Microbiology Exam1study guide

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Microbiology
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Study of organisms too small to be clearly seen by the unaided eye (microorganisms) Prominent Figures in Microbiology
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Anthony van Leeuwenhoek (1632-1723)
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  • First person to observe and describe microorganisms accurately
  • Conflict over Spontaneous Generation
  • Living organisms can develop from nonliving or decomposing matter

 

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Francesco Redi (1626-1697)
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  • Disproved spontaneous generation for large animals
  • Showed that maggots on decaying meat came from fly eggs

 

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John Needham (1713-1781)
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  • His experiment
  • Mutton broth in flasks→ boiled → sealed
  • Results: became cloudy and contained microorganisms

 

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Lazzaro Spallanzani (1729-1799)
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  • His experiment
  • Broth in flasks → sealed → boiled
  • Results: no growth of microorganisms

 

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John Tyndall (1820-1893)
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  • Demonstrated that dust carries microorganisms
  • Showed that if dust was absent, nutrient broths remained sterile, even if directly exposed to air
  • Also provided evidence for the existence of exceptionally heat-resistant forms of bacteria

 

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Agostini Bassi (1773-1856)
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Showed that a disease of silkworms was caused by a fungus

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M.J. Berkeley (ca. 1845)
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Demonstrated that the great Potato Blight of Ireland was caused by a water mold

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Henrich de Bary (1853)
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Showed that smut and rust fungi caused cereal crop diseases
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Joseph Lister (1827-1912)
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  • Provided indirect evidence that microorganisms were the causal agents of disease
  • Developed a system of surgery designed to prevent microorganisms from entering wounds as well as methods for treating instruments and surgical dressings
  • His patients had fewer postoperative infections

 

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Charles Chamberland (1851-1908)
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  • Developed porcelain bacterial filters used by Ivanoski an Beijerinck to study tobacco mosaic disease
  • Determined that extracts from diseased plants had infectious agents present which were smaller than bacteria and passed through the filters
  • Infectious agents were eventually shown to be viruses

 

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Edward Jenner (ca. 1798)
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  • Used a vaccination procedure to protect individuals from smallpox
  • This preceded the work establishing the role of microorganisms in disease

 

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Emil von Behring (1854-1917)

Shibasaburo Kitasato (1852-1931)

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  • Developed antitoxins for diphtheria and tetanus
  • Evidence for humoral immunity

 

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Elie Metchnikoff (1845-1916)
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  • Discovered bacteria-engulfing, phagocytic cells in the blood
  • Evidence for cellular immunity

 

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Sergei Winogradsky (1856-1953)

Marinus Beijerinck (1851-1931)

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  • Studied soil microorganisms and discovered numerous interesting metabolic processes (eg., nitrogen fixation)
  • Pioneered the use of enrichment cultures and selective media

 

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Alexander Fleming (1929)
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  • Discovered that the fungus Penicillium produced what he called penicillin
  • The first antibiotic that could successfully control bacterial infections

 

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Louis Pasteur (1822-1895)
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  • His experiments:                                                                                             • Placed nutrient solution in flasks                                                 • Created flasks with long, curved necks                                       • Boiled the solutions                                                                       • Left flasks exposed to air                                                             • Results: no growth of microorganisms
  • Final blow to theory of spontaneous generation
  • Showed that the pebrine disease of silkworms was caused by a protozoan

     

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    Pasteur and Roux
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    Discovered that incubation of cultures for long intervals between transfers caused pathogens to lose their ability to cause disease
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    Pasteur and his coworkers
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    • Developed vaccines for chicken cholera, anthrax, and rabies
    • Demonstrated that alcohol fermentations and other fermentations were the result of microbial activity

     

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    Robert Koch (1843-1910)
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    • Established the relationship between Bacillus anthracis and anthrax
    • Used criteria developed by his teacher Jacob Henle (1809-1895)
    • These criteria now known as Koch’s postulates
    • Still used today to establish the link between a particular microorganism and a particular disease

     

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    Koch’s Postulates
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    • The microorganism must be present in every case of the disease but absent from healthy individuals
    • The suspected microorganism must be isolated and grown in a pure culture
    • The same disease must result when the isolated microorganism is inoculated into a healthy host
    • The same microorganism must be isolated again from the diseased host

     

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    Koch’s work led to discovery or development of:
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    • Agar
    • Petri dish
    • Nutrient broth and nutrient agar
    • Methods for isolating microorganisms

     

