Conjoint analysis of physio-biochemical, transcriptomic, and metabolomic reveals the response characteristics of solanum nigrum L. to cadmium stress.

Cadmium (Cd) is a nonessential element in plants and has adverse effects on the growth and development of plants. However, the molecular mechanisms of Cd phytotoxicity, tolerance and accumulation in hyperaccumulators Solanum nigrum L. has not been well understood. Here, physiology, transcriptome, and metabolome analyses were conducted to investigate the influence on the S. nigrum under 0, 25, 50, 75 and 100 µM Cd concentrations for 7 days. Pot experiments demonstrated that compared with the control, Cd treatment significantly inhibited the biomass, promoted the Cd accumulation and translocation, and disturbed the balance of mineral nutrient metabolism in S. nigrum, particularly at 100 µM Cd level. Moreover, the photosynthetic pigments contents were severely decreased, while the content of total protein, proline, malondialdehyde (MDA), H2O2, and antioxidant enzyme activities generally increased first and then slightly declined with increasing Cd concentrations, in both leaves and roots. Furthermore, combined with the previous transcriptomic data, numerous crucial coding-genes related to mineral nutrients and Cd ion transport, and the antioxidant enzymes biosynthesis were identified, and their expression pattern was regulated under different Cd stress. Simultaneously, metabolomic analyses revealed that Cd treatment significantly changed the expression level of many metabolites related to amino acid, lipid, carbohydrate, and nucleotide metabolism. Metabolic pathway analysis also showed that S. nigrum roots activated some differentially expressed metabolites (DEMs) involved in energy metabolism, which may enhance the energy supply for detoxification. Importantly, central common metabolism pathways of DEGs and DEMs, including the "TCA cycle", "glutathione metabolic pathway" and "glyoxylate and dicarboxylate metabolism" were screened using conjoint transcriptomics and metabolomics analysis. Our results provide some novel evidences on the physiological and molecular mechanisms of Cd tolerance in hyperaccumulator S. nigrum plants.

Enhancing aerobic composting performance of high-salt oily food waste with Bacillus safensis YM1.

To alleviate the inhibitory effects of salt and oil on food waste compost, the compost was inoculated with salt-tolerant and oil-degrading Bacillus safensis YM1. The YM1 inoculation could effectively improve compost maturation index. Compared with uninoculated group, the oil content and Cl- concentration in the 0.5% YM1-inoculated compost decreased significantly by 19.7% and 8.1%, respectively. The addition of the YM1 inoculant substantially altered the richness and composition of the microbial community during composting, as evidenced by the identification of 47 bacterial and 42 fungal biomarker taxa. The enrichment of some oil-degrading salt-tolerant microbes (Bacillus, Haloplasma, etc.) enhanced nutrient conversion, which is crucial for the improved maturity of the YM1 compost. This study demonstrated that YM1 could regulate both abiotic and biotic processes to improve high-salt and oily food waste composting, which may be an effective inoculant in the industrial-scale composting.