Organotin compounds and aquatic bacteria: A review

Abstract

Organotins are toxic to microorganisms. Trisubstituted organotins (R3SnX) are considered more toxic than disubstituted (RoSnX2) or monosubstituted (RSnX3) compounds, and tetrasubstituted compounds (R4Sn) are not considered toxic. In the R3Sn series propyl-, butyl-, pentyl-, phenyl-and cyclohexyltins are the most toxic to microorganisms. Toxicity towards aerobes in the R3Sn series is related to total molecular surface area and to the octanol:water partition coefficient, Kow, which is a measure of hydrophobicity. Care must be taken when testing the toxicity of tin compounds in the laboratory, for a number of biological, chemical and physical factors can influence the apparent toxicity. Although TBT is generally the most toxic of the butyltins, there are instances where monobutyltin (MBT) is as toxic, or more toxic, than TBT to microorganisms. Thus, debutytation in the sequence TBT --* DBT -~ MBT --* Sn does not detoxify TBT for all microorganisms. Some microorganisms can methylate inorganic or organic tins under aerobic or anaerobic conditions. Methylation can also occur by chemical means and the relative contributions of biotic and abiotic mechanisms are not clear. It is difficult to isolate a pure culture which can methylate tin compounds aerobically, and it is difficult to isolate a pure culture which degrades TBT, suggesting that microbial consortiums may be involved in transformations of organotins in the aquatic environment. Methylation and debutylation alter the adsorbtivity and solubility of tin compounds; thus, microorganisms can influence the environmental mobility of tin. TBT-resistant microorganisms can be isolated, and in some of them resistance to TBT can be plasmid-mediated.

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

“…Results (Table 1) confirm these data. The toxicity of diorganotins increased with the length of the alkyl chain (Davies and Smith, 1980;Cooney, 1995). In the present tests dimethyltin (B) generally exhibited the lowest inhibiting effect.…”

“…Dibutyltin A in some cases suppressed the respiration rate and chlorophyll a content to a greater extent than some tributyltins (for example, I and K for the chlorophyll a content and J and L for the respiration rate). 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).…”

“…However, this is not a general rule. In the R 3 SnX series propyl-, butyl-, pentyl-, phenyl-, and cyclohexyltins are the most toxic to microorganisms (Cooney, 1995).…”

Biodiversity of organotin resistant Pseudomonas from west coast of India

“…In general, organotin toxicity to microbes decreases in the following order: R 3 SnX > R 2 SnX 2 > RSnX 3 > R 4 Sn. Microorganisms accumulate organotin in the cell wall envelope by a non energy requiring process, organotins such as tripropyl, tributyl and triphenyltin seem to be highly toxic to bacteria and fungi (Cooney and Wuertz 1989;Laurence et al 1989;Cooney 1995). Several reports have been documented on isolation and characterization of tributyltin (TBT) resistant bacteria from soil, marine and estuarine environment (Hallas and Cooney 1981;McDonald and Trevors 1988;Wuertz et al 1991;Fukagawa et al 1992;Suzuki et al 1992;Pain and Cooney 1998;Stasinakis et al 2005).…”

Review: Biodegradation of tributyltins (organotins) by marine bacteria

“…38,57,58 This can be achieved by biotic and abiotic factors, with UV and chemical cleavage being the most important abiotic factors in aquatic and terrestrial ecosystems. 51,58 Although the degradation of organotins has been shown to be mediated by microorganisms, information is still severely limited in relation to the mechanism of degradation the tolerance mechanisms of microbes and their relative significance and also the role of anionic radicals in the degradation process in natural habitats.…”