattered in cytoplasm or associated with RER
  –   Larger than prokaryotic ribosomes
  –   Function in protein synthesis




                                                      31
           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




                                                  32
Figure 5.13 A model of the
       cytoskeleton




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    Survey of Eukaryotic Microbes
•   Fungi
•   Algae
•   Protozoa
•   Parasitic worms




                                    36
           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




                                                       37
           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




                                                  38
Figure 5.15




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Figure 5.16c




               40
              Fungal Nutrition
• All are heterotrophic (vs. nutritional autotrophs)
• 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


                                                       41
Figure 5.17 Nutritional sources for fungi




                                        42
           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

                                                      43
Figure 5.18




              44
           Fungal Reproduction
• Primarily through spores formed on reproductive
  hyphae
• Asexual reproduction – spores are formed
  through budding or mitosis; conidia or
  sporangiospores




                                              45
Figure 5.19




              46
         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



                                                  47
Figure 5.20 Formation of zygospores




                                      48
Figure 5.21 Production of ascospores




                                       49
Figure 5.22 Formation of basidiospores in a mushroom




                                                  50
           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)
                                                  51
            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


                                                    52
               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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            Histoplasmosis




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        Dermatophytes - Ringworm




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            Ringworm




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     Pneumocystis (carini) jiroveci in
                  lung




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Crytptococcosis




     Mickey Dufilho   59
   Deuteromycota – Fungi Imperfecti
• Lack sexual spore state
• As sexual cycle is found, they are
  reassigned to the correct taxonomic
  grouping
• Causes confusion – Blastomyces and
  Histoplasma – also known as Ajellomyces
• Example – Coccidioides immitis, Candida
  albicans, Cladosporium, and Strachybotrys
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            Cutaneous blastomycosis




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            Coccidioides immitis




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Coccididoidomycosis –
subcutaneous abscesses




        Mickey Dufilho   63
Candida albicans




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            Fungal Identification
•   Cornmeal, blood and Sabouraud’s Agar
•   Asexual spore forming structures and spores
•   Hyphal type
•   Colony texture and pigmentation
•   Physiological characteristics
•   Genetic make up

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Kingdom Protista




                   68
         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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                      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



                                                      76
Figure 5.27




              77
             Protozoan Identification
•    Classification is difficult because of diversity
•    Simple grouping is based on method of motility,
     reproduction, and life cycle
    1.   Mastigophora – primarily flagellar motility, some flagellar
         and amoeboid; sexual reproduction
    2.   Sarcodina – primarily amoeba; asexual by fission; most
         are free-living
    3.   Ciliophora – cilia; trophozoites and cysts; most are free-
         living, harmless
    4.   Apicomplexa – motility is absent except male gametes;
         sexual and asexual reproduction; complex life cycle – all
         parasitic
                                                                 78
            Mastigophora – flagellates




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Sarcodina – amebas




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Ciliophora – ciliates




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Apicomplexa




              82
   Important Protozoan Pathogens
• Pathogenic flagellates
   – Giardia lamblia
   – Tichomonas vaginalis
   – Trypanosomes – Trypanosoma
      • T. brucei – African sleeping sickness
      • T. cruzi – Chaga’s disease; South America
• Infective amebas
   – Entameba histolytica – amebic dysentery; worldwide




                                                          83
               Giardia lamblia
•   pathogenic flagellate
•   unique symmetrical heart shape
•   cysts can survive for 2 months in environment
•   cysts enter duodenum, geminate, & travel to
    jejunum to feed & multiply
•   causes giardiasis – diarrhea, abdominal pain
•   diagnosis is difficult because organism is shed in
    feces intermittently
•   Treatment: quinacrine or metronidazole
•   agent is killed by boiling, ozone, & iodine
                                                         84
Giardia lamblia




     Mickey Dufilho   85
              Trichomonas
• Small, pear-shaped
• 4 anterior flagella & an undulating
  membrane
• Exist only in trophozoite form
• 3 infect humans
   – T. vaginalis
   – T. tenax
   – T. hominis
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            Trichomonas




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                Trichomonas vaginalis
• causes an STD called trichomoniasis
• reservoir is human urogenital tract
• 50% of infected are asymptomatic
• strict parasite, cannot survive long outside of host
• 3 M cases a year, a top STD
• female symptoms – foul-smelling, green-to-yellow
  discharge; vulvitis; cervicitis; urinary frequency &
  pain
• male symptoms – urethritis, thin, milky discharge,
  occasionally prostate infection
• metronidazole
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              Hemoflagellates
•   live in blood & tissues of human host
•   obligate parasites
•   cause life-threatening and debilitating zoonoses
•   spread by blood-sucking insects that serve as
    intermediate hosts
• acquired in specific tropical regions
• have complicated life cycles & undergo
    morphological changes
• Trypanosoma
• Leishmania
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               Leishmania
• Leishmaniasis is a zoonosis transmitted
  among mammalian hosts by female sand
  flies that require a blood meal to produce
  eggs
• infected macrophages carry the pathogen
  into the skin & bloodstream, giving rise to
  fever, enlarged organs & anemia
• Kala azar is the most severe & fatal form

