Mini-metagenome analysis of psychrophilic electroactive biofilms based on single cell sorting

Understanding the metabolic function of psychrophilic electroactive bacteria is important for the investigation of extracellular electron transfer (EET) mechanisms under low temperatures (4-15 °C). In this study, Raman activated cell ejection coupled high throughput sequencing was used to accurately generate a mini-metagenome of psychrophilic bacterial community. Hierarchical cluster analysis of the Raman spectrum could accurately select the target Geobacter cluster. The high relative abundance of the membrane transport functional genes ftsEX in the biofilm community indicated an adaptation to reduced temperature, which aided survival of the electroactive bacteria under low temperature. The basal metabolism such as citrate cycle and glycolytic pathway maintained the electron pool for the EET process. The identification of iron (III) transport system genes in high abundance indicated their presence in an active metabolic reaction for potential electron transfer process. It showed the potential involvement c-type cytochromes (coxA and cox1) activity in EET. These results indicated that psychrophilic Geobacter had effective EET mediated by c-type cytochromes at low temperatures.