Chapter 12: The Eukaryotes: Fungi, Algae, Protozoa, Helminths• Mycology is the study of fungi• Mycosis = fungal disease• All fungi are Chemoheterotrophs – live on

preformed organic matter– Excrete extracellular enzymes to digest organic

matter and break it down to simple products that it absorbs

– Major decomposer of dead plant matter which recycles elements

• Ex. Cellulase: cellulose (plants, wood) to glucose used for energy

– Most are aerobic (molds) or facultative anaerobes (yeasts)

Molds and fleshy fungi - multicellular

• Thallus = body consist of long filaments of cells joined together = hyphae– Septate – partitions between cells, may have pores

between cells so cytoplasm mixes with adjacent cells, 1 or 2 nuclei/cell

– Coencytic = non septate, many nuclei– Hyphae grow by elongating at tips, fragmentation– Vegetative hyphae – obtains nutrients– Aerial hyphae- bears reproductive spores– Mass of hyphae = mycelium– Cell walls contain chitin, same as exoskeletons of

arthropods ex Insects

Yeasts - unicellular

• Budding (reproduction) – yeast forms a bud on its surface that elongates– Parent cell nucleus divides, one nucleus migrates into

the bud– Cell wall forms between yeast and bud and bud

breaks off

• Pseudohyphae = buds fail to detach and from a short chain of cells– Candida albicans – attaches to epithelial cells as

yeast but forms pseudohyphae to invade deeper into tissue

Yeasts - unicellular

• Capable of facultative anaerobic growth– Aerobic respiration

• Yeast + O2 metabolize CH2Os to CO2 + H2O

– Anaerobic respiration• Yeasts without O2 ferments CH2Os to ethanol and

CO2– Brewing, wine making, baking industries

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Dimorphic fungi – most are pathogenic

• Dimorphism = 2 forms of growth – yeast or mold– Temperature dependent

• Moldlike at 25 degrees C• Yeasts at 37 degrees C

• Life cycle– Filamentous fungi can reproduce asexually –

fragmentation or spores and reproduce sexually by spores– Fungal spores can survive hot, dry environments but not

like endospores• Asexual spores – produced by hyphae of a single

fungus– Conidiospores = conidium (pl. conidia) = uni or

multicellular spores not enclosed in a sac

Asexual spores

– Conidiospores Pg 349• Produced in a chain at the end of a

coniophore ex. Aspergillus • Arthroconidia – formed by

fragmentation ex. Coccidiodes immitis – pulmonary mycoses

• Blastoconidia buds coming off parent cell – some yeasts ex. Candida albicans, Cryptococcus (lungs)

Asexual spores

• Chlamydoconidium – spore formed within a hyphal segment ex. Candia albicans

• Sporangiospore – spore formed in a sac = sporangium at the end of an aerial hyphae called a sporangiophore ex. Rhizopus

Conidiospores - Aspergillus

Sexual reproduction

• Sexual spores result from the fusion of nuclei from 2 opposite mating strains

• Pg. 350 shows both asexual and sexual reproduction in Rhizopus

Classification of fungi by phylum

• Zygomycota = conjugation fungi, bread molds ex. Rhizopus stolonifer– Hyphae = coenocytic– Asexual reproduction = sporangiospores– Sexual reproduction = zygospores = thick walled

spores formed from union of 2 opposite mating strains– Habitat = soil, saprophytic = lives on decaying plant

material

Classification of fungi by phylum

• Ascomycota - sac fungi ex. Aspergillus niger (used to make Beano), Penicillium (Abs)– Hyphae – septate, some yeasts– Asexual reproduction = conidia (means dust,

becomes airborne)– Sexual reproduction = ascospores which are

contained in an ascus– Habitat = soil, saprophytic

Classification of fungi by phylum

• Basidiomycota – club fungus, mushrooms ex. Cryptococcus neoformans (inhalation of spores causes lung disease)– Hyphae = septate– Asexual reproduction = fragmentation– Sexual reproduction = basidiospores– Habitat = soil, bird feces

Fungal infection = mycosis5 classifications

• Systemic mycoses – infection deep within the body– Can infect a # of tissues and organs– Transmission – inhalation of spores

