Agro-ecosystems experience huge losses of land every year due to soil erosion induced by poor agricultural practices such as intensive tillage. Erosion can be minimized by the presence of stable soil aggregates, the formation of which can be promoted by bacteria. Some of these microorganisms have the ability to produce exopolysaccharides and lipopolysaccharides that "glue" soil particles together. However, little is known about the influence of tillage intensity on the bacterial potential to produce these polysaccharides, even though more stable soil aggregates are usually observed under less intense tillage. As the effects of tillage intensity on soil aggregate stability may vary between sites, we hypothesized that the response of polysaccharide-producing bacteria to tillage intensity is also determined by site-specific conditions. To investigate this, we performed a high-throughput shotgun sequencing of DNA extracted from conventionally and reduced tilled soils from three tillage system field trials characterized by different soil parameters. While we confirmed that the impact of tillage intensity on soil aggregates is site-specific, we could connect improved aggregate stability with increased absolute abundance of genes involved in the production of exopolysaccharides and lipopolysaccharides. The potential to produce polysaccharides was generally promoted under reduced tillage due to the increased microbial biomass. We also found that the response of most potential producers of polysaccharides to tillage was site-specific, e.g., Oxalobacteraceae had higher potential to produce polysaccharides under reduced tillage at one site, and showed the opposite response at another site. However, the response of some potential producers of polysaccharides to tillage did not depend on site characteristics, but rather on their taxonomic affiliation, i.e., all members of Actinobacteria that responded to tillage intensity had higher potential for exopolysaccharide and lipopolysaccharide production specifically under reduced tillage. This could be especially crucial for aggregate stability, as polysaccharides produced by different taxa have different "gluing" efficiency. Overall, our data indicate that tillage intensity could affect aggregate stability by both influencing the absolute abundance of genes involved in the production of exopolysaccharides and lipopolysaccharides, as well as by inducing shifts in the community of potential polysaccharide producers. The effects of tillage intensity depend mostly on site-specific conditions.

中文翻译：

---

特定地点的条件改变了土壤结构稳定剂（例如胞外多糖和脂多糖）的细菌生产者对耕作强度的反应。

由于集约耕作等不良农业做法引起的水土流失，农业生态系统每年都会遭受巨大的土地损失。稳定的土壤团聚体的存在可以最大限度地减少侵蚀，细菌可以促进其形成。其中一些微生物能够产生将土壤颗粒“粘合”在一起的胞外多糖和脂多糖。然而，人们对耕作强度对产生这些多糖的细菌潜力的影响知之甚少，尽管通常在不太强度的耕作下观察到更稳定的土壤团聚体。由于耕作强度对土壤团聚体稳定性的影响可能因地点而异，我们假设多糖产生细菌对耕作强度的反应也由地点特定条件决定。为了研究这一点，我们对从传统耕作土壤和减耕土壤中提取的 DNA 进行了高通量鸟枪测序，这些土壤来自以不同土壤参数为特征的三个耕作系统田间试验。虽然我们证实耕作强度对土壤团聚体的影响是特定地点的，但我们可以将团聚体稳定性的提高与参与胞外多糖和脂多糖生产的基因绝对丰度的增加联系起来。由于微生物生物量的增加，减少耕作通常会提高生产多糖的潜力。我们还发现，大多数潜在的多糖生产者对耕作的反应是特定地点的，例如，草酸杆菌科在减少耕作的情况下在一个地点具有更高的生产多糖的潜力，而在另一地点则表现出相反的反应。然而，一些潜在的多糖生产者对耕作的反应并不取决于地点特征，而是取决于它们的分类学隶属关系，即对耕作强度做出反应的放线菌的所有成员都具有更高的胞外多糖和脂多糖生产潜力，特别是在减少耕作的情况下。这对于聚集体稳定性尤其重要，因为不同类群产生的多糖具有不同的“粘合”效率。总体而言，我们的数据表明，耕作强度可能通过影响胞外多糖和脂多糖生产所涉及的基因的绝对丰度以及诱导潜在多糖生产者群落的变化来影响聚集体稳定性。耕作强度的影响主要取决于具体地点的条件。