Foundations in Microbiology - Download Now PowerPoint by QCT277

VIEWS: 8 PAGES: 49

									Survey of Eukaryotic Microbes
• Fungi
• Algae
• Lichens




Chapters 5 & 22
Talaro
Foundations in Microbiology     1
Kingdom Fungi
•   100,000 species divided into 2 groups
     – macroscopic fungi
     – microscopic fungi
•   Heterotrophic none are autotrophic on their own
•   Majority are harmless saprobes living off dead and decaying plants & animals
•   Some are parasites, but none are obligate
     – Mycoses
•   Optimal growth temperature generally mesophilic 20o - 40oC but many can grow at 4oC
•   Extremely widespread distribution in many habitats
•   Reproduce through spores formed on special reproductive hyphae
     – Asexual reproduction
          • Spores are formed through budding or conidia formation
     – Sexual reproduction
          • Spores are formed following fusion of male & female strains & formation of sexual
            structure
          • Sexual spores are one basis for classification
•   Mycology – the study of fungi


                                                                                      2
                Septum
                crosswall
                Aseptate or coenocytic
                       Conidium
                       asexual spore


        hypha



Mycelium           Body of Mold
A mass of hyphae
                                 3
Asexual spores on aerial mycelia




                             4
Four Main Divisions
                             •Plasmogamy - haploid nucleus of donor
•       Zygomycetes          cell (+) penetrates cytoplasm of recipient
                             cell (__)
•       Ascomycetes
                             • Karyogamy - (+) and (__) nuclei fuse to
•       Basidiomycetes       form a diploid zygote nucleus

•       Deuteromycetes       • Meiosis - diploid nuclei gives rise to
    •     No sexual spores   haploid nuclei

    •     Called by many the Fungi Imperfecti




                                                                        5
Zygomycetes




              6
Ascomycetes




              7
Unicellular Fungi - Yeast
• Two general classes - budding and fission yeast

• Cell division distinguishes two classes

• Budding yeast do not divide evenly

• Fission yeast divide evenly
                                            Saccharomyces cerevisiae




                                            Ascomycetes with an
                                            infrequent sexual stage
     Schizosaccharomyces pombe

                                                                      8
Basidomycetes




                9
Fungi as Infectious Agents
 • Molds & yeasts are widely distributed in air, dust,
   fomites & normal flora
 • Humans are relatively resistant
 • Fungi are relatively nonpathogenic except to
   immunosupressed patients
 • Only 300 have been linked to disease in animals,
   of the 100,000 fungal species
 • Human mycoses are caused by true pathogens and
   opportunistic pathogens




                                                         10
Dimorphic Fungi




                  11
Fungal Infection
 • Systemic Mycoses
     • Deep infection, usually multiple organs affected, not
       transferable from organism to organism

 • Subcutaneous Mycoses
     • Infection beneath surface of skin, requires implantation of
       hyphae or spores via puncture wound

 • Cutaneous Mycoses
    • Caused by dermatophytes (infect epidermis, hair or nails),
      secrete keritinase, human to human transmission

 • Superficial Mycoses
     • Localized along hair shafts and superficial (surface) epithelial
       cells
                                                                     12
Antifungal Compounds
• Antifungals are placed into 3 categories based on their
  mode of action
   – Azoles
      • Inhibit the synthesis of ergosterol, the main fungal sterol in the plasma
        membrane
      • e.g., Miconazole
   – Polyenes
      • Interact with fungal membrane sterols and creates pores in the plasma
        membrane
      • e.g., Amphotericin B
   – 5-fluorocytosine
      • Cytosine analog
      • Inhibits nucleic acid synthesis
      • Fungal infections of the blood, lungs, heart & CNS and urinary tract




                                                                            13
Systemic Mycoses caused by True Pathogens
 •   Histoplasma capsulatum
 •   Coccidioides immitis
 •   Blastomyces dermatitidis
 •   Paracoccidioidomycosis brasiliensis




                                            14
Histoplasma capsulatum
• Histoplasmosis
• Typically dimorphic
• Distributed worldwide, most prevalent in eastern
  & central regions of US
• Grows in moist soil high in nitrogen content
• Inhaled conidia produce primary pulmonary
  infection that may progress to systemic
  involvement of a variety of organs & chronic lung
  disease
• Amphotericin B
   – Polyene
• Ketoconazole
   – Azole                                            15
Histoplasma capsulatum


                         25 ºC         36 ºC
                         Hyphal growth Yeast like colony


                         Histoplasmosis!!




