The Eukaryotic Members of the Microbial World

Chapter 12

Algae

   Diverse group of eukaryotic organisms Use light to convert carbon dioxide and water to carbohydrates Includes both microscopic unicellular and macroscopic multicellular organisms

Algae

 Classification of algae  Algae not a distinct classification term  Grouped for identification based on numerous properties  Photosynthetic pigments  Cell wall structure  Type of storage products  Mechanism of motility  Mode of replication  Names are derived from major color displayed by group

Algae

 Algal habitats  Found in both fresh and salt water and soil  Aquatic algae major producers of oxygen  Also important users of carbon dioxide  Algae often grow where other life forms can’t  Often first to become established in barren environments

Algae

 Structure of algae  Can be both micro and macroscopic  Can float free or be propelled by flagella or filaments  Macroscopic algae are multicellular  Contain numerous structures for specific functions   Holdfast anchors organism to firm substrate Stapes hold blades which are the major photosynthetic portion of algae  Gas-containing bladders to help maintain blades in proper position for maximum sunlight

Algae

 Structure of algae  Cell wall  Rigid structure made mostly of cellulose  Diatoms have silicon dioxide incorporated in cell wall  Cell structures  Have membrane bound nucleus containing DNA  Have both chloroplast and mitochondria   Chloroplast for photosynthesis Mitochondria for respiration

Algae

 Algae reproduction    Most single cell algae reproduce through binary fission  Chromosome goes through mitosis Some algae reproduce through fragmentation  Portion of parent organism breaks off to form new organism Sexual reproduction through meiosis also occurs

Algae

 Algae do not cause disease directly   Numerous algae produce toxin  Toxins are poisonous to humans Some species such as dinoflagellates produce neurotoxins  Dinoflagellates eaten by shellfish and produce toxin  Toxin accumulates in shellfish tissues  Human eat shellfish and suffer paralytic shellfish poisoning

Protozoa

 Microscopic unicellular organisms  Lack photosynthetic capability   Usually motile Reproduce by asexual fission

Protozoa

 Classification of protozoa  Not a unified group  Lumped together as unicellular organism lacking chlorophyll  Traditionally divided into groups based on mode of locomotion  Some belong to phylum Sarcomastigophora  Includes two subphyla   Mastigophora Sarcodina

Protozoa

 Classification of protozoa  Mastigophora  Includes flagellated protozoa  Most significant include 

Giardia lamblia, Leshmania

species

Trichomonas vaginalis

and

Trypanosoma

species  Sarcodina  Move by means of pseudopodia 

Entamoeba hystolytica

produces disease in humans

Protozoa

 Classification of protozoa  Other phylum include  Ciliophora   Organism have cilia

Balantidium coli

only pathogenic ciliate  Apicomplexa  Cause most serious protozoan disease 

Plasmodium

species causes malaria  Microspora  Cause sever infection in immunocompromised

Protozoa

 Protozoan habitats  Majority are free-living  Found in marine, fresh water and terrestrial habitats  Essential decomposers  Require large amounts of moisture  Important part of food chain  Protozoa eat bacteria and serve as food for larger species  Help maintain ecological balance in soil  Important in sewage disposal  Results in decrease of sewage solids

Protozoa

 Structure of protozoa  Cell wall  Lack cell wall  Shape determined by material beneath plasma membrane  Cell structures  Have membrane bound nucleus and organelles  Lack photosynthetic chloroplasts  Have specialized structures for movement  Cilia, flagella or pseudopodia  Protozoa grouped by mode of locomotion

Protozoa

 Protozoan reproduction  Life cycles complex  Often require more than one habitat or host  Polymorphic  Can exist as trophozoite or as cyst  Both sexual and sexual reproduction common  Many replicate via binary fission  Many replicate by schizogony   Many fissions Nucleus divides numerous times then cell produces numerous single celled organisms

Fungi

 Describes a taxonomic classification of organisms  No longer includes slime molds and water molds  Fungi require organic compounds for energy and as a carbon source  Most are aerobic or facultative anaerobe  Large number of fungi cause disease in plants  Only a few cause disease in humans

