## 5 Characterization of Genetic Differences in the FMO Complexes with other Species and Strains
### Genetic and Structural Differences between Species and Strains and Their Manipulation  
The FMO complex is characteristically present in GSB and it has actually been key for further identification of species and strains [16; 18; 66]. The gene codifying the FMO complex (_fmoA_ gene) presents small variations within the distinct species and strains of green sulfur bacteria, resulting in a growing phylogenetic tree [16; 18]. Regardless of this fingerprint characteristic, these genetic variations have consequences in the final protein structure of the FMO complex. In the cases of _C. tepidum_ and _P. aestuarii_, a comparison between their crystal structures (with PDB IDs 3 BSD and 3 EOJ, respectively) using a basic local alignment search tool (BLAST) reveals a 78% of identical amino acids and a total of 87% of similarities, due to the fact that some amino acids that differ between both structures have similar behaviours and characteristics as their substitutes. These structural differences for the _fmoA_ gene can be observed in Figure 17, where the FMO complex of both organisms are being overlapped in Figure 17A, and their differences are highlighted in blue in accordance to their respective sequences shown in Figure 17C. The green arrows and pink serpentine lines are a linear representation of the protein \(\beta\)-sheet and \(\alpha\)-helix structures, respectively. Figure 17B, shows an overlap of the 24 BChls (8 BChls per monomer) of both organisms exhibiting tiny differences derived from punctual changes in the orientation by the insertion of alternative amino acids, then reflected in more extended parts of the structures. Slight orientation shifts are observed between the molecules as an effect of the different protein structures, which surely modifies slightly their dipolar momenta as well as their relative orientations, thus changing the respective Hamiltonians \(H_{S}\). Such differences are then responsible from the deviations in the quantum fingerprint observed in Figure 15.  
Living organisms can be exploited for chromophore assembly given they possess the genetic blueprints and molecular machinery for their biosynthesis [67]. Genetic engineering and biotechnology provide a new approach towards designing efficient energy transport by manipulating these organisms but their correlation with quantum properties could set a bridge between the design and the functioning effects. For such a goal, the selection and structural arrangement of chromophores, and inter-chromophoric couplings play a crucial role. Some challenges for the customization of energy transfer mechanisms are the structural control of the individual light-harvesting pigments and the achievement of beyond-Forster energy transport [67]. The manipulation of such structures in living organisms is possible by the use of programmable genes that can modify the positioning of the binding sites, thus enabling the creation of defined chromophore networks and ultimately controlling the energy transfer [67] or other notable novel applications in quantum processing taking advantages from biological-based structures as quantum walks [30; 32] and incoherent quantum evolution [10]. The possibility to track the discrete differences in the molecular structure of FMO versions into a mapping on the continuous quantum features as those in Figure 15 is a future challenge.