Responses of zebrafish (Danio rerio) cells to antibiotic erythromycin stress at the subcellular levels

The role of bacterial metabolism in human gut colonization

Can we anticipate the emergence of the next pandemic antibiotic-resistant bacterial clone? Addressing such an ambitious question relies on our ability to comprehensively understand the ecological and epidemiological factors fostering the evolution of high-risk clones. Among these factors, the ability to persistently colonize and thrive in the human gut is crucial for most high-risk clones. Nonetheless, the causes and mechanisms facilitating successful gut colonization remain obscure. Here, we review recent evidence that suggests that bacterial metabolism plays a pivotal role in determining the ability of high-risk clones to colonize the human gut. Subsequently, we outline novel approaches that enable the exploration of microbial metabolism at an unprecedented scale and level of detail. A thorough understanding of the constraints and opportunities of bacterial metabolism in gut colonization will foster our ability to predict the emergence of high-risk clones and take appropriate containment strategies.

Assessing the ecotoxicity of florfenicol exposure at environmental levels: A case study of histology, apoptosis and microbiota in hepatopancreas of Eriocheir sinensis

The intensification of production practices in the aquaculture industry has led to the indiscriminate use of antibiotics to combat diseases and reduce costs, which has resulted in environmental pollution, posing serious threats to aquaculture sustainability and food safety. However, the toxic effect of florfenicol (FF) exposure on the hepatopancreas of crustaceans remains unclear. Herein, by employing Chinese mitten crab (Eriocheir sinensis) as subjects to investigate the toxic effects on histopathology, oxidative stress, apoptosis and microbiota of hepatopancreas under environment-relevant (0.5 and 5 μg/L), and extreme concentrations (50 μg/L) of FF. Our results revealed that the damage of hepatopancreas tissue structure caused by FF exposure in a dose-and time-dependent manner. Combined with the increased expression of apoptosis-related genes (Caspase 3, Caspase 8, p53, Bax and Bcl-2) at mRNA and protein levels, activation of catalase (CAT) and superoxide dismutase (SOD), and malondialdehyde (MDA) accumulation, FF exposure also induced oxidative stress, and apoptosis in hepatopancreas. Interestingly, 7 days exposure triggered more pronounced toxic effect in crabs than 14 days under environment-relevant FF concentration. Integrated biomarker response version 2 (IBRv2) index indicated that 14 days FF exposure under extreme concentration has serious toxicity effect on crabs. Furthermore, 14 days exposure to FF changed the diversity and composition of hepatopancreas microbiota leading remarkable increase of pathogenic microorganism Spirochaetes following exposure to 50 μg/L of FF. Taken together, our study explained potential mechanism of FF toxicity on hepatopancreas of crustaceans, and provided a reference for the concentration of FF to be used in culture of Chinese mitten crab.

Metabolomic analysis reveals the toxicity mechanisms of bisphenol A on the Microcystis aeruginosa under different phosphorus levels

Harmful cyanobacterial blooms have been a global environmental problem. Discharge of anthropogenic pollutants and excess nutrient import into the freshwater bodies may be the biggest drivers of bloom. Bisphenol A (BPA), a typical endocrine-disrupting compound, is frequently detected in different natural waters, which was a threat to the balance of aquatic ecosystem. Yet mechanistic understanding of the bloom and microcystin generation under combined pollution conditions is still a mystery. Herein, the cellular and metabolomic responses to BPA exposure and phosphorus (P) levels in Microcystis aeruginosa were investigated throughout its growth period. The results showed that the stress response of M. aeruginosa to BPA was characterized by a decrease in growth density, an increase in P utilization, an increase in ATPase activity, a disruption of the photosynthetic system, and an increase in the production and release of microcystins (MCs). However, these effects are highly dependent on the growth stage of the cyanobacterial cell and the magnitude of the added P concentration. In addition, exposure to a high concentration (10 μM) of BPA significantly stimulated the production of 20.7% more and the release of 29.2% more MCs from M. aeruginosa cells at a low P level. The responses of reactive oxygen species (ROS), superoxide dismutase (SOD) and malondialdehyde (MDA) suggested that exposure to BPA exposure at a low P level can lead to oxidative stress in M. aeruginosa. In addition, the differentially expressed 63 metabolites showed that cell growth, energy generation and photosynthesis were mainly regulated by the metabolic network of 3-phosphoglyceric acid (3-PGA), D-glucose 6-phosphate, UDP-α-D-galactose and UDP-N-acetyl-D-galactosamine (UDP-GalNAc) metabolism. Amino acids and lipid metabolism collectively mediated MCs production and release. These findings will provide important references for the control of harmful cyanobacterial blooms under combined pollution.

Sulfamethoxazole (SMX) Alters Immune and Apoptotic Endpoints in Developing Zebrafish (Danio rerio)

Sulfamethoxazole (SMX) is a broad-range bacteriostatic antibiotic widely used in animal and fish farming and is also employed in human medicine. These antibiotics can ultimately end up in the aquatic ecosystem and affect non-target organisms such as fish. To discern the effect of SMX on developing zebrafish embryos and larvae, we investigated a broad range of sub-lethal toxicity endpoints. Higher concentrations of SMX affected survivability, caused hatch delay, and induced malformations including edema of the yolk sac, pericardial effusion, bent tail, and curved spine in developing embryos. Lower levels of SMX provoked an inflammatory response in larvae at seven days post fertilization (dpf), as noted by up-regulation of interferon (ifn-γ) and interleukin 1β (il-1β). SMX also increased the expression of genes related to apoptosis, including BCL2-Associated Agonist of Cell Death (bad) and BCL2 Associated X, Apoptosis Regulator (bax) at 50 µg/L and decreased caspase 3 (casp3) expression in a dose-dependent manner. SMX induced hyperactivity in larval fish at 500 and 2500 µg/L based upon the light/dark preference test. Collectively, this study revealed that exposure to SMX can disrupt the immune system by altering host defense mechanisms as well as transcripts related to apoptosis. These data improve understanding of antibiotic chemical toxicity in aquatic organisms and serves as a baseline for in-depth environmental risk assessment of SMX and antibiotics.