Concentration of Microbial Populations from Aquatic Environments by Vortex Flow Filtration

Vortex Flow Filtration was used to concentrate particulate DNA, chlorophyll a and bacteria from freshwater, estuarine, coastal and oligotrophic marine environments. A Membrex Benchmark System with either a 100 kD or a 0.45-mu-m filter and a large-scale Pacesetter System with a 100 kD filter were used. The Benchmark System is ideal for processing 100 ml to 50 l of water, while the Pacesetter is designed for working with volumes from 20 l up to hundreds of liters. The Benchmark System with a 100 kD filter yielded an average recovery of 81.7, 83.3 and 80.5% respectively for particulate DNA, chlorophyll a and bacteria. The efficiency of recovery with the Pacesetter System was 38.0, 38.1 and 43.6% respectively for particulate DNA, chlorophyll a, and bacteria. The filtration rate was 66.5 +/- 10 l h-1 for the Pacesetter and 7.8 l h-1 for the Benchmark System with the 100 kD filters. Our results indicate that the Benchmark System is suitable for quantitive studies that require a high efficiency of recovery using small volumes of water, while the Pacesetter is more suited for qualitative studies that require concentrating microbial populations from large quantities of water for genetic and molecular phylogenetic studies.