Dimethyl phthalate damages Staphylococcus aureus by changing the cell structure, inducing oxidative stress and inhibiting energy metabolism

Dimethyl phthalate(DMP), used as a plasticizer in industrial products, exists widely in air,water and soil.Staphylococcus aureus is a typical model organism representing Gram-positive bacteria.The molecular mechanisms of DMP toxicology in S.aureus were researched by proteomic and transcriptomic analyses.The results showed that the cell wall, membrane and cell surface characteristics were damaged and the growth was inhibited in S.aureus by DMP.Oxidative stress was induced by DMP in S.aureus.The activities of succinic dehydrogenase(SDH) and ATPase were changed by DMP, which could impact energy metabolism.Based on proteomic and transcriptomic analyses, the oxidative phosphorylation pathway was enhanced and the glycolysis/gluconeogenesis and pentose phosphate pathways were inhibited in S.aureus exposed to DMP.The results of real-time reverse transcription quantitative PCR(RT-qPCR) further confirmed the results of the proteomic and transcriptomic analyses.Lactic acid, pyruvic acid and glucose were reduced by DMP in S.aureus, which suggested that DMP could inhibit energy metabolism.The results indicated that DMP damaged the cell wall and membrane, induced oxidative stress, and inhibited energy metabolism and activation in S.aureus.

The intestinal microbiome of an Indo-Pacific humpback dolphin(Sousa chinensis)stranded near the Pearl River Estuary,China

The mammalian intestinal microbiome is critical for host health and disease resistance.However,the cetacean intestinal microbiota remains relatively unexplored.By using high-throughput 16S rRNA gene sequencing,we analyzed intestinal bacterial samples from an Indo-pacific humpback dolphin(Sousa chinensis)stranded near the Pearl River Estuary in China.The samples included 3 anatomical regions(foregut,midgut,and rectum)and 2 anatomical locations(content and mucus).Our analyses revealed that the dolphin intestinal bacteria contained 139 operational taxonomic units(OTUs),dominated at the phyla level by Firmicutes(47.05%in the content;94.77%in the mucus),followed by Bacteroidetes(23.63%in the content;1.58%in the mucus)and Gammaproteobacteria(14.82%in the content;2.05%in the mucus).The intestinal bacteria had a small core community(15 OTUs,accounting for 99.74%of the reads),some of which could be potentially pathogenic to both human and dolphins.As an alternative to sampling the dolphin intestinal bacteria,fecal sampling could be used.Additionally,function potentials such as,xenobiotics biodegradation,beta-lactam resistance,and human disease-related pathways,were detected in the dolphin intestinal bacteria.These findings provide the first baseline knowledge of the intestinal microbiome of the Indo-Pacific humpback dolphin,which may offer new insights into cetacean conservation by using microbial surveillance.