eukaryotes – general

EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 1

Eukaryotes – General

= “true nucleus”

appeared in fossil record about 1.2-1.5BY ago(2.1 - 2.5 Billion years ago)??? ck

larger cells (100-500µm vs 1-5µm):100x’s larger than prokaryotes

only one cell produces all the tasks essential for life(same as bacteria but much more efficiently since eukaryotes)

compartmentalizationnucleus, organelles

makes them much more efficient than bacteria

Origin of Eukaryotes

eukaryotic cells probably arose from two processes:

1. infolding of cell membrane to form membranebound nucleus and possibly the endoplasmic reticulum and golgi bodies

2. endosymbiosis of other prokaryotes probablyproduced mitochondria and chloroplasts and possibly the eukaryoticflagellum

evidence:

there are examples today of suchendosymbiosis

chloroplasts and mitochondria are the size ofmost bacteria

chloroplasts and mitochondria have bacterial chromosome (circular ring of DNA)

they also have bacterial RNA and bacterialenzymes

and replicate by binary fission as do bacteria


Kingdom Protista – General

~65,000 species described up to 200,000 species probable

simplest eukaryotic organisms(the other kingdoms are mainly multicellular.

very efficient cells compared to procaryotic cells

most metabolically diverse group of eucaryotes(but not more so than bacteria)

diverse group of organelles with highly developeddivision of labor

found anywhere there is water or moisture:freshwaters,marine environments,damp soil,leaf litter,snow,ice

important part of plankton:organisms that drift with currents

most unicellular, some colonial, filamentous, some (seaweeds) multicellular

multicellular forms with specializations of cells fordifferent functions:

reproductionphotosynattachmentreproductionflotationetc

autotrophs and heterotrophs

most aerobica few lack mitochondria and are anaerobic

Movement

most protists are motile


5 x’s faster(but only ~5x’s body length, vs bacteria 10-50x’s body

length at 50µm/s)eg. Paramecium 2700 µm/seg. Chlamydomonas 200µm/s

useciliaflagellaamoeboid motionglidingnonmotile

Reproduction and Life Cycles

highly varied reproduction and life cycles

true mitosis and meiosis to produce gametes

reproduce asexually and sexuallyasexually:

buddingfission & multiple fission

sexually:some by conjugation (eg. Spirogyra)some by syngamy

isogamy = similar gametesanisogamy = similar shape but

one is largeroogamy =

female is larger, nonmotilemale is smaller, motile

some produce gametes in single celled gametangium

many have both a feeding and a resistant stage intheir life cycle

some have alternation of sexual and asexualgenerations


200,000 species described

polyphyletic ie. not a natural grouping, some divide protists into 5 or 6separate kingdomsand 50 phyla

major types of organisms (Note: these are notevolutionary groupings, they are groupings of convenience, an notnecessarily the same groupings as in your text, or in other books):

1. Algae (22,000 species + fossils)mostly single celled, colonial, somemulticellular photosynthetic protists, mostwith cell wall

2. Protozoa (31,000 species + fossils)mostly single celled or colonial,heterotrophs, non photosynthetic, mostlymotile

3. Slime Molds (1,100 species)mostly complex life cyclesinvolving amoeba-like stage and fungal spore-like stage,

alternating sexual and asexual reproduction, heterotrophs


Protists - Algae

~22,000 species

diverse group of mostly photosynthetic protists

almost all are photosynthetic autotrophs=use sunlight as energy source to make organic

food

then store food as starch, leucosin, laminarin,paramylon, lipids

contain same pigment for photosynthesis as do plants chlorophyll

most also have additional “accessory” pigments

restricted to damp or wet environments:oceans, hot springsponds, atmosphere (droplets)lakes, snow,rivers, bark,soil, etc.;

most are aquatic and form phytoplankton

base of food chain in aquatic environmentsdensity only few 1000/literbut ocean area is so great that their

total productivity is:3 x’s production of all worlds grasslands and4 x’s all croplands

the larger, multicellular algae are found closer toshore usually attached to substrate in shallow water

they provide both food and shelter for many otherorganisms

a few are terrestrialfound on tree trunks and damp soil

many are symbiotic with fungi and animals

classification based on:


1. type of accessory photosynthetic pigment2. type of energy reserves3. cell wall composition

Classification

Phylum: PyrrophytaPhylum: Chrysophyta almost all single celled speciesPhylum: Euglenophyta

Phylum: Rhodophyta large multicellular speciesPhylum: Phaeophyta (no true tissues though)

Phylum: Chlorphyta mixture of unicellular, colonial andmulticellular forms

1. Fire Algae (Dinoflagellates, Pyrrophyta)

~1000 sp

unicellular

most are armoredproduce cell walls of fused interlocking cellulose plates

usually with spines

each species has a distinctive shape

2 flagella in grooves perpendicular to each other=> cause organism to spin like a top while moving

foreward

photosynthetic pigment = Chlorophyll a and orange carotenoids

food storage as starch

many symbiotic in coral animals as zooxanthellae

blooms of dinoflagellates color water red or brown= red or brown tides

some produce powerful toxins which can kill fish and other organisms that eat them

eg. 100,000’s of fish may die


eg. red tides in florida and tropical islands

eg. 1980, Maine coast – costs $7M losses

shellfish often not hurt by toxins but can accumulate and concentrate them

may make them dangerous to humans

some are bioluminescent= “burning of the sea” at night


2. Diatoms (glass algae, Chrysophyta, golden-brownalgae)

~10,000 sp

most abundant group of algae

major base of aquatic food chains (fw and marine)=phytoplankton

single celled (unicellular)

very distinctive group

cell walls:

no cellulose, has protein = pectin

also contains silica

radial symmetry

CW in two parts (petri dish)

CW of large numbers of intricately shaped pits,pores and passageways

pigments: chlorophyull a and fucoxanthin

food storage as leucosin

no cilia or flagella

some have gliding movement = slime trail

Reproduction:

asexual:shell halves separate andnew smaller shell is secreted to fit into old shell

half

sexual:male and female cells unite to formzygote which secretes new shell


Economic Impact

all oil reserves were formed mainly by diatom deposits

source of diatomaceous earth= chalky rock composed of diatom shells (fossil)

(white cliffs of Dover)

silica in shells make them useful for:filterscementplasterpaperpaintpesticidesabrasives


3. Euglenoids

~800 sp

small group

unicellular,

motile by flagellum

mostly freshwater

mainly in eutrophic ponds and pools(=lots of nutrients and organic material, eg farm ponds)

most unusual feature is lack of cell wall

flexible pellicle covering instead

food stored as paramylon (a polysaccharide found nowhere else inliving world)

has stigma = photoreceptor => attracted to light

has chloroplasts but can survive without them as well(lives in dark like protozoan)


4. Green Algae

~7000 sp

most diverse group of algae in sizes and shapes

most are freshwater

some terrestrial

found in a wide variety of habitats includingsnowtree trunkssoil

diverse body forms,

some form lichens with fungi;

mostly unicellular and colonial,

some coenocytic siphonous,

filaments or sheets;

probably gave rise to plant kingdom;

motile by flagella,

very similar cell structure to plants:pigments mainly chlorophyll a and bfood stored as starchcell wall mainly of cellulose

plants probably evolved from a green alga

some with light sensitive “eyespot” = stigma

some multicellular filamentous forms andsmall seaweeds (eg sea lettuce)

some chlamydomonas-like cells live in colonies of4,8,16 or 32

they are connected by cytoplasmic strands


most spectacular colonial form is Volvox:500-60,000 cellsfront and back endsvegetative and reproductive cellsproduce daughter colonies within adult sphere

tendency toward multicellularity


5. Brown Algae (phaeophyta)

~1500 sp

all multicellular seaweeds,

almost all marine

usually inhabit cooler, rocky shores, intertidal areas

most large seaweeds are in this group

giant kelp can grow 300 ft long

kelp beds can be so dense they are essentiallyjungles

provide food and home for numerous sea creatures

cell wall of cellulose

complex specializations of cells into structures ofspecific functions:

bladestipe (stalk)floatsholdfast – attaches to solid surface

rapid growth rate: can renew tissues 1-5 x’s/yr

pigments: chlorophyll a and brown fucoxanthin gives them a dark brown or olive green appearance

stores foods as laminarin and lipids

life cycle usually involvesalternation of generations:

seaweed produces sporangiumsporangium produces male or female sporesspores grow into male or female sporophytessporophyte produces egg or spermzygote produces seaweed again