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    Prokaryotic cells
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    • Lack true membrane
    • delimited nucleus

     

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    Eukaryotic cells
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    • Have a membrane-enclosed nucleus
    • More complex morphologically and are usually larger than prokaryotic cells

     

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    1st living organisms on Earth were microorganisms
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    • The Universal Ancestor
    • Single-celled rod shaped anaerobic prokaryote

     

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    Photosynthesis thought to have evolved early in Earth’s history
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    Fossil evidence places evolution of cyanobacteria and oxygenic photosynthesis to ≈ 3 billion years ago
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    Three Domains of Life
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    • Archaea
    • Bacteria
    • Eucarya

     

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    The Universal Phylogenetic Tree
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    The root of the tree suggests that the three domains have a single common ancestor, but Archaea and Eucarya evolved independently of Bacteria.
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    Prokaryotic Evolution
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    • Results in microbial diversity which upon selection determines the development of new species
    • Genetic heritable genetic changes in Archaea and Bacteria are introduced by
    1. Mutation
    2. Lateral gene transfer
    3. Prokaryotic Classification and Taxonomy

     

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    Taxonomy (Three Parts)
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    • Classification: arrangement of organisms into groups (taxa; s., taxon)
    • Nomenclature: assignment of names to taxa
    • Identification- determination of taxon to which an isolate belongs

     

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    Natural Classification
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    • Arranges organisms into groups whose members share many characteristics
    • 1st classification in 18th Century developed by Linnaeus
    • Based on anatomical characteristics
    • Doesn’t necessarily provide information on evolutionary relatedness

     

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    Phenetic Classification
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    • Group together based on mutual similarity of phenotypes
    • Can reveal evolutionary relationships, but not dependent on phylogenetic analysis
    • Doesn’t weigh characters
    • Best systems compare as many attributes as possible

     

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    Phylogenetic Classification
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    • Also called phyletic classification systems
    • Phylogeny
    • Evolutionary development of a species
    • Usually based on direct comparison of genetic material and gene products (This approach more feasible because when Woese and Fox proposed using rRNA nucleotide sequences to assess evolutionary relatedness of organisms)

     

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    Binomial System of Nomenclature
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    • Devised by Carl von Linne’ (Carolus Linnaeus)
    • Each organism has two names
    1. Genus name- italicized and capitalized or underlined (eg., Escherichia)
    2. Species epithet-italicized but not capitalized, yet underlined (eg., coli)
    3. Can be abbreviated after first use (eg., E. coli)

     

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    Techniques for Determining Microbial Taxonomy and Phylogeny (Table 19.5)
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    • Classical Characteristics
    • Molecular Characteristics

     

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    Six Supergroups
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    • Opisthokonta
    • Archaeplastids
    • Amoebozoa
    • Rhizaria
    • Chromalveolata
    • Excavata

     

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    The Five-Kingdom System
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    • No longer accepted
    • Scientists prefer to see evolutionary relationships
    • Major problem is lack of distinction between archaea and bacteria
    • Kingdom Protista is too diverse to be taxonomically useful
    • Boundaries between kingdoms Protista, Plantae and Fungi are ill-defined

     

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    Bergey’s Manual of Systematic Bacteriology
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    How we classify bacteria
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    Giardia
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    • Causes diarrhea, common among children, pets
    • Found in untreated water
    • Cysts are very resistant
    • Can resist effects of chlorine
    • Greatest protection is process of filtration (in water)

     

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    Giardiasis
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    • Caused by Giardia intestinalis
    • Forms cysts and trophozoites
    • Transmission usually by cyst-contaminated water
    • Asymptomatic human carriers are common
    • 30,000 cases reported yearly

     

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    Life Cycle of Giardia (simple)
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    • Exposure to quadnucleated cyst (fecal/oral/route)
    • Excystment in small intestine
    • Plasmotomy- quad to 2 binucleated trophs
    • 2 Trophozoites in intestines (active feeding stage)—adhere to cells
    • Binary fission
    • Encystment in large intestine into quadnucleated cyst
    • Cyst exits in feces
    • Giardiasis…

     

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    Clinical Manifestations
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    • Acute giardiasis- severe diarrhea, epigastric pain, cramps, voluminous flatulence and anorexia
    • Chronic gastritis- intermittent diarrhea with periodic appearance of remission of symptoms

     

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    Parabasilla – Trichonymphida
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    • Obligate mutuals of wood-eating insects such as termites
    • Digests cellulose in their gut

     

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    Parabasilla – Trichomonadida
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    • Symbionts of digestive, reproductive and respiratory traits of many vertebrates, including humans
    • Some strains are human pathogens
    • Trichomoniasis: Most common STD—7.4 million new cases every year in the U.S.

