Chapter 5: The Microbial World Part Two: Unicellular Eukaryotes

The Classification of Organisms Domain BacteriaDomain ArchaeaDomain Eukarya Kingdom Protista Kingdom Animalia Kingdom Plantae Kingdom Fungi EukaryotesProkaryotes

Kingdom: Protista The 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 SSome species float free and conduct photosynthesis. OOther species move around and eat food particles like animals. SSome do both! A dinoflagellate in motion. Courtesy of Dinoflagellates by Jean-Marie Cavanihac, France. Dinoflagellates

Diatoms Phylum: Heterokontophyta Class: Bacillariophyta  Unicellular, though many species aggregate in chains or clusters.  Have a cell wall composed of silica (SiO 2 )  Nearly 16,000 species  Mostly planktonic  About 50% of species marine/ and 50% inhabit freshwater

Diatoms Physical 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. facilities/sem/diatoms.html

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

Diatoms Physical Morphology  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.

Diatoms Physical Morphology  Two main skeletal plans: centrate – are radially symmetrical mostly found in marine environments pennate – are bilaterally symmetrical mostly found in freshwater environments Melosira Pinnularia

Diatoms Reproduction  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. uk.org.uk/mag/wimsmall/diadr.html

Diatoms Reproduction Mostly reproduce asexually by cell division. From Castro, P. & M.E. Huber (2005) Marine Biology, 5 th ed. McGraw-Hill, Boston, MA.

Diatoms Ecological 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. uk.org.uk/mag/wimsmall/diadr.html

Diatoms Ecological 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

Dinoflagellates General 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 Gonyaulax polyedra Video

Dinoflagellates General 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.Marine Botany group in the Department of Marine Ecology

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

Coccolithophorids (Coccoliths) “round stone bearers”  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

Coccolithophores Implications for Ocean Science  form blooms  contribute 1.5 million tons of calcite to ocean sediments limestone & chalk deposits  produce CO 2  increase ocean albedo  important food source for zooplankton Sample, Sharron. "Remote Sensing of the Ocean." 21 Jun NASA. 2 Apr 2008.

Phylum: Cryptophyta Cryptophytes  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: Granuloreticulosa Foraminiferans  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 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

Foraminiferans

Foraminiferans

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

Radiolarians

Radiolarians

Radiolarians

Radiolarians

Radiolarians

Radiolarians

Phylum: Ciliophora Ciliates  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 Monterey Bay Aquarium Research Institute. 2 Apr Geisen, Markus. "Syracosphaera Courtesy of Young, Jeremy. The Natural History Museum. London. Accessed 2 Apr King, Michael D.. "What is a Coccolithophore?." Earth Observatory. NASA. 2 Apr 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 (5): ; doi: /molbev/msj066 Moran, Dawn. "Tintinnid." Oceanus the magazine that explores the ocean depths. 02 Mar Woods Hole Oceanographic Institution. 16 Nov Sample, Sharron. "Remote Sensing of the Ocean." 21 Jun NASA. 2 Apr 2008.