Strange bacteria in a California lake appeared to thrive on something completely unexpected - arsenic.

The finding led to speculation that life forms on other planets could be very, very different to animals from Earth - and could 'live on' substances that are poisonous to us.

But two new papers have found that the strange creatures don't use arscenic to live - although the bacteria are highly tolerant to it.

The saga began when scientists led by Felisa Wolfe-Simon of NASA's Astrobiology Institute published a paper that said the bacteria, found at Mono Lake in eastern California, could grow by substituting arsenic for phosphorus.

The researchers had looked at Mono Lake because of its high arsenic levels, and they reported their conclusions from lab experiments.

Their paper raised eyebrows because phosphorus was considered essential to life, while arsenic, while chemically similar, is a poison.

If the bacteria can break the rules like this, some argued, who knows what kinds of life may be possible beyond Earth?

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