Table 2. Summary of potential virulence mechanisms of tested strains and their association with nematode killing.
| Strain: a | B.ceno HI2424 | B.ceno AU1054 | B.ceno AU1107 | B.ceno J2315 | B. ceno PC184 | B.cep ATCC 25416 | B. cep HI2284 | B.mul ATCC 17616 | B. mul HI2240 | B.amb AMMD | B. amb HI2502 | E. coli OP50 | P. aerug. PA14 |
| Nematodes killed in liquidb | 67±4% | 58±2% | 3±0% | 75±3% | 17±4% | 35±2% | 66±2% | 2±1% | 21±1% | 53±1% | 74±1% | 5±2.6% | 3±2.0% |
| Nematodes killed on PGS agarc | 44±5% | 10±0% | 12±10% | 43±2% | – | 43±1% | 23±3% | 6±2% | – | 70±6% | – | 0±0% | 7±1.4% |
| Nematodes killed by toxin productiond | 84±4% | 50±5% | 0±0% | 80±6% | – | – | 39±5% | 0±0% | – | – | 43±1% | 0±0% | 41±12% |
| Protease productione | 3 | 0 | 1 | 2.5 | – | 0 | 0 | 0 | – | 4 | 2.5 | 0 | – |
| Swarming motilityf | 4.7±1.2 | 0 | 5.0±0.0 | 9.5±0.4 | 0 | 0 | – | 0 | – | 0 | 0 | 0 | – |
| C8-AHL productiong | 5.18±0.18 | 18.37±0.76 | 5.16±0.42 | 6.54±0.46 | 2.04±0.11 | 18.52±0.36 | 1.90±0.03 | 18.98±0.38 | 5.57±0.34 | 1 | 1.33±0.03 | ||
| Supernatant attractionh | 3.55±0.63 | 1.0±0.51 | 7.25±1.46 | 4.44±1.37 | – | 2.63±0.52 | – | 1.04±0.23 | – | 0.97±0.41 | – | 1 | 1.08±0.01 |
a. B. ceno = B.cenocepacia; B. cep = B.cepacia; B. mult = B. multivorans; B. amb = B. ambifaria, P. aerug = P. aeruginosa.
b. Liquid killing = mean percentage of nematodes killed by ∼120 h, ± SEM (n = 3). Burkholderia strains vary significantly in lethality, F = 155.3, p<0.0001.
c. PGS agar killing = mean percentage of nematodes killed by 48 h on high-osmolarity PGS agar; ± SEM, (n = 3) -- = not determined. Burkholderia strains vary significantly in lethality, F = 36.57 p<0.0001.
d. Toxin-mediated killing = mean percentage of nematodes killed by a toxin secreted by the test strain after 24 h; the toxin traversed a filter and was localized in agar. (± SEM, n = 3). nd = not determined. Burkholderia strains vary significantly in lethality, F = 129.2 p<0.0001.
e. Protease production = mm of clearing beyond colony growth after 40 h on milk agar. Readings were identical from three replicates, which prevents analysis of variance.
f. Swarming motility = mean mm of surface migration beyond the dense zone of swimming motility on 0.35% T-Soy agar after 24 h, (± SEM, n = 3). Motility varies significantly among Burkholderia strains: F = 53.8, p<.0001.
g. C8-HSL production = GFP emission at 514 nm following excitation at 475 nm of pAS-C8 in P. putida F117, scaled for OD600 of the log-phase Bcc culture prior to extracting its supernatant. Numbers are fold-increases over E. coli OP50, the negative control (mean ± SE, n = 6). Readings varied significantly among Burkholderia strains: F = 338, p<0.0001.
h. Supernatant attraction = ratio of worms (mean ± SE, n = 3) found near droplet of supernatant of test strain relative to that of E. coli following 1 h of incubation. Supernatants from different strains varied in their attractiveness, F = 7.37, p = 0.001.