Chapters 14, 15, 16

These lecture notes will provide an outline of information from the lectures. They are not complete. They should be used to help follow the lecture and as a guideline for information I think is important. You will need to fill in the gaps.


These notes were updated January 28, 2001, and are ready for printing by Spring 2001 Med Micro. students.

Chapters 14, 15, 16

Chapter 14, pp. 440-457

I.    Fungi A.    Are Eukaryotic
B.    Have cell wall composed of CHITIN
C.    Do not have flagella
D.    Are chemotrophs 1.    Most are aerobic or facultatively anaerobic a)    The facultatively anaerobic fungi are fermenters 2.    Rarely, a few may be anaerobic E.    Are heterotrophs
F.    Require a high concentration of sugar in their environment
G.    Are mostly acidophilic (pH 5-6)
H.    Most are mesophiles, but barely! 1.    Grow around 25o C.
2.    Pathogens thrive at 37o C. a)    Pathogens are generally dimorphic-yeasts at 37o C. and molds at 25o C. I.    Reproduction is both sexual (meiosis) and asexual (mitosis) 1.    Reproductive cell is called the endospore, or spore, for short a)    Sexual spores result from the fusion of nuclei from two opposite mating strains of the same fungus species
b)    Asexual spores are formed by one organism only 2.    Do not confuse fungal endospores with bacterial endospores! J.    Symbiosis: 1.    Most are mutualistic a)    Decomposers (saprobes)
b)    Along with bacteria, are the principal decomposers of carbon compounds on earth 2.    A few are parasitic a)    Most of the parasites are pathogens of plants
b)    A few species, however, are pathogens of man and animals (1)   Most at risk are immunocompromised individuals K.    Have commercial value 1.    Useful sources of food and industry products L.    Mycology: study of fungi 1.    Mycologist: one who studies fungi II.   Structures of the Fungi A.    Hypha (plural, hyphae) is the structural unit 1.    This is a Eukaryotic cell and it is visible microscopically
2.    It is filamentous in appearance
3.    It may contain one or more nuclei
4.    Its cell wall contains chitin, which provides rigidity and strength B.    Hyphae may be separated by septa (singular, septum) 1.    Septa are cross wall that contain pores that allow the adjacent cytoplasms to mix
2.    The septa add further to physical rigidity of the cell and also limit osmotic losses if the wall of a particular hypha is compromised C.    A thick mass of hyphae is a MYCELIUM, which is visible macroscopically III.    Classifying the Fungi A.    There are four phyla 1.    The phyla divisions are based on the method of sexual reproduction B.    Zygomycetes 1.    Form zygospores C.    Basidiomycetes 1.    Form basidiophores
2.    Clinically important fungi include: a)    Cryptococcus neoformans D.    Ascomycetes 1.    Form ascospores
2.    Clinically important fungi include: a)    Histoplasma capsulatum
b)    Blastomyces dermatidis
c)    Claviceps purpurea
d)    Aspergillus
e)   Pneumocystis carinii
f)    Penicillum
g)    The dermatophytes (1)   Trichophyton
(2)   Microsporum E.    Deuteromycetes 1.    Have never been observed to form sexual spores a)    Thus, have no known sexual cycle
b)    rRNA analysis, however, places most Deuteromycetes in either the Ascomycete or the Basdiomycete phylum 2.    Clinically important fungi include: a)    Candida albicans
b)    Coccidioides immitis
c)    Sporothrix schenkii
d)    Epidermophyton (1)    Also a dermatophyte IV.    Another Way to Group the Fungi A.    According to the form they take on 1.    This is a descriptive grouping and has nothing to do with classification systems B.    Yeasts: 1.    Single-celled organisms
2.    May be round, oval, cylindrical
3.    Usually 3-5 micrometers in diameter
4.    Reproduce by binary fission and a process called budding C   . Molds: 1.    Filamentous organisms
2.    One filament is called a hypha (plural hyphae)
3.    A group of hyphae is a mycelium (plural mycelia)
4.    Hyphae develop from fungal spores, which are 3-30 micrometers in diameter
5.    Only a small portion of the mycelium is visible on the surface of bread/fruits/tissues; the rest is buried deep within D.    Mushroom: 1.    Mycelia that appear above the surface of the substrate (the substance the fungus is decomposing) and which produce reproductive spores E.    Dimorphic fungi 1.    Capable of growing both as yeast forms and mold (mycelium-containing) forms, depending on the environmental conditions
2.    Most pathogenic fungi are dimorphic: they grow as molds in the soil; their spores, easily carried in the air are infective and develop into yeast forms in humans that cause disease V.    Reproduction in Fungi A.    Asexual: 1.    Fruiting body is the principal structure of asexual reproduction a)    Fruiting body contains thousands of spores (1)   All of the spores are genetically identical and the result of mitosis
(2)   Each germinates to reproduce a new hypha that will become a mycelium 2.    Another form of asexual reproduction occurs in some hypha that are capable of fragmenting directly into a spore
3.    Yet another form of asexual reproduction is budding, which results from the cell becoming swollen at one edge and forming a new bud or cell (yeasts) B.    Sexual: 1.    Fruiting body is principal structure
2.    Cells of opposite mating types come together and fuse
3.    Nuclei fuse, mixing the chromosomes
4.    Meiosis occurs
5.    Spores will develop from this VI.   Fungal Disease in Humans A.    Caused in one of four ways 1.    Allergic reaction to fungal spores or hyphae
2.    Reaction to toxins produced by fungi
3.    Actual fungal infection (growth of fungus in human) a)    Mycosis: any fungal infection (1)   Systemic mycoses occur deep within the body
(2)   Subcutaneous mycoses occur beneath the skin
(3)   Cutaneous mycoses are caused by dermatophytes (literally, "skin plants") and infect the epidermis, hair, and nails
(4)   Superficial mycoses are localized along hair shafts and superficial epidermal cells
(5)   Opportunistic mycoses are pathogenic to immunosuppressed individuals 4.    Fungal destruction of human food supply, resulting in starvation and death

