Impact of culture conditions on the biofilm and cell morphology of Shewanella oneidensis MR-1

Abstract:

[Objective] Although Shewanella oneidensis MR-1 is a typical electroactive model bacterium, its biofilm morphology remains to be systematically studied. This work aims to improve the understanding of biofilm morphology of S. oneidensis MR-1, thus providing basic data to support its role as a model strain. [Methods] Culture conditions such as medium type, buffer concentration, vitamins, trace elements, inorganic salts, electron shuttles, donors, and acceptors were taken as the variables to be studied. The biofilm was cultured under potentiostatic conditions and examined by scanning electron microscopy. [Results] The cells were mostly straight and short in low-concentration (30 mmol/L and 100 mmol/L) buffer solutions while became curled and elongated in high-concentration (200 mmol/L and 300 mmol/L) buffer solutions. The shortage of vitamins, trace elements, and inorganic salts made the biofilm become compact and attach closely to the electrode. The addition of an electron shuttle substantially thickened the biofilm, while a lack of an electron acceptor led to serious cell lysis within one day. In addition, a cable-like structure as long as 100 μm was observed in the biofilm, which indicated a long-distance electron transfer survival strategy of S. oneidensis MR-1. [Conclusion] Changing the medium type, buffer concentration, electron shuttles, donors, and acceptors can regulate the biofilm and cell morphology of S. oneidensis MR-1.