     

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    Euglenozoa
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    • Commonly found in fresh water
    • 1/3 are photoautotrophic, rest are chemoorganotrophs/heterotrophic
    • Has characteristics of algae and protozoans
    • Euglena is the representative genus:
    • Cell bounded by plasmalemma (cell membrane)

     

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    Trypanosomes
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    Parasites of plants and animals – big game animals in Africa are carriers
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    Leishmaniasis
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    • Caused by members of genus Leishmania
    • Includes systemic and skin/membrane damage
    • Occasional cases in U.S.—common in the rest of the world: 1.5 million cases each year
    • Flagellated protists
    • Visceral Leishmaniasis—500,000 cases/year

     

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    Trypanosoma Cruzi
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    • Causes S. American Sleeping Sickness (Chagas disease)
    • 10,000,000 people have it
    • Transmitted by “kissing bugs”: bite around the lips and defacate
    • Causes damage to nervous system

     

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    T. gamiense and T. rhodesiense
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    Cause of African Sleeping Sickness
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    Trypanosomiasis
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    • Caused by trypanosomes
    • Group of flagellated protists
    • Transmitted by tsetse flies—(African trypanosomiasis) or kissing bug (Chagas’ disease)
    • Reservoirs include domestic cattle and other animals
    • Motile parasites in blood

     

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    African Trypanosomiasis
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    Interstitial inflammation and necrosis with in lymph nodes and small blood vessels of brain and heart, leading to lethargy and death within 1-3 years
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    American Trypanosomiasis (Chagas)
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    Heart disease and other disorders due to destruction of parasitized cells in the liver, spleen, lymph nodes, and the central nervous system
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    Amoeba Proteus
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    • Commonly used in student labs
    • Present in this phylum

     

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    Entamoeba Histolytica
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    • Causes amoebic dysentery
    • Major parasitic disease
    • More serious than Giardia
    • More invasive organism
    • Not as common in the U.S.

     

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    Entamoeba Histolytica Life Cycle: (Simple)
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    • Exposure to quadnucleated cyst (fecal/oral/route)
    • Excystment in small intestine
    • Schizogony– quad into four single nucleated trophozoites
    • 4 Trophozoites—intestine to other areas—invasive
    • Binary fission
    • Encyst in large intestine into quadnucleated cyst

     

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    Amebic Meningoencephalitis
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    • Caused by the free-living Amoebae Naegleria and Acanthamoeba
    • Caused by jumping in water
    • Enters through sinuses into brain
    • Found in swimming holes
    • 10 cases/year, causes death

     

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    Radiolaria
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    • Most have internal skeleton made of siliceous material : “pretty” structures—when organisms die off, structures remain
    • Sexual and asexual reproduction used

     

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    Foraminifera
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    • Also forms pretty structures
    • Called forams
    • Filopodia are arranged in branching network (reticulopodia)
    • Have characteristics tests arranged in multiple chambers that are sequentially added as organism grows
    • Foram tests make up most modern-day chalk, limestone and marble

     

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    Dinoflagellata (dinoflagellates)
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    • Red tides (have been classified as algae)
    • Large group found in marine plankton
    • Cause phosphorescence and toxic blooms • Eg., Paralytic Shellfish Poisoning—caused by gonyaulax

     

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    Ciliophora
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    Paramecium (ciliated)
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    Plasmodium
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    • Cause of Malaria – Caused by a bite of an infected mosquito—Anopheles mosquito (biological vector)
    • Biological Vector– life cycle occurs in vector itself
    • Mechanical Vector– moves organism from one place to another (eg., housefly, cockroach)

     

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    Malaria Life Cycle
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    • Sporozoites transferred from the salivary gland of the Anopheles mosquito
    • Sporozoites removed from blood by liver and spleen
    • Undergo schizogony into merozoites
    • Some merozoites stay in liver, some merozoites enter circulatory system and invade erythrocytes

     

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    Erythrocytic Cycle
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    • Merozoites transform into trophozoites
    • Trophozoites feed on hemoglobin and then undergo nuclear division into 16-32 nuclei—now called “Schizont”
    • Schizogony—merozoites burst from erythrocytes into circulatory system
    • Merozoites invade more erythrocytes, etc.
    • Cyclical—every 40-72 hours depending on species producing the characteristic fever and chills
    • Some merozoites differentiate into micro and macro gametocytes which stay in the erythrocyte
    • When bitten by a mosquito, the gametocytes are transferred