Chapter 15, pp. 473-482

I.    Protozoa A.    Eukaryotic
B.    Unicellular
C.    Microscopic
D.    Many are pathogens
E.    Have no cell wall 1.    Some, however, have a pellicle a)    Pellicle is a thick, rigid structure outside protozoan cell membranes F.    Most have specialized structures for movement 1.    Examples are cilia, flagella, pseudopodia a)    Eukaryotic flagella are different from prokaryotic flagella (1)   These have the characteristic "9+2" arrangement of microtubules that are found in all eukaryotic flagella G.    Most are chemotrophs
H.    Most are heterotrophs 1.    Trophozoites are the feeding forms
2.    Cysts are the dormant, highly resistant stage that some can enter when conditions (food) are not optimal I.    Symbiosis: 1.    Most are saprobes (decomposers)
2.    Some are parasites J.    Most are aerobic
K.    Reproduction 1.    Usually asexual (mitosis) a)    Includes binary fission, longitudinal fission, transvere fission, and multiple fission (schizogony) (1)   Schizogony occurs when the nucleus divides many times and the cell produces many small, single-celled organisms as a result
(2)   The result is the release of large numbers of parasites into the host at one time 2.    Some have a sexual stage (meiosis)
3.    Life cycles involve different stages a)    During these different stages, the organism assumes different forms (1)   That is, it DIFFERENTIATES into another form II.   Classification A.    There are four phyla, based on mode of locomotion 1.    Sarcodina, which move by pseudopodia a)    Clinically significant Sarcodines include (1)   Acanthamoeba, which causes corneal infections in people with contact lenses
(2)   Entamoeba histolytica, which causes amoebic dysentery
(3)   Naegleria fowleri, which causes primary amoebic meningoencephalitis (PAM) 2.   Mastigophora, which move by flagella a)   Clinically significant Mastigophores include (1)   Giardia lamblia, which causes Giardiasis, a disease of the small intestine
(2)   Leishmania species, which cause visceral and cutaneous Leishmaniasis
(3)   Trichomonas vaginalis, which causes a sexually transmitted disease
(4)   Trypanosoma species, which cause African sleeping sickness and Chagas' disease 3.   Ciliophora a)   Includes the Ciliates, which move by cilia
b)   There is only one known pathogen in this group (1)   Balantidium coli produces ulcers in the large intestines
(2)   Pigs are its major reservoir 4.   Apicomplexan a)   Includes the Apicomplexans, which cannot move
b)   These are also known as Sporozoans
c)   These cause some of the most serious protozoan disease of humans
d)   Their life cycles are extremely complex and involve multiple hosts and alternating sexual and asexual reproductive phases (1)   Vectors are important in transmission
(2)   Definitive hosts harbor the adult (sexually mature) parasite
(3)   Intermediate hosts harbor the larval (asexual) stage of the parasite e)   Clinically significant Apicomplexans include: (1)   Plasmodium species, which cause malaria
(2)   Toxoplasma gondii, which causes toxoplasmosis
(3)   Cryptosporidium parvum, which causes cryptosporidiosis and is most virulent in the immunocompromised
(4)   Babesia microti, which causes a disease similar to malaria
(5)   Cyclospora cayetanensis, which causes cyclosporiasis

