Influence of nitrate-storing sulfur bacteria on the nitrogen and phosphorus cycle of the ocean

储存硝酸盐的硫磺细菌在大多数含有游离硫化氢的海洋沉积物中都很丰富，并可能达到很高的生物量。它们除了对海洋硫循环中的氧化部分很重要外，还会干扰沉积物的氮循环。到目前为止，有迹象表明，硫磺细菌可能通过三种不同的方式改变其栖息地的总氮收支：反硝化、将硝酸盐异化还原为氨，甚至可能是固氮。在某些条件下，它们还可能产生大量的一氧化二氮，这是一种温室气体。这个项目的第一个目标是调查这些过程中的每一个发生在什么条件下。初步研究还表明，到目前为止所调查的所有储存硝酸盐的硫磺细菌都含有大量内部储存的聚磷酸盐。这一发现表明，这组细菌也可能对海洋的磷循环产生重大影响，特别是在一些最近发现磷矿成因的地区，它们以非常高的生物量出现。因此，本项目的第二个重点是开展关于聚磷酸盐积累和释放的生理实验和田间调查。

Nitrate-storing sulfur bacteria are abundant in most marine sediments containing free hydrogen sulfide and may reach very high biomasses. Apart from their importance for the oxidative part of the marine sulfur cycle they also interfere with the nitrogen cycle of the sediment. Until now there are indications for three different ways in which sulfur bacteria may change the total nitrogen budget of their habitats: denitrification, dissimilatory reduction of nitrate to ammonia and possibly even nitrogen fixation. Under certain conditions they may also produce significant amounts of nitrous oxide, which is a green house gas. The first goal of this project is to investigate under which conditions each of these processes occur. Preliminary studies have also shown that all nitrate-storing sulfur bacteria investigated so far contain high amounts of internally stored polyphosphate. This finding indicates that this group of bacteria may also have great influence on the phosphorus cycle of the ocean, especially as they occur in very high biomasses in some areas where recent phosphorite genesis is found. Therefore, the second focus of this project is to carry out physiological experiments and field investigations concerning the accumulation and release of polyphosphate.