Lab 3 - Introduction to Microbial Eukaryotes

3 major body forms

1. Ciliate (Paramecium): have many short cilia on their surface which allow them to move rapidly and feed

2. Amoeboid (Amoeba): are irregular shaped and move slowly by cytoplasmic streaming via their pseudopodia

3. Flagellate (Euglena): have whip-like flagella(um) to move quickly

functions of the cytoskeleton

• structure

• adhesion to surfaces

• movement

composition of the cytoskeleton

• microtubules: part of cilium or flagellum

• intermediate filaments: ropes of keratin proteins, not used for movement

• microfilaments: used in amoeboid movement

• motor proteins

amoeboid movement

use pseudopodia: temporary extensions of the cytoplasm formed by actin subunits that assemble into microfilaments

flagellate movement

• flagellum: a whip-like flexible rod with a central core of microtubules made up of two tubulin subunits

• use motor proteins dynein and kinesin

• eukaryotes typically have 1-12

ciliate movement

• like a shorter version of a flagellum

• cell may have may have 100’s-1000’s of cilia on its surface

phagocytosis

• allows for solid food to be taken directly into the cell

• food is taken into a membrane-bound vacuole which contains digestive enzymes

• nutrients released into cytoplasm

endosymbiotic theory

• eukaryotic organelles could be the products of a symbiosis between bacteria and eukaryotes

• mitochondria and chloroplasts arose only once in eukaryotes (primary endosymbiosis) but have been repeatedly lost, modified, and transferred between lineages

what evidence supports the endosymbiotic theory?

• mitochondria and chloroplasts are haploid, have circular DNA, and reproduce via binary fission

• mitochondria are closely related to proteobacteria and chloroplasts are closely related to cyanobacteria

• the mitochondria and chloroplast genome are more similar to bacterial genomes than eukaryotic genomes

LECA

Last Eukaryotic Common Ancestor

secondary endosymbiosis

when a eukaryote gains its chloroplasts by engulfing a plant

tertiary endosymbiosis

eukaryote gains its chloroplasts by engulfing another microbial eukaryote

life cycle

events from birth until death including growth, changes in body form, sexual maturation, and reproduction

asexual reproduction in microbial eukaryotes

genotype is copied, creating an offspring that is genetically identical (but not necessarily morphologically identical)

what is phase contrast microscopy used for?

to view transparent parts of a live specimen without using stains to enhance visibility (stains usually kill it)

body forms of Naegleria gruberi

can switch between amoeboid and flagellate

slime molds (plasmodial vs cellular)

• resemble fungi, but are distantly related

• cool, moist, microenvironments

• highly mobile, amoeboid body form

• consume food via endocytosis

distance matrix

• a way to summarize the percent difference in nucleotide sequence between taxa

• can be used to draw unrooted trees that show relative relationships

Euglena

• green

• very abundant in lab samples

• movement:

• magnification:

• size:

Amoeba

• often surrounded by small microbial eukaryotes Chilomonas (food source)

• movement:

• magnification:

• size:

Blepharisma

• large, pink, slipper shaped ciliates

• movement:

• magnification:

• size:

Chlamydomonas

• circular algae, apical flageallae

• movement: jittery motion

• magnification:

• size: small

Paramecium

• movement: quick

• magnification:

• size:

Stentor

• green ciliates, irregular-trumpet shaped

• movement:

• magnification:

• size: large

setup of Naegleria experiment

• grow Naegleria in the presence of food and without food to see if body form changes in response to removal of food source

• count # of amoeboid vs non-amoeboid at 15 minute intervals

how to estimate organism size using microscope

• compare organism size to the field diameter of 10X and 40X objective lenses

• field diameter decreases as magnification increases

how to calibrate microscope

1. move objective lens to 10X

2. move filter wheel on condenser to Ph1

3. find phase centering telescope

4. remove right eyepiece

5. replace right eyepiece with phase contrast telescope

6. use phase contrast alignment knobs to center phase contrast rings so that they superimpose each other exactly

How did the mitochondria of eukaryotes evolve?

• primary endosymbiosis: eukaryote engulfs a proteobacteria, which becomes the mitchondria

• results in two membranes

• evolved only once

evidence for primary endosymbiosis of mitochondria

• double membrane

• mitochondria have circular DNA, like proteobacteria

how did chloroplasts evolve in eukaryotes?

• initially evolved in plantae via primary endosymbiosis: eukaryote engulfed a cyanobacterium —> became chloroplast with 2 membranes

• evolved once, but were transferred to other lineages via secondary endosymbiosis: eukaryote (w/o chloroplast) engulfs a plantae (that already has chloroplast) —> results in chloroplast with 3-4 membranes

• monophyletic

protists

• eukaryotes that are not plants, animals, or fungi

• non-monophyletic

• mostly microscopic and unicellular, but can be multicellular or form colonies

are eukaryotes monophyletic or non-monophyletic?

monophyletic

unicellular vs colonial vs multicellular

• unicellular: one cell does everything

• colonial: many cells are attached, but there is no division of labor/responsibilities

• multicellular: many cells are attached and they have different functions

eukaryotic synapomorphies

• linaer DNA

• membrane bound organelles: nucleus, mitochondria, chloroplast

• cytoskeleton

• mitosis

phagocytosis

• organism takes in large particles

• may/may not digest them

• if they don’t digest them, they may form a membrane around them to form a symbiont