The bacterium legionella pneumophila and related bacteria are common in natural water sources such as rivers, lakes and reservoirs, but usually in low numbers.

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DNA. Alternatively, it can be smuggled in inside a bacterium (splicing extra genes into bacteria for this purpose is easy).

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For the study, researchers from the University of Vermont analysed volatile organic compounds (VOCs) given off in exhaled breath by different bacteria as well as different strains of the same bacterium.

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Some will be vaccinated with the bacteria, which although from the same family as the tuberculosis bacterium, does not cause any disease.

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They also said they were able to differentiate between two species of bacteria and two different strains of the same P. aeruginosa bacterium.

BBC: Lung infection identified using 'breath-print'

Because the naturally occurring, ubiquitous "ice-plus" bacterium was a "pest, " therefore, according to the EPA's reasoning, other bacteria intended to displace it and mitigate its effects would be considered pesticides.

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