Table 1.
Quantification of bacterial 16S rRNA and PAH–RHDα genes and transcripts in soils from 0 to 10 days.
| Day 0 | Day 2 | Day 4 | Day 6 | Day 8 | Day 10 | Time effect | ||
|---|---|---|---|---|---|---|---|---|
| 16S rRNA | ||||||||
| DNA | Bare | 2.1 ± 0.1 × 108 | 4.2 ± 1.1 × 108 | 6.8 ± 2.2 × 108 | 6.4 ± 0.7 × 108 (AB) | 7.4 ± 0.7 × 108 | 8.6 ± 3.3 × 108 | * |
| Bulk planted | – | 5.2 ± 0.8 × 108 | 4.8 ± 0.4 × 108 | 3.7 ± 0.8 × 108 (B) | 5.1 ± 0.9 × 108 | 5.7 ± 0.7 × 108 | n.s. | |
| Rhizospheric | – | – | – | 8.5 ± 1.2 × 108 (A) | 6.1 ± 0.5 × 108 | 8.0 ± 0.6 × 108 | n.s. | |
| cDNA | Bare | 1.1 ± 0.1 × 108 | 7.0 ± 4.3 × 108 | 2.1 ± 0.1 × 108 | 1.1 ± 0.1 × 109 | 1.3 ± 0.3 × 109 (AB) | 1.0 ± 0.4 × 109 (AB) | ** |
| Bulk planted | – | 1.1 ± 0.3 × 109 | 5.8 ± 1.5 × 108 | 9.4 ± 1.2 × 108 | 5.3 ± 0.2 × 108 (B) | 4.9 ± 1.0 × 108 (B) | n.s. | |
| Rhizospheric | – | – | – | 2.0 ± 0.6 × 109 | 2.1 ± 0.8 × 109(A) | 2.2 ± 0.2 × 109 (A) | n.s. | |
| PAH–RHDα GN (% ratio to 16S) | ||||||||
| DNA | Bare | 0.020 ± 0.003 | 0.131 ± 0.087 (B) | 0.509 ± 0.261 | 0.099 ± 0.044 (B) | 0.223 ± 0.046 | 0.036 ± 0.020 (B) | * |
| Bulk planted | – | 2.513 ± 1.107 (A) | 1.637 ± 1.099 | 0.772 ± 0.251 (A) | 0.498 ± 0.180 | 0.407 ± 0.165 (AB) | n.s. | |
| Rhizospheric | – | – | – | 1.271 ± 0.270 (A) | 0.821 ± 0.398 | 0.611 ± 0.30 (A) | n.s. | |
| cDNA | Bare | b.q. | 0.005 ± 0.005 | 0.003 ± 0.001 | 0.000 ± 0.000 | 0.001 ± 0.000 | 0.000 ± 0.000 | n.s. |
| Bulk planted | – | 0.029 ± 0.014 | 0.008 ± 0.002 | 0.003 ± 0.001 | 0.001 ± 0.001 | 0.001 ± 0.000 | * | |
| Rhizospheric | – | – | – | 0.002 ± 0.001 | 0.001 ± 0.001 | 0.000 ± 0.000 | n.s. | |
| PAH–RHDα GP (% ratio to 16S) | ||||||||
| DNA | Bare | 12.285 ± 0.950 | 12.603 ± 3.674 | 5.637 ± 1.763 | 6.594 ± 0.615 | 7.132 ± 0.138 (B) | 4.902 ± 0.650 (B) | * |
| Bulk planted | – | 7.333 ± 0.134 | 8.378 ± 0.237 | 7.639 ± 0.546 | 11.032 ± 1.101 (A) | 10.175 ± 0.887 (A) | ** | |
| Rhizospheric | – | – | – | 6.622 ± 0.432 | 11.044 ± 0.768 (A) | 10.256 ± 0.373 (A) | ** | |
| cDNA | Bare | 0.003 ± 0.003 | 0.009 ± 0.006 | 0.010 ± 0.005 | 0.144 ± 0.133 | 0.013 ± 0.007 | 0.012 ± 0.007 | n.s. |
| Bulk planted | – | 0.009 ± 0.008 | 0.137 ± 0.111 | 0.033 ± 0.027 | 0.025 ± 0.006 | 0.118 ± 0.048 | n.s. | |
| Rhizospheric | – | – | – | 0.068 ± 0.057 | 0.032 ± 0.009 | 0.078 ± 0.045 | n.s. | |
Values are mean ± s.e.m. (n = 3). b.q., below quantification limit of the qPCR assay. For statistical analysis, b.q. values were replaced by zero. Values for 16S rRNA and PAH-RHD were log- and arcsin-transformed, respectively. The effect of sample type (bare, bulk planted, or rhizospheric soil) was tested separately for each gene, time point, and nucleic acid using ANOVA with post-hoc Tukey test, and letters denote significantly different groups (P ≤ 0.05). The effect of time was tested separately for each sample type using ANOVA (
*
P ≤ 0.05;
**
P ≤ 0.01).