Akinobu Echigo and colleagues, from Toyo University and the Noda Institute for Scientific Research in Japan, analysed bacteria found in non-saline soil collected in gardens, fields and roadways in the Tokyo area. From their soil samples, they isolated halophilic bacteria - bacteria that are able to survive in a high-salt environment - by growing the bacteria in a culture medium with a salt concentration of at least 20%.

Their results show that approximately 1 in 200,000 of the bacteria found in the soil samples were halophilic, and the bacteria came from at least seven different families.

Halophilic bacteria thrive in environments where the average concentration of salt is 3-15%. The salt concentration in the soil the authors analysed was 20 to 100 times lower than that, and it seems unlikely that the halophilic bacteria found in this soil originated there. Most of the halophilic bacteria were present in the soil as endospores: reproductive cells with a hard coat that protects them against adverse environmental conditions.

Surprisingly, the same proportion of endospores was found in saline soil closer to the coast. The authors deduce from these findings that the endospores may have been carried to the Tokyo area by winds or dust storms, and possibly originated in salt lakes in Inner Mongolia in China.

This study adds to the evidence that dust storms in Asia can have implications in geographically remote countries. Previous studies have shown that dust storms in Northern China and Mongolia can cause myriad problems elsewhere, including respiratory problems, loss of livestock and crops and disruption of communication.

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