Plasmids in both Escherichia coli and Staphylococcus aureus contain an "operon" that confers resistances to arsenate, arsenite, and antimony(III) salts. The systems were always inducible. All three salts, arsenate, arsenite, and antimony(III), were inducers. Mutants and a cloned deoxyribonucleic acid fragment from plasmid p1258 in S. aureus have lost arsenate resistance but retained

The biotransformation of Hg(II) by cyanobacteria was investigated under aerobic and pH-controlled culture conditions. Mercury was supplied as HgCl 2 in amounts emulating those found under heavily impacted environmental conditions where bioremediation would be appropriate. The analytical procedures used to measure mercury within the culture solution, including that in the cyanobacterial cells, used reduction under both acid and alkaline conditions in the presence of SnCl 2 . Acid reduction detected free Hg(II) ions and its complexes, whereas alkaline reduction revealed that meta-cinnabar (␤-HgS) constituted the major biotransformed and cellularly associated mercury pool. This was true for all investigated species of cyanobacteria: Limnothrix planctonica (Lemm.), Synechococcus leopoldiensis (Racib.) Komarek, and Phormidium limnetica (Lemm.). From the outset of mercury exposure, there was rapid synthesis of ␤-HgS and Hg(0); however, the production rate for the latter decreased quickly. Inhibitory studies using dimethylfumarate and iodoacetamide to modify intra-and extracellular thiols, respectively, revealed that the former thiol pool was required for the conversion of Hg(II) into ␤-HgS. In addition, increasing the temperature enhanced the amount of ␤-HgS produced, with a concomitant decrease in Hg(0) volatilization. These findings suggest that in the environment, cyanobacteria at the air-water interface could act to convert substantial amounts of Hg(II) into ␤-HgS. Furthermore, the efficiency of conversion into ␤-HgS by cyanobacteria may lead to the development of applications in the bioremediation of mercury.Mercury in the form of divalent ions constitutes the bulk of that in soils, where it is bound to organic compounds, to clay, and as sulfides (31). Although industrialization in the beginning of the last century is the cause of most of the mercury contamination found in the environment today, rainfall continues to carry mercury [Hg(II)] into aquatic and terrestrial systems worldwide (16,44). Despite a comprehensive knowledge of the mercury cycle and the aquatic chemistry of its constituents (12, 43, 52), several microbial taxa have not been characterized with respect to their roles in the biotransformation of this heavy metal.Several mercury biotransformation mechanisms have been described previously (4,12,39,41), and of these, prokaryotic methylation and reduction to Hg(0) may play only limited roles in the biotransformation of Hg(II) in aquatic environments (15,19). Furthermore, the reduction reaction simply refracts meteorologically precipitated Hg(II) back into the atmosphere. As such, it follows that other processes must make significant contributions to the biogeochemical cycle of Hg even though relative quantitative data are scarce (31). Insight into this area requires an understanding of the major biotransformation processes leading to mercury retention in ecosystems.The lack of quantitative, mechanistic data behind cellular accumulation versus that for volatilization of Hg is evident even in the eukar...

The influence of metallic, cations (added at 10 μM‐1 mM) on the uptake of orthophosphate from 0.2–10 μM solution by Synechococcus leopoliensis (Racib.) Komarek was investigated. All cations tested except Mg2+ and Zn2+ stimulated phosphate uptake. The most pronounced stimulation of phosphate uptake was caused by Ca2+·Ca2+ markedly decreased the half‐saturation concentration for orthophosphate uptake, apparently by acting upon the metabolic processes of phosphate transport into the cell. Phosphate did not influence Ca2+ fluxes across the cell‐surface.

Phosphate uptake by the blue-reen alga Oscillatoria limnetica Lem-merman is stimulated by micromolar concentrations of Ca2". The calmodulin antagonists 4-(3-(2(trifluoromethyl)phenylthiazin-1O-yljpropyl)-I-piperazine ethanol-Ha and its monofluoro-analog inhibit orthophosphate uptake of Oscillatoria limnetica by over 97% implying involvement of calmodulin in this process. A calmodulin-like protein was quantitated in cell-free extracts from 0. limnetica by radioimmunoassay.Phosphate uptake has been investigated in a range oforganisms including bacteria, algae, fungi, and higher plants (2,5,12,14,(18)(19)(20)(21)(22). While stimulation of Pi uptake by various cations has been widely reported (5,11,(18)(19)(20)(21)23

The biotransformation of Hg II in pH-controlled and aerated algal cultures was investigated. Previous researchers have observed losses in Hg detection in vitro with the addition of cysteine under acid reduction conditions in the presence of SnCl 2 . They proposed that this was the effect of Hg-thiol complexing. The present study found that cysteine-Hg, protein and nonprotein thiol chelates, and nucleoside chelates of Hg were all fully detectable under acid reduction conditions without previous digestion. Furthermore, organic (R-Hg) mercury compounds could not be detected under either the acid or alkaline reduction conditions, and only ␤-HgS was detected under alkaline and not under acid SnCl 2 reduction conditions. The blue-green alga Limnothrix planctonica biotransformed the bulk of Hg II applied as HgCl 2 into a form with the analytical properties of ␤-HgS. Similar results were obtained for the eukaryotic alga Selenastrum minutum. No evidence for the synthesis of organomercurials such as CH 3 Hg ؉ was obtained from analysis of either airstream or biomass samples under the aerobic conditions of the study. An analytical procedure that involved both acid and alkaline reduction was developed. It provides the first selective method for the determination of ␤-HgS in biological samples. Under aerobic conditions, Hg II is biotransformed mainly into ␤-HgS (meta-cinnabar), and this occurs in both prokaryotic and eukaryotic algae. This has important implications with respect to identification of mercury species and cycling in aquatic habitats.