Complete genome sequence of the 4-hydroxybenzoate-degrading bacterium Gymnodinialimonas sp. 57CJ19, a potential novel species from intertidal sediments.

A bacterium Gymnodinialimonas sp. 57CJ19, was isolated from the intertidal sediments of Aoshan Bay, and further assays showed that it has the ability to degrade the antibacterial preservative 4-hydroxybenzoate. The complete genome sequence was sequenced, and phylogenomic analyses indicated that strain 57CJ19 represents a potential novel species in the genus Gymnodinialimonas (family Rhodobacteraceae). Its genome contains a 3,861,607-bp circular chromosome with 61.25% G + C content. Gene prediction revealed 3716 protein-encoding genes, 41 tRNA genes, 3 rrn operons, and 3 non-coding RNA genes. Functional annotation revealed a complete metabolic pathway for 4-hydroxybenzoate. The genome sequence of strain 57CJ19 provides new insights into the potential and underlying genomic basis of aromatic compound pollutant degradation by marine bacteria.

Molecular structure and evolution characteristics of dissolved organic matter in groundwater near landfill: Implications of the identification of leachate leakage.

Landfills can cause groundwater contamination, the pollution characteristics in groundwater near landfill sites have been extensively investigated, while the rapid identification of leachate leakage remained unclear. Comprehensively characterizing dissolved organic matter (DOM) is crucial for tracing the source, species, and migration of contaminants within groundwater and protecting groundwater sources. Here, we showed that DOM composition from newer landfills was mainly composed of newly-produced tryptophan and tyrosine, and protein-like and humic-like substances were more abundant in landfills that were relatively older. DOM in landfill groundwater was initially dominated by outputs from microbial activities, followed by terrigenous input. Leaked leachate contained an additional dye-derived fluorescent matter at the excitation/emission wavelength of 240-260/440-460 nm that was absent in uncontaminated groundwater. Leachate leakage increased the concentrations of humic-like substance, DOM molecular weight, and microbial activity in the downstream groundwater, resulting in the microorganisms rapidly multiply and secrete large amounts of microbial metabolism by-products, making them suitable indicators of groundwater pollution. Three criteria were proposed to establish an interpretable fluorescence method to identify leachate pollution. The obtained results provide a novel insight into not only the monitoring, early warning, and identification but also the transport, fate and removal or transformation of groundwater leachate in landfills.

Interaction and coexistence characteristics of dissolved organic matter with toxic metals and pesticides in shallow groundwater.

The long-term and large-scale utilization of fertilizers and pesticides in facility agriculture leads to groundwater pollution. However, the coexistence and interactions between organic fertilizers (i.e., organic matter), toxic metals, and pesticides in shallow groundwater have seldom been studied. Thus, the study sought to characterize said interactions via fluorescence, ultraviolet-visible spectroscopy (UV-Vis), and Fourier-transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy and chemometric techniques. The results indicated that groundwater DOM was comprised of protein-, polysaccharide-, and lignin-like substances derived from organic fertilizers. Protein-like substances accounted for the binding of Co, Ni, and Fe, while polysaccharide- and lignin-like substances were mainly responsible for Cr and Mo complexation. Moreover, lignin- and polysaccharide-like substances played a key role in the binding of pesticides (i.e., dichlorodiphenyltrichloroethane [DDT], endosulfan, γ-hexachlorocyclohexane [γ-HCH], monocrotophos, chlorpyrifos, and chlorfenvinphos), rendering the conversion of γ-HCH to ß-hexachlorocyclohexane (ß-HCH) and the degradation of DDT to dichlorobenzene dichloroethylene (DDE) ineffective. However, the presence of protein-like substances in groundwater benefited the degradation and conversion of γ-HCH and α-endosulfan. Redundancy analyses showed that lignin- and polysaccharide-like matter had the most impacts on the coexistence of DOM with toxic metals and pesticides.