RESEARCH PAPER The Interactive Effect of Dietary Curcumin and Silver Nanoparticles on Gut Microbiota of Common Carp (Cyprinus carpio) Zohre Khorshidi 1 • Kourosh Sarvi Moghanlou 1 • Ahmad Imani 1 • Shahryar Behrouzi 2 Received: 17 April 2016 / Accepted: 29 September 2016 Ó Shiraz University 2016 Abstract Discharge of silver nanoparticles (AgNPs) into aquatic ecosystems is inevitable due to their vast industrial applications. Thus, the present study aimed to evaluate the protective effect of dietary curcumin supplementation against AgNPs toxicity to the gut microbiota of common carp (Cyprinus carpio) including total bacteria count, mesophilic, lactic acid bacteria and Enterobacteriaceae. Nine different treatments including different combinations of dietary AgNPs (0, 0.05 and 0.15 g/kg feed) and cur- cumin (0, 0.75 and 1.5 g/kg feed) in three respective replicates were designed. The trial was conducted under natural photoperiod condition for 60 days. Samples were taken on days 20, 40 and 60. Our results showed that dietary AgNPs contamination resulted in reduced intestinal bacterial count in a dose dependent manner, however, dietary curcumin inclusion level of 0.75 g/kg remarkably reduced the toxicity of AgNPs to intestinal microflora of common carp at least at 0.05 g/kg AgNPs (p \ 0.05). The results also indicated that there were highly significant relationships (p \ 0.001) between intestinal microflora count and dietary curcumin and AgNPs concentrations which were dependent upon exposure time. Beta values for different terms of regression equations implied that AgNPs concentration had remarkable effects on different bacteria classes of gut microbiota (-0.75, -0.89, -0.73 and -0.84 for total bacteria, mesophilic bacteria, lactic acid bacteria and Enterobacteriaceae count, respectively). Conclusively, microflora population change might be assumed as an indication of environmental pollutions in aquatic ecosys- tems health assessment programs especially for newly emerging nano-materials. We also showed curcumin pro- tected intestinal microflora against feed-born nanosilver particles. Keywords Curcumin Á Enterobacteriaceae Á Lactic acid bacteria Á Mesophilic bacteria Á Nanosilver Á Total bacterial count 1 Introduction Nanoparticles (NPs) are defined as materials possessing two or three dimensions between 1 and 100 nm. NPs show unique properties depending on their shape, size, surface, structure and unusual physicochemical properties (Ober- do ¨rster et al. 2005). The exceptional properties of silver nanoparticles (AgNPs) such as, good conductivity, cat- alytic and antibacterial effects, have made them the largest and most important type of nanomaterial for commercial applications (Benn and Westerhoff 2008). Manufactured nanomaterial and NPs discharge into environment now appears un avoidable since growing number of products containing these materials are rapidly marketed and applied worldwide (Aitken et al. 2006), meaning that both aquatic and terrestrial habitats will be exposed to manufacture NPs (Handy and Shaw 2007). Thus, the ecotoxicology of nanomaterial products has become a relatively newly emerging research field (Handy et al. 2008). Gills, liver, gut, and sometimes the brain might be target organs of NPs. For example, it has been shown that AgNPs affect liver oxidative status of Japanese medaka (Oryzias & Kourosh Sarvi Moghanlou k.sarvimoghanlou@urmia.ac.ir 1 Department of Fisheries, Faculty of Natural Resources, Urmia University, Nazlou Campus, 11th km of Serow Road, Urmia, Islamic Republic of Iran 2 Caspian Sea Ecology Research Center, Sari, Islamic Republic of Iran 123 Iran J Sci Technol Trans Sci DOI 10.1007/s40995-016-0130-8