     

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    Sexual Cycle
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    • Micro and macro gametocytes form into gametes in gut of mosquito
    • Micro and macro gametes undergo syngamy
    • Ookinete (zygote) develops into oocyst
    • Oocyst undergoes nuclear division
    • Oocyst ruptures to release sporozoites
    • Sporozoites penetrate salivary gland
    • The mosquito is now infective

     

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    Toxoplasma
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    • Cause of toxoplasmosis
    • Cat litter—cyst in cat feces
    • Pregnant women—causes very severe birth defects
    • Very diverse parasite

     

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    Cryptosporidiosis
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    • Caused by Cryptosporidium parvum                               • Apicomplexan that forms cysts, sporozoites and merozoites
    • Fecal/oral/route
    • Controlled in our water supply through filtration
    • Can be fatal in immunocompromised individuals

       

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      A Chromalveolata Subgroup

      Diatoms—Protists (autotrophs)

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      • Same shells formed as Radiolaria and Foraminifera (heterotrophs)
      • Found in marine plankton
      • Produce 40%-50% of organic carbon in ocean

       

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      Volvox
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      • Colonial organism
      • Many unicellular organisms functioning together like multicellular

       

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      Fungi
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      • Chemoheterotrophic, not photosynthetic
      • Found wherever moisture, the appropriate temperature and suitable organic nutrients are present
      • Exist as filamentous hyphae • Mycelium- mass of hyphae
      • Secrete exoenzymes to digest insoluble matter, then absorb the solubilized nutrients
      • Have two reproductive structures                                                          • Sporangia from asexual spores                                                  • Gametangia from sexual spores (gametes)
      • A (+) and a (-) strain form a sexual spore
      • Appear genetically identical but together form spores (Rhizopus)

       

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      Mycotoxicology
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      Study of fungal toxins (micotoxins) and their effects
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      Mycoses
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      Disease caused by fungi
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      Mycoses Distribution
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      • Primarily terrestrial—found in moist soil
      • Many are pathogenic in plants or animals

       

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      Mycoses Structure (Thallus)
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      • Undifferentiated structure
      • Body or vegetative structure of a fungus (more animal like)
      • Cell walls usually composed of chitin– store food as glycogen

       

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      Yeasts
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      • Unicellular fungi
      • Reproduce asexually, often by budding
      • Reproduce sexually by formation of spores

       

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      Molds
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      • Filamentous (hyphae)
      • May be septate or nonseptate

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      Dimorphism
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      • Some change from a yeast to a mold
      • YM shift—caused by temperature                                                              • Outside or room temperature—mold                                              • Body temperature—yeast

       

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      Mycoses Nutrition and Metabolism
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      • Most are saprophytes                                                                                  • Obtain nutrients from dead organic material
      • Secrete hydrolytic enzymes
      • Chemoorganoheterotrophs
      • Glycogen in primary storage polysaccharide
      • Most are aerobic

       

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      Photoautotrophic
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      • Gets its carbon from photosynthesis—organic or inorganic
      • Gets its energy from light and carbon dioxide

       

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      Chemoorganotrophic/Chemoheterotrophic
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      Gets carbon from organic sources and breaks it down for energy
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      Mixotrophic
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      Can use both organic and inorganic forms of carbon
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      Protozoa
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      Traditionally referred to chemoorganotrophic protists
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      Algae
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      • Some are multicellular (kelp, seaweed)                                                             ? Photosynthetic protists                                                       ? Originally referred to all simple aquatic plants

       

       

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      Asexual
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      • Transverse fission
      • Budding
      • Spore production                                                                                        ? Conidia- different types, extended from hyphae                          ? Sporangiospores—enclosed in a sac

       

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      Sexual
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      Involves union of compatible nuclei followed by formation of sexual spores (zygospores, ascopspores, or basidiospores)
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      Zygomycetes
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      • Nonseptate hyphae
      • Asexual sporangia

       

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      Ascomycetes
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      • Septate hyphae
      • Asexual conidiospores

       

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      Basidiomycetes
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      • Septate
      • No asexual spores
      • Ex. Cryptococcus neoformans—cryptococcosis                  • Systemic infection, primarily of lungs and central nervous system

       

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