Table 4.

Filtration efficiency of Isopore polycarbonate filters in the presence of microbial aggregates and other particlesa

IsolateConcn of isolate (CFU/ml)bParticle sourceConcn of total bacteria in particle source (CFU/ml)e% Recoveryf
P. fluorescensPF130A1.93 × 106 Leaf washingc 093
5.06 × 105 Leaf washing2.03 × 106 101
4.76 × 105 Leaf washing7.47 × 105 96
4.16 × 104 Leaf washing7.47 × 105 113
5.16 × 103 Leaf washing7.47 × 105 98
7.60 × 105 Biofilm cultured 8.40 × 103 97
P. putidaMC1-1001.01 × 106 Biofilm culture4.54 × 105 93
H. alveiMC1-0573.75 × 105 Biofilm culture5.78 × 104 90
C. aquaticumMC1-1081.24 × 106 Biofilm culture4.11 × 105 94
  • a Efficiency is expressed as the percentage of cells of rifampin-resistant strains of pure-culture, prefiltered bacteria that pass across filters in mixed suspensions containing biofilms and other particles.

  • b Mean concentration of prefiltered, pure-culture isolates, determined on rifampin-containing medium, in mixtures containing biofilms or other particles.

  • c Suspensions were obtained by washing leaves of broad-leaf endive in sterile buffer. The frequency of naturally occurring rifampin-resistant bacteria was <10−2 for these washings.

  • d Suspensions were obtained as described in the text. The frequency of naturally occurring rifampin-resistant bacteria was <2 × 10−4 for these cultures.

  • e Mean concentrations of total bacteria from leaf washings or biofilm cultures in the mixtures containing pure-culture suspensions.

  • f Percent rifampin-resistant CFU recovered from the mixtures. These values are the means of four to eight independent filtrations for each mixture.