**3.2 Microscopical level: engineered microorganisms**

Modern climate change mitigation techniques have included the use of biotechnology and engineering technologies at the cellular level in recent years. Microorganisms, both autotrophic and heterotrophic, can be genetically modified to boost their CO2 sequestration ability, notably by increasing microbial CO2 fixing and decreasing CO2 release. Due to the presence of a complete CO2-fixing pathway and the ability to transfer energy from sunlight and inorganic compounds into cellular metabolites, autotrophic bacteria have evolved to subsist only on CO2. Heterotrophic microbes, on the other hand, rely on organic substances to thrive [42]. Therefore, the autotrophs could be engineered to improve the efficiency of their CO2-fixing pathway, energyharvesting systems and to regulate their cell resources, whereas the heterotrophs could be engineered to improve their carboxylation reactions in the metabolic pathways, to establish non-native CO2-fixing bypass and ultimately to engineer them into autotrophs (**Table 1**).


*Regenerating Soil Microbiome: Balancing Microbial CO2 Sequestration and Emission DOI: http://dx.doi.org/10.5772/intechopen.104740*

#### **Table 1.**

*Selected strategies to improve microbial CO2 sequestration.*

Modifications of both autotrophic and heterotrophic microorganisms to increase their efficiency in CO2 sequestration *via* genetic engineering approaches are highly promising strategies for mitigating climate change. Lower costs of production and the naturally rapid growth rate of soil microorganisms should accelerate its adoption as a reliable CO2 sequestration strategy. Furthermore, microbial CO2 sequestration can be applied directly to complement agricultural activities on the same land compared with conventional CO2 sequestration technologies that require purpose-built infrastructures that compete for land resources [53].
