2) persisted throughout the sampling period (21 days following bacterial inoculation), and even increased when the invA gene copy numbers decreased in Experiment B (4.6 cells g−1 soil on day 21). The increase in Experiment A was not as marked (5.9 cells g−1 soil on day 21). In Experiment A, invA gene copies were only detected from plant roots grown in soil Raf inhibitor review fertilized with manure slurry inoculated with the highest dose of S. Weltevreden, i.e. 106 cells g−1 soil. However, the bacteria were not consistently detected in all replicates on all sampling occasions (Table 2). At day 7 postinoculation, no replicate root samples contained detectable levels of invA. After 14 days, a positive
PCR product was obtained from one of five replicates. This tendency increased
throughout the sampling period, with four positive replicates at day 21 and positive products from all five replicate samples at day 28 (Table 2). In Experiment B, all replicates at all sampling occasions contained detectable amounts of invA, although the numbers significantly decreased from 6.0 log gene copies at day 1 to 5.0 log gene copies at day 21 postinoculation (P≤0.0005) (Fig. 3). We detected no invA gene copies on spinach leaves at any of the sampling dates in Experiment A. In contrast, in Experiment B, S. Weltevreden was detected on spinach leaves from all five replicates at days 0 and 7 postinoculation (Table 3). At day 14, invA gene PLX4720 copies were identified in two of five replicates, and at the last sampling date (day 21; Table 3) the corresponding number was one of five replicates. Moreover, there was a significant decrease in the number of invA gene copies estimated in
leaves between days 0 and 7 (P<0.05). Our results revealed that Salmonella is able to persist in soil, showing only a slight reduction in bacterial numbers over a 4-week evaluation period (Fig. 1). As no significant decline in bacterial cell numbers was found over the time-span of the present study, which might have indicated the presence of dead cells, we concluded that the cells detected are most likely living. The Carnitine palmitoyltransferase II minor reduction in S. Weltevreden cell numbers during the evaluation period in the current study emphasizes the importance of keeping the intervals between manure application and plant harvest as long as possible, as the survival of Salmonella in soil is time dependent (Doyle & Erickson, 2008). Moreover, the density and survival length of S. Weltevreden in soil correlated well with bacterial inoculation levels, with larger numbers of initial bacteria resulting in higher bacterial densities in soil throughout the sampling period (Fig. 1). This finding is in agreement with several reports showing that the number of Salmonella cells initially present influences the length of survival in soil, sometimes as much as up to several months after manure spreading (Jones, 1986; Baloda et al., 2001). In the current study, we evaluated the persistence of S.