The analysis of 142 agricultural soil samples collected in organic farms across Poland with the intent to evaluate the level of DDT contamination resulted in more than 80% of the soils containing DDT. The ΣDDT (sum of all metabolites and isomers) concentration ranged between 0.005 and 0.383 mg/kg ΣDDT, with an average value of 0.064 mg/kg ΣDDT. However, the majority of plant samples collected from the crops growing on the sampled soils did not contain detectable DDT residues. The high DDT pollution levels detected in samples from four voivodeships (regions) among those monitored have been hypothesised to be linked to horticultural productions occurring to the sampled fields and typical of those regions, particularly in big-sized farms, during the period of DDT application, as well as the number of pesticides landfills present in these voivodeships. The elaboration of the o,p′-DDT/p,p′-DDT and DDT/(DDE + DDD) ratios to appraise the source or the period of contamination suggested that the contamination originated from past use of DDT rather than from impurities of more recent applications of other formulated substances. Such outcome thus suggests that the risk of contamination of organic products is likely derived from general environmental pollution levels rather than from the use of unauthorised substances in organic farming productions. Data from a trial with artificial contamination of soils indicated that using the DDT/(DDE + DDD) ratio in the presence of a low level of contamination could be less reliable than in highly contaminated soils.

The establishment of living mulches in organic orchards could potentially improve the orchard biodiversity and, when specific plant species are selected, provide additional eco-services and functions, including adequate weed management. This study was conducted in an organically managed apple orchard in Skierniewice (Poland) to assess the effect of two selected living mulching species: Alchemilla vulgaris and Mentha piperita. They were assessed on weed control, weed biodiversity, tree nutritional status, root dry weight density (RDWD), and other root morphological traits compared to a natural soil cover (control). Overall, both living mulches produced 42.5% more dry biomass, increased weed species number (+29%), and increased soil coverage (+33%) compared to control mowed plots. The apple leaf chlorophyll index and nutrient content were higher in the presence of both living mulches than in the control. In addition, apple trees had 30–46% higher root dry weight densities, even though other root morphological traits were not affected by the treatments. The results suggested that the tree row can be managed with living mulches of herbs; these species have the potential to provide an additional income to the farmer, as well as beneficial effects for the orchard biodiversity, without impairing the tree root development and nutrient status.

Biochemical, physiological and genomic comparisons of two Pseudomonas strains, assigned previously to the Pseudomonas jessenii subgroup, which are efficient SDS-degraders were carried out. A GO enrichment analysis showed that the genomes of SDS-degraders encode more genes connected with bacterial cell wall biosynthesis and alkanesulfonate monooxygenase activity than their closest relatives from the P. jessenii subgroup. A transcriptomic analysis of the most promising strain exposed to detergent suggests that although SDS can be later utilized as a carbon source, in early stages it influences cell envelope integrity, causing a global stress response followed by cell wall modification and induction of repair mechanisms. Genomes of the analyzed strains from P. jessenii group encode multiple putative sulfatases and their enzymatic activity was experimentally verified, which led to the identification of three novel enzymes exhibiting activity toward SDS. Two of the novel alkylsulfatases showed their highest activity at pH 8.0 and the temperature of 60^∘C or 70^∘C. One of the enzymes retained its activity even after 1 h of incubation at 60^∘C. Ions like K⁺ and Mg²⁺ enhanced enzymatic activity of both proteins, whereas Cu²⁺ or EDTA had inhibitory effects.

Due to their particular properties, detergents are widely used in household cleaning products, cosmetics, pharmaceuticals, and in agriculture as adjuvants tailoring the features of pesticides or other crop protection agents. The constantly growing use of these various products means that water soluble detergents have become one of the most problematic groups of pollutants for the aquatic and terrestrial environments. It is thus important to identify bacteria having the ability to survive in the presence of a large quantity of detergent and efficiently decompose it to non-surface active compounds. In this study, we used peaty soil sampled from a surface flow constructed wetland of a wastewater treatment plant to isolate bacteria that degrade sodium dodecyl sulfate. We identified and initially characterized 36 Pseudomonas spp. strains that varied significantly in their ability to use SDS as their sole carbon source. Five strains having the closest taxonomic relationship to the P. jessenii subgroup appeared to be the most efficient SDS degraders, decomposing from 80% to 100% of the SDS present in an initial concentration 1 g/L in less than 24 hours. Despite isolation from a single soil sample, the strains exhibited significant differences in their SDS degradation rate, their resistance to high detergent concentration (ranging from 2.5 g/L up to 10 g/L or higher), and in chemotaxis toward SDS on a plate test. Mass spectrometry revealed several SDS degradation products, 1-dodecanol being dominant; however, traces of dodecanal, 2-dodecanol, and 3 dodecanol were also observed, but no dodecanoic acid. Moreover, resistance against high SDS concentrations exceeding 10 g/L seemed to correlate with the number of bands visible on zymography gels used for testing for the presence of enzymes having potential alkyl sulfatase activity. The strains that presented two bands on zymography tolerated much higher SDS concentrations, whereas strains characterized by one band on zymography showed a significantly higher rate of SDS desulfurylation. The above observations suggest that the identified strains isolated from peaty soil exhibit exceptional capabilities for resistance to SDS and detergent decomposition, and they should therefore be considered as a valuable source of biotechnological tools for future bioremediation and industrial applications.