Distribution of ferric reducing bacteria and anoxygenic phototrophic bacteria in the Yellow River beach and paddy soil

Abstract:

[Objective] To explore the distribution of ferric reducing bacteria (FeRB) and anoxygenic phototrophic bacteria (AnPB) in the soil along the Yellow River. [Methods] Soil samples were collected from the beach and paddy fields at the Yuanyang section of the Yellow River. High-throughput sequencing of 16S rRNA gene and quantitative real-time PCR were combined with statistical analysis to reveal the structure and abundance of FeRB and AnPB and the main environmental factors affecting the bacteria. [Results] The dominant FeRB families (genera) were Hydrogenophilaceae (Thiobacillus), Bacillaceae (Bacillus), Clostridiaceae, Rhodobactereace (Rhodobacter) and Geobacteraceae (Geobacter). The dominant AnPB families (genera) were Rhodobactereace (Rhodobacter), Chloroflexaceae (Chloronema) and Acetobacteraceae (Roseomonas). The relative abundance of Rhodobacteraceae (AnPB) was negatively correlated with that of Bacillaceae and Clostridiaceae (FeRB). The relative abundance of Sphingomonadaceae (AnPB) was negatively correlated with that of Hydrogenophilaceae and Clostridiaceae (FeRB). Soil nitrate nitrogen (NO₃^--N) was negatively correlated with the relative abundance of Rhodobacteraceae but positively correlated with that of Geobacteraceae. Ferrous ions (Fe²⁺) explained 13.5% and 41.8% of the community variations of FeRB and AnPB, respectively; pH explained 65.7% and 42.8%, respectively. The number of total bacteria (BAC), Geo(thermo)bacter (GEO) and phototrophic purple bacteria (PPB) in the Yellow River beach was 2.52 (±3.43)×10⁹, 5.21 (±7.58)×10⁷ and 2.9 (±3.70)× 10⁷ copies/g dry soil, respectively, and that in the paddy soil was 3.82 (±1.29)×10¹⁰, 3.05 (±2.44)×10⁸ and 4.31 (±0.90)×10⁸ copies/g dry soil, respectively. Moreover, the PPB in the upmost soil layer (0-1 cm) were significantly more than those in the 1-2 cm and 2-3 cm soil layers. Fe²⁺ explained 81.5% variations in the absolute abundance of BAC, GEO and PPB. [Conclusion] The potential community of FeRB and AnPB and the abundance of GEO and PPB varied between different soil types. Overall, Fe²⁺ played a key role in shaping the distribution pattern of FeRB and AnPB.