Characterizing iron reducing microorganisms from anoxic ferruginous lake sediments

Abstract

Lake Matano, Indonesia is a well-known ancient ocean analogue as its anoxic ecosystem in the subsurface sediments allow the growth of microorganisms capable of mediating anaerobic oxidation coupled to iron reduction. An anoxic, ferric iron rich BSR was kept for 163 days to culture iron reducing bacteria in an environmental sample from Lake Matano sediment. Microscopy analysis was performed periodically to look for morphology trends using DAPI staining. Phylogenetic analysis was performed using CARD-FISH microscopy to target the Geobacter genus, known for electroactive abilities through pilA and interactions with iron particles. Cell counts correlated with iron reduction throughout the culturing period indicating iron reducing microorganisms were present in the environmental sample. Filamentous, coccus, bacillus and vibrio morphologies were observed through the culturing period with vibrio and bacillus being predominant at later stages of the culture. Particle association instances were observed at days 20, 62, 86 and 126 and DIET interactions at day 86. Characterizing these microorganisms opens a broad range of possibilities for wastewater treatment (strip mining groundwater contamination), use in bioelectrochemical systems biofilms (due to external electron transport pilA) and understanding the importance of this microorganisms in Iron cycling.