## 3 Results
### Gene Clusters and Pathway Associated with Lutein and Zexanthin Biosynthesis
\begin{table}
\begin{tabular}{c c c c c} \hline
**Pathway** & **Genes** & **Coded Protein/Enzyme** & **Catalytic Substrate** & **Catalytic Product** \\ \hline \multirow{8}{*}{Terpenoid backbone biosynthesis} & \multirow{2}{*}{_spmA_} & Cofactor dependent & Glycerate-3-phosphate & Glycerate-2-phosphate \\  & & Phosphoglycerate mutase & Glycerate-3-phosphate & Glycerate-2-phosphate \\  & & Cofactor independent & Glycerate-3-phosphate & Glycerate-2-phosphate \\  & _spm1_* & Phosphoglycerate mutase & Oxaloacetate & Phosphoenol-pyruvate \\  & _pckA_* & Phosphoenolpyruvate carboxylase & Oxaloacetate & Phosphoenol-pyruvate \\  & _pckG_* & Phosphoenolpyruvate carboxylase & Oxaloacetate & Phosphoenol-pyruvate \\  & _eno_ & Phosphoppyruvate hydrate & Glycerate-2-phosphate & Phosphoenol-pyruvate \\  & _pykF_ & Pyrruvate kinase & Phosphoenol-pyruvate & Pyruvate \\  & _kora_ & 2-oxoxacid oxidoreductase & pyruvate & Acetyl-CoA \\  & _accF_ & Dihydroloripate acetyltransferase transferase & S-Acetyl-dihydropoamide-E & Acetyl-CoA \\  & _accE_ & Pyruvate dehydrogenase & Pyrruvate & S-Acetyl-dihydropoamide-E \\  & _lpd_ & Dihydrolipoyl dehydrogenase & Dihydrolipoamide-E & Lipoamide-E \\  & _spD_ & Propionaldehyde dehydrogenase & Acetate & Acetaldehyde \\  & _frmA_ & Ethanol dehydrogenase & Acetaldehyde & Ethanol \\ \hline \multirow{8}{*}{Carbon fixation pathways in prokaryotes} & \multirow{2}{*}{Acetate-CoA carboxylase} & Acetate & Acetel-CoA \\  & & Acetate kinase & Acetate & Acetyl phosphate \\  & _accA_ & Acetyl-CoA carboxylase & Acetyl-CoA & Malonyl-CoA \\  & _vqE_ & Acetyl-CoA acetyltransferase transferase & Acetoacetyl-CoA & Acetyl-CoA \\  & _acA_* & Cis-aconites & Cis-Acointate & Citrate \\  & _icd_ & Oxalouscuctate decarboxylase & 2-oxoglutrate & Isoccitrate \\  & _propB_* & 2-oxoglutrate ferredoxin & Succinyiyi-CoA & 2-oxoglutrate \\  & _ppdK_ & Pyruvate-phosphate ligase & Pyrruvate & Phosphoenol-pyruvate \\  & _ppC_ & Phosphoenolpyruvate carboxylase & Phosphoenol-pyruvate & Oxaloacetate \\  & _mdh_ & Malate dehydrogenase & Oxaloacetate & (S)-malate \\  & _fumA_ & Fumarate hydratase & (S)-malate & Fumarate \\  & _sdhA_ & Succinate dehydrogenase & Fumarate & succinate \\  & _sdhB_ & Succinate dehydrogenase & Fumarate & succinate \\  & _sucC_ & Succinate-CoA ligase & Succinate & Succinyi-CoA \\  & _metF_ & Methylenetetrahydrofolate reductase & 5,10-Methylene-THF & 5-Methyl-tetrahydroofolate \\  & _folD_ & Methylenetetrahydrofolate & & 5,10-Methenyl-THF & 5,10-Methylene-THF \\  & _mce_ & Methylmalonyl-CoA epimerase & (S)-Methylmalonyl-CoA & (R)-Methylmalonyl-CoA \\  & _scpA_ & Methylmalonyl-CoA mutase & (R)-Methylmalonyl-CoA & Succinyi-CoA \\  & _meh_* & 3-methylfumaryl-CoA hydratase & 3-Methylfumaryl-CoA & (38)-Citramally-CoA \\  & _fldA_* & 2-methylfumaryl-CoA isomerase & 2-Methylfumaryl-CoA & 3-Methylfumaryl-CoA \\ \hline \multirow{8}{*}{Carbon fixation pathways  
The lutein and zeaxanthin synthesis genes in _Sphingomonas morindae_ sp. NBD5 and _Sphingopyxis_ sp. USTB-05 genomes mainly exist in the terpenoid backbone biosynthesis pathway and the carotenoid biosynthesis pathway, which are roughly the same (Figures S4 and S5). Both strains are the presence of \(\beta\)-carotene 3-hydroxylase, which is involved in the last step of lutein and zeaxanthin synthesis, and its corresponding code gene is _crtR_. This is a fact that lycopene exists as a synthetic intermediate, which is synthesized through glycolysis pathway, terpenoid backbone biosynthesis pathway and carotenoid biosynthesis pathway (Figure 4).