Terahertz vibrational signature of bacterial spores arising from nanostructure decorated endospore surface

Abstract

This theoretical effort is the first to explore the possible hypothesis that terahertz optical activity of Bacillus spores arises from normal vibrational modes of spore coat subcomponents in the terahertz frequency range. Bacterial strains like Bacillus and Clostridium form spores with a hardened coating made of peptidoglycan to protect its genetic material in harsh conditions. In recent years, electron microscopy and atomic force microscopy has revealed that bacterial spore surfaces are decorated with nanocylinders and honeycomb nanostructures. In this article, a simple elastic continuum model is used to describe the vibration of these nanocylinders mainly in Bacillus subtilis, which also leads to the conclusion that the terahertz signature of these spores arises from the vibration of these nanostructures. Three vibrating modes: radial/longitudinal, torsional and flexural, have been identified and discussed for the nanocylinders. The effect of bound water, which shifts the vibration frequency, is also discussed. The peptidoglycan molecule consists of polar and charged amino acids; hence, the sporal surface local vibrations interact strongly with the terahertz radiation.

Cellular effects of terahertz waves

“…Development of the THz dosimetry is of crucial importance for biomedical applications of THz technology in such demanding branches as label-free diagnosis of malignant and benign neoplasms, 3 , 4 , 8 – 16 sensing of glycated tissues and blood in context of diabetes diagnosis, 1 , 19 – 21 determining the degree of traumatic injuries 22 and viability 30 of tissues, and even emerging methods of single cells, microorganisms, bacteria, and viruses sensing. 286 – 291 Also, THz dosimetry is of crucial importance for the rapidly developing 6G wireless communications that will reportedly span sub-THz and THz frequencies. 292 There is no doubt that such a wide range of THz technology applications, which involve interaction between THz waves and different biological systems, would stimulate the development of THz safe limits in the nearest future.…”