Isolation and characterization of Iron-Manganese oxidizing bacteria from Gikondo urban marshland, Rwanda

Iron (Fe) and Manganese (Mn) oxidizing bacteria (IMnOB) play a crucial role in the oxidation and removal of Fe and Mn in aquatic ecosystems. Marshlands shelter a broad spectrum of biota, sequester CO2, and influence climate resilience. Additionally, they are hotspots of wastewater pollution; thus, they may shelter various bioremediators. Previous works have explored the isolation and characterization of IMnOB in soil, water, wastewater, and medical settings. However, IMnBO have not been isolated in urban marshlands so far. This study aimed to isolate, identify, and phylogenetically characterize the IMnOB from the surface water of Gikondo marshland in Rwanda. Bacterial culturing showed rusty (yellow) and brown colonies of iron-oxidizing bacteria (IOB) and manganese-oxidizing bacteria (MnOB), respectively. Furthermore, Sanger sequencing data revealed that bacterial colonies were similar to two distinct Betaproteobacterial species. One group clustered with Ralstonia pickettii, while the other clustered with Pseudomonas sp. with high homology to Pseudomonas seleniipraecipitans. Taken together, bacteria culturing and Sanger sequencing revealed that the isolates were assigned to the versatile metabolic genera Ralstonia and Pseudomonas. These results suggested that isolated bacterial species could serve as inocula for the improved simultaneous removal of Fe and Mn in water treatment systems.