Composition and Distribution Analysis of Bioaerosols Under Different Environmental Conditions

Understanding the biological composition of the environmental particulate matter is important for the study of its significant impacts on human health and disease spread. In this bioaerosol sampling method and analysis, may have a wide application in many fields of study such as environmental monitoring and airborne pathogen detection. To determine the total particulate number, first equip an airborne laser particle counter with a sensor to monitor the temperature and relative humidity.

Then, collect the particle matter by the air sampling port on the top of the airborne laser particle counter and use the test modules inside the sampler to measure the size of each class of particles simultaneously every five minutes. To collect particulate matter samples by cyclonic aerosol samplers, set a cyclonic aerosol sampler to collect a sample flow of 323 liters per minute for a six hour collection period and use the automatic cleaning function to wash the inside of the sampler three times with sterile water. Then, place the sampler alone on a shelf or floor and start the collection.

At the end of the collection period, store all of the samples at 20 degrees Celsius, protected from light, until their analysis. For particulate matter collection by filters, equip a high volume air sampler with 20.32 x 25.4 square centimeter filters and set the sample to a flow rate of 1, 000 liters per minute for the appropriate collection period. At the end of the collection period, store all of the samples at 20 degrees Celsius, protected from light, until their analysis.

For biological composition analysis of filter collected samples, place each filter into a 50 milliliter conical tube with the sample facing inward and the back of the filter facing towards the tube wall. Add 10 beads into the central area of each tube toward the side of the filter containing the sample and vortex the tube for 15 minutes at room temperature. Transfer the liquid from each tube into new 50 milliliter tubes and amplify the V1 to V3 region of the bacterial 16S recombinant DNA and the ITS region of the fungal recombinant RNA operon by polymerase chain reaction according to standard protocols.

For sampling and cultivation of culturable airborne bacteria and fungi, set an international standard Andersen six-stage sampler to a flow rate of 28.3 liters per minute for a 35 minute collection period and place a soybean casein digest agar culture plate into each stage of the sampler. Sample the six stages with the Andersen six-stage sampler as defined by the aerodynamic diameters of the airborne particles, depositing the bacterial particles onto the culture plates as they are collected. Culture the airborne bacteria collection plates at 37 degrees Celsius for 24 to 48 hours before counting the colony forming units of bacteria on each sample plate for each stage.

After 48 to 72 hours of culture, collect the bacteria from each plate into two milliliter centrifuge tubes and extract the DNA with a multi-source DNA extraction kit according to standard protocols. In this representative sampling from a dairy farm, the concentration of aerosol particles was highest in December and lowest in October, possibly due to changes in temperature and humidity. The concentration of the inhalable aerosol particles able to reach the deep respiratory tract accounted for more than 99%of the total particle concentration causing serious potential hazards for humans and animals.

Here, analysis of the bioaerosol samples collected during hazy days at the campus of Beijing Institute of Technology on December 20th, 2016, indicates that the cyclonic aerosol sampler collected many more genera of bacteria than the high volume air sampler with filters. Both samplers demonstrated an equal collection efficiency and almost the same number of genus abundances for fungi collection however. As illustrated in this figure, an Andersen six-stage sampler can be used to collect the different types of airborne culturable bacteria present in different environments, such as in the four different types of piggeries assessed in this study.

Subsequent culture of the airborne samples revealed that the content of the different predominant bacteria genera varied between the different facilities. There are many factors, such as temperature, humidity, bioaerosol concentration and the environmental conditions that should be considered when the type of aerosol sampling method is being determined. Metagenomics can also be used to acquire the genetic information as a whole without the need to separate out individual organisms.

Our protocols and our results may help other researchers all over the world to further explore the health impacts of fungal and bacterial bioaerosols under different environmental conditions.