Unit 6--Microbiology

Chapter 20

Protists

Endosymbiotic theory

• Heterotrophic bacteria have plasmids (DNA loop) & simple ribosomes in their cytoplasm

• Mitochondria have circular DNA & bacteria-like ribosomes

• So…Eukaryotic cells may have engulfed prokaryotic cells & by mutualism created the “first mitochondria.”

• Autotrophic bacteria are Cyanobacteria with chlorophyll

• So, Eukaryotic cells may have engulfed prokaryotic cyanobacteria & by mutualism created the “first chloroplast.”

Characteristics

• Mostly unicellular

• Eukaryotic cells

• Most diverse kingdom:– Photosynthesis, like plants (algae)– Ingest food, like animals (protozoans)– Absorb food, like fungus (slime mold)

Classifying protists

PROTIST

Protozoan Algae Slime mold

heterotroph autotroph saprobe

Consume Produce Decompose

Animal-like Plant-like Fungus-like

DNA evidence shows that some archaebacteria may have been ancestors of protists.

Phylum…example…distinguishing characteristics

• Zoomastigina…Trypanosome

• Causes Sleeping sickness

• All are flagellated• Other examples

include those living symbiotically within termite intestine

Phylum…example…distinguishing characteristics

• Rhizopoda…ameba• Moves by

pseudopods = cytoplasmic extensions

• Feed by phagocytosis = surrounding & engulfing

Phylum…example…distinguishing characteristics

• Foraminifera…Forams

• Ameba-like body within a shell-like test

• Often build-up accumulates after many years

Electron microphotograph of Radiolarian, a marine Protist

Phylum…example…distinguishing characteristics

• Ciliophora … paramecium

• All are ciliated• Macro & micronuclei• Oral groove & gullet

bring food into vacuole

• Contractile vacuole pumps out water

See page 501

Phylum…example…distinguishing characteristics

• Sporozoa…Plasmodium

• Causes Malaria• Carried by female

Anopheles mosquito• During bite: insect

saliva inserted or infected blood ingested by insect

See page 503

Plasmodium attacking red blood cells and rupturing RBC

Phylum…example…distinguishing characteristics

• Euglenophyta…Euglena

• Animal-like flagella, eyespot, and reservoir (to ingest)

• Plant-like chloroplasts for photosynthesis

Euglena structures

Pellicle – EM image

See page 507

Phylum…example…distinguishing characteristics

• Bacillariophyta…Diatoms

• Unicellular marine algae; main producer in the sea

• Glass-like cell walls of silica

• Unique shapes

Phylum…example…distinguishing characteristics

• Dinoflagellata…dinoflagellates

• Unicellular algae; 2nd only to diatoms as main producer

• Often has flagella, plates, spikes, and other projections

• Causes “red tide”

Bioluminescence

Phylum…example…distinguishing characteristics

• Rhodophyta…red algae

• Small, multicellular algae

• May be an epiphyte on larger algae

• Used to make agar

Phylum…example…distinguishing characteristics

• Phaeophyta…brown algae

• Largest, multicellular algae

• Includes Kelp, which may grow 100 ft

• Plant-like body with holdfasts, stalks and blades, & air bladders for support

Sargasso Sea

Sargassum

Many square kilometers of the open Atlantic Ocean between the islands of the Azores and the Bahamas are covered by huge, floating algae called Sargassum. Known as the Sargasso Sea, this area of warm water is named for the brown algae that dominate its surface.

Uses of red and brown algae

Carrageenan

Agar

Seaweed

Phylum…example…distinguishing characteristics

• Chlorophyta…green algae

• Ancestors of plants

• In all environments, even on land

• Unicellular to multicellular (sea lettuce)

• Ex: Volvox and Spirogyra

Conjugation in Paramecium

Phylum…example…distinguishing characteristics

• Myxomycota… plasmodial slime mold

• A mass of cytoplasm containing many nuclei

• Uses spores to survive harsh conditions

Acellular slime mold plasmodium

Cellular slime mold