Directed regulation of anammox communities based on exogenous siderophores for highly efficient nitrogen removal.

It is expected that the quicker domestication of anaerobic ammonia oxidation (anammox) communities and the enhancement of their nitrogen transformation capability can be achieved through targeted regulation of anammox communities. Iron cast a vital role in the growth and metabolism of anammox bacteria. Specific siderophores offer promising prospects for the targeted regulation of anammox communities by facilitating the efficient utilization of iron. Two siderophores-enterobactin and putrebactin-exclusively for Ca. Brocadia and Ca. Kuenenia were developed to specifically regulate anammox communities towards different directions, respectively. Anammox communities in the reactors evoluted targetedly towards Ca. Brocadia-dominated communities and Ca. Kuenenia-dominated communities, respectively, leading to a maximum increase in community nitrogen removal capacity by 84.64±0.55% and 210.26±0.57%, respectively, under different nitrogen concentrations. It was indicated that siderophores could regulate anammox communities by redistributing iron resources in a targeted manner based on the analyses of transcriptome and proteome. This study provides novel insights into the rational selection and utilization of exogenous siderophores as an effective implement to manipulate anammox communities and create communities with high nitrogen removal ability fleetly.

Affinity difference determines the assembly and interaction mode of anammox community reconstructed by siderophores.

Anammox community is the core of anammox process. The constancy of the anammox community determines the stability of the anammox process and the ability of withstand environmental impact. Community stability is influenced by the assembly and interaction mode of the community. This study aimed to explore the assembly, interaction mode, and stability of anammox community influenced by two siderophores (enterobactin and putrebactin) specific for Ca. Brocadia and Ca. Kuenenia as produced in our previous research. Siderophores improved the stability of the anammox community, among which vulnerability dropped by 30.02 % and 72.53 % respectively. Enterobactin and putrebactin altered the succession speed and assembly pattern of communities, with a respective increase of 9.77 % and 80.87 % in the deterministic process of anammox community assembly, respectively. Enterobactin and putrebactin reduced the dependence of Ca. Brocadia and Ca. Kuenenia on companion bacteria by 60 items and 27 items respectively. The affinity of different siderophore-Fe with bacterial membrane receptors caused variations in community reconstruction, with Ca. Brocadia and Ca. Kuenenia exhibiting the highest affinity with enterobactin-Fe (-11.4 kcal/mol) and putrebactin-Fe (-9.0 kcal/mol), respectively. This study demonstrated how siderophores can enhance the stability of anammox process by regulating assembly and interaction mode of anammox community, while also revealing the underlying molecular mechanisms.