1183965 - 3D Cellular Ultrastructure of Disinfected Foodborne Bacteria and Fungus via Transmission X-Ray Microscopy and Soft X-Ray Tomography (Student Poster #19)

Foodborne pathogens cause food contamination and eventually lead to a human health issue. Many researchers have used fishery waste as a disinfection agent. However, the changes of cellular structure in response to the disinfection remain unclear. We hypothesized that the deformation of cellular structure is the critical step of a disinfection process. This study aimed to observe the variation of 3D microbial ultrastructure during the disinfection process and to identify the disinfection mechanism by using synchrotron-based Transmission X-ray tomography (TXM) and Soft X-ray tomography (SXT). The performance of chitosan (CTS) and calcined oyster shell (COS) powder were fabricated and used to investigate the disinfection efficacy of Gram-positive (Staphylococcus aureus), Gram-negative (Klebsiella pneumoniae, Escherichia coli), and Fungus (Aspergillus niger). The CTS was derived from the acetylation of the shrimp shell. Findings revealed that COS could generate oxidative reactive oxygen species (ROS), and then the ROS attack the surface of microorganisms. The NH3+ groups on the CTS resulted in a positively charged surface, which interfered with the negatively charged surface of microbial and altered the cell permeability. The disruption of the cell structure of microorganisms by CTS and COS leads to cytoplasm leakage, consequently increasing the solution relative conductivity. Before the reaction, the bacteria cells were spindle-shaped and intact. After 2 h reaction with both CTS and COS the cell walls of K. pneumoniae had obvious cell sag and damage, which is solid evidence of a severe attack by ROS and interfered by NH3+ groups. The TXM 3D morphologies showed that the cell already had deformation after interaction with CTS and COS for 6 h. SXT images also showed that the organelles of A. niger could not maintain a healthy state after 6 h reaction. This study combines the 3D structural morphologies and electron microscopy images with cellular physiological characteristics to build a comprehensive view of cellular inactivation via CTS and COS.