Fungi

 Classification of fungi  Can be both micro and macroscopic  Cell wall consist of chitin  No flagellated cells  Four groups of true fungi  Zygomycetes  Basidiomycetes  Ascomycetes  Deuteroomycetes  A.k.a fungi imperfecta  Classification in groups based on sexual reproduction  Except d where sexual reproduction is not seen

Fungi

 Classification of fungi  Zygomycetes  Includes common bread mold

Rhizopus

 Ascomycetes  Includes the fungi of Dutch elm disease  Basidiomycetes  Includes common mushroom and puffballs  Deuteromycetes  Includes medically and commercially important species including the penicillium

Fungi

 Classification of fungi  Grouping of fungal forms    Yeasts  Single celled fungi  Spherical, oval or cylindrical  Reproduction through binary fission or budding Molds   Filamentous fungi contain hyphae  Reproductive spore is single celled  divide into new form collection of hyphae called mycelium germinates to develop hyphae  cells Dimorphic fungi  Can grow as yeast or mold depending on environment  Many pathogenic fungi are dimorphic

Fungi

 Fungal habitats   Found in virtually every habitat  Mainly terrestrial Fungal spores found throughout the earth  Uncountable numbers found in air  Major cause of asthma  Growth requirements of fungi    Slightly moist environment with high humidity  70% or higher pH range varies  Most grow well in slightly acidic environment Most are aerobic   Some yeast facultative Some fungi obligate anaerobes

Fungi

 Fungal diseases in humans  Cause disease in one of four ways  Allergic reaction  Result from inhaling fungal spores  React to fungal toxin   Many have hallucinogenic properties Certain species produces alflatoxin implicated in cancer  Mycoses  Fungi grows on or in the body  Economic impact  Destroy human food supply causing starvation

Fungi

 Symbiotic relationships of fungi  Form several symbiotic relationships with other organisms  Lichens result from relationship between fungi and photosynthetic organism   Relationships are very close  Fungus provides protection and growing platform  Other organism supplies nutrient Mycorrhizae symbiosis with roots of plants  Increases absorptive property of roots  Allow plant partners to grow in dryer climates

Fungi

 Economic importance of fungi  Many are important commercially 

Saccharomyces

bread used in production of beer, wine and  Many important for cheese production  Penicillin, griseofulvin as well as other antimicrobials are made from fungi  Elimination of disease causing fungi from commercial crops vitally important  Fungi used in genetic and biochemical studies  Yeast genetically engineered to produce human insulin

Slime Molds and Water Molds

 Used to be considered types of fungi  They are completely unrelated  Good example of convergent evolution  Two organisms develop similar characteristics and adaptations but not related on molecular level

Slime Molds and Water Molds

  Acellular slime molds  Terrestrial organisms   Non motile Reproduction depends of formation of dispersible spores  Acellular slime molds readily visible in environment  Plasmodium formed from nucleus spreads over surface of decaying matter Cellular slime molds  Has vegetative form made of ameba like cells  Single cells congregate into form called slug  Slug forms fruiting body and spores

Slime Molds and Water Molds

 Water molds  A.k.a Oomycetes  Members of heterokonts  Do not have chlorophyll  Once considered fungi  Due to morphology  Form masses of white thread on decaying matter  Zoospores cause serious disease of food crops

Multicellular Parasites: Arthropods and Helminths

 Arthropods include  Insects such as mosquitoes responsible for transmission of malaria and fleas which transmits plague  Ticks responsible for transmission of Rocky Mountain Spotted Fever and Lyme disease   Lice responsible for transmission of typhus and other fevers Mites transmit scabies  Helminths include nematodes, cestodes and tremetodes  Cause disease by invading host tissues and robbing nutrients  Nematodes invade gastrointestinal tract and blood stream   Cestodes associated with meats especially pork  Transmission results from consumption of uncooked meat Trematodes  Can be found discharged in waters such as lakes and ponds