Chapter 5: The Microbial World Part Two: Unicellular Eukaryotes.

Chapter 5:The Microbial World

Part Two:

Unicellular Eukaryotes

The Classification of Organisms

Domain Bacteria Domain Archaea Domain Eukarya

Kingdom Protista

Kingdom Animalia

Kingdom Plantae

Kingdom Fungi

EukaryotesProkaryotes

Kingdom: ProtistaThe Unicellular Algae

Algae (singular: alga) are simple mostly aquatic mostly photosynthetic eukaryotic lack flowers have no true roots, stems, or leaves

A Constant Struggle Unicellular algae are mostly planktonic - must

do two things to survive: Remain in the photic zone where light is abundant. Remain dispersed in the water column to obtain

dissolved nutrients.

Strategies to slow their sinking rate… increase SA:V ratio create zig-zagging chains and spirals possess cellular projections contain low-density oils and fats have gas-filled vesicles

Unicellular Algae – A Difficult Classification

Some species float free and conduct photosynthesis.

Other species move around and eat food particles like animals.

Some do both!A dinoflagellate in motion. Courtesy of Dinoflagellates by Jean-Marie Cavanihac, France.

http://www.microbeworld.org/htm/aboutmicro/microbes/types/protista.htm

DiatomsPhylum: HeterokontophytaClass: Bacillariophyta

Unicellular, though many species aggregate in chains or clusters.

Have a cell wall composed of silica (SiO2)

Nearly 16,000 species

Mostly planktonic

About 50% of species marine/ and 50% inhabit freshwater

http://micro.magnet.fsu.edu/primer/techniques/hoffmangallery/diatom.html

DiatomsPhysical Morphology

The siliceous skeletons of diatoms preserved in lake sediment, Lake Toskaljarvi, Finland.

The image represents an area approximately 70 µm (7/100 mm) wide.

Sample courtesy of Prof. Roy Thompson and Shirley Derrick, Geology and Geophysics, University of Edinburgh.

www.geos.ed.ac.uk/ facilities/sem/diatoms.html


From Castro, P. & M.E. Huber (2005) Marine Biology, 5th ed. McGraw-Hill, Boston, MA.


Frustule – the glassy, box-like shell of diatoms consisting of two tight-fitting halves. Epitheca – upper, outside fitting

half that overlaps the hypotheca Hypotheca – lower, inside fitting

half May contain intricate perforations,

spines, or projections.

http://www.ucmp.berkeley.edu/chromista/diatoms/diatommm.html


Two main skeletal plans:

centrate – are radially symmetrical mostly found in marine environments

pennate – are bilaterally symmetrical

mostly found in freshwater environments

http://www.ucmp.berkeley.edu/chromista/diatoms/diatomsy.html

Melosira Pinnularia

DiatomsReproduction

Mostly reproduce asexually by cell division. Each half of the frustule separates, and

each secretes a new smaller, hypotheca. Small diatoms may regain their former size,

by forming an auxospore. Auxospores can be produced by the

expansion of a frustule or by sexual reproduction of an egg cell and a sperm cell from separate diatoms.

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/wimsmall/diadr.html

DiatomsReproduction


Mostly reproduce asexually by cell division.

From Castro, P. & M.E. Huber (2005) Marine Biology, 5th ed. McGraw-Hill, Boston, MA.

DiatomsEcological Role in Aquatic Environments

Important open-water primary producers, especially in arctic and temperate food chains.

Contain yellow-brown carotenoid pigments as well as chlorophyll a and c.

When nutrient and light conditions are favorable, rapid reproduction called a bloom occurs.

Get smaller Due to silicate limitations in the water.

Blooms usually occur in late winter/early spring.


DiatomsEcological Role and Human Applications

When diatoms sink out of the photic zone and die they form thick deposits called diatomaceous ooze.

Fossil deposits of diatoms found on land are called diatomaceous earth.

Mined and used for: swimming pool and aquarium filters clarifying beer abrasive cleansers sound and temperature insulation toothpaste.

Diatomaceous earth deposit near Lovelock, NV. © Judy Mosby

http://epod.usra.edu/archive/epodviewer.php3?oid=160608 http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/wimsmall/diadr.html

DinoflagellatesGeneral Characteristics

unicellular, planktonic marine posses two flagella outer armor, or theca,

composed of a cell wall of cellulose

may have spines, pores, or other projections

reproduce by simple cell division

http://www.mbari.org/staff/conn/botany/dinos/alimon/default.htm

Gonyaulax polyedra

Video

DinoflagellatesGeneral Ecology

most photosynthesize – important primary producers zooxanthellae in corals

many can ingest food particles Pfeisteria sp.

some possess light-sensitive pigment spot

some release toxins – form HABs some bioluminescent

Leucocryptos marina (Braarud) Butcher 1967, Marine Botany group in the Department of Marine Ecology, Göteborg University, Sweden.

