Cyanobacteria, Bacillariophyta & Dinophyta
Objective
Today we will examine members of the Cyanophyta, Bacillariophyta and Dinophyta. We will
become familiar with aspects of their diversity, variation in morphology, and special thallus
features.
Notebook Requirements (13 drawings)
1) Oscillatoria - draw & label
2) Anabaena - draw & label
3) Nostoc -draw & label
4) Gloeotrichia - draw & label
5) Rivularia- draw & label
6) Stigonema - draw & label
7) Tolypothrix - draw & label
8) Centric diatom-identify 2, draw & label
9) Pennate diatom-identify 2, draw & label
10) Dinoflagellate-identify 2, draw & label
Introduction - Cyanbacteria
The Cyanobacteria (blue-green algae) are found within the domain Bacteria. Although the exact
number of species is debatable, many sources estimate there to be about 4,484 species
Cyanobacteria lack membrane bound organelles. However, given that they have chlorophyll A
and release oxygen through photosystems I & II, we will consider them to be “algae.” The
Cyanobacteria (also called the Cyanophyta) are the oldest organisms to give off oxygen via
Photosystems I and II and are estimated to have existed for 3.9 billion years; fossil stromatolites
(layered rocks formed by accretion of minerals around cells) date back to the Precambrian
period.
The Cyanobacteria are ubiquitous, occurring in both seawater and freshwater, on unconsolidated
substrata—endolithically in deserts and in Antarctic ice, and epilithically on tropical intertidal
limestone. They are important fixers of nitrogen, contribute to toxic red tides, and were some of
the first organisms to give off oxygen, thus playing a pivotal role in creating Earth’s oxidizing
atmosphere. Many species possess specialized thick-walled cells called heterocysts that aid in
nitrogen fixation by separating the site of nitrogen fixation from sources of oxygen.
Systematics - Cyanobacteria
Order
Thallus
Characteristics
Examples
Oscillatoriales
filamentous
fragmentation, hormogonia production,
no specialized cells
Oscillatoria,
Trichodesmium
Nostocales
filamentous
May have heterocysts, hormogonia and
akinetes, may have true or false
branching
Anabaena, Gloeotrichia
Nostoc,Callothrix,
Rivularia, Tolypothrix,
Cylindrospermum,
Stigonema
Spirulinales
filamentous
Spiral filament
Spirulina
Draw and label each specimen. Note the overall thallus morphology and any specialized cells.
Please make sure you label the Filament, Trichome, Mucilaginous Sheath, Heterocyst, and
Akinete) (if applicable).
Cyanobacteria- prepared specimans
Order OscillatorialesOscillatoria - Planktonic, hormogonia, freshwater
Q: What are hormogonia?
Q: How does Oscillatoria fix nitrogen without having specialized cells?
Order Nostocales
Anabaena - Planktonic, Produces neurotoxins that become release when they are ingested by
animals, akinetes & heterocysts visable, negative phototaxis—can steer the tip of the
filament towards light.
Q: What is the purpose of heterocysts?
Q: What is the purpose of gas and starch vacuoles? How can these vacuoles affect
movement in CyanoBacteria?
Nostoc- Often associated with fungi in lichens, filamentous, can form colonies, akinetes &
heterocysts visable
Q: How can you distinguish between Anabaena & Nostoc? Compare and contrast their
structure.
Gloeotrichia –akinates and heterocysts visable at tip
Q: What are akinetes?
Rivularia- draw & label
Q: How can you distinguish Gloeotrichia from Rivularia? Compare and contrast their
structure.
Stigonema - Inhabits moist rocks and soil, often associated with fungi in lichens, filaments
can be multiple cells in width (multiseriate)
Q: What type of branching does Stigonema exhibit?
Tolypothrix- Planktonic, often in freshwater lakes
Q: What type of branching does Tolypothrix exhibit?
Bacillariophyta & Dinophyta- live specimans
Identify, observe, draw and label:
2 Pennate diatom & 2 Centric diatom- label Raphe, Frustule, Girdle, Epithecum,
Hypothecum
Q: What type of life history do diatoms exhibit?
Q: How do diatoms move?
Q: Why do some diatoms form chains?
Q: What are diatoms made of?
2 Dinoflagellate- label Epicone, Hypocone, Undulipodium (Transverse & Longitudinal)
Q: What type of life history do dinoflagellates exhibit?
Q: How do dinoflagellates move?
Q: What is the purpose of spines?
Q: What are dinoflagellates made of?
Order Oscillatoriales
Order Nostocales
Anabaena spp
Akinete
Heterocyst
Heterocyst Akinete
Gloeotrichia spp
Nostoc spp
Rivularia spp.
Stigonema spp.- true branching
Tolypothrix- false branching, often occurs at