Fossil fuel also represent a reservoir of carbon. Carbon cycling occurs through atmosphere, ocean and through living and dead organisms. According to one estimate, 4 × 10¹³ kg of carbon is fixed annually in the biosphere through photosynthesis. A considerable amount of carbon returns to the atmosphere as CO₂ through respiratory activities of the producers and consumers. Decomposers also contribute substantially to CO₂ pool by their processing of waste materials and dead organic matter of land or oceans. Some amount of the fixed carbon is lost to sediments and removed from circulation. Burning of wood, forest fire and combustion of organic matter, fossil fuel, volcanic activity are additional sources for releasing CO₂ in the atmosphere.

The role of bacteria in the carbon cycle is :

Breakdown of organic compounds

The correct answer is Option (1)- Breakdown of organic compounds

Carbon cycle is series of processes that interconverts the carbon compounds in the environment. It recycles the carbon back in the environment.Bacteria are decomposers, which means they break down dead organisms and other organic matter. This process releases carbon dioxide into the atmosphere, which is a key step in the carbon cycle.Through this decomposition, they release carbon dioxide (CO₂) into the atmosphere, contributing to the carbon cycle.

Bacteria also play a role in other steps of the carbon cycle, such as chemosynthesis and nitrogen fixation. However, their primary role is to break down organic compounds.