The data suggest that spores for the three letters were grown using the same process, says Michael.It is not clear how tin and iron made their way into the culture, he says.

• 这些数据表明三封邮件中的孢子均采用同一种培养方式培养出来，迈克尔说，但是我们仍不清楚铁和锡是如何混入菌株的。