Highly Efficient Capture of Marine Microbial Strains in Seawater Using Bare Fe₃O₄ Magnetic Beads

We develop a method to capture marine bacterial strains at high efficiency to replace the conventional two-step collecting method. Lab-made, Fe₃O₄ magnetic beads were used to firstly verify the feasibility of capture in artificial seawater, using Bacillus velezensis. Almost 100% of the bacteria could be captured and separated within 10 min. Then, the salinity of capture medium was proved to have the most marked effect on the capture process. After that, the broad application and high efficiency of capture were verified using four different bacterial strains from the Pacific Ocean. Subsequently, through adjusting the salinity, the capture efficiency for Pseudoalteromonas sp. and Halomonas meridiana was increased from 20 to ~ 80% in a seawater system, which was used to simulate the in-situ capture conditions. Finally, mixed strains in seawater were successfully captured, and their genomic DNAs were isolated and analyzed. Bare Fe₃O₄ magnetic beads were initially applied to capture marine microorganisms and this method is convenient and highly efficient and thus has great potential to replace the conventional two-step method.