Silicoflagellates

very small (2-20 µm) photosynthetic marine have a hard skeleton of

silica (plasticity) 2-8 spines projecting have two flagella reproduce by simple cell

division – produce blooms

http://www.mbari.org/staff/conn/botany/phytoplankton/phytoplankton_silicoflagellates.htm

Coccolithophorids (Coccoliths)“round stone bearers”

0.2 - 40 µm unicellular, usually spherical photosynthetic flagellated cell wall of calcareous plates

(made of calcite) called coccoliths.

prefer still, nutrient-poor water of mild temperature

reproduce asexually mostly, but also sexually

Coccolith Variation

CoccolithophoresImplications for Ocean Science

form blooms contribute 1.5 million

tons of calcite to ocean sediments limestone & chalk

deposits produce CO2 increase ocean

albedo important food

source for zooplankton

Sample, Sharron. "Remote Sensing of the Ocean." Science@NASA. 21 Jun 2005. NASA. 2 Apr 2008 <http://science.hq.nasa.gov/oceans/living/sensing.html>.

Phylum: CryptophytaCryptophytes

Small (<100 µm), unicellular Found in freshwater and marine

environments. contains endosymbiont chloroplasts that

have retained their DNA (nucleomorph) possess red & green photosynthetic

pigments Two flagella for movement No presence in the fossil record.

Phylum: GranuloreticulosaForaminiferans

protozoans – ‘first animals’ Heterotrophic Unicellular

shell or test, made of calcium carbonate

pseudopodia – retractable cytoplams extensions for movement.

eat diatoms live attached to the bottom;

few planktonic species form foraminiferan ooze –

indicator of oil deposits and the ages of sediments

http://images.google.com/imgres?imgurl=http://www.dkimages.com/discover/previews/755/234382.JPG&imgrefurl=http://www.dkimages.com/discover/Home/Plants/Fungi-Monera-Protista/Protozoa/Pseudopods/Foraminiferans/Foraminiferans-4.html&h=344&w=425&sz=25&hl=en&start=1&um=1&tbnid=2TKvN05SOCwBaM:&tbnh=102&tbnw=126&prev=/images%3Fq%3Dforaminiferans%26ndsp%3D20%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN

Foraminiferan Diversity

http://images.nbii.gov/details.php?id=65322&cat=Protists

ForaminiferansForaminiferans

Phylum: Polycystina:Radiolarians

planktonic protozoans 2-30 µm ubiquitous, but most abundant in low

latitude oceans secrete shells of silica

thin pseudopodia capture food

most predatory some symbiotic with

algae some filter feed

can form large colonies sink to bottom to form

radiolarian ooze (siliceous ooze)

more resistant to pressure than foraminiferans

can reproduce asexually and sexually

http://micro.magnet.fsu.edu/micro/gallery/radiolarians/radiolarians.html

RadiolariansRadiolarians

Radiolarians

Phylum: CiliophoraCiliates

Protozoans with cilia Small (usually > 100µm) May be free-living or colonial May be commensal, parasitic, or

predatory Important in microbial loops of the open

ocean (cycle DOM into plankton)

Phylum: Ciliophora Tintinnids

Marine ciliates Create vase-like

shells called loricas. Eat a wide variety of

cells and detritus.

Tintinnids

References

Braby, Caren E.. "Coccolithophorids Quick Facts." Phytoplankton. 2001. Monterey Bay Aquarium Research Institute. 2 Apr 2008 <http://www.mbari.org/staff/conn/botany/phytoplankton/phytoplankton_coccolithophorids.htm>.

Geisen, Markus. "Syracosphaera anthos".Plakntonnet@Roscoff. 2001. Courtesy of Young, Jeremy. The Natural History Museum. London. Accessed 2 Apr 2008 <http://www.mbari.org/staff/conn/botany/phytoplankton/phytoplankton_coccolithophorids.htm>.

King, Michael D.. "What is a Coccolithophore?." Earth Observatory. NASA. 2 Apr 2008 <http://eobglossary.gsfc.nasa.gov/Library/Coccolithophores/printall.php>.

Lane, C. E., Khan, H., MacKinnon, M., Fong, A., Theophilou, S., and Archibald, J.M. Insight into the Diversity and Evolution of the Cryptomonad Nucleomorph Genome Molecular Biology and Evolution 2006 23(5):856-865; doi:10.1093/molbev/msj066

Moran, Dawn. "Tintinnid." Oceanus the magazine that explores the ocean depths. 02 Mar 2007. Woods Hole Oceanographic Institution. 16 Nov 2008 <http://www.whoi.edu/oceanus/viewSlideshow.do?clid=1410&aid=2473&mainid=5580&p=5578&n=5582>.

Sample, Sharron. "Remote Sensing of the Ocean." Science@NASA. 21 Jun 2005. NASA. 2 Apr 2008 <http://science.hq.nasa.gov/oceans/living/sensing.html>.

Chapter 5: The Microbial World Part Two: Unicellular Eukaryotes.

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