| Staphylococcus aureus is a kind of important clinical pathogenic bacteria, and the infection caused by MRSA, together with hepatitis B and AIDS have become three main infection chronic diseases in the world. The typical staphylococcus aureus is spherical, and in the shape of grape cluster under microscope, that is why it is called "staphylococcus". Meanwhile, because it can generate a kind of golden carotenoid, it earned the name of staphylococcus aureus. This golden carotenoid staphyloxanthin enhanced bacterial resistance ability of oxidative stress and the phagocytosis of host neutrophile granulocyte, which can help bacteria escape from host immune system and establish close connection with bacterial virulence. Therefore, the blocking of the biosynthesis of staphylococcus flavin may become new effective means of treating MRSA infection as expected.The efficient and accurate detection of staphylococcus flavin in staphylococcus aureus is the precondition for understanding its mechanism of toxication as well as biosynthesis, and screening new antibiotics. However, the operation of traditional quantitative methods based on solvent extraction is complicated and toxic methyl alcohol is used. Laser Tweezers Raman Spectroscopy (LTRS) combined optical tweezers and Raman spectroscopy; it imprisons the living cells in solution by suing highly converged laser beam; then, it stimulates the molecular Raman scattering inside cells through increasing the light beam of imprisoned cells instantaneously. This technology fully combined with the advantages of confocal microscopy, optical tweezers and Raman spectroscopy, and improved detection sensitivity as well as accuracy, which is the powerful tool for researching chemical substance content and structural variation of single living cell in physiological status.Therefore, in this thesis, based on the method of determining the staphylococcus flavin in staphylococcus aureus by LTRS, we deeply researched the influence of environmental factor as well as growth condition on the biosynthesis of staphylococcus flavin, and understood the relation method of bacterial pigment content and staphylococcus aureus’ ability of resisting oxidative stress. The main aspects of our work are as follows:1. Research the influence of environmental factor as well as growth condition on the biosynthesis of staphylococcus flavin based on LTRS determination method, such as the influences of external temperature, pH value, different glucose concentration and different nitrogen sources; to study the fluctuation rule of staphylococcus flavin contents accumulated inside staphylococcus aureus cells within one growth cycle (vaccinate 0-24h).2. Explore the feasibility of LTRS when being applied to screen and evaluate the synthesis of staphylococcus flavin to immunosuppressive medication. By selecting the drugs that have become literatures and verified that the synthesis of staphylococcus flavin can restrain vitality to research whether there is negative correlation between different flavone concentrations and the accumulated concentration of staphylococcus flavin inside staphylococcus aureus, which is dose-effect relationship.3. Research the antioxidant protection of taphylococcus flavin on staphylococcus aureus by using LTRS; meanwhile, add the pigment synthesis inhibitor in different concentrations to the same bacterial strain to make the contents of pigment accumulated inside the bacterium become different. Determine the content of taphylococcus flavin inside cells based on LTRS and compare different pigment contents of staphylococcus aureus’ toleration of reactive oxygens such as H2O2 and single oxygen. Evaluate the correlation of survival rates between contents of staphyloxanthin and staphylococcus aureus under oxidative stress. |
