Team:BUCT-China/Results
Results
Parts 1:
At the beginning of the experiment, we wanted to verify that our idea, the possibility of plastic biodegradation by bacteria, was correct. So, SEM and FTIR technique (Fourier Transform infrared spectroscopy) were used.
Fig.1.SEM images of the degradation of PE under different conditions.Scale bar 2μm，MAG x30k.
（A）The image of the degradation of PE by ultraviolet light after 12 hours.
（B）The image of the degradation of PE by Microbulbifer hydrolyticus after 30 days.There are obvious cracks on the PE surface.
From the SEM images that the experimental group can clearly see the plastic crack. This shows the potential of this strain to degrade PE.
Fig.2.FTIR spectra of PE standards and the sample after reaction with bacteria.
(A) 2918.8- -CH3;2849.5- -CH2-;1466.0- -CH2-;722.6- -(CH2)N-,N>4; PE structure.
(B) Extra peaks in the range of 3000-3500,3392.2 -OH,3195.7-unsaturated and 1644.9-contain double bonds.
That means under the action of this bacteria, it does have a certain effect on plastic(PE) degradation.From the control group, the plastic is a straight carbon chain.In the experimental group, there have several extra small peaks.And indicate the insertion of oxygen atoms and the generation of double bonds.But the peaks intensity are low, which means that the PE is oxidized to a low degree.
What do these figures say?
After sem analysis, we could see cracks and other traces of degradation on the surface of the plastic film, so our idea was preliminarily proved to be correct. We suspect that enzyme systems in microbes greatly accelerate the degradation of plastics.In addition, we analyze the newly generated bonds and explain the mechanism based on this guess.
Part 2:
After whole genome sequencing and COG gene annotation,we get the gene circle map.
After all CDs were classified by COG, in addition to the protein types necessary for life process , the protein with the highest expression was carbohydrate metabolic protein.We can infer that this bacteria has a good ability to use carbohydrates.
Fig.3. genome sequencing
Fig.4.KEGG pathways
As the KEGG analysis shows, some proteins are relevant to the xenobiotics biodegradation and metabolism. So the bacteria is proved to have the capability to degrade some harmful foreign materials through its detoxification pathway. Basically, it is common to see various oxidase involved in the pathway of detoxification. So it could be speculated that the bacteria very likely have some special oxidase and degradation pathway which may also be effective in PE degradation.
After GO analysis, it was found that some proteins in the bacteria are special in the aspect of molecular function, particular in electron carrier activity, which further proved the existence of oxidase. Because oxidase is capable to catalyze the oxidation of substrate mainly by carrying electrons.
Fig.5. Bar chart of GO
We found the oxidase gene exactly through gene sequencing and we registered it as a new biological parts.
Part 3:
Future
We have determined the role of oxidase in the biodegradation process through data analysis, but the pathway after oxidase is not clear. Therefore, we will continue to find other important enzymes in the biodegradation process so that they can be optimized.
After the biodegradation of PE by the strain we used, we have obtained about 18-20 carbon chains. How to make them high value-added is the ultimate significance of the project.