LAB 1 - Winogradsky Column

Question 1

Sergei Winogradsky discoveries

Answer 1

• Lithotrophy
• Chemoautotrophy
• Development of techniques to harness metabolic capabilities of microbes

Question 2

Sediments become progressively more ________ with depth from surface

Answer 2

Anaerobic

Question 3

Two groups of microbes restricted to aerobic or anaerobic conditions

Answer 3

• Sulfate reducing bacteria
• Anaerobic marine photosynthetic bacteria

Question 4

Sulfate reducing bacteria and anaerobic marine photosynthetic bacteria

Answer 4

Rely on the activities of other microbes to generate both the appropriate conditions of anaerobiosis and appropriate substrates to enable growth

Question 5

Winogradsky column

Answer 5

• Type of enrichment culture in which the population and activities of aerobic and anaerobic microbes are stimulated
• Provides numerous gradients of nutrients, oxygen/anaerobiosis, and light
• The products of the activities of one population become the substrates for the growth of other populations, the column thus becomes a microcosm of interacting biological and metabolic processes

Question 6

What processes occur in the winogradsky column overtime with regard to oxygen and other nutrient gradients?. Comment on the conditions necessary for, or which enhance, the microbiological changes that have occurred within the column.

Answer 6

• The surface remains oxygen-rich, supporting aerobic bacteria and photosynthetic organisms like cyanobacteria.
• Deeper layers become anaerobic as oxygen is consumed, favoring sulfate-reducing bacteria that produce hydrogen sulfide (H₂S).
• Organic matter decomposition drives nutrient cycling, while light penetration enables photosynthesis. Over time, the column shifts from aerobic to anaerobic conditions

Question 7

What are the major groups of photosynthetic prokaryotes and what characteristics are important in identifying them

Answer 7

• Cyanobacteria
• Purple sulfur bacteria
• Purple non-sulfur bacteria
• Green sulfur bacteria
• Heliobacteria
• key characteristics differentiating photosynthetic prokaryotes are their pigments, electron donors, oxygen production (oxygenic or anoxygenic)

Question 8

Did you observe black deposits in any of the columns? Where were these located and what do you think they are?

Answer 8

• Black deposits are typically observed in the anaerobic, lower regions of the Winogradsky column.
• They are likely iron sulfide (FeS), formed when sulfate reducing bacteria reduce sulfate to hydrogen sulfide (H₂S), which reacts with iron in the sediment.

Question 9

Materials of a winogradsky column

Answer 9

• Fine sediment from a pond or beach supplemented with 0.25% calcium carbonate and 0.5% calcium OR sodium sulfate
• Shredded paper or hay (for cellulose)
• Additional anaerobic layer of unsupplemented sediment
• Ambient water to saturate the sediment
• Placed in strong natural light to support photosynthesis