First report of a toxic Nodularia spumigena (Nostocales/ Cyanobacteria) bloom in sub-tropical Australia. II. Bioaccumulation of nodularin in isolated populations of mullet (Mugilidae).

Fish collected after a mass mortality at an artificial lake in south-east Queensland, Australia, were examined for the presence of nodularin as the lake had earlier been affected by a Nodularia bloom. Methanol extracts of muscle, liver, peritoneal and stomach contents were analysed by HPLC and tandem mass spectrometry; histological examination was conducted on livers from captured mullet. Livers of sea mullet (Mugil cephalus) involved in the fish kill contained high concentrations of nodularin (median 43.6 mg/kg, range 40.8-47.8 mg/kg dry weight; n = 3) and the toxin was also present in muscle tissue (median 44.0 µg/kg, range 32.3-56.8 µg/kg dry weight). Livers of fish occupying higher trophic levels accumulated much lower concentrations. Mullet captured from the lake 10 months later were also found to have high hepatic nodularin levels. DNA sequencing of mullet specimens revealed two species inhabiting the study lake: M. cephalus and an unidentified mugilid. The two mullet species appear to differ in their exposure and/or uptake of nodularin, with M. cephalus demonstrating higher tissue concentrations. The feeding ecology of mullet would appear to explain the unusual capacity of these fish to concentrate nodularin in their livers; these findings may have public health implications for mullet fisheries and aquaculture production where toxic cyanobacteria blooms affect source waters. This report incorporates a systematic review of the literature on nodularin measured in edible fish, shellfish and crustaceans.

Occupational and environmental hazard assessments for the isolation, purification and toxicity testing of cyanobacterial toxins.

Cyanobacteria can produce groups of structurally and functionally unrelated but highly potent toxins. Cyanotoxins are used in multiple research endeavours, either for direct investigation of their toxicologic properties, or as functional analogues for various biochemical and physiological processes. This paper presents occupational safety guidelines and recommendations for personnel working in field, laboratory or industrial settings to produce and use purified cyanotoxins and toxic cyanobacteria, from bulk harvesting of bloom material, mass culture of laboratory isolates, through routine extraction, isolation and purification. Oral, inhalational, dermal and parenteral routes are all potential occupational exposure pathways during the various stages of cyanotoxin production and application. Investigation of toxicologic or pharmacologic properties using in vivo models may present specific risks if radiolabelled cyanotoxins are employed, and the potential for occupational exposure via the dermal route is heightened with the use of organic solvents as vehicles. Inter- and intra-national transport of living cyanobacteria for research purposes risks establishing feral microalgal populations, so disinfection of culture equipment and destruction of cells by autoclaving, incineration and/or chlorination is recommended in order to prevent viable cyanobacteria from escaping research or production facilities.

Copper transfer from the Cu(I) chaperone, CopZ, to the repressor, Zn(II)CopY: metal coordination environments and protein interactions.

Extracellular copper regulates the DNA binding activity of the CopY repressor of Enterococcus hirae and thereby controls expression of the copper homeostatic genes encoded by the cop operon. CopY has a CxCxxxxCxC metal binding motif. CopZ, a copper chaperone belonging to a family of metallochaperones characterized by a MxCxxC metal binding motif, transfers copper to CopY. The copper binding stoichiometries of CopZ and CopY were determined by in vitro metal reconstitutions. The stoichiometries were found to be one copper(I) per CopZ and two copper(I) per CopY monomer. X-ray absorption studies suggested a mixture of two- and three-coordinate copper in Cu(I)CopZ, but a purely three-coordinate copper coordination with a Cu-Cu interaction for Cu(I)2CopY. The latter coordination is consistent with the formation of a compact binuclear Cu(I)-thiolate core in the CxCxxxxCxC binding motif of CopY. Displacement of zinc, by copper, from CopY was monitored with 2,4-pyridylazoresorcinol. Two copper(I) ions were required to release the single zinc(II) ion bound per CopY monomer. The specificity of copper transfer between CopZ and CopY was dependent on electrostatic interactions. Relative copper binding affinities of the proteins were investigated using the chelator, diethyldithiocarbamic acid (DDC). These data suggest that CopY has a higher affinity for copper than CopZ. However, this affinity difference is not the sole factor in the copper exchange; a charge-based interaction between the two proteins is required for the transfer reaction to proceed. Gain-of-function mutation of a CopZ homologue demonstrated the necessity of four lysine residues on the chaperone for the interaction with CopY. Taken together, these results suggest a mechanism for copper exchange between CopZ and CopY.

Models for Arginine-Metal Binding. Synthesis of Guanidine and Urea Ligands through Amination and Hydration of a Cyanamide Ligand Bound to Platinum(II), Osmium(III), and Cobalt(III).

Dimethylcyanamide (N identical withCNMe(2)) has been coordinated to both hard and soft electrophiles ((NH(3))(5)Co(3+), (NH(3))(5)Os(3+), (dien)Pt(2+)) which activate ( approximately x10(6)) the nitrile toward attack by nucleophiles such as ammonia and hydroxide. Amination with liquid ammonia gave a rare coordinated guanidine (N,N-dimethylguanidine) ligand, which NMR spectra and X-ray crystal structures show to be charge neutral rather than anionic. Crystals of [(NH(3))(5)CoNH=C(NH(2))NMe(2)](S(2)O(6))(3/2).H(2)O, CoC(3)H(26)N(8)O(10)S(3), were triclinic, space group P&onemacr;, a = 11.565(2) Å, b = 10.629(5) Å, c = 8.026(1) Å, alpha = 84.93(3) degrees, beta = 76.01(1) degrees, gamma = 73.82(3) degrees, V = 919.2(5) Å(3), Z = 2, and R(F)() (R(w)(F)()) = 0.038 (0.047) for 3262 observed reflections (I > 3.0 sigma(I)). Crystals of [(dien)PtNH=C(NH(2))NMe(2)](CF(3)SO(3))(2), PtC(9)H(22)N(6)O(6) S(2)F(6), are monoclinic, space group P2(1)/c, a = 13.857(4), b = 14.748(4) Å, c = 22.092(4) Å, beta = 105.38(2) degrees, V = 4353(2) Å(3), Z = 8, and R(F)() (R(w)(F)()) = 0.034 (0.038) for 6778 reflections. Coordination geometries around the metals are octahedral and square planar, respectively, the guanidine skeletons being planar with bond angles and lengths characteristic of the metal-imino (rather than metal-amino) tautomer. The complexes are very stable in coordinating solvents (DMSO; water, pH 3-11) indicating high affinity of guanidine ligands for metal ions. Hydration of the dimethylcyanamide ligand is base-catalyzed, and first-order in [OH(-)] (0.05-0.5 M NaOH; k = k(s) + k(OH)[OH(-)], k(OH) = 2-5 M(-)(1) s(-)(1), 25 degrees C), in each case producing coordinated N,N-dimethylurea ([dienPtNHCONMe(2)](+), [(NH(3))(5)CoNHCONMe(2)](2+), [(NH(3))(5)OsNHCONMe(2)](2+)). Hydration rates are surprizingly similar despite differing radial extensions of the metal d-orbitals, a finding consistent with their comparable polarizing powers but contrary to expectation from other work. The relevance of metal activation of nitriles to biological systems is discussed.