Soil is an environment with numerous niches, where bacteria are exposed to diverse conditions. Some bacteria are exposed earlier than others to pressure, and the emission of signals that other bacteria can receive and perceive may allow a better response to an eminent stimulus. To shed light on how bacteria trigger their response and adapt to changes in the environment, the intra- and interspecific influences of volatiles on bacterial strains growing under non-stressed and cadmium-stressed conditions were assessed. Each strain was exposed to its volatiles emitted by cells growing under different conditions to test whether the environment in which a cell grows influences neighboring cells. The five genera tested showed different responses, with Rhizobium displaying the greatest influence. In a second experiment, 13 strains from different genera were grown under control conditions but exposed to volatiles released by Cd-stressed Rhizobium cells to ascertain whether Rhizobium's observed influence was strain-specific or broader. Our results showed that the volatiles emitted by some bacteria under stress are differentially perceived and translated into biochemical changes (growth, alteration of the antioxidant response, and oxidative damage) by other bacteria, which may increase the adaptability and resilience of bacterial communities to environmental changes, especially those with a prooxidant nature. Cadmium (Cd) contamination of soils constitutes a risk to the environment and human health. Here, we showed the effects of Cd exposure on bacteria and how volatile communication influences the biochemistry related to coping with oxidative stress. This knowledge can be important for remediation and risk assessment and highlights that new biological features, such as volatile communication, should be considered when studying and assessing the impact of contaminants on soil ecosystems.

Chromated copper arsenate (CCA) is a wood preservative containing Cr, Cu, and As and leaching of these heavy metals into agricultural fields raises concern about food safety. The heavy metals enter the plants due to hydrophilic nature and prevalent mobility by damaging the photosynthetic process and hindering metabolism of plants. Phytoremediation is one of the constructive methods employed in mitigation of toxic metals from the soil. Nevertheless, only limited studies have been conducted on the effect of heavy metals and chelating agents on biochemical parameters in tree species. Overall, the present study advocates the possible effects of CCA components, EDTA and DTPA, on total carbohydrates, protein, and chlorophyll content of Acacia auriculiformis and Casuarina equisetifolia seedlings. Experiments on the effect of CCA and chelating agents on biochemical parameters of seedlings were conducted in potting medium. The plastic pots transplanted with 1-month-old seedlings of Acacia auriculiformis and Casuarina equisetifolia were supplied with sufficient air-dried soil and compost followed by treatment of six different concentrations (250-2500 mg kg(-1) soil) of CCA. Simultaneously, in a separate set of experiments, pots with planting media were supplied with CCA (1000 mg kg(-1) soil) followed by treatment of four different concentrations of EDTA and DTPA (0.1-1.5 mu M kg(-1)). The leaves of 6-month-old seedlings of both tree species exposed to different concentrations of CCA and chelating agents were harvested and the amount of total carbohydrates, protein, and chlorophyll content was estimated by spectrophotometric methods. The results of different treatments were compared with the control. Results of the study showed significant decrease (p <= 0.05) in the amount of total carbohydrates, proteins, and chlorophyll content with an increase in concentrations of CCA (750-2500 mg kg(-1)) in the seedlings of A. auriculiformis and C. equisetifolia. Similarly, the seedlings of both tree species treated with 1.5 mu M kg(-1) each of EDTA and DTPA showed significantly (p <= 0.05) increased total carbohydrate, proteins, and chlorophyll content. The studies conclude that the CCA components affect the total carbohydrate, protein, and chlorophyll content of the A. auriculiformis and C. equisetifolia seedlings. However, moderate to higher concentrations of EDTA and DTPA were effective in ameliorating CCA toxicity.