Hormesis Effects of Amoxicillin on Growth and Cellular Biosynthesis of Microcystis aeruginosa at Different Nitrogen Levels

Abstract

Coexisting antibiotic contaminants have potential to regulate cyanobacterial bloom, and the regulation is likely affected by nitrogen supply. A typical cyanobaterium Microcystis aeruginosa was cultured with 0.05-50 mg L(-1) of nitrogen and exposed to 100-600 ng L(-1) of amoxicillin for 7 days. Algal growth was not significantly (p > 0.05) affected by amoxicillin at the lowest nitrogen level of 0.05 mg L(-1), stimulated by 600 ng L(-1) of amoxicillin at a moderate nitrogen level of 0.5 mg L(-1) and enhanced by 100-600 ng L(-1) of amoxicillin at higher nitrogen levels of 5-50 mg L(-1). Amoxicillin affected chlorophyll-a, psbA gene, and rbcL gene in a similar manner as algal growth, suggesting a regulation of algal growth via the photosynthesis system. At each nitrogen level, synthesis of protein and polysaccharides as well as production and release of microcystins (MCs) increased in response to environmental stress caused by amoxicillin. Expression of ntcA and mcyB showed a positive correlation with the total content of MCs under exposure to amoxicillin at nitrogen levels of 0.05-50 mg L(-1). Nitrogen and amoxicillin significantly (p < 0.05) interact with each other on the regulation of algal growth, synthesis of chlorophyll-a, production and release of MCs, and expression of ntcA and mcyB. The nitrogen-dependent stimulation effect of coexisting amoxicillin contaminant on M. aeruginosa bloom should be fully considered during the combined pollution control of M. aeruginosa and amoxicillin.

Nutrient removal by Chlorella vulgaris F1068 under cetyltrimethyl ammonium bromide induced hormesis

“…Similarly, the low concentration of amoxicillin (0-600 ng/L) significantly enhanced protein (31.81 %) and polysaccharides (43.75 %) contents of M. aeruginosa (p < 0.05), which agreed well with our observation (Fig. 3a, b) (Liu et al 2015a). …”

“…Similarly, Azizullah et al (2014) reported that the liquid detergent at low concentration (<0.05 %) slightly increased the values of Fv/Fm, quantum yield, and rETR, which might have been due to a possible stimulatory effect of low doses of toxins. Additionally, Liu et al (2015a) found that M. aeruginosa exhibited hormesis on exposure to 0-500 ng/ L amoxicillin due to the evident increase (22.58 %) in photosynthetic activity brought about by the stimulating electron transport in photosynthesis process and upregulation of the psbA and rbcL gene expression. However, the decrease in Fv/Fm, ΦII, Fv/Fo, and rETR values indicated higher concentrations (>15 ng/L) of CTAB which inhibited the photosynthetic activity of alga.…”

“…This suggests that the increased synthesis of proteins and polysaccharides content are an adaptive response to mild environmental stress (Liu et al 2015a).…”

“…evoked vast concerns. For example, 100 ng/L of amoxicillin increased synthesis of proteins and polysaccharide by enhancing photosynthesis in Microcystis aeruginosa derived from the upregulation of ntcA and mcyB gene expression (Liu et al 2015a). Likewise, low dose responses to surfactants were also previously ignored and yet, they were widely applied in households and industries and discharged into the municipal wastewater after use (Chen et al 2014).…”

Influence of mixed antibiotics on Microcystis aeruginosa during the application of glyphosate and hydrogen peroxide algaecides

“…The extraction, cleanup, and quantification processes were described in detail in a previous study by our group (Liu et al. ,b). The content of the MCs was calculated according to Equation , where N was the cell density of Microcystis aeruginosa , and C ex and C in were the extracellular and intracellular concentrations of the sum of the three MCs.…”