• Enters the lungs and then spreads to other body tissues

• Not contagious

– Live in soil– Histoplasmosis and coccidiodomycosis – both

pulmonary mycosis

Fungal infection = mycosis5 classifications

• Subcutaneous mycoses – infection beneath the skin caused by saprophytic fungi that live in the soil and on vegetation– Transmission – by direct implantation of spores or

hyphae into puncture wounds • Cutaneous mycoses

– Dermatophytes = fungi that live only on epidermis,– hair, nails– Secrete enzyme keratinase wh/ degrades keratin in

hair, skin, nails– Transmission – direct contact – human to human,

animal to human

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Fungal infection = mycosis5 classifications

• Superficial mycosis – along hair shafts, surface epidermal cells, found in the tropics ex. Ringworm

• Opportunistic pathogen – normally harmless but is pathogenic in debilitated host, ex. Ab tx, lung disease, immune disorder– Pneumocystis – leading cause of death in AIDS px– Mucormycosis – Rhizopus, Mucor – px w/ diabetes,

leukemia, or being txed w/ immunosuppressive drugs

Fungal infection = mycosis5 classifications

• Opportunistic pathogen cont. – Aspergillosis – Aspergillus – px w/ lung

disease, cancer who have inhaled the spores– Cryptococcus and Penicillium – can be fatal to

AIDS px– Yeast infections (candidiasis) – Candida

albicans – occurs vaginally or as thrush in newborns, AIDS px, or px on Abs

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Lichens

• Are a combination of a a green alga or a cyanobacterium and a fungus growing together in a mutualistic relationship – both benefit

• The algae provide the nutrients and the fungi provide attachment and protection from desiccation

• Provides erythrolitmin - dye used in litmus paper

Lichens

• Are used for indicator organisms for air pollution

• Some lichens cause allergic contact dermatitis in humans

• Major food source for caribou and reindeer– After the 1986 Chernobyl nuclear disaster,

lichens absorbed radioactive cesium -137 from the air and 70,000 reindeer raised for food in Lapland had to be destroyed

Algae

• Are unicellular or multicellular • Habitat – aquatic, soil, trees, hair of sloths or

polar bears• Algae phyla

– Phaeophyta – brown algae = kelp – macroscopic in coastal waters

• Algin –thickener used in foods extracted from CW– Rhodophyta = red algae –live at greater ocean

depths than other algae• Lab agar comes from red algae• Carrageenan and agar used as thickening ingredients in

foods and pharmaceutical agents

Algae Phyla

• Chlorophyta = green algae – usually microscopic, contains chlorophyll a and b– Believed to have given rise to terrestrial plants– Unicellular or multicellular - can form filaments

• Bacillariophyta = diatoms– Unicellular or filamentous w/ CWs of pectin and silica

that fit together like a Petri dish– One of major algae in the oceanic food chain

(phytoplankton)– Used as polishing and insulating materials– Diatomaceous earth – filtering material

Algae Phyla

• Dinoflagellata = dinoflagellates– Unicellular algae, major part of phytoplankton– Some produce neurotoxins and are responsible for

many fish, marine mammals and some human deaths– Large concentrations – ocean deep red color = red

tide• Mollusks shouldn’t be harvested during a red tide-

concentrates neurotoxin and causes paralytic shellfish poisoning

Algae Phyla

• Oomycota = water molds pg 360 pix Decomposers that form cottony masses in fresh H2O

• Used to be classified as fungi but DNA analysis confirms they are more closely related to diatoms and dinoflagellates

• Responsible for Ireland’s great potato blight in 1800’s – millions died

• Zoospores = flagellated spores w/ 2 flagella• Causes mildew on grapes, effects fruit and veg

crops

algae

• 80% of Earth’s O2 is produced by planktonic algae as a by product of photosynthesis

• Increase in numbers of planktonic algae causes algal blooms

• When algae die in large numbers their decomposition depletes the level of dissolved O2 in the H2O – may kill fish

Protozoa = 1st animalsingle celled

• Trophozoite = feeding or growing stage• Reproduce asexually by fission, budding or

schizogony (multiple fission)• Sexual reproduction in some protozoa

– Ex. Ciliate - Paramecium by conjugation see pg. 362 fig. 12.16

• Can form cyst stage to survive when food, moisture, O2 are lacking, temp not right, toxic chemicals are present– Cysts can survive outside the host when excreted –

ready for new host

Protozoa

• Are aerobic heterotrophs but many intestinal protozoa are capable of anaerobic growth

