Evaluation of the toxicity of leaches from hydrothermal sulfide deposits by means of a delayed fluorescence-based bioassay with the marine cyanobacterium Cyanobium sp. NIES-981.

The commercial use of metals such as copper, lead, and zinc has markedly increased in recent years, resulting in increased interest in deep-sea mining of seafloor hydrothermal sulfide deposits. However, the full extent of the impact of deep-sea mining at hydrothermal field deposits on the environment remains unclear. In addition to impacting the deep sea, the leaching of heavy metals from extracted sulfide mineral may also affect the upper ocean zones as the sulfide rock is retrieved from the seafloor. Here, we used a delayed fluorescence-based bioassay using the marine cyanobacterium Cyanobium sp. NIES-981 to evaluate the toxicity of three sulfide core samples obtained from three drill holes at the Izena Hole, middle Okinawa Trough, East China Sea. Leaches from two of the cores contained high concentrations of zinc and lead, and they markedly inhibited delayed fluorescence in Cyanobium sp. NIES-981 compared with control. By examining the toxicity of artificial mixed-metal solutions with metal compositions similar to those of the leaches, we confirmed that this inhibition was a result of high zinc and lead concentrations into the leaches. In addition, we conclude that this delayed fluorescence-based bioassay is a viable method for use by deep-sea mining operations because it is quicker and requires less laboratory space and equipment than the standard assay.

Microbial F-type lectin domains with affinity for blood group antigens.

F-type lectins are fucose binding lectins with characteristic fucose binding and calcium binding motifs. Although they occur with a selective distribution in viruses, prokaryotes and eukaryotes, most biochemical studies have focused on vertebrate F-type lectins. Recently, using sensitive bioinformatics search techniques on the non-redundant database, we had identified many microbial F-type lectin domains with diverse domain organizations. We report here the biochemical characterization of F-type lectin domains from Cyanobium sp. PCC 7001, Myxococcus hansupus and Leucothrix mucor. We demonstrate that while all these three microbial F-type lectin domains bind to the blood group H antigen epitope on fucosylated glycans, there are fine differences in their glycan binding specificity. Cyanobium sp. PCC 7001 F-type lectin domain binds exclusively to extended H type-2 motif, Myxococcus hansupus F-type lectin domain binds to B, H type-1 and Lewisb motifs, and Leucothrix mucor F-type lectin domain binds to a wide range of fucosylated glycans, including A, B, H and Lewis antigens. We believe that these microbial lectins will be useful additions to the glycobiologist's toolbox for labeling, isolating and visualizing glycans.

Rapid ecotoxicological bioassay using delayed fluorescence in the marine cyanobacterium Cyanobium sp. (NIES-981).

The use of delayed fluorescence intensity as an endpoint for rapid estimation of the effective concentration (ECx) has been reported as an alternative to standard growth inhibition (at 72 h after exposure) in some algal species including Pseudokirchneriella subcapitata. In marine algae, although an approach of bioassaying using delayed fluorescence measurements has not been performed yet, its development would provide many benefits for marine environmental risk assessment. In this study, we selected marine cyanobacterium Cyanobium sp. (NIES-981) as our test algal species and demonstrated that this species is valid for the standard growth inhibition test based on criteria provide by Organization for Economic Co-operation and Development guidelines. Furthermore, standard inhibition tests and shorter period test using DF were performed in NIES-981 using five chemicals (3,5-DCP, simazine, diflufenican, K2Cr2O7, and CuSO4), and their EC50 and low-toxic-effect values (EC10, EC5, and NOEC) were determined from two dose-response curves. Based on comparisons of the two dose-response curves and the EC50 values, we conclude that DF intensity is useful as an endpoint for rapid estimation of EC50 in NIES-981.