TABLE 2.

Rates of Poterioochromonas sp. strain DS grazing on surfaces of treated or untreated cells of actinobacterial strain MWH-Po1 as well as on P. cosmopolitanus MWH-MoNR cellsa

StrainTreatmentGrazing rateb ± SD (no. of cells/flagellate/h)Cell volc ± SD (μm3)
MWH-Po1None1.3 ± 1.10.048 ± 0.006
MWH-Po1EDTA (0.2 M)6.2 ± 0.7*0.047 ± 0.006
MWH-Po1LiCl (0.5 M)5.5 ± 0.6*0.047 ± 0.007
MWH-Po1Formaldehyde (2%)6.7 ± 1.9**0.046 ± 0.007
MWH-MoNR1None3.8 ± 1.3**0.046 ± 0.007
  • a * and ** indicate significant differences from the values for untreated MWH-Po1 cells (P < 0.005 and P < 0.05, respectively; Student's t test). The cell volumes for treated MWH-Po1 and MWH-MoNR1 were insignificantly different from those for untreated MWH-Po1 cells (P > 0.01; Student's t test).

  • b Grazing rate = (initial abundance of MWH-Po1 − final abundance of MWH-Po1)/abundance of Poterioochromonas cells/incubation period. Prior to the experiment, strain MWH-Po1 and Poterioochromonas sp. strain DS were cultivated at 15 and 25°C, respectively. The experiments were performed at 25°C for 2 h (n = 3).

  • c DAPI-stained cells were measured (n = 100).