Aim:  To develop a novel laboratory procedure for the study of shock wave‐induced damage to Bacillus endospores. Methods and Results:  Bacillus atrophaeus endospores are nebulized into an aerosol, loaded into the stanford aerosol shock tube and subjected to shock waves of controlled strength. Endospores experience uniform test temperatures between 500 and 1000 K and pressures ranging from 2 to 7 atm, for a relatively short time (2–3 ms). During this process, the bioaerosol is observed using in situ laser absorption and scattering diagnostics. Additionally, shock‐treated samples are extracted for ex situ analysis including viability plating, flow cytometry and SEM imaging. Measurements indicate that endospores lose the ability to form colonies when heated to test temperatures above 500 K while significant breakdown in morphology is observed at test temperatures above 750 K. Conclusion:  These results demonstrate the disruption of essential biochemical pathways or biomolecules prior to the onset of significant endospore morphological deterioration. Significance and Impact of the Study:  This novel laboratory approach to study the interaction of endospores with shock waves provides an experimental means to investigate the mechanisms of endospore resistance to rapid heating. In addition, this methodology allows for the direct simulation of a blast wave–bioaerosol interaction in an atmospheric environment.

Aims:  Shock wave–induced damage to a variety of Bacillus endospore species is studied for a wide range of postshock temperatures and test times in oxidative and non‐oxidative gas environments. Methods and Results:  Bacillus atrophaeus and Bacillus subtilis endospores are nebulized into an aqueous aerosol, loaded into the Stanford aerosol shock tube (SAST) and subjected to shock waves of controlled strength. Endospores experience uniform test temperatures between 500 and 1000 K and pressures ranging from 2 to 7 atm, for either a short test time (∼2·5 ms) or a relatively long test time (∼45 ms). During this process, the bioaerosol is observed using in situ laser absorption and scattering diagnostics. Additionally, shock‐treated samples are extracted for ex situ analysis including viability plating and flow cytometry. For short test times, results are consistent with previous studies; all endospore species begin to lose the ability to form colonies when shock‐heated to temperatures above 500 K, while significant breakdown in morphology is observed for postshock temperatures above 700 K. Oxidative bath gases did not affect viability losses or morphological breakdown rates. Experiments with extended postshock test time showed increased viability loss with minimal morphological damage for shocks between 600 and 700 K. Conclusions:  Genetic differences between B. subtilis and B. atrophaeus endospores do not confer noticeable gains in resistance to shock heating. Oxidative environments do not exacerbate shock‐induced damage to endospores. Extended test time experiments reinforce our hypothesis that a temperature/time‐dependent inactivation mechanism that does not involve morphological breakdown exists at low‐to‐moderate postshock temperatures. Significance and Impact of the Study:  The methodology and experiments described in this paper extend the study of the interactions of endospores with shock/blast waves to new species and environmental conditions.

Experiments were conducted in a gas-driven shock tube to investigate shock wave-induced damage to Bacillus thuringiensis Al Hakam endospores over a wide range of post-shock temperatures in non-oxidative gas environments. The results were compared with previous studies on B. atrophaeus and B. subtilis and demonstrate that B. thuringiensis Al Hakam exhibited a qualitatively similar response to rapid shock heating, even though this strain has a significantly different endospore structure. B. thuringiensis Al Hakam endospores were nebulized into an aqueous aerosol, which was loaded into the Stanford aerosol shock tube, and subjected to shock waves of controlled strength. Endospores experienced uniform test temperatures between 500 and 1000 K and pressures ranging from 2 atm to 7 atm for approximately 2.5 ms. During this process the bio-aerosol was monitored using in situ time-resolved laser absorption and scattering diagnostics. Additionally, shock-treated bio-aerosol samples were extracted for ex situ analysis including viability plating, flow cytometry and scanning electron microscopy (SEM) imaging. B. thuringiensis Al Hakam endospores lost the ability to form colonies at post-shock temperatures above 500 K while significant breakdown in morphology was observed only for post-shock temperatures above 700 K. While viability loss and endospore morphological deterioration adhere to a similar framework across all endospore species studied, phenomena unique to B. thuringiensis Al Hakam were noted in the SEM images and optical extinction data. This initial characterization of the response of B. thuringiensis Al Hakam spores treated with shock/blast waves shows that these methods have potential for spore inactivation and detection.

High-lateral-resolution secondary ion mass spectrometry (SIMS) has the potential to provide functional and depth resolved information from small biological structures, such as viral particles (virions) and phage, but sputter rate and sensitivity are not characterized at shallow depths relevant to these structures. Here we combine stable isotope labeling of the DNA of vaccinia virions with correlated SIMS imaging depth profiling and atomic force microscopy (AFM) to develop a nonlinear, nonequilibrium sputter rate model for the virions and validate the model on the basis of reconstructing the location of the DNA within individual virions. Our experiments with a Cs beam show an unexpectedly high initial sputter rate (∼100 um·nm·pA·s) with a rapid decline to an asymptotic rate of 0.7 um·nm·pA·s at an approximate depth of 70 nm. Correlated experiments were also conducted with glutaraldehyde-fixed virions, as well as O and Ga beams, yielding similar results. Based on our Cs sputter rate model, the labeled DNA in the virion was between 50 and 90 nm depth in the virion core, consistent with expectations, supporting our conclusions. Virion densification was found to be a secondary effect. Accurate isotopic ratios were obtained from the initiation of sputtering, suggesting that isotopic tracers could be successfully used for smaller virions and phage.

several orders of magnitude higher than in uranium oxide, which then can also allow for helium transport out of the spent fuel.