When it comes to isolating DNA and RNA from all kinds of samples, the fastest and most thorough approach is high speed bead beating.  Whether you have microbes, mouse tissues, plant seeds and leaves, or difficult soils, homogenization using beads will break open cell walls and membranes and release the desired DNA and RNA so it can be isolated and purified.

Today there are many choices for beads to use and it can get confusing trying to figure out which is best for what you want to do. To make that easier for you, I am going to summarize the characteristics of all of the bead matrices we use at MO BIO Labs and what types of samples we recommend for them.

In a previous article, we discussed in great detail the homogenization conditions  recommended for RNA extraction. Today’s discussion will give you an overview of the entire selection of bead choices for both DNA and RNA.

Vortex :

We’ll start with bead tubes typically used on the vortex. The vortex is excellent for homogenization of samples for DNA work because it is gentle and allows for higher integrity DNA. 

0.15 mm Garnet: This is used for extracting DNA from microbial cultures, including pure cultures or bacteria pelleted out of water, urine, or blood sepsis cultures. This fine sand-like matrix has rough edges for excellent cell wall shearing, but is soft and does not damage DNA under vortex homogenization.

Kits used: We use this bead type in our UltraClean Microbial DNA Kit, PowerFood  DNA Kit (in a 0.5 ml tube)  and Bacteremia DNA Kit (in a 2.0 ml tube).

0.7 mm Garnet: This bead type looks more like different shaped rocks. They are very irregular in shape and a mixture of sizes from large to small. They are sharp and bulky and can break down any semi-solid matrix or chunky samples.

Kits used: We use this bead type for breaking down animal tissues on a vortex in the UltraClean Tissue and Cells DNA Isolation Kit and for soil DNA extraction in the UltraClean Soil and PowerSoil DNA Isolation Kits and the UltraClean Fecal DNA Isolation Kit, in a 2 ml tube. It also is provided in 15 ml tubes in the RNA PowerSoil Isolation Kit and UltraClean Water DNA Isolation Kit and in 50 ml tubes in the PowerMax Soil DNA Isolation Kit .

0.15mm/0.7 mm Garnet: A mixture of these bead types is used in the Powerwater DNA Isolation Kits and RapidWater DNA Isolation Kits in a special 5 ml bead tube.  We had to change the tube so that a complete 47 mm water filter membrane could fit inside the tube without bending.  We give more advice on how to choose a filter membrane and how to transfer it to the bead tube here. The combination of grinding beads allows for complete release of microbes from within and on top of the membrane surface for lysis in the bead tube.

0.25 mm Silica Carbide:  This bead type has a sharp flake like consistency. These are fine slivers of silica carbide that effectively tear open microbial cells and help shear genomic DNA. We use these for RNA preparations.

Kits used: We use this bead type for RNA purification from microbes in a 0.5 ml tube in the UltraClean Microbial RNA Isolation Kit.  We also use this bead in the Biostic Stabilized Blood RNA Isolation Kit to shear genomic DNA before binding RNA to a spin filter. It is extremely effective for reducing viscosity in RNA preps.

Vortex or High Powered Bead Beating:

Glass bead tubes can be used on both the vortex or the high powered bead beater. However, glass beads are the preferred choice for high powered bead beating, because they do not crush under high velocity.

0.1 mm Glass: The smallest glass bead is 0.1 mm glass. These are spherical in shape and because they are extremely hard they won’t break under high forces.  We find these to be the best choice for certain soils, such as clay, sediment or sand, and when extracting DNA from spores or fungus. We have found this type of bead to work well on both the vortex or PowerLyzer.

Kits used: We use these beads in the PowerLyzer UltraClean Microbial DNA Isolation Kit in a 0.5 ml tube and the PowerLyzer PowerSoil DNA Isolation Kit in a 2 ml tube.  More data showing their effectiveness for clay soils is here and coming soon in a new MO BIO Labs study we will publish online.

0.5 mm Glass: The next size up are the 0.5 mm glass eads which are spherical and also hard enough to be used in high powered bead beating. Although we do not employ these into any kits, they may be useful for isolation of DNA from fungus or samples where you need a slightly bigger bead to break down a tough matrix. We offer these in a 2 ml tube.

Bead Tubes for High Powered Bead Beating:

The following beads are large in size and used for breaking the toughest sample types or for RNA extraction. For this reason, a vortex typically does not have the force required for a complete extraction.

2.38 mm Metal Bead Tubes: This bead tube is used for plant DNA extraction in our lab. The metal beads are tough and can even be used on a vortex for soft plant tissue, such as leaf. For most plant samples, a high powered bead beating will release more DNA. The metal works well for plant DNA because the lysis buffer does not contain high concentrations of chaotropic salts that cause discoloration of the metal beads.  And these beads come in our Tough Tube which will not break under extreme forces.  

Kits used: We utilize this bead type in the PowerPlant DNA Isolation Kit.

1.4 mm Ceramic Bead Tubes:  The small ceramic beads are useful for RNA extraction in some applications where th sample is too small to be efficienctly broken by the 2.8 mm beads. We do not use the 1.4 mm ceramic in kits because we find that the larger 2.8 mm ceramic bead does the best job for all of the plants and animal tissues we’ve tested. However, these ceramic beads are available for custom applications. Sometimes ceramic beads are called zirconium by other suppliers. Zirconium is a ceramic material.

2.8 mm Ceramic Bead Tubes:  We use these for most applications involving the PowerLyzer. The 2.8 mm Ceramic Beads are great for isolation of RNA from all kinds of tissues and also from plant stem, leaves, and roots. The ceramic bead will not rust or change color in the presence of the strong lysis buffers used for RNA isolation. These also come pre-loaded in Tough Tubes.

Kits used: We use these in 2 ml bead tubes in the PowerLyzer UltraClean Tissue & Cells RNA Kit and the PowerLyzer UltraClean Plant RNA Kit.

All of these bead tubes are available as stand alone items in case you want to develop your own protocols and try your own combinations. We now offer most of the beads in bulk so you can save money and make your own bead tubes. Tough Tubes can be purchased separately as well.

If you have an application that does not fall into any of these descriptions and want help choosing beads for your sample, just let us know and we are happy to help. We are at technical@mobio.com.