Quick adaptation of Ralstonia Solanacearum to copper stress to recover culturability and growth in water and soil

Abstract

Cells of Ralstonia solanacearum were exposed to Cu in distilled water, and the resulting Cu-stressed non-culturable cells were inoculated to natural (non-pasteurized) and pasteurized soils in order to examine their culturability and recovery. Exposing the cells to 20 µM CuSO4 produced transitory non-culturable cells, which exhibited a remarkable recovery in culturability after incubation in the solution for 36 h, reaching a density near the initial level by 108 h. To determine whether such non-culturable cells actually "resuscitated" or multiplied after adapting to Cu toxicity, growth curves were constructed in order to contrast the rates of increase in culturable cell numbers between Cu-stressed or non-stressed inocula. Additionally, fresh non-stressed cells were exposed to CuSO4 in the presence of nalidixic acid by adding the antibiotic at different times after the onset of Cu stress to verify any cell multiplication during the population increase. The results revealed that the non-culturable cells surviving Cu toxicity adapted very quickly to Cu and began multiplying within 12 h, because only the Cu-stressed cells that were increasing in the exponential growth phase, but not those in the stationary phase, were killed by the antibiotic. Such cells exhibited an apparent tolerance to this metal when inoculated to a freshly prepared solution of CuSO4, and also detoxified the ion in the solution in which they grew. The presence of nutrients greatly counteracted the effect of Cu in water microcosms, since culturable cells were detected and increased in number even when exposed to 40 µM CuSO4. In contrast, when inoculated to non-pasteurized soil, Cu-stressed cells showed no such recoveries. However, when the soil was pasteurized before inoculation or added with nutrients, culturable cells were recovered and increased in number. This indicates that increased nutrient availability in soil allows Cu-stressed cells to quickly overcome the stress and increase in culturable populations

Biocontrol of bacterial wilt disease in tomato using Bacillus subtilis strain R31

“…In the absence of host plants, R. solanacearum can survive in soil or water for a long time ( Ascarrunz et al, 2011 ). Attempts to combat this bacterium through plant breeding, field sanitation, crop rotation, and the use of bactericides have not been successful.…”

Phytochemical Composition and Antibacterial Activity of Fruit Extract of Solanum incanum L. against Ralstonia solanacearum

“…The bacterium enters plants through wounds and lateral root emergence points and proliferate in the vascular system, causing clogging of xylem vessels which block xylematic flow, leading to yellowing of the leaves, general wilting and finally death of the plant [4]. Due to its greater capability to survive in soil as well as broad host range, it's very hard to eliminate once established in the soil [5]. Control of bacterial wilt disease majorly depends on use of chemical fumigants [6], nevertheless, this chemical fumigant is undesirable since they lead to development of resistant pathogen [7], they persist and accrue in the environment [8], increases human health risks [9] as well as high and hidden cost incurred during their use [10].…”