Back to: MICROBIOLOGY 400 LEVEL
Welcome to class!
Hello there, brilliant mind! It’s wonderful to have you here again. Today, we’re continuing our journey into how microbes quietly help keep life on Earth running smoothly. Just like we saw with carbon and nitrogen, two other important nutrients that cycle through nature are sulfur and phosphorus. These cycles might not be as famous, but they are just as essential—especially in supporting plant growth, clean water, and healthy soils. So, let’s take a closer look at Sulfur and Phosphorus Transformations and how microbes make them happen.
Sulfur And Phosphorus Transformations
Sulfur Transformations
Sulfur is found in amino acids, vitamins, and some enzymes. It’s vital for both plants and animals. Microorganisms are responsible for moving sulfur between its different forms in the environment.
Key Microbial Processes in the Sulfur Cycle:
Sulphur Oxidation
Certain bacteria like Thiobacillus convert hydrogen sulfide (H₂S) or elemental sulfur (S) into sulphate (SO₄²⁻), which is a form that plants can absorb from the soil.
For example, in places like Niger Delta swamps or dumpsites with rotting matter, sulphur-oxidising bacteria are at work.
Sulphate Reduction
In areas with little or no oxygen—such as deep soil or waterlogged environments—sulphate-reducing bacteria like Desulfovibrio convert sulphates into hydrogen sulfide (H₂S), a gas with a rotten egg smell.
Decomposition
When plants and animals die, decomposer bacteria break down organic matter and release sulphur back into the soil in a form that other microbes can act on.
Phosphorus Transformations
Phosphorus is needed for DNA, ATP (which gives cells energy), and cell membranes. Unlike nitrogen and carbon, phosphorus does not go into the atmosphere—it stays in the soil and water.
Key Microbial Processes in the Phosphorus Cycle:
Mineralisation
Microorganisms like Bacillus and Pseudomonas break down dead plants and animals, releasing inorganic phosphate (PO₄³⁻) into the soil.
Solubilisation
Some microbes produce acids that dissolve phosphate minerals in the soil, making phosphorus available to plants. These are called phosphate-solubilising bacteria (e.g. Aspergillus, Penicillium, Rhizobium).
Immobilisation
This is when microbes temporarily store phosphorus inside their cells, making it unavailable to plants. Later, when these microbes die, the phosphorus is released again through decomposition.
Mycorrhizal Associations
Some fungi form a close relationship with plant roots and help absorb phosphorus from the soil in exchange for sugars. These fungi are found even in Nigerian farmlands.
Why These Cycles Matter in Nigeria
Sulphur and phosphorus transformations help enrich our soil naturally, supporting farming in areas like Benue, Kano, and Ogun.
Microbial phosphorus release reduces the need for expensive chemical fertilisers.
Understanding these cycles helps us manage waste better and avoid water pollution from excess nutrients (e.g. in Lagos lagoons or the River Benue).
Summary
- Microbes are involved in transforming sulfur and phosphorus in nature.
- Sulphur is essential for proteins and vitamins, while phosphorus is needed for energy and DNA.
- Sulphur-oxidising bacteria like Thiobacillus convert sulphur into plant-usable forms.
- Sulphate-reducing bacteria like Desulfovibrio produce hydrogen sulfide in anaerobic environments.
- Phosphorus cycles do not involve the atmosphere—it stays in soil and water.
- Mineralisation releases phosphorus from dead organisms.
- Phosphate-solubilising microbes make phosphorus available to plants.
- Mycorrhizal fungi help plants absorb phosphorus.
- These cycles improve soil fertility and support agriculture in Nigeria.
Evaluation
- Name two microbes involved in the sulfur cycle and explain their roles.
- How do phosphate-solubilising microbes help in farming?
- What is the difference between mineralisation and immobilisation in the phosphorus cycle?
You’re gaining the knowledge that keeps ecosystems, farms, and even our food supply running smoothly. Keep going—you’re learning how to care for the Earth itself. Afrilearn is so proud to walk this learning journey with you. See you in the next class!