High pressure treated Bacillus subtilis spores Structural analysis by means of synchrotron and laboratory based soft X ray microscopy

Abstract

Measurements were carried out on high pressure treated HPT bacterial endospores of the Bacillus subtilis strain PS832 by means of laboratory LTXM and synchrotron based transmission soft X ray microscopy SynchTXM . Using LTXM at 500 eV HPT spores could be identified by a higher transparency, due to dipicolinic acid DPA release from the spore s core, and their shriveled appearance caused by air drying. Dormant spores were investigated at different photon energies at SynchTXM. Inner structures were visualized and it was shown that at a photon energy of 280 eV the micrographs yielded bigger absorption differences, and thus better contrast between the core coat and the peptidoglycan rich cortex. Tilt series of dormant and HPT spores were reconstructed. Virtual sections revealed the dormant spores core, cortex and coat without the need to physically slice the sample. It was also possible to visualize the inside of the HPT spores, which proved to be void of DP