Membrane filter (pore size, 0.22–0.45 μm; thickness, 150 μm) passing-through activity ofPseudomonas aeruginosaand other bacterial species with indigenous infiltration ability

Abstract

Bacteria growing on MF-Millipore filters (thickness, 150 Wm) passed through the underlying membrane by their infiltration activity. Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli passed through a 0.45-Wm pore size filter within 489 6 h. Pseudomonas aeruginosa, Serratia marcescens, and Listeria monocytogenes passed through a 0.3-Wm pore size filter. P. aeruginosa passed through a 0.22-Wm pore size filter. The membranes which allowed passing-through of bacteria showed normal bubble point values in the integrity test. Studies with isogenic S. marcescens mutants indicated that flagellum-dependent motility or surface-active exolipid were important in the passing-through. P. aeruginosa PAO1 C strain defective in twitching motility was unable to pass through the 0.22-Wm filter. Scanning electron microscopy showed bacteria passing-through the 0.22-Wm filter. Millipore membrane filters having welldefined reticulate structures will be useful in the study of infiltration activity of microbes.

Distinct Function of Pseudomonas aeruginosa Type IV Pili Disclosed in the Bacterial Pass‐Through of Membrane Filter with Smaller Pore Sizes

“…Consistent with these findings, SEM also indicated that the bacteria in the process of infiltration were not remarkably downsizing (5,11). The semi-quantitative studies showed that required times for the bacterial pass-through were dependent on the indicated filter pore sizes and bacterial species and strains (5). In the ordinary pressure filtration method (done in a very short time), passively streaming bacteria may be pushed into the narrow reticulate structure having 150 µm thickness (Fig.…”

“…Thus, indicated pore-size values with the membrane filters are not morphologically determined ones but are instead functional values for the ordinary pressure filtration method (11). Consistent with these findings, SEM also indicated that the bacteria in the process of infiltration were not remarkably downsizing (5,11). The semi-quantitative studies showed that required times for the bacterial pass-through were dependent on the indicated filter pore sizes and bacterial species and strains (5).…”

“…These pass-through-permitted filters were examined for the intactness and destructive effects due to the bacterial infiltration. The results obtained by the conventional filtration test and the bubble point test indicated intactness of the filters (5,11). Scanning electron micrographs (SEM) of uninoculated filters showed broad void spaces with longer distances (Ͼ1.0 µm) between polymer net fibers composing filters (5, 11).…”

“…By mutational studies with isogenic mutants, peritrichous flagella of Listeria monocytogenes were shown to work distinctly in the pass-through of membrane filters with a 0.45-µm pore size, but not with the 0.22-µm pore size (11). With regard to the type IV pili of Pseudomonas aeruginosa, twitching motilitypositive strain PAO1 T demonstrated the pass-through of 0.22-µm pore size filter, but the twitching motilitynegative strain PAO1 C did not (5). Although such results suggest contribution of type IV pili to the passthrough of the smaller sized pores, the mutational status of the strain PAO1 C has been unclear.…”

“…We have recently reported that many bacterial species point-inoculated on the surface of the membrane filter placed on a hard agar medium passed through the filter during long time incubation (10-96 hr) (5). These pass-through-permitted filters were examined for the intactness and destructive effects due to the bacterial infiltration.…”