# Metabolomics of _Pseudomonas aeruginosa_ Treated by Atmospheric-Pressure Cold Plasma
## 4 Discussion  
_Pseudomonas aeruginosa_ has the second highest infection rate among all bacteria and has strong drug resistance. As a new technology, cold atmospheric plasma has attracted extensive attention in sterilization applications. Studies have proved that atmospheric-pressure low-temperature plasma can effectively sterilize.  
Studies have demonstrated the bactericidal effect of atmospheric-pressure low-temperature plasma, and it is generally believed that reactive nitrogen oxides are responsible for the death of bacteria [24; 25; 26; 27]. Meanwhile, some scholars also explored the metabolites of _Pseudomonas aeruginosa_[41]. However, to our knowledge there is an absence of studies which have tested the effects of plasma treatment on bacterial metabolism.  
In this paper, we studied the entire metabolic process to understand the effect of plasma on bacterial metabolism. Firstly, we detected the physical and chemical properties of the portable device from the perspective of the emission spectrum and liquid phase active particles, and then detected and statistically analyzed the metabolites of the treatment group and the control group.  
We demonstrated that mass metabolic profiling using GC-TOF-MS mass spectrometry revealed many significant differences between the control and plasma treated _Pseudomonas aeruginosa_ groups. By KEGG analysis of metabolic pathways, we found that bacterial metabolites Melatonin and Thioacetamide in _Pseudomonas aeruginosa_ were significantly increased after plasma treatment. Both metabolites belong to organ heterocyclic compounds, which are the decomposition products of protein and amino acids [42], so the metabolic pathways related to protein amino acids are promoted, while Cellobiose is significantly reduced. The metabolites belong to phenylroploads and polyketides, which are the decomposition products of carbohydrates in bacterial metabolism, indicating that the glucose metabolism pathway is inhibited. The metabolic pathways of Glycolipid metabolism and Glycerophospholipid metabolism showed the most obvious changes. On these two pathway maps (found in the KEGG database), the differential metabolite (Glycerol 3-phosphate) is marked in red. For details, please check Supplementary File S1. So metabolic pathways are upregulated because of an increased metabolite content. Thus, plasma treatment inhibits glucose metabolism in _Pseudomonas aeruginosa_ and promotes the breakdown of proteins and amino acids, leading to bacterial death. While other researchers have studied the _Pseudomonas aeruginosa_ metabolome, some scholars showed that in the process of drug killing of _Pseudomonas aeruginosa_, the synthesis of lipopolysaccharide and pepti  
Figure 8: Pathway analysis diagram of group 1T versus group C.  
doglycan was significantly reduced, and the level of lipid amino acid was increased [43]. [PERSON] et al. showed that the metabolic pathway of killing _Pseudomonas aeruginosa_ included the destruction of carbohydrate metabolism, the reduction of amino sugar levels and the downregulation of the nucleotide bank [44]. [PERSON] et al. studied the metabolomic information of _Pseudomonas aeruginosa_ and found changes in carbohydrate catabolism and a metabolic shift to amino acid utilization [45]. It proved that plasma sterilization and drug sterilization caused similar metabolic changes in bacteria.