Researcher(s)
- Anthony Nguyen, Biological Sciences, University of Delaware
Faculty Mentor(s)
- Olushola Awoyemi, Earth Sciences, University of Delaware
- Clara Chan, Earth Sciences, University of Delaware
Abstract
Leptothrix ochracea is a filamentous iron-oxidizing microbe, present in freshwater environments. It is characterized by the creation of hollow, tube-shaped “sheaths.” Despite several attempts, L. ochracea has never been isolated. Past research had made impure cultures that had lots of sheaths, but very few L. ochracea cells. With relatively low cell counts and narrow understanding of its metabolism, the conditions it needs for growth and enrichment are not precisely known. By isolating it, knowledge of L. ochracea’s growth conditions can be used to control the iron cycle in freshwater bodies, which can significantly alter the flow of iron within and the ecosystem around it. In this study, liquid cultures were made using environmental water that was mixed with soil from iron mat sites and then filtered, containing trace nutrients that would boost chances of growth and isolation. We provided pyruvate, lactate, and ferrous sulfate as possible electron donors and carbon sources essential for growth and sheath production and altered oxygen levels and pH. Upon visible growth of orange-yellowish iron mats, microscopy was performed to determine the presence of sheaths and cells. After successful growth was observed, we made transfers towards obtaining pure cultures. Our results suggest that using sediment extract and water from the iron mat location supported growth. The enrichment cultures appear to perform better on low pyruvate or lactate combined with daily additions of ferrous iron. Enrichment cultures of Leptothrix spp. are likely present, but need genome sequencing to confirm. With a baseline of sediment extract with a suitable carbon source and consistent iron replenishment, a sufficient foundation is laid down to continue optimizing Leptothrix spp. cultures. Future cultures can be more efficient, and can focus on other factors that may impact growth. Isolating axenic L. ochracea will allow more experiments to test its growth and iron-oxidizing mechanisms.