Sargassum


=gulfweed, rockweed, seaholly

sargassum refers to ‘grapelike’ appearance of gas bladders

only seaweed that is not attached to a substrate it’s planktonic

sargasso sea~2/3rd ‘s area of cont UStrapped in ring of currents in atlantic

sargassum can live for many yearsreproduces mainly by fragmentationwhen it becomes too encrusted it slowy sinks

to bottomsome weed is blown to gulf shores by winds

and currents

entire ecosystem of different organisms highlyadapted to it: crabs, shrimp, pipefish, “furry white” bryozoa,sargassum fish “Histrio histrio”

lots of camoflage

Economic Impacts:

used as food especially in SE Asian countries;

Kelp

kelp forests in the pacific provide such products as Kombu, Barech and Seche.

Alginates

Alginates are derived from various species of brown algae including Macrocystis, Laminaria and Fucus.About half of the ice cream in the US contains alginates.

It is used to produce a smooth consistency and eliminate ice crystals in icecreams. It is also used in somecheeses and frostings.

alginates used to make a wound dressing that speeds healing of leg ulcers

Fertilizers:seaweeds contain iodine, K, N, Pequivalent to manure


6. Red Algae (rhodophyta)

~4000 sp

especially abundant in warm tropical waters,(found in deeper waters than green algae)

mostly marine

body of filaments or sheets

most are multicellular seaweedssome differentiation of cells into:

stalks, floats, blades in some speciesoften attached to substrate by holdfast

cell wall of cellulose but often has othercarbohydrates (eg. agar)

some can deposit calcium carbonate in their cellwalls

= coralline algae important component of coral reefs

pigments: include chorophyll a and red pigment = phycobilin (more effective at capturing light in deeper water))

food stored as starch

Economic Impacts:

thick starchy cell walls yield commercial quantities of agar Agar

Agar is extracted from several red seaweeds including Gelidium sp. and Gracilarid sp. It is used in themanufacture of processed cheese, mayonnaise, puddings, jellies, baking products and canned goods.

agar: capsules for pillscosmetic baseculture mediajellies, puddings and dessertsmayonnaisecanned goodssome cheeses

Nori


The red seaweed, Porphyra, is cultivated in Japan. There are several species that are roasted andsometimes soaked in sugar and soy sauce for soup flavorings, wrapped rice crackers and to make otheroriental dishes


Protists - Protozoa

~31,000 living species; ~10,000 of these are parasitic

animal like protists

share several animal-like traits:lack cell wall,most are motileheterotrophic nutrition,

animals probably evolved from some kind ofprotozoan

most are single cell (=solitary)

a few are colonial

most are microscopic (3-300µm)

have been found in all aquatic environments

form important part of plankton (=zooplankton)

some found in terrestrial habitats where moisture isabundant:

sandsoildecaying organic matter

some are parasitic or symbiotic in animals

most are motile byciliaflagellaamoeboid motion (form pseudopodia)

(found in amoebas and some flagellates)

can also use cilia or flagella to create water currentsfor feeding

most have optimum temperature range of36 – 40 º C (=96.8 – 104º F)

heterotrophs = feed by:


1. absorbing dissolved organic nutrientsthrough cell membrane

2. ingest solid particlesthrough a mouth-like opening (=cytostome)

eat bacteria, algae, other protozoa, etc

some are saprophytic(=eat decaying organic matter)

