Title : Diurnal variation of bacterial and fungal flora in ambient air in a tropical setting , in Settle plate method
Abstract:
Airborne bacteria and fungi exist as bioaerosols, which can cause a range of infectious diseases, allergic and toxic reactions. There can be temperature-specific variation in aerial microbial flora, which is important to know. There is also seasonal variation in microbial flora of air. Fungi in inner ambient air is more in summer and lesser in winter. Different types of fungi or bacteria need different amounts of moisture to reproduce and grow. The majority need a relative humidity (RH) of 60 % or more, though some can survive and multiply in even 20 % RH. Thus, decreasing temperature and moisture, creates a less hospitable environment for microorganisms to grow.These are pertinent because it can calculate the best time of the day to venture out. Generally, fungi are found more in outer air than indoor air, while for bacteria it is reverse.
Materials and methods: We analyzed data from other studies in this context and also did a small study regarding diurnal variation in bacteria and fungi in air of outdoor and indoor or closed space air by settle plate method in our campus. We used Egg yolk agar, Mueller Hinton agar and Sabouraud’s Dextrose agar (SDA) plates for this.
Results: According to other studies and also seconded by us, the bacterial count as well as variety was more in daytime and less in afternoons. Bacillus spp. was found more in outer air in noon time than afternoon. Staphylococci could be found all throughout the day. The diurnal variation of fungi like yeasts and molds are found to be less, however.
Conclusion: Mesophilic bacteria and fungi show optimal growth at temperatures of 25-40°C. On the other hand, when temperatures reach below 18°C/64°F, microorganism growth decreases. Possibly factors like ambient temperature and humidity also have a decisive role to play in aerial flora due to variation in concentration of suspended aerosols. Temperature, moisture and UV radiation are 3 things which are very important from public health viewpoint and also open up newer vistas of research.
