Aerobiological Stabilities of Different Species of Gram-Negative Bacteria, Including Well-Known Biothreat Simulants, in Single-Cell Particles and Cell Clusters of Different Compositions

Abstract

The ability to perform controlled experiments with bioaerosols is a fundamental enabler of many bioaerosol research disciplines. A practical alternative to using hazardous biothreat agents, e.g., for detection equipment development and testing, involves using appropriate model organisms (simulants). Several species of Gram-negative bacteria have been used or proposed as biothreat simulants. However, the appropriateness of different bacterial genera, species, and strains as simulants is still debated. Here, we report aerobiological stability characteristics of four species of Gram-negative bacteria (Pantoea agglomerans, Serratia marcescens, Escherichia coli, and Xanthomonas arboricola) in single-cell particles and cell clusters produced using four spray liquids (H 2 O, phosphate-buffered saline [PBS], spent culture medium [SCM], and a SCM-PBS mixture). E. coli showed higher stability in cell clusters from all spray liquids than the other species, but it showed similar or lower stability in single-cell particles. The overall stability was higher in cell clusters than in single-cell particles. The highest overall stability was observed for bioaerosols produced using SCM-containing spray liquids. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. Taken together, the results highlight the importance of careful and informed selection of Gram-negative bacterial biothreat simulants and also the accompanying particle size and composition. The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research.IMPORTANCE The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research. Taken together, the results highlight the importance of careful and informed selection of Gramnegative bacterial biothreat simulants and also the accompanying particle size and composition. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns.

Evaluation of four sampling devices for Burkholderia pseudomallei laboratory aerosol studies

“…Glycerol is essentially non-volatile at the conditions tested in the present study, and may have protected the organism against desiccation in the gelatin filter and Mercer cascade impactor. These observations are consistent with previous studies that have shown both that bacterial survival during aerosolization is affected by the composition of the initial suspension medium [43][44][45], and that glycerol can have protective effects on microorganisms in aerosols [46]. While the suspension liquids used in the present study were laboratory media, the observed sensitivity to desiccation is consistent with published reports indicating that natural substrates which facilitate water retention, such as sputum or clay soils, tend to preserve viability of Burkholderia spp.…”

The influence of temperature, humidity, and simulated sunlight on the infectivity of SARS-CoV-2 in aerosols

“…While SARS-CoV-2 is present in these particles, the vast majority of the particle mass is composed of other non-infectious, non-volatile components present in the suspension medium, with the virus representing only a small fraction of the particle mass. Therefore, the persistence of larger particle sizes which are known to be generated during other respiratory events, such as coughing or speaking (Chao et al 2009;Morawska et al 2009), should be investigated as the greater mass of non-infectious material associated with these particles has the potential to shield virus present within a particle from environmental insults, increasing its persistence in the environment (Dybwad and Skogan 2017;Kesavan et al 2013;Lighthart and Shaffer 1997). Another limitation of the present study relates to the particle composition of generated aerosols.…”

“…s c r i p t that the suspending medium can significantly affect the persistence of microorganisms(Dybwad and Skogan 2017). While the use of concentrated viral stocks was necessary to achieve quantifiable concentrations of infectious virus in the rotating drum chamber, the addition of the viral concentrate to the simulated saliva significantly changed both the protein content and fractional solids relative to the naïve simulated saliva.…”

Fresh Snowfall Microbiology and Chemistry are Driven by Geography in Storm-Tracked Events

“…More attention should be given to total bacterial communities in precipitation due to the magnitude of their abundance, potential for terrestrial impact, likely effects on cloud glaciation, and non-uniform patterns of deposition in snowstorm events (Figure 4). We know that bacteria/archaea/eucarya can be viable in aerosols (59), suggesting that the multitude of taxa that we find in snow may be contributing to atmospheric chemistry in - situ around Earth. Given all of the bio-physical / chemical influences on the atmosphere, bio-precipitation should be considered just as complex and variable—and storm-track should be considered and essential component of this variance.…”