Bacteria in the ocean that mediate the microbial carbon pump (MCP), are reported to substantially influence the carbon cycle of the Earth system. These tiny unicellular organisms, probably smaller than 1 micrometer are playing a disproportionately large role in a process called carbon sequestration. In this process, they take up labile organic carbon produced by phytoplankton, and transfer it into the recalcitrant form that can resist from degradation for thousands of years, and eventually remove carbon dioxide from the atmosphere. They act functionally as a “pump” by sucking anthropogenic greenhouse gases into the ocean interior, and thus regulating the global climate. Therefore, the MCP is considered an “invisible hand” behind the vast oceanic dissolved carbon reservoir.