3. ingesting solids or liquidsthrough cell membrane (phagocytosis &

pinocytosis)

food becomes enclosed in vacuole which travelsthrough cytoplasm

digestive enzymes are injected into the vacuoleand digest the food

undigested material is expelled by a reverseprocess (exocytosis) or through an “anal pore”

Life Cycles

a. most protozoa exist in a single form which feeds andreproduces

b. some alternate between two stages in their lifecycle:

troph = active vegetative feeding form

cyst = more resistant stage,low metabolic ratemay have wall of cellulose, silica or a

chitin-like substance

c. some parasitic forms have several different stagesin more than one host

Reproduction


reproduce both asexually and sexually:asexual: main form of reproduction

fission = divide in equal halves(not same as bacterial fission)eucaryotic fission involves mitosis

some split longitudinally (flagellages)

some split transversely (ciliates)

budding = unequal fission

multiple fission = >2 daughter cells(some flagellates, sarcodines, most sporozoans)

sexual: involves some exchange of genes

conjugation = exchange of a few genes(ciliates only)

syngamy = fusion of gametes

Classification

protozoa are classified according to presence and typeof motility:

amoeboid motionflagellacilianonmotile

Phylum: Sarcomastigophora

Subphylum: Mastigophora – 1 or more flagella

Subphylum: Sarcodina – amoeboid pseudopodia

Phylum: Ciliophora – ciliates

Phylum: Apicomplexa: - no cilia or flagella non motile all are parasitic


1. Amoebas

amoeba = “to change form”

Include protozoa that move by pseudopodia(=false feet)

related to changes in consistency of the cytoplasm:ectoplasm = gelendoplasm = liquid

organism can alternate between solid gel-like andliquid cytoplasm to produce pseudopodia;

simplest protozoans relatively few organelles

may be naked or enclosed within shell or case:

only phylum of protozoan with extensive fossilrecord

the shell may be composed of materials secretedby cytoplasm or

foreign material embedded in cement likesecretion

two most important shelled forms:radiolaria secrete a silica shell (SiO2), andforaminiferans produce calcium carbonate shells (CaCO3)

reproduce mostly asexually

a few reproduce sexually

Human Impacts:

Human pathogens include:

1. Entamoeba hystolytica

amoebic dysenteryesp tropics and areas of poor sanitation

(5% infection in temperate areas)humans only reservoirspread by fecal/oral route


invade intestinal mucosafeed on RBC’s90% are asymptomaticcan cause ulcerations and profuse bleeding in acute casescysts passed in fecesmay spread to liver, lungs, brain, etc

2. Naegleria fowleri

causes always-fatal primary amoebic meningoencephalitis orPAM

mature adults seem to be immuneprefers warm waters with a high iron contentmay prefer areas where other organisms have been wiped

out by natural or man made disasters (eg Mt. St.Helens)


2. Flagellates

cell membrane surrounded by pellicle

move using one or a few long flagella

some have “sail-like” undulating membrane(also used for food gathering and locomotion)

most are symbionts as either mutualists orcommensals

eg. such as those in the gut of termites

some are pathogenseg. such as Giardia, Trypanosoma,

most flagellates are not closely related to other protozoans probably include several phyla

Human Impacts:

Human Pathogens:

1. Trichomonas

several species (esp. T. vaginalis)human urogenital tract:

like acidity of female tractone of most common infections in US

(2.5 M inf/yr: 3-15% US infected)no cyst form requires personal contact

occasionally spread in communal baths and mother tochild

both male and female infectedesp in promiscuous young women who are already

infected with other STD’s~50% are asymptomatic carrierssymptoms: women -frothy, smelly green

discharge; painful urination

[T. tenax – 5-10% oral infectionsesp with poor oral hygeine]

2. Giardia


pear shapeddiarrheahumans are final (definitive) hostno intermediate hostsworldwide distributioninfect upper small intestineno invasive ability – saprophyticin large #’s can cause chronic diarrhea,

dehydrationcysts shed in fecesfecal/oral transmissionepidemics associated with contaminated water