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             Trypanosoma
• distinguished by their infective stage,
  trypomastigote is an elongate, spindle-
  shaped cell with tapered ends, eel-like
  motility
• 2 types of trypanosomiasis
   – T. brucei – African sleeping sickness
   – T. cruzi – Chagas disease – endemic to
     Central and South America
                                              92
          Trypanosoma brucei
• causes African Sleeping Sickness
• spread by tsetse flies
• harbored by reservoir mammals
• biting of fly inoculates skin with trypanosome,
  which multiplies in blood & damages spleen,
  lymph nodes & brain
• chronic disease symptoms are sleep disturbances,
  tremors, paralysis & coma
• treatment before neurological involvement
  melarsoprol, difluormethylornithine
                                                     93
            Trypanosoma cruzi
• causes Chagas disease
• reduviid bug (kissing) bug is the vector
• infection occurs when bug feces are inoculated into a
  cutaneous portal
• local lesion, fever, & swelling of lymph nodes,
  spleen, & liver
• heart muscle & large intestine harbor masses of
  amastigotes
• chronic inflammation occurs in the organs
  (especially heart & brain)
• treatment nifurtimox & benzonidazole
                                                     94
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Trypanosoma cruzi




                    96
       Entamoeba histolytica
• alternates between a large trophozoite,
  motile by means of pseudopods & a smaller
  nonmotile cyst
• trophozoite has a large nucleus and lacks
  most other organelles
• humans are the primary hosts
• ingested
• carried by 10% of world population
                                          97
Entamoeba histolytica




                        98
         Entamoeba histolytica
• cysts are swallowed & arrive at the small intestine;
  alkaline pH & digestive juices stimulate cyst to
  release 4 trophozoites
• trophozoites attach, multiply, actively move about
  & feed
• asymptomatic in 90% of patients
• ameba may secrete enzymes that dissolve tissues &
  penetrate deeper layers of the mucosa
• causing dysentery, abdominal pain, fever, diarrhea
  & weight loss
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Entamoeba histolytica




                        101
       Entamoeba histolytica
• life-threatening manifestations are
  hemorrhage, perforation, appendicitis, &
  tumorlike growths (amebomas)
• may invade liver & lung
• severe forms of disease result in 10%
  fatality rate
• effective drugs are iodoquinol,
  metronidazole, & chloroquine
                                             102
             Balantidium coli
• an occupant of the intestines of domestic animals
  such as pigs & cattle
• acquired by ingesting cyst-containing food or
  water
• trophozoite erodes intestine & elicits intestinal
  symptoms
• healthy humans are resistant
• rarely penetrates intestine or enters blood
• treatment – tetracycline, iodoquinol, nitrimidazine
  or metronidazole
                                                   103
Balantidium coli




                   104
       Apicomplexan parasites
• sporozoans
• lack locomotor organelles in the mature state
• alternate between sexual & asexual phases &
  between different animal hosts
• most form specialized infective bodies that are
  transmitted by arthropod vectors, food, water, or
  other means
   – Plasmodium
   – Toxoplasma
                                                      105
              Plasmodium
• causes malaria
• female Anopheles mosquito is the vector
• obligate intracellular sporozoan
• 4 species: P. malariae, P. vivax, P.
  falciparum & P. ovale
• 300-500 M new cases each year
• 2 M deaths each year
                                            106
              Plasmodium
• infective forms for humans (sporozoites)
  enter blood with mosquito saliva, penetrate
  liver cells, multiply, and form hundreds of
  merozoites, which multiply in & lyse RBCs.
• symptoms include episodes of chills-fever-
  sweating, anemia, and organ enlargement.
• therapy is chloroquine, quinine, or
  primaquine

                                           107
108
Figure 5.32




              109
110
            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


                                                   111
 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
                                                112
                Helminths
• Acquired through ingestion of larvae or
  eggs in food; from soil or water; some are
  carried by insect vectors
• Afflict billions of humans




                                               113
Figure 5.34 Parasitic Flatworms




                                  114
Figure 5.35




              115
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




                                               116
    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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