Table 2.

Mean retention rates of bacteria on three types of 5-μm-pore filtersa

StrainLSWP filtersSVLP filtersTMTP filters
No. of cells filteredb% Retained (mean ± SD)cNo. of cells filtered% Retained (mean ± SD)No. of cells filtered% Retained (mean ± SD)
Pseudomonas fluorescensPF130A9.57 × 107 0.03 ± 0.019.03 × 107 0.31 ± 0.039.65 × 107 <0.001d
Pseudomonas putidaMC1-1001.37 × 108 1.91 ± 0.151.33 × 108 1.32 ± 0.241.40 × 108 0.004 ± 0.003
Corynebacterium aquaticumMC1-0981.01 × 108 0.04 ± 0.019.50 × 107 2.29 ± 0.139.75 × 107 0.004 ± 0.002
Corynebacterium aquaticumMC1-1088.17 × 107 0.04 ± 0.018.03 × 107 0.34 ± 0.037.95 × 107 <0.001d
Hafnia alveiMC1-0576.17 × 107 0.52 ± 0.036.60 × 107 0.54 ± 0.005.55 × 107 <0.002d
  • a The filters are described in Table 1. Retention rates were determined for bacterial suspensions prefiltered across SVLP filters.

  • b Values represent the mean number of bacteria in three 50-ml aliquots of suspensions passed across each type of filter. Each suspension had been prefiltered across polyvinylidene fluoride filters (5-μm-diameter pores) before the population sizes were determined.

  • c Values represent the mean and standard deviation (SD) of the percentage of bacteria retained on the filters for three independent filtrations.

  • d The number of bacteria on the filters was below the detection limit (1,000 CFU/filter) for all filters in this test. Hence, the percent retention rate was estimated by using the detection limit.