3. Trypanosoma (African Sleeping Sickness)

esp in Africa20,000 cases/yr (1988)two hosts:

tsetse fly = definitive hosthumans and other animals

intermediate hostsmoves into blood and lymphatic systemaffects CNS: personality changes,

behavior changes, headaches, apathy, NM disorders,sleepiness, emaciation

may result in death from coma,malnutrition, secondary infections

4. Chagas disease (T. cruzi)

Mexico, Central America, So. Americaonly a few cases in extreme SW US40-50% of population in So. Americareservoirs: rodents, possums, armadillosvector: “kissing bug”: bites lips, defecates while

feeding and may be rubbed into wound by scratchingbite

most dangerous to childrensymptoms somewhat similar to sleeping sicknessmay also affects many organs; eg. brain, heart,

intestines

5. Leishmania

zoonosisespecially in equatorial areas


transmitted by phlebotomid (sandfly) vectorinjected directly into human hostreproduces inside WBC’stwo forms:

cutaneous form:begins with skin ulcer at site of infectionmay recur after healingmay spread to nose, lips, palate, throatdeath from bacterial infection

systemic form:produces high intermittant feverenlarged spleen, liver and lymph glands75-90% death rate


3. Ciliates

The largest most diverse group of single celled'protozoan' protists;

genetically as diverse as entire animal kingdom

mostly are freeliving

in a wide variety of habitats.

motile by means of cilia= 1000’s oarlike projections

produce coordinated movements

fastest of the protozoans

a few are nonmotile: attached to substrate by stalk

use cilia for feeding, not movement

Wide variation in #’s and kinds of organelles:

more than one nucleus,some macronucleus => vegetative chores

micronuclei (up to 80) => sexual reproduction

“mouth” and throatlike area,most feed on microorganisms – have mouthlike cytostome;opens into a throat; food vacuole forms at end of throat

contractile vacuoles, etcsome fw forms use to remove incomming water

trichocysts

some ciliates can steal chloroplasts from the algaethey eat

Reproduction:asexual: binary fissionsexual: conjugation: portion of micronuclei are

exchanged between + and – forms

Human Impacts:


Human Pathogens:

1. Balantidium coli

ony ciliate that is a human parasitezoonosis: esp in sheep, cattle, pigs, horsesrare in USesp in hosts with weakened defensescan be asymptomaticcauses erosion of intestinal liningproduces nausea, vomiting, bloody diarrhea


4. Apicomplexa (Sporozoa)

All members of this group are nonmotile

are endoparasites

most have fairly complex life cyclessame species exists in lots of different formsalternating between forms that reproduce sexually

and those that reproduce asexually.

Human Impacts:

Human parasites include:

1. Plasmodium (malaria)single most important disease hazard for

people traveling to foreign lands(esp. Asia, Africa, Latin America)

worldwide infects 270M and kills 2M/yrin some parts of world is chronic

relatively rare in US (usually travelers)4 species, all can infect humansrequires two hosts to complete life cycle:

sexual reprodoccurs in Anopheles mosquitoreproduces in salivary glands

asexual reproductionoccurs in humansconcentrates in liver

symptoms: cyclic chills/fever, headache every 3-4 daysif not treat may be self limiting but may be reservoir for up

to 3 yearscan produce irreversible damage to liver, spleen, kidneys

and brainmost effective prevention is elimination of mosquitoWHO has been trying to eliminate it but with little successmosquitoes have developed resistance to insecticideshas developed antibiotic resistanceexperimental vaccines being testedsome living in endemic areas have developed

genetic resistance to disease (sickle cell)

2. Toxoplasma

zoonosis


cats are main reservoir and definitive hosthumans contract by contaminated soil, cat feces (litter box),

infected meatgenerally no human-human transferasymptomatic in adultsif pregnant can cross placenta and cause retardation,

blindness and convulsions in embryo or newborn

3. Pneumocystis

common secondary infection of AIDS victims


Protists:Slime Molds & Water Molds

~1100 species

Superficially resemble fungi;nonphotosyntheticbody of threadlike filaments = hyphae fruiting body a sporangium producing spores

