TABLE 1.
Culture-dependent and real-time PCR-monitored necrotrophic growth of L. pneumophilaa
| Inoculum |
L. pneumophila CFU/ml (SD)
|
L. pneumophila mip gene copies/ml (SD)
|
||
|---|---|---|---|---|
| 0 h | 96 h | 0 h | 96 h | |
| L. pneumophila (approx 106 cells) | 7.8 × 105 (2.5 × 105) | 2.5 × 105 (1.3 × 105) | 2.4 × 106 (8.6 × 105) | 6.2 × 105 (6.3 × 104) |
| L. pneumophila + 109 live P. putida cells | NA | 3.7 × 106 (1.9 × 106) | ||
| L. pneumophila + 103 dead P. putida cells | 4.2 × 105 (2.6 × 105) | 3.5 × 106 (9.6 × 105) | ||
| L. pneumophila + 104 dead P. putida cells | 3.8 × 105 (9.5 × 104) | 9.8 × 105 (4.5 × 105) | ||
| L. pneumophila + 105 dead P. putida cells | 6.5 × 105 (3.6 × 105) | 3.5 × 106 (1.8 × 106) | ||
| L. pneumophila + 106 dead P. putida cells | 4.5 × 105 (3.1 × 105) | 4.6 × 106 (1.7 × 106)* | ||
| L. pneumophila + 107 dead P. putida cells | 6.9 × 105 (2.6 × 105) | 9.1 × 106 (2.0 × 106)* | ||
| L. pneumophila + 108 dead P. putida cells | 5.3 × 106 (1.1 × 106)* | 4.8 × 107 (9.6 × 106)* | ||
| L. pneumophila + 109 dead P. putida cells | 1.1 × 107 (7.2 × 106)* | 8.9 × 107 (2.0 × 107)* | ||
| L. pneumophila + 109 dead E. coli cells | 6.3 × 106 (2.6 × 106)* | 6.5 × 107 (1.3 × 107)* | ||
| L. pneumophila + 109 dead L. plantarum cells | 6.0 × 105 (4.2 × 105) | 7.5 × 105 (5.2 × 105) | ||
| L. pneumophila + 109 dead B. subtilis cells | NA | 1.8 × 105 (8.6 × 104) | ||
| L. pneumophila + 108 dead A. castellanii cells | 6.8 × 106 (3.0 × 106)* | 4.8 × 107 (1.3 × 107)* | ||
| L. pneumophila + 109 dead S. boulardii cells | 5.5 × 106 (2.8 × 106)* | 1.1 × 107 (8.2 × 106)* | ||
| L. pneumophila + heat-treated biofilm | NA | 2.9 × 107 (7.6 × 106)* | ||
a
Necrotrophic growth of L. pneumophila in sterile tap water on heat-killed (30 min, 60°C) microbial cells was measured. All L. pneumophila starting concentrations were approximately 106 CFU/ml. Quantification of L. pneumophila cells during 96 h was performed using plate counts on BCYE agar and real-time PCR targeting of the mip gene. Numbers presented are mean values of five repetitive experiments for which each separate experiment was measured in triplicate. An asterisk indicates significant necrotrophic growth of L. pneumophila compared to the starting concentration. NA, not available due to bacterial overgrowth.