Medically important Phyla of protozoa chart pg 367

• Archaezoa – eukaryotes that lack mitochondria– 2 or more flagella – whip like– Trichomonas vaginalis – urinary and genital tract

infections• Has undulating membrane (pg 363) and no cyst stage• Transmitted by sexual intercourse, toilet seats, towels

– Giardia lamblia (intestinales) – found in small intestine of mammals

• Excreted in feces as cysts to be ingested by next host• Dx = id cysts in feces

Medically important Phyla

• Microspora – obligate intracellular parasites that also lack mitochondria– Cause chronic diarrhea and keratoconjuctivitis

(inflammation of the conjunctiva) esp. in AIDS pxs

• Amoebozoa – move and engulf food by pseudopods– Entamoeba histolytica – only pathogenic amoeba

found in human intestine – 10% pop. May be infected• Causes amoebic dysentery• Transmitted by ingestion of cyst excreted in feces

Medically important Phyla

• Acanthamoeba – Can grow in tap water and infects the cornea

of the eye and cause blindness

• Apicomplexa – intracellular parasites whose life cycle involves several hosts– Ex. Plasmodium vivax causes malaria,

transmitted to humans by female Anopheles mosquito

Life cycle of Plasmodiumpg 365

• Definitions:– Trophozoites – feeding or growing stage

• Sporozoites – in mosquito• Merozoites – in humans

– Intermediate host - organism that harbors the larval or asexual stage

– Definitive host – organism that harbor the adult, sexually mature form of parasite

Life cycle of Plasmodiumin humans

• Humans – intermediate hosts, asexual reproduction takes place – Liver – mosquito bite infects human w/

sporozoites wh/ travel thru the blood into the liver

• Sporozoites are removed from the blood and enter the liver cells

• They undergo asexual reproduction or schizogony to form 1000s of merozoites

Life cycle of Plasmodiumin humans

• Humans– Merozoites leave the liver to infect RBCs– RBCs

• Merozoites infect and reproduce in RBCs• The RBCs then rupture and release merozoites

which infect more RBCs– Their waste products cause the fever and chills

characteristic of malaria when RBCs rupture

• Some merozoites develop into gametocytes (male, female)

Life cycle of Plasmodiumin Mosquitos

• Mosquitos – definitive hosts, sexual reproduction takes place – Mosquito picks up gametocyte when bite

infected human• Gametocyte travel to mosquito intestine and begin

sexual cycle• Gametocytes unite to form a zygote wh/ forms an

oocyst where sporozoites are formed

– Sporozoites migrate to the mosquito salivary glands where they are transmitted to human’s blood w/ the next bite

Apicomplexacontinued

• Cryptosporidium – causes intestinal infection– Transmission is by feces, H2O, nosocomial

infections

• Toxoplasma gondii– Intracellular parasite - causes toxoplasmosis– Transmitted through cat feces and is

dangerous for pregnant women• Can cause problems in fetus including stillbirth

Medically important Protozoan Phyla

• Ciliophora – ciliates, cilia for movement and to bring food into mouth– Balantidium coli – only ciliate that is a

human parasite• Cause severe dysentery • Cysts excreted in feces

• Euglenozoa – 2 groups – Euglenoids

• photoautotrophs

Phylum Euglenozoa

• Euglenoids cont.– Pellicle = semi-rigid plasma membrane– Anterior flagella, red eyespot that senses light

• Hemoflagellates –blood parasites transmitted by bites of blood feeding insects– Have a long slender body and undulating membrane– Trypanosoma brucei gambiense – causes African sleeping

sickness from bite of tse tse fly– Trypanosoma cruzi – causes Chagas’ disease – bite of kissing

