An exquisitely detailed chemical structure enables microbes to selectively choose beneficial phosphorus over its poisonous cousin, arsenic, even when the dangerous chemical far outweighs the essential one. A unique method of chemical bonding helps the bacteria’s phosphate-binding proteins sniff out phosphorus, according to researchers in Israel, France and Switzerland. It’s yet another in a string of papers, this one published in an online edition of the journal Nature, responding to a claim that bacteria could subsist on arsenic.