Biosorption of tributyltin and other organotin compounds by cyanobacteria and microalgae

Abstract

Biosorption of triorganotin compounds by the cyanobacteria Synechocystis PCC 6803 and Plectonema boryanum and the microalga Chlorella emersonii, incubated in 2-(N-morpholino)ethanesulphonic acid (MES) buffer, pH 5.5, in the presence of 0.5 mM organotin (supplied as chlorides), increased with molecular mass of the organotins, the order being triphenyltin > tributyltin (Bu3SnC1) > tripropyltin >/trimethyltin~>triethyltin. In the butyltin series, monobutyltin biosorption was lowest, although levels of dibutyltin uptake were greater than for Bu3SnC1. Cyanobacterial Bu3SnC1 biosorption was complete in 5 min with no subsequent accumulation. In contrast, a second phase of uptake in C. emersonii resulted in an approximate 2.4-fold increase in cellular Bu3SnC1 between 5 min and 2 h. The external pH had a marked influence on biosorption of Bu3SnC1 by Synechocystis PCC 6803 and P. boryanum, with maximal uptake at pH 5.5 and 6.5, respectively. Effects of pH were less evident in C. emersonii. In all the organisms examined, no inhibition of Bu3SnC1 biosorption was observed between 0.05 and 50 mM NaC1. However, an increase in the external NaC1 concentration from 50 to 500 mM resulted in, an approximate 55-65% reduction in Bu3SnC1 uptake. Biosorption increased at increasing Bu3SnC1 concentrations (0.25-3.0 mM). Saturation of Bu3SnC1 biosorption at the higher concentrations was most evident in the cyanobacteria, although uptake levels were greater in these organisms at ~<2 mM Bu3SnC1. Theoretical maximum biosorption levels at complete cell saturation, derived from reciprocal Langmuir plots, were approximately 565, 525 and 1050 nmol Bu3SnC1 mg -1 dry weight, for Synechocystis PCC 6803, P. boryanum and C. emersonii, respectively.

The Effects of Organotin Compounds on Growth, Respiration Rate, and ChlorophyllaContent ofScenedesmus quadricauda

“…McDonald and Trevors (1988) and Cooney (1995) observed that toxicity of OTCs increased from the OTCs with the methyl group, to the OTCs with the butyl, pentyl, and phenyl groups. Further, an increase in the n-alkyl chain length sharply decreased biological activity (Davies and Smith, 1980;Avery et al, 1993). Present studies did not confirm the former observations.…”

“…The toxicity of benzyl-, phenyl-, and tributyltins is very similar (Davies and Smith, 1980), as confirmed by the current findings. Tributyltins and, especially, triphenyltins were highly toxic for algae (Wong et al, 1982;Avery et al, 1993). The high toxicity of tributyl-and triphenyltins for all tested parameters, except respiration activity, was generally confirmed in the present tests with the alga S. quadricauda.…”

Biosorption: critical review of scientific rationale, environmental importance and significance for pollution treatment

“…While such schemes may inform or explain some biosorptive phenomena, definitions are not absolute and there can be varying properties of metal species rather than absolute distinctions, as well as borderline categories. Some behaviour will be affected by metal concentration, 52 as well as the relative metal concentrations in mixtures where competitive effects may occur. The hard/soft scheme predicts that bonds formed between hard acids and hard ligands will be predominantly ionic whereas soft acid-ligand complexes are more covalent in character.…”

“…156 This could be due to the involvement of amine and sulphydryl functional groups that are active on cell surfaces of living cells but which may be denatured in dead biomass, where phosphate and carboxylate groups may be more significant. 52 A further mechanistic complication is where living cell systems are used. Many biosorption researchers do not restrict themselves to dead biomass or purified products, and a variety of mechanisms may be exhibited, depending on growth and other conditions, that lead to metal accumulation.…”

Uma visão da química bioinorgânica medicinal

“…Este gráfico é uma maneira simplificada de representar a distinção entre íons metálicos duros e macios. Ele fornece qualitativamente a série de Irving-Williams 18,19 .…”