                                                16
Subcutaneous Mycoses
 •   Mycetoma or Eumycetoma
 •   Madurella mycetomatis
 •   Agricultural workers
 •   Ketoconale
     – Azole
 • Itraconazole
     – Azole
 • Amputation




                              17
Cutaneous Mycoses
• Infections strictly confined
  to keratinized epidermis
  (skin, hair, nails) are called
  dermatophytoses - ringworm
  & tinea
• 39 species in the genera
  Trichophyton, Microsporum,
  Epidermophyton
• Communicable among
  humans, animals, & soil
• Infection facilitated by
  moist, chafed skin


                                   18
• Ringworm of scalp (tinea capitis) affects scalp & hair-
  bearing regions of head; hair may be lost
• Ringworm of body (tinea corporis) occurs as inflamed,
  red ring lesions anywhere on smooth skin
• Ringworm of groin (tinea cruris) “jock itch” affects
  groin & scrotal regions
• Ringworm or foot & hand (tinea pedis & tinea
  manuum) is spread by exposure to public surfaces;
  occurs between digits & on soles
• Ringworm of nails (tinea unguium) is a persistent
  colonization of the nails of the hands & feet that
  distorts the nail bed
                                                     19
Ringworm Treatment
 • Ointments containing
   – Tolnaftate
      • Azole
   – Miconazole
      • Azole
   – Lamisil
      • Azole
   – Griseofulvin
      • Inhibits fungal microtubules



                                       20
Tinia Capitis




                Tinea Corporis



                                 21
Trichophyton

               Ringworm of the extremities




                              Tinia unguium
                                      22
Superficial Mycoses
  • Tinea versicolor
    causes mild scaling,
    mottling of skin
  • White piedra is
    whitish or colored
    masses on the long
    hairs of the body
  • Black piedra causes
    dark, hard concretions
    on scalp hairs




                             23
Opportunistic Mycoses
Opportunistic fungal pathogen

Host’s defense must be impaired.

Fungus has a weak or nonexistent
virulence in a host with a normal
functioning immune system.
Candida albicans
 • Normal flora of oral cavity, genitalia, large intestine or
   skin of humans
 • Account for 80% of nosocomial fungal infections
 • Account for 30% of deaths from nosocomial infections
 • Thrush
    – Occurs as a thick, white, adherent growth on the mucous
      membranes of mouth & throat
 • Vulvovaginal yeast infection
    – Painful inflammatory condition of the female genital region
      that causes ulceration & whitish discharge
 • Cutaneous candidiasis
    – Occurs in chronically moist areas of skin and burn patients


                                                                25
Candida albicans




                     Candida




                   Cryptococcus



                           26
Cryptococcus neoformans
 • A widespread encapsulated yeast that inhabits
   soils around pigeon roosts
 • causes Cryptococcosis
 • Common infection of AIDS, cancer or diabetes
   patients
 • Infection of lungs leads to cough, fever, & lung
   nodules
 • Dissemination to meninges & brain can cause
   severe neurological disturbance & death

                                                27
Cryptococcus neoformans




                          28
Pneumocystis carinii
 • A small, unicellular fungus that causes pneumonia (PCP)
    – The most prominent opportunistic infection in AIDS patients
 • This pneumonia forms secretions in the lungs that block
   breathing & can be rapidly fatal if not controlled with
   medication
 • Pentamidine
    – Mode of action is unclear
    – Investigations indicate that the drug inhibits the synthesis of
      DNA, RNA, phospholipids and proteins
 • Cotrimoxazole
    – Folate inhibitor
    – Azole


                                                                  29
Pneumocystis carinii
Fungal cysts in lung tissue




                              30
Aspergillus
• Very common airborne soil
  fungus
• 600 species
    – 8 involved in human disease
• Inhalation of spores causes
  fungus balls in lungs and
  invasive disease in the eyes,
  heart, & brain
• Amphotericin B
    – Polyene
•   Nystatin
    – Polyene



                                    31
Zygomycosis

• Zygomycetes are extremely abundant saprobic
  fungi found in soil, water, organic debris, & food
• Genera most often involved are Rhizopus, Absidia,
  & Mucor
• Usually harmless air contaminants invade the
  membranes of the nose, eyes, heart, & brain of
  patients with either diabetes or malnutrition with
  severe consequences.


