Faculty of Chemistry, Biotechnology and Food Science, University of Life Sciences, Ås, Norway.
Curr Microbiol. 2024 Sep 18;81(11):365. doi: 10.1007/s00284-024-03869-5.
Benthic habitats are the largest habitats on Earth, being essential for marine ecosystem functioning. Benthic habitats are particularly vulnerable towards pollution and anthropogenetic influence due to general oligotrophic nature. We, therefore, simulated pollution events involving nitrate and sulphate, in combination with organic carbon. We then observed the microbiota composition the following month. Surprisingly, upon nitrate addition, an abrupt response was observed between two and three weeks after the pollution event. We observed a threefold reduction in species richness, with a dominance of the genus Pseudarchobacter within the Campylobacteriota phylum, concurring with a decrease in nitrification potential and an increase in Dissimilatory Nitrate Reduction to Ammonium (DNRA) and a regain in denitrification. Likewise, addition of sulphate contributed to a delayed response with reduction in species richness albeit weaker than for nitrate, leading to a shift towards potential spore-forming Firmicutes. There was also an increase in DNRA, but only for the oxic conditions, concurring with a regain in sulphate reductio and denitrification. For the nitrate addition experiments, the delay in response could potentially be attributed to the genus Pseudarchobacter which rely on sulphides for denitrification, while for the sulphate addition experiments, the delayed response might be explained by the germination of spores. The late increase of DNRA may indicate a shift towards a different metabolic regime for nitrogen. In conclusion, our microcosm experiments revealed delayed abrupt microbiota shifts resembling tipping points that can potentially be overlooked in natural ecosystems.
底栖生境是地球上最大的生境，对海洋生态系统的功能至关重要。由于普遍的贫营养性质，底栖生境特别容易受到污染和人为影响。因此，我们模拟了涉及硝酸盐和硫酸盐的污染事件，同时结合了有机碳。然后，我们在下个月观察了微生物群落的组成。令人惊讶的是，在添加硝酸盐后，在污染事件发生后的两到三周内观察到了一个突然的反应。我们观察到物种丰富度减少了三倍，其中假单胞菌属在弯曲杆菌门中占主导地位，同时硝化潜力降低，异化硝酸盐还原为氨（DNRA）增加，反硝化作用恢复。同样，添加硫酸盐也导致了物种丰富度的减少，尽管比硝酸盐的减少程度要弱，这导致了潜在的孢子形成厚壁菌门的转移。DNRA 也有所增加，但仅在有氧条件下，这与硫酸盐还原和反硝化作用的恢复一致。对于硝酸盐添加实验，延迟反应的原因可能是依赖硫化物进行反硝化作用的假单胞菌属，而对于硫酸盐添加实验，延迟反应可能是由于孢子的萌发。DNRA 的后期增加可能表明氮的代谢机制发生了转变。总之，我们的微宇宙实验揭示了延迟的突然微生物群落转变，类似于可能被自然生态系统忽视的临界点。
