## 4 Discussion
Genes involved in metabolic categories such as nutrient metabolism, molecule transport, transcription, DNA replication, and repair are fundamental to ensuring the survival and adaptation of _Geobacillus_ sp. G4 in extreme environments [18]. Nutrient metabolism and molecule transport ensure that the bacterium can absorb and process a wide variety of carbon and energy sources, which is essential in habitats with limited resources or adverse conditions. Genes related to transcription and replication ensure the regulation and efficient reproduction of genetic material, while DNA repair genes are crucial for maintaining genomic integrity, especially in environments that expose the organism to stress factors such as heat, radiation, or oxidative compounds [77]. The presence of pathways for glucose-6-phosphate and fructose-6-phosphate metabolism highlights the adaptation of _G. thermoleevorans_ G4 to carbohydrate-rich environments. Furthermore, enzymes associated with cellulose and cellobiose processing indicate a robust capacity to degrade lignocellulosic materials, an important resource for biofuel production, as well as efficient adaptation for energy production via glycolysis, reflecting the metabolic versatility and adaptation of _Geobacillus_ to various ecological niches, including extreme environments [78]. The _G. thermoleevorans_ G4 strain also harbors genes related to antibiotic resistance, such as the vanY/vanB_cl and vanT/vanG_cl clusters, associated with glycoptide resistance [79], with similarity ranging from 34% to 36% with other _Geobacillus_ species. These findings suggest potential for studies on antimicrobial resistance, which could have important implications for understanding the evolution of bacterial resistance. This study highlights the identification of seven biosynthetic gene clusters associated with secondary metabolites, including betalactones, terpenes, and, notably, fengycin. Fengycin is a well-known antimicrobial lipoprotein typically produced by mesophilic _Bacillus_ species; however, its occurrence in thermophilic _Geobacillus_ species has not been previously reported [80; 81]. Studying fengycin from _G. thermoleevorans_ G4 could uncover novel structural features, enhanced stability, or unique biological activities, highlighting its potential for innovative industrial and pharmaceutical applications. During carbon starvation, bacteria activate specific mechanisms, including the expression of genes such as _cstA_, _relA_, and _spoT_, to maintain cellular viability. The _cstA_ gene encodes a peptide transporter that is upregulated during nutrient limitation and regulated by _CsrA_, while _relA_ and _spoT_ mediate the stringent response through the synthesis of (p)ppGpp, which modulates global gene expression and protein synthesis to adapt to stress conditions [82; 83; 84]. To preserve genomic integrity, _G. thermoleevorans_ G4 possesses conserved DNA repair systems such as nucleotide excision repair (NER) and mismatch repair (MMR). NER, involving _uvrA_, _uvrB_, and _uvrC_, is critical for correcting UV-induced lesions and bulky adducts [85]. Likewise, MMR, mediated by _mutN_ and _mutL_, ensures replication fidelity by removing base mismatches [86]. Extremophilic organisms have adapted these systems with functional versatility to cope with high-stress environments. Oxidative stress responses in _G. thermoleevorans_ G4 include enzymes such as superoxide dismutase (_sodA_), catalase (_katA_), and alkyl hydroperoxide reductase (_alpC_), which detoxify reactive oxygen species (ROS). The overexpression of _alpC_, for instance, enhances tolerance to oxidative damage, as shown in other bacterial models [87]. Under heat stress, genes such as _dnaK_, _groeL_, and _clpXP_ are upregulated, functioning as molecular chaperones and proteases that maintain protein folding and quality control. These genes are regulated by the transcriptional repressor _hrCA_, which functions as a protein thermosenor in thermophilic organisms [88].