Bluegreen Bacteria or Cyanobacteria:

Phylum Cyanophyta

Class: Cyanobacteriae

Oscillatoria

Where are they found?

• temperate polluted waters
• fresh & marine waters throughout the world
• warm to moist soils
• symbiotic relationships with amobae, protozoa, diatoms, sea anemones, cycads, and with fungi in the form of lichens
• unusual: in hot springs where they lay travertine (carbonate deposits) and in 2-4 cm mats 5m under arctic ice
• In warm shallow pools some form stromatolites, large carbonate deposits, some of which date back about 2.7 BYA

  Gloeocapsa - cells bound together only by mucilaginous matrix

Morphology:

Some are only single cells, most form colonies Chains and filiments can be bound to form sheets and other surfaces by a mucilaginous matrix Sheaths as well as the cells themselves may be pigmented yellow, red, brown, green or violet Thylakoids are single membrane Unusually large cell size for prokaryotes - up to 60 micrometers in diameter Nitrogen fixing in specialized cells- heterocysts Some can grow heterotrophically

Nostoc : Note the heterocyst

Colors:

• approx. 1/2 of 1,500 known species are blue-green in color due to the pigments chlorophyll a (green) and phycocyanin (blue);
• others are red in color due to additional phycoerythrin pigment (ex. Red Sea);
• others are yellowish due to carotenoid pigments.

Food storage:

• storage of nitrogenous compounds as cyanophycin (in heterocysts)
• carbohydrates and lipids

Movement:

• No flagella
• filamentous forms glide by rotating on axis by twisting fibrils inside the cell walls & secreting a mucilagenous sheath

Reproduction:

• asexual via cell fission and fragmentation of colonies (in some species at the heterocyst)
• delayed reproduction via akinetes, resist freezing and stress, can germinate decades later
• no sex in the usual sense (ie gametes); genetic recombination like other bacteria
• in symbionts, wait to divide with host cell; act as chloroplast with no cell wall

Ecological significance:

Fossils 3.5 BYA; started to produce oxygen 3 BYA, which allow buildup of ozone Bottom of the food web Blooms: floating scum in summer, toxic when die and decompose, oxygen levels drop w/ decomposition; foul water taste and odor Toxic forms can hit fish directly or become toxic when ingested, usually mild Parasitic in humans and other animals Clog up water supply filters, soften water excessively Food to humans limited; Spirulina Fix nitrogen: very important role in oceans, may fix 1/4 of N; in human rice paddies act as fertilizers

anabaena - important in N-fixing

Class: Prochlorobacteriae

Discovered recently on sea squirts and deep dim light ocean layers, may be one of the top 2 species in oceans

Single cell prokaryotes, bright green in color (chl a & b); no phycobilins, do have carotenoids, double membrane thylakoids.

Special interest: closely related to the organisims that may have given rise to the chloroplast, containing chl a & b.