Sulphur Cycle Definition, Steps, Diagram, Importance and Facts

Sulphur is one of the elements that can be found in the greatest quantities on our planet. It is a non-metal that is yellow in colour, brittle, odourless, and tasteless. Sulphur can be found in many different types of proteins. Methionine, cystine, and cysteine are examples of amino acids that include sulphur that can be directly absorbed by plants.

The combustion of fossil fuels, volcanic activity, and the breakdown of organic molecules are all processes that result in the emission of sulphur into the atmosphere.

Sulphur is typically found buried deep inside the rocks and minerals of the soil. The weathering of rocks and geothermal vents both contribute to its release into the environment. 

Sulphur cycle

The following is an explanation of the process known as the sulphur cycle:

• The process of rocks being exposed to the elements causes the release of sulphur.

• When sulphur comes into contact with air, it undergoes a chemical reaction that transforms it into sulphates.

• Plants and microorganisms are responsible for the conversion of sulphates into organic forms after they have taken up the sulphate.

• After that, the organic form of sulphur is ingested by the animals through the food that they eat, and this causes sulphur to travel up the food chain.

• When the animals pass away, part of the sulphur is released as a byproduct of the decomposition process, and some of it is taken up by the bacteria that consume the dead animals.

• Sulphur is released directly into the atmosphere through a number of natural processes, the most well-known of which are volcanic eruptions, the evaporation of water, and the decomposition of organic waste in swamps. This sulphur is brought down to earth by precipitation. 

Steps of sulphur cycle

The following is an outline of the significant stages of the sulphur cycle: 

Decomposition of Organic Compounds 

The breakdown of proteins results in the release of amino acids that include sulphur. Desulfotomaculum bacteria are responsible for the reduction of sulphates to hydrogen sulphide (H2S). 

Oxidation of Hydrogen Sulphide to Elemental Sulphur

Hydrogen sulphide oxidised to yield elemental sulphur. The first step in the oxidation process is taken by certain photosynthetic bacteria belonging to the families Chlorobiaceae and Chromatiaceae. 

Oxidation of elemental sulphur

The plants are unable to immediately make use of the elemental sulphur that is present in the soil. Chemolithotrophic bacteria are responsible for its subsequent transformation into sulphates. 

Reduction of sulphates

Desulfovibrio desulfuricans is responsible for the reduction of sulphates to hydrogen sulphide. This is accomplished in two stages:

• In the beginning, ATP is utilised in order to convert the sulphates into the sulfites.

• Second, the transformation of sulfite into hydrogen sulphide via the reduction process. 

Importance of sulphur cycle 

The sulphur cycle is of the utmost importance since it elucidates the workings of a variety of biomolecules, which is necessary for a full comprehension of their processes. The sulphur cycle maintains equilibrium in the concentration of sulphur across the earth’s many reservoirs, contributing to the preservation of the planet’s habitability and the ecological system that supports life on it. 

Due to the fact that sulphur is frequently found in nature in a combined state with other elements such as iron, phosphorus, nitrogen, and so on, the availability of several other elements is also affected by the sulphur cycle. These elements include: The terrestrial component of the sulphur cycle is made up of a number of biological activities, each of which plays an important part in increasing the amount of sulphur that is accessible for use by microbial life and plant life. The chemoautotrophic sulphur bacteria that are a part of the food chain are responsible for converting the chemical energy into a variety of various forms, which ultimately results in an increase in the amount of biomass on the planet. 

The sulphur cycle can be used to gain an understanding of the physiology of the various microorganisms that are involved in the process of sulphur conversion. Studying the metabolic pathways of sulphur in pathogenic bacteria like Mycobacterium tuberculosis is important for a number of different reasons that have to do with the treatment of various medical conditions. Sulphur is a major source of energy in these bacteria. The process of sulphur mineralization that is part of the sulphur cycle is a natural method for the disposal of waste because it is also responsible for the regeneration of the sulphur compounds. 

Human impact 

The global sulphur cycle is significantly altered as a result of human activity. Burning fossil fuels like coal, natural gas, and other fossil fuels has resulted in a significant increase in the quantity of sulphur found in the atmosphere and ocean as well as a reduction in the amount of sedimentary rock that can absorb sulphur. In the absence of human influence, sulphur would remain bound up in rocks for millions of years, during which time it would be liberated only after being uplifted by tectonic events and then subjected to the processes of erosion and weathering. Instead, there is a steady increase in the amount of drilling, pumping, and burning that is taking place. In the most contaminated locations, there has been a thirtyfold increase in the amount of sulphate that has settled there. 

Conclusion

One of the components that are necessary for the formation of proteins and vitamins is sulphur. Amino acids are the building blocks of proteins, and some of these amino acids have sulphur atoms. Proteins and enzymes in plants, as well as animals that obtain their supply of sulphur from plants, require the presence of sulphur in order to operate properly. Sulfur that has been dissolved in water can be taken up by plants. These plants are consumed by animals, which allows them to obtain the necessary amount of sulphur to sustain their health.