Table 3.

Mean retention rates of bacteria on Isopore polycarbonate filtersa

Bacterial populationNo. of CFU filteredd% Retention (mean ± SD)e
Broad-leaf endive epiphytesb 2.12 × 107 1.20 ± 0.76
1.85 × 107 1.67 ± 0.95
1.18 × 106 0.41 ± 0.21
1.12 × 106 4.06 ± 1.98
1.05 × 105 0.64 ± 0.44
6.87 × 104 3.15 ± 1.29
Parsley epiphytesc 5.31 × 107 0.59 ± 0.37
7.83 × 106 0.21 ± 0.15
7.73 × 105 0.20 ± 0.03
  • a Retention rates were determined for bacterial suspensions previously filtered with the same type of filter.

  • b These mixed populations were obtained by washing 200 g of leaves of field-grown broad-leaf endive in 1 liter of phosphate buffer and recovering the liberated microorganisms by filtration with nitrocellulose filters (0.22-μm-diameter pores).

  • c These mixed populations were obtained by washing 85 g of leaves of field-grown parsley in 1 liter of buffer and filtering them as described for the endive epiphytes.

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

  • e SD, standard deviation.