fungus like, but: produce flagellate reproductive cells and

some have cell wall of cellulose,others with cell walls of chitin

feeding stage is amoeba-like motile

common in cool, moist shady placeseg. crevasses of rotting wood

most easily found in summer and early fall

fruiting body is the most likely to be seen very small (~1-2mm) goblets, globes, plumules with or without a stalk often colored yellow, orange, red

for most of a slime molds life it exists as a thin, free-living mass of protoplasm up to several inches across that moves aroundand engulfs bacteria and organic matter

it is thick and slimy to the touch

after its feeding period it moves out of its normalhabitat and goes to a drier, more exposed location to produce a fruitingbody

fruiting bodies can also be produced by absence of food, changesin moisture, pH, temperature

once begun, it cannot be reversed

some can produced a hardened resistant sclerotiumto survive adverse conditions


fossils of this group has the distinction of being the firsttrue fossil that actually shows an organism caught in the act of sexualreproduction (65MY)

Classification:

three major Phyla:1. plasmodial slime molds (Myxomycota)2. cellular slime molds (Acrasiomycota)3. water molds (Oomycota)


1. Plasmodial Slime Molds

~700 species

life cycle has two major stages:feeding stage (nonreproductive)sporangia (reproductive)

feeding stage = plasmodiumwall-less amoeba-like masslarge single cellthin streaming masses of cytoplasmcreep along in amoeboid fashioncan cover an area of several square yards (to 30 g = ~ 1oz)growth continues as long as there is adequate food and

moisturewhen in short supply they migrate away from feeding area

(often seen crossing roads, lawns, climbing trees, etc)some species form extensive growths on lawns, croplands

do little, if any, damage

eg. Fuligo septica plasmodium (shades of war of the worlds)

1973 found in Dallas suburb & reported in paper appeared on lawns as bright yellow masses spread over large areas described in paper as a “pulsating yellow blob” blobs broke apart when sprayed with hose but pieces continued to crawl around caused local panic: must be indestructible aliens from space or mutant bacteria that might take over the earth excitement soon dissipated once identified biologists “saved the world!”

when food supply dwindles reproduction is initiatedplasmodium divides into numerous moundseach mound forms cells surrounded by cell wallsproduce multicellular fruiting body = sporangiumhas cell walls on cellsvery similar to those of fungiproduces very resistant reproductive spores

spores are haploid cells


flagellated (=swarm cells)or amoeba like (=myxamoeba)

this group is probably more closely related to amoebas than to fungi

Economic Importance:

Veracruz Mexico:some are collected, fried and eaten by indigenous

peoplescalled “cacade luna”


2. Cellular Slime Molds

~70 species

superficially resemble the plasmodial slime molds

also closely resemble amoeba

life cycle also involvesfeeding stagereproductive stage

feeding stage consist of individual amoeba-like cellswhen food or moisture runs out cells aggregateform a single multicellular organism = pseudoplasmodium

(=slug)the slug develops a stalked structure (the fruiting body) which

produces spores


3. Water Molds

~580 species

mainly soil and water borne organisms

once classified with fungi: have hyphae and myceliumbut differ significantly in fundamental structures and biochemistry

most commonly seen as the fuzzy filaments on deadaquarium fish

hyphae are coenocytic (= 1 giant multinucleate, filamentous cell)

has both asexual and sexual reproductive stages:asexual: zoosporangium producing zoosporessexual: antheridium and oogonium producing oospores

Economic Impacts:

some are serious plant pathogenseg. downy mildew

affects grapesintroduced into France in late 1800’salmost destroyed the wine industryproblem was accidentally solved using copper

sulfate and lime

eg. Phytophthora infestansCause of Irish Potato Famine (1845-7)

in Irelandvirtually the entire Irish potato crop was wiped

out in one week> 1 million deaths from starvationbegan large scale emmigration of Irish to US

within a decade the population of Irelanddropped 50%: 8M -> 4M

eg. other Phytophthora specieshave caused widespread destruction of many

crops throughout the world:pineapplestomatoes,rubber,onionsstrawberries


applessoybeanstobaccocitrus

eukaryotes – general

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