Bacteria metal ions

Two classes of aldolase enzymes are found in nature. Animal tissues produce a Class I aldolase, characterized by the formation of a covalent Schiff base intermediate between an active-site lysine and the carbonyl group of the substrate. Class I aldolases do not require a divalent metal ion (and thus are not inhibited by EDTA) but are inhibited by sodium borohydride, NaBH4, in the presence of substrate (see A Deeper Look, page 622). Class II aldolases are produced mainly in bacteria and fungi and are not inhibited by borohydride, but do contain an active-site metal (normally zinc, Zn ) and are inhibited by EDTA. Cyanobacteria and some other simple organisms possess both classes of aldolase. 

It is now apparent that bacteria have developed resistance to heavy metals and the detoxifying process is initiated and controlled by metallo-regulatory proteins which are able selectively to recognize metal ions. MerR is a small DNA-binding protein which displays a remarkable sensitivity to Hg +. The metal apparently binds to S atoms of cysteine and this has been a major incentive to recent work on Hg-S chemistry. 

Aldol reactions occur in many biological pathways, but are particularly important in carbohydrate metabolism, where enzymes called aldolases catalyze the addition of a ketone enolate ion to an aldehvde. Aldolases occur in all organisms and are of two types. Type 1 aldolases occur primarily in animals and higher plants type II aldolases occur primarily in fungi and bacteria. Both types catalyze the same kind of reaction, but type 1 aldolases operate place through an enamine, while type II aldolases require a metal ion (usually 7n2+) as Lewis acid and operate through an enolate ion. 

The primary target of studies on photocatalytic semiconductor suspensions has been water cleavage by visible light. Suspension-based photocatalytic processes are also useful for the removal of inorganic (metal ions) and organic pollutants, the reduction of CO2, the photodestruction of bacteria and viruses, and various organic reactions an example is the use of Pt-loaded CdS for the photocatalytic racemization of L-lysine [210]. 

In this section we summarise the manner in which i -metals. Fig. 6, and where possible specifically the platinum complexes of concern here, interact with biological molecules. Some radio-tracer studies have been carried out on the distribution of platinum complexes in whole bacteria grown in media inocculated with the metal ion. The results are summarised in Table 11. It is noteworthy that the bacteriocidal complex [PtClg]2- was taken up almost entirely by the cytoplasmic protein whereas the filamentous forming neutral species, [Pt(NHs)2Cl4], was... 

Collins Y.E., Stotzky G. Factors affecting the toxicity of heavy metals to microbes. In Metal Ions and Bacteria, Beveridge T.J, Doyle R.J., eds. New York, NY Wiley, 1989. 

Protection from any poisonous metal ions liberated from their sulfides by oxidation by 02 was secured by the use of strong chelating agents in the cytoplasm, most of which are proteins, or small molecules, thiolates, which were connected to exit pumps or to chemical metabolic tricks for metal ion neutralisation (sequestration). The genes that code for these proteins are usually to be found on plasmids in the cytoplasm of the bacterial cells (Section 5.15). Bacteria adapt very quickly to... 

Beveridge, T.J. and Doyle, R.J. (1989) Metal Ions and Bacteria, Wiley,... 

The Langmuir and Freundlich equations have often been employed to model the sorption of metal ions by bacteria. Mullen et al. (1989) used the Freundlich isotherm to describe the sorption of Cd and Cu by B. cereus, B. subtilis, E. coli and P. aeruginosa over the concentration range of 0.001-lmM. The respective values of the Freundlich constant (Kf) indicated that E. coli was most efficient at sorbing Cd2+ and Cu2+. 

Savvaidis I, Hughes M, Poole R (1992) Differential pulse polarography a method of directly measuring uptake of metal ions by live bacteria without separation of biomass and medium. FEMS Microbiol Lett 92 181-186 Savvaidis I, Hughes MN, Poole RK (2003) Copper biosorption by Pseudomonas cepacia and other strains. World J Microbiol Biotechnol 19 117-121 Scott JA, Palmer SJ (1988) Cadmium biosorption by bacterial exopolysaccharide. Biotechnol Lett 10 21-24... 

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