Ocean microbes

Question 1

What are the 5 ocean basins?

Answer 1

Arctic, Pacific, Atlantic, Indian, Southern (Antarctic ocean)

Question 2

Oceanic islands

Answer 2

Typically a result of volcanic activity and not associated with the continental shelf

Often isolated with endemic flora/fauna

Productive marine environment (local upwelling)

Question 3

What are oceanic islands hotspots for?

Answer 3

Evolutionary novelty

Hawaiian Bobtail Squid (Euprymna scolopes) - Uses bioluminescence for counter-shading at night

Luminescence derived from Vibrio fischeri hosted within specialised light organ - chromatophores

Question 4

What are abyssal plains?

Answer 4

Marine snow – dead decomposed things

Fuelled by ephemeral (occasional) nutrients

Question 5

What are byssal plains?

Answer 5

Fuelled by allochthonous input from the water column

Highly ephemeral nutrient/ food

Specialised taxa - e.g. bone eating worms that burrow into whale bones

Worms have symbiosis with bacteria so they can digest bone

Question 6

What are hydrothermal vents?

Answer 6

Extreme environments (e.g. high temperature, high H2S and CO2 concentrations)

Highly productive - fuelled by sulphur metabolising bacteria

Bacteria symbiotic with giant tube worms - bacteria metabolise so worms don’t eat anything

Riftia pachyptila harbour sulphur oxidising bacteria their ‘gut’ (trophosome)

Question 7

How much water in the ocean what percentage does it cover?

Answer 7

98% of earths water is the oceans

Covers 70% of earths surface

Volume 1.3 x 10^9 km^3

Question 8

How do oceans shape the planet?

Answer 8

Determinate of contemporary weather/climate

Reservoir for important element/chemicals (e.g. carbon, phosphate, water)

Source of atmospheric oxygen - allowing plants to grow - photosynthesis by the cyanobacteria

Question 9

How much of global primary production occurs in the oceans? What does this impact?

Answer 9

(45%) of global primary production occurs in the oceans

Impacts atmospheric CO2 concentration - result of photosynthetic microbes

Question 10

What are the limitations of ocean photosynthesis?

Answer 10

Confined to upper sunlit waters (the photic zone)

Challenging for organisms to survive - low nutrient availability

Question 11

What is flow cytometry? What has it found?

Answer 11

Detects very small cells and their properties - Laser passes past cell showing wavelengths of light

Two cyanobacterial species dominate the worlds oceans:
Prochlorococcus
Synechococcus

Question 12

Size, population and formation/ adaption of Prochlorococcus?

Answer 12

Cells 0.5-0.7 um

Unusually form of chlorophyll a/b

Global population - 3x10^27 - fixes 4 gigatons of carbon yr-1

Adapted to warm tropical, oligotrophic regions/mid latitudes

Question 13

Size, population and adaption of Synechococcus?

Answer 13

1.5 um diameter

Globally distributed - 1x10^6

Everywhere but dominant at higher latitudes

Question 14

How are Prochlorococcus and Synechococcus highly diverse and highly adaptable?

Answer 14

Ecotypic diversity

High rates of gene transfer between cells (horizontal gene
transfer – HGT)

Question 15

What are ecotypes?

Answer 15

Ecotypes are genetically and physiologically defined subgroups of a species that occupy different ecological niches

E.g. differently adapted to light/temperature

Question 16

How is Prochlorococcus ectopically diverse?

Answer 16

100s of ecotypes and highly flexible genome

Each cell 1,700 to 2,500 genes

> 80,000 genes across all know ecotypes (largest known pan- genome)

Enormous amount of genes

High rates recombination – maintains ecotypic diversity

Horizontal gene transfer by cyanophage – i.e. viruses (transduction)

HGT via production of DNA/RNA containing vesicles - Vesicles containing genetic material bind with other cells

Question 17

Why has the primary producer niche in the oceans has been filled by a couple of highly adaptable species rather than many different species?

Answer 17

Very low nutrient concentrations mean that advantageous to have high surface:volume