BIOL 456 Microbe-Microbe Symbiosis pt. 2

Red Algae

• Primary Endosymbiosis

• Mostly marine, but some freshwater and terrestrial

• Can be unicellular or multicellular

• a.k.a. Rhodophyta ( greek for ‘rose plant’)

• color is from phycoerythrin, an accessory pigment

Green Algae

Primary Endosymbiosis

• are also called chlorophytes

• Closely related to plants

• Most inhabit freshwater, but some are marine or terrestrial

• Can be unicellular to multicellular

• Have sexual and asexual reproduction

Diatoms

Secondary Endosymbiosis (red algae)

• Responsible for ~40% of primary productivity in the ocean!

• Over 100,000 species of diatoms

• Unicellular

• Freshwater and marine habitats

• Cell walls are made of silica

• Exhibit radial and pinnate symmetry

• Appeared on Earth about 200 million years ago

Diatoms

a naturally occurring, soft, sedimentary rock

Many uses

• Abrasive

• Insecticide

• Absorbent

• a stabilizing component of dynamite

• thermal insulator.

Coccolithophore

Secondary Endosymbiosis (red algae)

• Calcium carbonate plates (or scales) called coccoliths

• Important for global Carbon cycle- production of CaCO3 is a CO2 sink

• Calcification can:

• Accelerate photosynthesis

• Protect from photodamage

• Protect from viruses and grazing organisms

• Almost exclusively marine and are found in large numbers throughout the sunlight zone of the ocean.

Coccolithophore

• Chalk

• soft, white, porous, sedimentary carbonate rock

• Primarily CaCO3

• formed by coccoliths fallen to the sea floor.

Dinoflagellates

• Secondary endosymbiosis (red algae)

• Diverse marine and freshwater phototrophic organisms

• Single celled

• Have two flagella with different insertion points on the cell

• Some are free-living, and others live symbiotically with corals

• Dense suspensions of these cells are called red tides (Figure 17.10)

Dinoflagellates

• can bloom and have harmful effects in nutrient polluted warm waters

• Some associated with red tides produce a neurotoxin

• Associated with fish kills and human poisoning

• Pfiesteria piscicida is a genus of toxic _______ responsible for massive fish kills

Microbe-Microbe Ectosymbiosis

A symbiotic relationship where one organism lives on the outside of another organism.

• The smaller symbiont is often attached to the surface of the larger organisms.

Lichens

• A mutualistic relationship between a fungus and an alga or cyanobacterium

• Alga is photosynthetic and produces organic matter

• The fungus provides a habitat within which the phototrophic partner can grow protected from desiccation and erosion

Lichens

• Leafy or encrusting microbial symbioses

• Often found growing on bare rocks, tree trunks, house roofs, and the surfaces of bare soils.

Lichens

Morphology of the _______ is primarily determined by the fungal partner – many fungi can form

_____ while the diversity of phototrophs is much lower

• Fungi can secrete organic acids that promote dissolution of organic nutrients from rock surfaces

• Fungal partner protects phototroph from dehydration

• Typically grow slowly – a 2cm diameter lichen may be several years old.

Consortia

In freshwater there are microbial mutualisms called _______

Consortia “Chlorochromatium aggregatum”

Consist of green sulfur bacteria (called epibionts) and a flagellated rod-shaped bacterium

• _______ given a "genus species" name

• Green sulfur bacteria are obligate anaerobic phototrophs

• Provide partner with organic carbon (food)

• Flagellated rod allows for movement- also anaerobes

• Provide cyanobacteria with access to ideal niche via motility

Consortia

• Often found in the thermo/chemocline of stratified freshwater lakes worldwide.

• Can account for over half of the bacterial biomass in lakes

• Movement allows them to adjust to changing gradients of light, oxygen, and sulfide,

Predatory Bacteria

Fungal Parasites of Algae

reduced genomes

Many prokaryotic protist symbionts have _______

Prokaryote- Protist

_________ symbiosis are very common.

Evolutionary Pressures

prokaryote-protist vs prokaryote-animal symbioses:

• Many Similarities

• Common ________