TABLE 2.
Predominant 18S rRNA gene sequences clustering with free-living protozoa obtained from the biofilm in BBT flasks with growth of L. pneumophila and/or L. anisa after ≥20 days of incubation at 37°C
| Water type | BBT flask | Growth in flaska |
L. pneumophila/H. vermiformis ratiob (log10) | % of clones clustering with: |
Predominant OTU clustering with protozoa |
||||
|---|---|---|---|---|---|---|---|---|---|
| L. pneumophila | H. vermiformis | Protozoa | H. vermiformis | Organism with highest similarity (accession no.) | Similarity (%) | % of clones | |||
| Biomass from limestone filter bed (supply A) | I | + | + | 1.1 | 100 | 100 | Hartmannella vermiformis (AY680840) | 99.5 | 100 |
| Installation A2 (supply A) | II | + | + | 3.0 | 100 | 93 | H. vermiformis (AY680840) | 100 | 93 |
| Biomass from sand filter bed (supply B) | I | + | − | >6.8f | 91 | <2 | Rhinosporidium sp. (AY477020) | 89.3 | 73 |
| II | + | + | 2.0 | 97 | 93 | H. vermiformis (AY680840) | 99.8 | 97 | |
| III | + | − | >6.6f | 16 | <3 | Uncultured cercozoan clone (AY620304) | >97.7 | 80 | |
| Installation B1 (supply B) | II | −c | + | 1.9e | 100 | 27 | Sphaeroeca volvox (Z34900) | 83.6 | 73 |
| Installation B2 (supply B) | I | +c | + | 2.0 (2.3e) | 100 | 100 | H. vermiformis (AY680840) | 100 | 100 |
| II | −c | + | 2.9e | 100 | 100 | H. vermiformis (AY680840) | 100 | 100 | |
| Biomass from granular activated carbon filter bed (supply D) | I | + | + | 3.4 | 100 | <13 | Nuclearia simplex (AF484687) | 100 | 100 |
| Biomass from sand filter bed (supply D) | II | + | + | 1.6 | 92 | 92 | H. vermiformis (AY680840) | 100 | 100 |
| Water from Rhine River (autumn) | I | + | − | >5.6f | 15 | <5 | Neoparamoeba sp. (AF371972) | 95.6 | 67 |
| II | + | − | >5.7f | 87 | <4 | Uncultured eukaryote from treated water of groundwater supply B (EU860860) | 93.9 | 100 | |
| Water from Rhine River | I | + | + | 5.5f | <3 | <3 | No protozoan observed | ||
| (winter) | II | + | + | 2.1 | 61 | 52 | H. vermiformis (AY680840) | 99.8 | 86 |
| Treated sewage | II | + | − | >4.6f | 52 | <4 | Diphylleia rotans (AF420478) | 99.3 | 100 |
| Cooling tower 1 | I | + | + | 2.7 | 42 | 21 | H. vermiformis (AF426157) | 100 | 50 |
| II | + | + | 2.1 | 50 | 17 | H. vermiformis (AF426157) | 99.8 | 33 | |
| Cooling tower 5 | I | + | − | >4.5f | 64 | <4 | Echinamoeba thermarum (AJ489262-AJ489268)g | 96.2-98.7 | 79 |
| II | + | −d | 3.6 | 89 | 7 | E. thermarum (AJ489262-AJ489267-AJ489268)g | 96.2-98.9 | 42 | |
+, significant growth (P < 0.05); −, no growth.
Log-transformed ratio between the maximum concentration of L. pneumophila and the maximum concentration of H. vermiformis.
Significant growth (P < 0.05) of L. anisa in the BBT flask.
H. vermiformis was detected, but no significant growth was observed.
Log-transformed ratio between the maximum concentration of L. anisa and the maximum concentration of H. vermiformis.
Log-transformed L. pneumophila/H. vermiformis ratio exceeds the tolerance limit of L. pneumophila/H. vermiformis ratio for the control group (4.5).
More than one OTU with highest similarity to E. thermarum.