Analyses of gene expression and physiological changes in Microcystis aeruginosa reveal the phytotoxicities of three environmental pollutants

Abstract

When the concentrations of ampicillin (Amp), atrazine (Atr) and cadmium chloride (Cd) reach excessive quantities, they become toxic to aquatic organisms. Due to the acceleration of the industrialization and the intensification of human activities, the incidence and concentrations of these types of pollutants in aquatic systems are increasing. The primary purpose of this study was to evaluate the short-term effects of Amp, Atr and Cd on the physiological indices and gene expression levels in Microcystis aeruginosa. These three pollutants significantly induced antioxidant activity but continuously accelerated the cellular oxidative damage in microalgae, which suggests an imbalance between the oxidant and the antioxidant systems. Amp, Atr and Cd also decreased the transcription of psaB, psbD1 and rbcL; the lowest transcription of these genes was only 38.1, 23.7 and 7% of the control, respectively. These three pollutants affected nitrogen (N) and phosphorous (P) uptake by inhibiting the transcription of N or P absorbing and transporting related genes, and they down regulated the transcription of microcystin-related genes, which caused a decrease of microcystin levels; and the lowest level of microcystin was only 42.4% of the control. Our results suggest that these pollutants may cause pleiotropic effects on algal growth and physiological and biochemical reactions, and they may even affect secondary metabolic processes.

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

“…The rbcL gene encodes the large subunit of ribulose bisphosphate carboxylase catalyzing the primary chemical reaction of carbon assimilation [34]. Previous studies have verified the positive correlation between psbA and rbcL via electron transport in microalgae under various environmental stresses [13]. In the present study, increased chlorophyll-a content and stimulated psbA expression also led to the up-regulated expression of rbcL in M. aeruginosa.…”

“…The negative correlation between ntcA expression and nitrogen concentration was further verified by this study. The mcyB gene is a member of the mcy gene cluster encoding the synthetases of MCs, and the ntcA gene is a transcriptional activator factor binding to the promoter regions of the mcy gene cluster [13]. According to Fig.…”

“…16S rRNA gene was used as the housekeeping gene. PCR primers for the housekeeping gene and six target genes were designed according to previous studies [7,13,21]. Reaction mixture (25 μL) consisted of 1 μL of reverse-transcribed cDNA, 0.5 μL of 10 μM forward primer, 0.5 μL of 10 μM reverse primer, 12.5 μL of 2× PCR Master Mix, 1 μL of 10× SYBR Green I Nucleic Acid Gel Stain, and 9.5 μL of sterile milli-Q water.…”

“…A pharmaceutical limonene was found to inhibit algal growth and production of MCs while stimulate the release of MCs in M. aeruginosa [10]. Heavy metals including arsenic [11] and cadmium [12], an antibiotic ampicillin, and an herbicide atrazine [13] inhibited the growth of M. aeruginosa via photosynthesis and antioxidant systems. However, most of these studies were conducted at enhanced test concentrations, and only several studies focused on the effects of contaminants on cyanobacteria at their actual contamination levels.…”

Chlamydomonas reinhardtii cells adjust the metabolism to maintain viability in response to atrazine stress

“…Nitrate reductase activity decreased in cells of C. moewusii exposed to paraquat (Prado et al, 2009b) in a concentration-dependent manner and similar results were also obtained in C. reinhardtii exposed to atrazine (unpublished data). Decreased expression of genes controlling nitrogen assimilation has also been observed upon exposure to heavy metals and atrazine in the cyanobacteria Microcystis aeruginosa (Qian et al, 2012). Nitrogen assimilation and carbon fixation are highly coordinated in unicellular algae, so that an herbicide that finally should interfere in the photosynthetic carbon fixation goes on to also interferes in enzymatic activities in nitrogen assimilation (Prado et al, 2009b).…”