Chapter 12 The Eukaryotic Members of the Microbial World

12.1 Algae KingdomProtist Nutritional TypePhotoautotroph MulticellularitySome Cellular Arrangement Unicellular, colonial, filamentous, tissues Food Acquisition MethodDiffusion Characteristic FeaturesPigments Embryo FormationNone

 Algae use light energy to convert water and carbon dioxide to carbohydrates and other cellular products  Algae contain chlorophyll a and other pigments but differ from land plants because they lack vascular systems and have simple reproductive structures  They do not directly infect humans but some produce toxins that can cause paralytic shellfish poisoning

Structure of algae  It can be microscopic or macroscopic  Macroscopic algae are multicellular organisms with specialized structures that perform specific functions  Holdfast – holds the algae in place, but does not absorb water like a root would  Stipe – the algal stalk  Blade – leaf-like structures that perform photosynthesis  Bladder – floats that help maintain position of the algae

Cell Walls  Rigid and mostly composed of cellulose  Some species may have other compounds in their walls  Carrageenan and agar are harvested and used in foods as stabilizing compounds  Diatoms have silica dioxide incorporated into their cell walls

Eukaryotic cell structures  Nucleus – contains the genetic information within the chromosomes  Chloroplasts – contain the light trapping pigments  Mitochondria – cellular respiration is performed

Algal Reproduction  Single celled algae will reproduce asexually by binary fission, but the nuclear material will have to undergo mitosis  Some multicellular filamentous species will reproduce by fragmentation  Sexual reproduction occurs in other algal species, where a diploid zygote is genetically unique from its parents

Paralytic Shellfish poisoning  A number of algae produce toxins that are poisonous to humans and animals  Dinoflagellates (Pyrrophyta) produce red tides which release brevetoxin, which kills fish  Other dinoflagellates (Gonyaulax) produce neurotoxins that are ingested by shellfish without harm.  When humans eat the shellfish, they suffer symptoms that can lead to death

Phaeophyta  Brown algae (kelp)  Cellulose and alginic acid cell walls  Multicellular  Chlorophyll a and c, xanthophylls  Store carbohydrates  Harvested for algin

Rhodophyta  Red algae  Cellulose cell walls  Most are multicellular  Chlorophyll a and d, phycobiliproteins  Store glucose polymer  Harvested for agar and carrageenan

Chlorophyta  Green algae  Cellulose cell walls  Unicellular or multicellular  Chlorophyll a and b  Store glucose polymer

Diatoms  Pectin and silica cell walls  Unicellular  Store oil  Fossilized diatoms formed oil

Dinoflagellates  Cellulose in plasma membrane  Unicellular  Chlorophyll a and c, carotene, xanthins  Store starch  Some are symbionts in marine animals  Neurotoxins cause paralytic shellfish poisoning

12.2 Protozoa KingdomProtist Nutritional TypeChemoheterotroph MulticellularityNone Cellular ArrangementUnicellular Food Acquisition MethodAbsorptive; ingestive Characteristic FeaturesMotility; some form cysts Embryo FormationNone

Characteristics of Protozoa  Microscopic, unicellular organisms that are not photosynthetic  Usually motile at some stage in their life  Reproduce by asexual fission

Protozoan Habitats  Majority are free-living and found in marine, fresh water, or terrestrial habitats  Decomposers in many environments  Some species are parasitic, living on or in a host  Marine species make up zooplankton, which is important in aquatic food chains  They eat bacteria and algae

Structure of Protozoa  Protozoa lack the rigid cellulose cell wall of algae  Shape is determined by the rigidity or flexibility of the materials below the membrane

 They have a membrane bound nucleus and other organelles  They are not photosynthetic  Many will have cilia, flagella, or pseudopodia for locomotion

Protozoan Reproduction  Life cycles are sometimes complex, involving more than one habitat or host  They can have several body forms during their life cycle, making them polymorphic  Can exist as a trophozoite (feeding) or cyst (resting)

Protozoa and Human Disease  Animals and humans are able to contract diseases from protozoa  Toxoplasmosis, malaria, and sleeping sickness are caused by protozoa

Figure 12.16b Archaezoa  No mitochondria  Multiple flagella  Giardia lamblia  Trichomonas vaginalis (no cyst stage)

Amoebozoa  Move by pseudopods  Entamoeba  Acanthamoeba

Ciliates  Move by cilia  Complex cells  Balantidium coli is the only human parasite

Euglenozoa  Move by flagella  Euglenoids  Photoautotrophs

Euglenozoa  Move by flagella  Hemoflagellates  Trypanosoma spp.  Sleeping sickness  Chagas’ disease

12.3 Fungi Mycology is the study of fungi KingdomFungi Nutritional TypeChemoheterotroph MulticellularityAll, except yeasts Cellular Arrangement Unicellular, filamentous, fleshy Food Acquisition MethodAbsorptive Characteristic FeaturesSexual and asexual spores Embryo FormationNone

