Native hypersaline sulphate reducing bacteria contributes to iron nanoparticle formation in saltpan sediment: A concern for aquaculture

Abstract A hypersaline dissimilatory sulphate reducing bacterium, strain LS4, isolated from the sediments of Ribander saltpan, Goa, India was found to produce (Fe 2 O 3 ) maghemite nanoparticles. The presence of maghemite nanoparticles was also detected in the same sediment. Strain LS4 was isolated anaerobically on modified Hatchikian's media at 300 psu, growing optimally at 30 °C, 150 psu salinity and pH 7.8. Based on biochemical characteristics and 16S rRNA sequence analysis, the strain LS4 belongs to genus Desulfovibrio . This isolate synthesized iron oxide nanoparticles in vitro when challenged with FeCl 3 & FeSO 4 in the growth medium. The biological nanoparticles were characterized to be Fe 2 O 3 nanoparticle of 19 nm size by X-ray diffraction, transmission electron microscopy, fourier transform infrared spectroscopy, scanning electron microscopy and energy-dispersive x-ray spectroscopy. Maghemite nanoparticles (5.63 mg g −1 ) were isolated from the saltpan sediment by magnetic separation which showed similar characteristic features to the Fe 2 O 3 nanoparticle produced by strain LS4 with an average size of 18 nm. Traditionally Goan saltpans were used for aquaculture during the non-salt making season, thus effects of these nanoparticles on Zebra fish embryo development were checked, which resulted in developmental abnormalities and DNA damage in a dose dependent manner. With the increasing nanoparticle concentration (0.1 mg.L −1 to100 mg.L −1 ), the mortality rate increased with a decrease in the hatching rate (93.05 ± 2.4 to 25 ± 4.16%) and heart rate (150–120 beats per minute). The nanoparticle exposed embryos developed malformed larvae with a characteristic of pericardial edema, curved body, curved notochord, curved tail and curved tail tip. These results suggest that strain LS4 might be playing a role as a contributor in the formation of iron oxide nanoparticle in the Ribander saltpan sediment, however; its high concentration will have a negative impact on aquaculture in these saltpans.