Chapter 16, pp. 509-510; 515; 519; 528

I.   The Multicellular Parasites A.   Animal Kingdom 1.   Three phyla of interest a)   Platyhelminthes (1)   Two classes of importance (a)   Trematoda (flukes)
(b)   Cestoda (tapeworms) b)   Nemathelminthes (AKA as Nematodes)
c)   Arthropods (1)   Three classes of importance (a)   Arachnida (mites and ticks)
(b)   Insecta (lice, fleas, flies, mosquitoes, "six-legged bugs")
(c)   Crustacea (copepods, crayfish, crabs) 2.   Eukaryotic
3.   No cell wall
4.   Chemotrophs
5.   Heterotrophs
6.   Symbosis: parasitic relationships II.   Platyhelminthes A.   AKA the Flatworms
B.   Bilateral symmetry
C.   Complex reproductive systems 1.   Many are hermaphroditic
2.   Have both male and female reproductive organs in the same organism D.   Class Trematoda 1.   The Flukes are the parasitic worms of this class
2.   Two hosts a)   Intermediate host, harboring larval form
b)   Definitive host, harboring sexually mature, adult form 3.   Clinically significant flukes a)   Blood flukes (1)   Schistosoma species, which cause Schistosomiasis b)   Liver flukes (1)   Clonorchis sinensis (Chinese liver fluke)
(2)   Fasciola hepatica (human liver fluke) c)   Intestinal fluke (1)   Fasciolopsis buski d)   Lung fluke (1)   Paragonimus westermani E.   Class Cestoda 1.   AKA as tapeworms
2.   Consist of a scolex (head region) and proglottids (segments) a)   Scolex may have hooks or suckers for attachment
b)   New proglottids form from behind the scolex, thus pushing the more mature proglottids to the rear
c)   The most mature proglottids are called gravid, because they are filled with fertilized eggs (1)   They are infectious 3.   Generally require both a definitive and an intermediate host
4.   Live in the human's large intestine a)   Absorb nutrients here
b)   No need for a digestive system 5.   Clinically significant tapeworms: a)   Taenia saginata (beef tapeworm)
b)   Taenia solium (pork tapeworm)
c)   Diphyllobothrium latum (fish tapeworm)
d)   Hymenolepis nana (dwarf tapeworm)
e)   Echinococcus granulosus (dog tapeworm) (1)   Exception with this one is that dog is the definitive host
(2)   Man, if infected, becomes an intermediate host III.   Nemathelminthes A.   AKA the Roundworms
B.   These contain a digestive tract with mouth and anus
C.   These have separate sexes
D.   Following fertilization of the female by the male, eggs hatch to larvae that resemble the adults 1.   Growth follows E.   Clinically significant roundworms 1.   Enterobiums vermicularis (pinworm)
2.   Trichuris trichiura (whipworm)
3.   Ascaris lumbricoides (this one is synonymous with "roundworm infection")
4.   Trichinella spiralis (trichinosis)
5.   Ancylostoma duodenale (Old World hookworm)
6.   Necator americanus (New World hookworm)
7.   Strongyloides stercoralis
8.   Wuchereria bancrofti (filariasis)
9.   Dracunculus medinensis (Guinea worm disease)
10.   Loa loa (eye worm) IV.   Arthropods A.   Are of clinical importance because they may serve as vectors 1.   Vectors are arthropods that carry pathogenic microorganism a)   Mechanical vectors
b)   Biological vectors B.   Class Arachnida 1.   Have 8 legs
2.   Clinically significant Arachnids include a)   Ticks (1)   Rickettsia rickettsii (Rocky Mountain spotted fever)
(2)   Borrelia burgdorferi (Lyme disease) b)   Mites (1)   Sarcoptes scabei (scabies) C.   Class Insecta 1.   Have 6 legs
2.   Mosquito a)   Anopheles species carries Plasmodium (malaria)
b)   Culex species carries the viruses that cause Equine encephalitis (St. Louis, Western, Eastern, etc.) and West Nile infection
c)   Aedes aegypti carries the viruses that cause Yellow Fever, Dengue, Western equine encephalitis, and West Nile infection 3.   Flea a)   Yersinia pestis (the Plague)
b)   Leishmania species 4.   Deer Flies a)   Francisella tularensis (Tularemia)
b)   Loa loa
c)   Hanta virus 5.   Tsetse Fly a)   Trypanosoma species 6.   Reduviid Bug a)   Trypanosoma cruzi (Chagas' Disease) 7.   Louse a)   Rickettsia prowazekii (Typhus) 8.   House Fly a)   A MECHANICAL VECTOR of many viral and bacterial pathogens D.   Class Crustacea 1.   The copepods are intermediate hosts for Diphyloobothrium latum and Dracunculus medinensis
2.   Certain crayfish and crabs are the intermediate hosts for Paragonimus westermani






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