In nitrogen-limited boreal forests, associations between feathermoss and diazotrophic cyanobacteria control nitrogen inputs and thus carbon cycling, but little is known about the molecular regulators required for initiation and maintenance of these associations. Specifically, a benefit to the cyanobacteria is not known, challenging whether the association is a nutritional mutualism. Targeted mutagenesis of the cyanobacterial alkane sulfonate monooxygenase results in an inability to colonize feathermosses by the cyanobacterium Nostoc punctiforme, suggesting a role for organic sulfur in communication or nutrition. Isotope probing paired with high-resolution imaging mass spectrometry (NanoSIMS) demonstrated bidirectional elemental transfer between partners, with carbon and sulfur both being transferred to the cyanobacteria, and nitrogen transferred to the moss. These results support the hypothesis that moss and cyanobacteria enter a mutualistic exosymbiosis with substantial bidirectional material exchange of carbon and nitrogen and potential signaling through sulfur compounds.

在氮限制的北方森林中，羽毛苔藓和固氮蓝藻之间的关联控制氮输入，从而控制碳循环，但对启动和维持这些关联所需的分子调节剂知之甚少。具体来说，对蓝藻的益处尚不清楚，这对这种关联是否是一种营养共生关系提出了质疑。蓝藻烷烃磺酸盐单加氧酶的靶向诱变导致蓝藻点状念珠菌无法定殖羽毛苔藓，表明有机硫在交流或营养方面的作用。同位素探测与高分辨率成像质谱 (NanoSIMS) 相结合，证明了伴侣之间的双向元素转移，碳和硫都被转移到蓝藻中，而氮被转移到苔藓中。这些结果支持这样的假设，即苔藓和蓝细菌进入共生的外共生关系，碳和氮的大量双向物质交换以及通过硫化合物的潜在信号传导。