bug (face) – trypanosome in feces wh/ gets in bite

Helminths – parasitic worms

• Phylum Platyhelminthes = flatworms– 2 groups = trematodes and cestodes

• Trematodes = flukes– Flat, leaf shaped bodies, suckers to hold them

in place, – Paragonimus westermani – lung fluke pg 373

life cycle• Adult lives in bronchioles of mammals where

hermaphroditic adults lay eggs into the bronchi

Helminths – parasitic worms

• Paragonimus westermani cont.– Sputum w/ eggs is coughed up, swallowed,

and excreted w/ feces– Eggs have to make it to H2O to find

intermediate hosts (snail, crayfish)– Transmission – ingestion of undercooked

crayfish– Dx –eggs in sputum or feces

Helminths – parasitic worms

• Cestodes = tapeworms– Lack a digestive tract, absorb nutrients thru

cuticle– Scolex = head with suckers and hooks for

attachment– Proglottids = body segments wh/ are

produced by neck of scolex• Mature proglottids contain both male and female

reproductive organs• Those farthest from scolex are bags of eggs

Cestodes = tapeworms

• Humans as definitive hosts– Taenia saginata – beef tapeworm

• Proglottids ingested by grazing animals• Larvae migrate to muscle (meat) where they

encyst as cysticerci• If you eat infected meat all but the scolex is

digested– It anchors itself to the small intestine and starts

producing proglottids

Cestodes = tapeworms

• Humans as definitive hosts cont.– Taenia solium = pork tapeworm

• Adult worms in human intestines lay eggs that pass out w/ feces and are eaten by pigs

• Eggs hatch into larvae wh/ encyst in pigs muscles• Transmission by eating undercooked pork – not in US

– Human-going in larvae-in adult- leaving eggs

• Eggs shed by 1 person and ingested by another – eggs hatch and encyst in brain and other body parts causing cysticercosis – now human intermediate host

– Human – eggs leaving – human eggs ingested – larvae hatch and encyst

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Cestodes = tapeworms

• Humans as intermediate hosts pg 375– Echinococcus granulosus = dog tapeworm

• Dogs, coyotes – definitive hosts• Eggs transmitted by dog feces or saliva after dog

licks self• Eggs hatch in the small intestine and larvae

migrate to liver or lungs• Larvae develop into hydatid cyst wh/ contain brood

capsules wh/ can produce 1000s of scoleces• Sx = abdominal and chest pain, coughing up blood

Nematoda = roundworms

• Free-living and parasitic• Cylindrical, tapered at each end• Complete digestive system• Most are dioecious (male and females) –

males are smaller than females and have spicules on posterior end to guide sperm into female genital pore

• Human infection can be divided into whether the egg or larvae is infective

Nematode eggs infective for humans

• Enterobius vermicularis = pinworm– Spends entire life in humans– Adults in large intestine– Female migrates to anus to lay eggs on

perianal skin– Eggs ingested by the same host or another

person thru contaminated bedding or clothes– Dx. Graham sticky-tape method

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Nematode eggs infective for humans

• Ascaris lumbricoides – large (30 cm), infects over 1 billion ww– Dioecious w/ sexual dimorphism = male and female

different • Male smaller w/ curled tail

– Adults live in small intestine of humans only– Feed on semi-digested food– Eggs excreted in feces > ingested by another host >

hatch in sm intestine > burrow out of intestine and enter blood where they are carried to the lungs to grow > coughed up and swallowed and return to the Small Intestine to mature into adults (now can repro)

Nematode larvae infective for humans

• Necator americanus, Ancylostoma duodenale = adult hookworms that live in the small intestine of humans– eggs are excreted in feces– Larvae hatch in soil where they enter host by

penetrating skin– Larvae enter blood or lymph vessels and are carried

to lungs > coughed up in sputum > swallowed and carried to small intestine

– Dx by eggs in feces, avoid by wearing shoes

Nematode larvae infective for humans

• Trichinella spiralis – causes trichinellosis by eating undercooked pork or game animals (bear) w/ larval cysts in ms– Larvae are freed from cysts in small intestine >

mature into adults > sexually reproduce > females give birth to live larvae wh/ enter lymph and BVs > they migrate to ms and other tissue where they encyst and remain until eaten by another host

– Dx = microscopic exam of larvae in ms biopsy– Prevention = cook meat

Arthropods = Insects, Arachnids

• Have segmented bodies, hard external skeletons, jointed legs

• If carry pathogenic microorganisms = vectors table on pg 378– Mechanical vectors transport pathogens on

feet or body ex. Flies– Biological vectors - pathogens multiply in

vectors and are transmitted thru saliva or feces

Body & Crab Lice