Evaluating the impact of bead media diameter and material composition on bacterial cell lysis and genomic DNA extraction

Mechanical lysis of bacteria is a common alternative to enzymatic, detergent, or tonicity-based methods. Mechanical lysis is needed in areas of research where introducing chemicals can compromise either the assay or the analyte and is achieved in a variety of ways, one of which is bead beating. Bead beating utilizes small beads of various sizes and composition to contact the sample with high energy to facilitate lysis. This type of lysis can be achieved using many different types of equipment from laboratory vortexers to specialized bead mills. Maximizing the amount of lysis is important for both consistency of analyte extractions and increasing yield when sample size is limited. Herein, we evaluate two bead media compositions (borosilicate glass and yttria-stabilized zirconium oxide) and two sizes of each of those compositions (0.5 mm and 0.1 mm) to analyze what factors are most important to achieve the maximum amount of lysis using cultures of Escherichia coli, Staphylococcus epidermidis, and Nocardia brasiliensis. Speed, time, number of beads, and mass were all controlled to identify the ideal size, composition, force and duration to maximize cell lysis while maintaining nucleic acid integrity. In order to evaluate lysis efficiency cells were disrupted then plated to enable colony counting. After each processing step, genomic DNA was purified, quantified, and analyzed by gel electrophoresis to evaluate genomic DNA integrity. In all cases, it was determined that bead diameter played a greater role in lysis efficiency when compared to bead material even though kinetic energy of the zirconium oxide beads is 2X greater than the glass at a given tube velocity. E. coli was lysed at greater than 90% total cell lysis in three minutes at a tube velocity of 4.2 m/s (Figure 1). No DNA degradation was observed after homogenization for 1 minute. Increasing amounts of DNA shearing was observed as processing was increased (Figure 2). This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.