Classification of Fungi  All fungi have chitin in their cell wall, and do not have any flagellated cells  Most are classified by their method of sexual reproduction

Common Groupings of Fungal Forms  Yeasts are single-celled fungi that can be spherical, oval, or cylindrical  Some reproduce by binary fission  Others reproduce by budding

 Molds are filamentous fungi  One filament is called a hypha, and a collection is called the mycelium  Hyphae absorb nutrients

Fungal Dimorphism  Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C

Fungal Habitats  Found virtually everywhere on earth where organic material exists  Mainly terrestrial  Some species of fungus can only grow on one specific organism (like a plant), while others are quite versatile and can attack anything

Growth Requirements of Fungi  Most prefer slightly moist environments with a relative humidity around 70% or more  Many prefer a pH around 5.0 or lower  They secrete enzymes that degrade organic materials  Most are aerobic, but some can be facultative anaerobes and carry out fermentation

Fungal Disease in Humans  Fungi cause disease in four ways: 1. Allergic reaction to a fungal spore or vegetative cell 2. Reaction to a toxin made by the fungus 3. Fungi can grow on the body causing a disease called a mycoses 4. Fungi can destroy human food supply

 Allergic reactions result from inhaling fungi or their spores  Fungi produce toxins that have many effects  Ergot – has hallucinogenic properties  Aflatoxins (Aspergillus) have carcinogenic toxins, and ingestion could lead to liver cancer

Mycoses  Superficial – affect hair, skin, or nails  Intermediate – limited to the respiratory tract, skin and subcutaneous tissue  Systemic – affect deep tissues

Medically Important Phyla of Fungi  Zygomycota  Ascomycota  Anamorphs  Basidiomycota

Ascomycota  Sac fungi  Septate  Teleomorphic fungi  Produce sexual and asexual spores  Ascospores and frequently conidiospores  Aspergillus (opportunistic, systemic mycosis)  Blastomyces dermatitidis, Histoplasma capsulatum (systemic mycoses)  Microsporum, Trichophyton (cutaneous mycoses)

Basidiomycota  Club fungi  Septate  Produce basidiospores and sometimes conidiospores  Cryptococcus neoformans (systemic mycosis)

Economic Effects of Fungi  Saccharomyces cerevisiae: Bread, wine, HBV vaccine  Trichoderma: Cellulase  Taxomyces: Taxol  Entomophaga: Biocontrol  Paecilomyces: Kills termites

Lichens  Mutualistic combination of an alga (or cyanobacterium) and fungus  Alga produces and secretes carbohydrates; fungus provides holdfast

Economic Effects of Lichens  Dyes  Antimicrobial (Usnea)  Litmus

12.4 Slime Molds and Water Molds  Acellular and Cellular types  Terrestrial organisms living on soil, leaf litter, or surfaces of decaying wood  Non motile and reproduction depends on spore production

Oomycota  Decomposers and plant parasites  Phytophthora infestans responsible for Irish potato blight  P. cinnamoni infects Eucalyptus  P. ramorum causes sudden oak death  Water molds  Cellulose cell walls  Multicellular  Chemoheterotrophic  Produce zoospores

12.5 Multicellular Parasites  Arthropods include insects, ticks, lice, and mites  Serve as vectors that transmit other microbes to humans  Helminths include nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes).  Cause disease by invading a hosts tissues and robbing nutrients

Arthropods as Vectors  May transmit diseases (vectors)  Kingdom: Animalia  Phylum: Arthropoda (exoskeleton, jointed legs)  Class: Insecta (6 legs)  Lice, fleas, mosquitoes  Class: Arachnida (8 legs)  Mites and ticks

Figure  Mechanical vector  An arthropod picks up microbe on feet and transmits it  Biological vector  Microbe multiplies in vector  Definitive host  Microbe’s sexual reproduction in vector

Helminths KingdomAnimalia Nutritional TypeChemoheterotroph MulticellularityAll Cellular ArrangementTissues and organs Food Acquisition Method Ingestive; absorptive Characteristic FeaturesElaborate life cycles Embryo FormationAll

Helminths (Parasitic Worms)  Kingdom: Animalia  Phylum: Platyhelminthes (flatworms)  Class: Trematodes (flukes)  Class: Cestodes (tapeworms)  Phylum: Nematoda (roundworms)

Characteristics of Helminths  Reduced digestive system  Reduced nervous system  Reduced locomotion  Complex reproduction

Life Cycle of Helminths  Monoecious (hermaphroditic)  Male and female reproductive systems in one animal  Dioecious  Separate male and female  Egg  larva(e)  adult

Human as Definitive HostTaenia saginataCysticerci in beef muscle Intermediate Host Echinococcus granulosus Adult in dog