The Effect of Phosphate Buffer on Aerosol Size Distribution of Nebulized Bacillus subtilis and Pseudomonas fluorescens Bacteria
Titel:
The Effect of Phosphate Buffer on Aerosol Size Distribution of Nebulized Bacillus subtilis and Pseudomonas fluorescens Bacteria
Auteur:
Johnson, D. L.
Verschenen in:
Aerosol science and technology
Paginering:
Jaargang 30 (1999) nr. 2 pagina's 202-210
Jaar:
1999-02-01
Inhoud:
During bioaerosol research microorganisms are frequently aerosolized from phosphate-buffered suspension via air-jet nebulization. Buffer will therefore be present in organism-free droplets (''empties") as solutes in hydrous surface coatings of airborne organisms or as dry surface coatings on organisms. It might be expected that the buffer would influence the resulting aerosol size distribution and that the influence might vary with relative humidity. In this work we examined the effect of various buffer concentrations on the aerosol size distribution of Bacillus subtilis (B. subtilis) and Pseudomonas fluorescens ( P. fluorescens ) at various relative humidities. Microorganism suspensions in distilled deionized water and phosphate-buffered water were prepared and nebulized from a 3-jet Collison nebulizer into a sampling chamber maintained at 10% relative humidity. The aerosol was then conducted to a second chamber to which moist air was added to achieve the target relative humidity. Particle aerodynamic size distributions were measured at 10, 20, 40, 60, 80, and 90% relative humidity. Buffer concentrations used were 0, 2.5, 5, 7.5, and 10%. Phosphate buffer substantially affected the indicated aerodynamic size distribution of both bioaerosols, with greater effect seen for the Gram-positive B. subtilis than for the Gram-negative P. fluorescens . The effects were most pronounced above 80% relative humidity. Further, aerosol size distributions of B. subtilis , but not P. fluorescens , were affected by relative humidity even in the absence of buffer, suggesting a species-related difference in hygroscopic growth. Growth predicted from theory was generally consistent with observed behavior, although uncertainties remain concerning organismand instrument-related influences on measured behavior.
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