Expansion in the size is an indispensable stage in the granular sludge life cycle, but little attention has been payed to the enlargement mechanism of granular sludge. Here, we propose a novel anammox granule enlargement mechanism by the self-assembly of heterogenous granules. Two different colors of anammox granules, dark-red granules (DR-Granules) and bright-red granules (BR-Granules) were found in an expanded granular sludge bed reactor. These two heterogenous granules were not isolated but were assembled into granules with a larger DR-Granule in the center and many smaller BR-Granules aggregated on the surface, increasing the overall granular size. Their physiochemical characteristics in terms of EPS, adherence, rheological properties, and microbial compositions, were identified and compared to elucidate the interaction between the different colors of granules. The BR-Granules created 92% more extracellular polymeric substances than the DR-Granules. This material blocked the passage of gas and substrate, leading to BR-Granules smaller size and a yield stress approximately 48% lower than that of the DR-Granules. Nevertheless, the BR-Granules had compact extracellular protein secondary structures and a high adherence rate to the surface of the DR-Granules, upon which they formed a compact adhered layer. These unique features enabled them to directionally adhere to DR-Granules in the core, that is, two heterogenous colors of granules self-assembled into large anammox granules. The enlargement mechanism was further supported by the abundance of K-strategy Ca. Kuenenia in the DR-Granules (inner layer) being higher than in the BR-Granules (outer layer; 2.9 ± 0.4% vs. 0.4 ± 0.1%; p = 0.0003) and by visualized confirmation that the larger BR-Granules wrapped around smaller DR-Granules inside. This demonstrates that heterogenous anammox granules actively self-assemble into large granules, which is an important step in the lifecycle of anammox granules.

粒度的增长是颗粒污泥生命周期中必不可少的阶段，但对颗粒污泥的扩大机理却很少关注。在这里，我们通过异质颗粒的自组装提出了一种新型的厌氧氨氧化颗粒增长机制。在膨胀的颗粒污泥床反应器中发现了两种不同颜色的厌氧氨氧化颗粒：深红色颗粒（DR-颗粒）和亮红色颗粒（BR-颗粒）。这两个异质颗粒不是分离的，而是组装成具有较大DR-颗粒在中心且许多较小的BR-颗粒聚集在表面的颗粒，从而增加了总体颗粒大小。它们在EPS，附着力，流变性质和微生物组成方面的理化特性，进行鉴定和比较以阐明不同颜色颗粒之间的相互作用。与DR颗粒相比，BR颗粒产生的细胞外聚合物质多92％。这种材料阻止了气体和基质的通过，导致BR-Granules的尺寸更小，屈服应力比DR-Granules的应力低约48％。然而，BR-颗粒具有紧密的细胞外蛋白二级结构和对DR-颗粒表面的高粘附率，在其上形成了紧密的粘附层。这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了 与DR颗粒相比，BR颗粒产生的细胞外聚合物质多92％。这种材料阻止了气体和基质的通过，导致BR-Granules的尺寸更小，屈服应力比DR-Granules的应力低约48％。然而，BR-颗粒具有紧密的细胞外蛋白二级结构和对DR-颗粒表面的高粘附率，在其上形成了紧密的粘附层。这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了 与DR颗粒相比，BR颗粒产生的细胞外聚合物质多92％。这种材料阻止了气体和基质的通过，导致BR-Granules的尺寸更小，屈服应力比DR-Granules的应力低约48％。然而，BR-颗粒具有紧密的细胞外蛋白二级结构和对DR-颗粒表面的高粘附率，在其上形成了紧密的粘附层。这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了 导致BR-Granules的尺寸更小，屈服应力比DR-Granules低约48％。然而，BR-颗粒具有紧密的细胞外蛋白二级结构和对DR-颗粒表面的高粘附率，在其上形成了紧密的粘附层。这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了 导致BR-Granules的尺寸更小，屈服应力比DR-Granules低约48％。然而，BR-颗粒具有紧密的细胞外蛋白二级结构和对DR-颗粒表面的高粘附率，在其上形成了紧密的粘附层。这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了 这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了 这些独特的功能使它们能够定向粘附到核心的DR-颗粒上，即两种异质颜色的颗粒自组装成大的厌氧氨氧化颗粒。扩大机制进一步得到了ķ -strategy的Ca. DR-颗粒（内层）中的Kuenenia高于BR-颗粒（外层; 2.9±0.4％vs.0.4±0.1％; p  = 0.0003），并且通过可视化确认较大的BR-颗粒包裹在较小的颗粒周围DR-颗粒内部。这表明异质厌氧氨氧化颗粒可主动自组装成大颗粒，这是厌氧氨氧化颗粒生命周期中的重要一步。