The atmosphere also has ecological diversity

When analyzing the molecular aerosol samples (aerosols) extracted from two US cities, the researchers counted at least 1,800 different species of bacteria in the air. To conduct this study, Dr. Gary Andersen and colleagues at Lawrence Berkeley National Laboratory used a new method, the DNA chip.

The researchers analyzed air samples in the cities of San Antonio and Austin for 4 months. The bacterial population is present in many aerosol molecules and is very similar, similar in each city. They mainly change according to atmospheric conditions, such as hot and dry weather, making it easy for bacteria to release spores.

The US Department of Defense funded this study with the goal of understanding the normal concentration of bacteria in the air to easily detect an abnormal rate that may be related to terrorism. This study also allows assessing the impact of climate changes on airborne bacterial populations.

The wind carries the Atlantic Ocean with dust from distant Sahara desert, an important source of atmospheric aerosols (Photo: Navy.mil)

Bacteria are not the only biological components present in aerosol molecules. Pieces of skin, feathers, pollen, algae, fungi or viruses are also found in about 3 tons of seeds that are released each year in the earth's atmosphere. In 2004, German researcher Ruprecht Jaenicke confirmed that bio-particles accounted for 25% of aerosol gas in some areas at some point.