## 4 Discussion
To address this issue, ANI and dDDH analyses, combined with complete genome sequences, provide more precise phylogenetic resolution [65]. In our study, ANI and dDDH analyses revealed that _Geobacillus_ sp. G4 is closely related to _G. thermolevorans_ KCTC3570, with ANI values above 97% and dDDH values exceeding 83%. These results are consistent with previous studies indicating that species such as _G. kaustophilus_ and _G. thermolevorans_ could be conspecific, suggesting ongoing taxonomic revisions [66]. Phylogenetic analysis corroborates this relationship, showing that _Geobacillus_ sp. G4 aligns within the _G. thermolevorans_ clade, indicating an evolutionary proximity. In the genome of _G. thermolevorans_ G4, key enzymes for the degradation of complex carbohydrates, such as amylases and pullulanase, were identified. These enzymes play essential roles in breaking down starch and pullulan into simpler sugars. These enzymes are widely reported in other _Geobacillus_ strains [57], reflecting the metabolic versatility of this bacterium in starch and sucrose degradation. The enzymatic classes of hydrolases, transferases, and oxidoreductases are essential for the metabolism and adaptation of _Geobacillus_ to extreme environments. Hydrolases enable the breakdown of biomolecules and the acquisition of nutrients under limited conditions. Transferases regulate biosynthesis and metabolic pathways, facilitating environmental adaptation. Oxidoreductases are crucial for energy production and defense against oxidative stress. The abundance of these enzymes in the _G. thermolevorans_ sp. G4 genome highlights its ability to adapt and survive in harsh environments. Concerning the biotechnological potential of _G. thermolevorans_, extensive research has focused on identifying enzymes capable of withstanding extreme environmental conditions, such as elevated temperatures and the presence of inhibitory substances [67; 68]. Several enzymes from extremophiles have been identified as interesting tools for industrial processes, including biomass deconstruction in biorefinery [69; 70]. Here, we describe a new strain of _G. thermolevorans_ with the potential to produce several industrially relevant enzymes, including more specific endoglucanases (evaluated against carboxymethylcellulose) and pectinases. Cellulases derived from organisms capable of surviving extreme temperatures are extensively documented targets for biotechnological applications because of their ability to withstand prolonged exposure to high temperatures while maintaining catalytic activity [71; 72]. The capacity of _G. thermolevorans_ to grow in the presence of pectin highlights its potential to degrade other complex carbohydrates present in plant cell walls. Despite an increasing number of reports describing thermophiles that can grow in the presence of cellulose-based polymers, there are few studies describing such organisms as capable of growing in the presence of other complex carbohydrates, such as pectin. The ability of _G. thermolevorans_ to grow in the presence of pectin may indicate its diverse potential to degrade such complex polymers, which require enzymes with different modes of action, including esterases, lyases, and glycosyl hydrolases [73; 74]. To date, the potential of this bacterium to degrade complex carbohydrates has not been explored; however, closely related species have been described as potential producers of pectin lyases [75]. The strain explored in the present study could grow in the presence of starch, which may be a direct consequence of the diversity of starch-degrading enzymes produced by this organism. _G. thermolevorans_ has been reported to be a good producer of hyperthermostable amylases, including maltogenic \(\alpha\)-amylase [76]. The results shown in the present study and previous literature call attention to further heterologous expression and characterization of such enzymes with untapped biotechnological potential.