In medicine and food industry, bacterial colonisation on surfaces is a common cause of infections and severe illnesses. However, the detailed quantitative information about the dynamics and the mechanisms involved in bacterial proliferation on solid substrates is still lacking. In this study we investigated the adhesion and detachment, the individual growth and colonisation, and the cell size control of Escherichia coli (E. coli) MG1655 on polyethylene terephthalate (PET) surfaces. The results show that the bacterial growth curve on PET exhibits the distinct lag and log phases, but the generation time is more than twice longer than in bulk medium. Single cells in the lag phase are more likely to detach than clustered ones in the log phase; clustered bacteria in micro-colonies have stronger adhesive bonds with surfaces and their neighbours with the progressing colonisation. We show that the cell size is under the density-dependent pathway control: when the adherent cells are at low density, the culture medium is responsible for coordinating cell division and cell size; when the clustered cells are at high population density, we demonstrate that the effect of quorum sensing causes the cell size decrease as the cell density on surfaces increases.
FTIR and confocal laser micro‐Raman spectroscopy methods were used to investigate the differences in chemical bond types, bond energy, and skeleton connection system between rice starch heated in a microwave and rice starch heated rapidly using a traditional method. The temperature of the peak absorption position of CH mode vibration of microwaved sample was lower and the temperature of peak position of CO related mode vibration on skeleton of microwaved sample were higher than those of the rapid heating sample, but there were no changes to other skeletal mode vibrations such as glycosidic linkage and pyranose ring. Overall, microwave‐heat treatment did not change the type of chemical groups in starch molecules, and induce the formation of new chemical group bonds, or change the way that they interact with each other in rice starch. Furthermore, the vibrational energy of the chemical‐bond of microwave‐treated rice starch changes gradually during the heating process.
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