                                                  32
Alga / Algae
• Photosynthetic protists
    – Some biologists refer to them as algae
• Photoautotrophic
    – Contain chloroplasts with chlorophyll & other pigments
    – Produce large proportion of atmospheric O2
• Provide basis of food web in most aquatic habitats
• Not classified as plants
    – Lack many plant structures
         • Cuticle, vascular tissues, cell wall primarily composed of cellulose
• Cell wall
    – Contains cellulose, unique polysaccharides & variety of glycoproteins
•   May or may not have flagella
•   Microscopic forms are unicellular, colonial, filamentous
•   Macroscopic forms are colonial & multicellular
•   Most are free-living in fresh and marine water
•   Some inhabit soil or trees
•   Water required for all aspects of life
    – Cellular support, reproduction, and nutrient acquisition                    33
Algae
• Classified
  according to
  types of pigments
  & components of
                       Littoral zone is
  the cell wall        defined as the
• Must use pigment     area between the
                       high water and
  that absorbs light   low water marks
  l that has not
  been filtered out


                               34
35
36
Dinoflagellates
• Unicellular algae - plankton
• Interlocking cellulose plates embedded
  in plasma membrane, structural
  integrity
• Two flagella, propel by spinning
   through water
• Photosynthetic, uses conventional chlorophyll, also accessory
 pigments

• Some exist in as endosymbionts
   • Jellyfish, corals & mollusks
   • Provide food to host organism through photosynthesis, host
     organism protects dinoflagellate from environment
                                                                  37
• Some produce toxins and cause of PARALYTIC SHELLFISH
  POISONING

• Paralytic shellfish poisoning side affect of RED TIDE

• Toxins produced by dinoflagellates accumulate in shellfish

• Toxin harmless to shellfish, very harmful
  (sometimes fatal) to other life

• Eating poorly prepared contaminated shellfish
  (oysters on the half shell) causes paralytic
  disease




                                                               38
Diatoms
•   Phytoplankton
•   Unicellular or chains
•   Silica cell wall
•   Two symmetrical sides
•   Marine, freshwater & soil
•   Two halves
•   Carbon cycle
•   Silicon cycle

                                Progressively
                                smaller       39
Brown Algae
• Kelp
• Brown algae include the largest protists
• Macroscopic - can reach lengths of 50 m (Macrocystis pyrifera)
• Rapid growth rate - 20 cm/day
• Many commercial uses
    •Thickener for cooking, rubber tires, hand lotions




                                                                   40
Red Algae / Rhododphyta
• Occupy greater depths than other algae
• Red pigment allows algae to absorb blue light
• Source of agar
    • Bacteriological growth medium
• Source of carrageenan
    • Thickening agent
    • Evaporated milk, ice cream




                                                  41
Green Algae
• Many plant like characteristics
   • Cellulose cell wall, chlorophyll a and b, starch for
     energy storage
• Hypothesized ancestors of terrestrial plants
• Either unicellular or multicellular
• Most are microscopic




                                                            42
    Lichens
•   Combination of fungus and photosynthetic organisms
    • photobiont or phycobiont
        • Green algae, cyanobacterium
        • Yellow green algae or brown algae
        • There are some examples of a lichens containing both green
           algae and cyanobacteria
•    Placed in kingdom fungi, classified based on fungal partner
    • Ascomycetes & Basidiomycetes
•    Symbiotic relationship benefits both partners
    • Harshes environments
        • Deserts to Antartica
        • Primary colonists – require water
        • Resistant to dessication
•   Obligatory for the fungus
    • Relationship is typically not obligatory for the photobiont
                                                              43
community.iexplore.com/photogallery/   www.anta.canterbury.ac.nz/




                                                                    44
                                         Soredium spread by
Soredium                                 wind




           Algal cells are not endosymbionts
           There is one example of the cyanobacteria as
           true endosymbionts

                                                          45
• Lichens are not plants and do not have roots
• Grown on the surface of rocks, soil, sand, walls,
  roofs and monuments
• Lichens also grow as epiphytes on other plants
  – Trunks and branches of trees
• Secrete organic acids which breaks down
  substratum
  – Part of nutrient cycling
• Very slow growing organisms
• Important food source for reindeer
• Bioindicator species

                                                 46
47
Fructicose




             48
Reproduce by fragmentation




A few algal cells surrounded
by fungal hyphae

                    49

								
To top