Metal assimilation metals

Figure 5. Digestion strategies in molluscs. Modified from [68] Decho, A. W. and Luoma, S. N. (1996) Flexible digestion strategies and trace metal assimilation in marine bivalves in Limnol. Oceanogr., 41, 568-572. Reproduced with permission...

While recognizing that this is a supreme example of reductionist simplification, it nonetheless allows us to situate the three model systems that we will consider here, because the mechanisms of metal assimilation are often significantly different. Finally, once the metal ions have been assimilated, they must be incorporated into the corresponding proteins, we have already presented in Chapter 3 a brief consideration of some of the ways in which metal centres, whether individual metal ions or more complex metal clusters, are engineered into their metalloprotein targets. 

The importance of metal assimilation for bacteria is perhaps best illustrated by the correlation between the efficacy of iron uptake systems and virulence in many strains of pathogenic... 

The obvious and fundamental concept that results from such elucubrations, one that is now supported, documented and quantified in several experimental data sets, is that the toxic effect of a trace metal is caused by its interference with the uptake, assimilation or utilization of another, essential trace metal. Trace metals are to various degrees coordinative analogs of each other, toxicity occurs when a metal binds competitively to a ligand site involved in the transport, assimilation or utilization of an essential metal whose function it cannot emulate. (In some cases metals can replace others with reasonably good efficiency). As a result, the study of trace metal toxicity in microalgae must commence with a study of trace metal nutrition, a scientifically sound if paradoxical situation. 

Other reactions leading to NH4 removal from soil solution besides microbial nitrogen assimilation, metal-ammine formation, or adsorption onto mineral surfaces, involve NH3 fixation by incorporating it as NH2 in aromatic rings of humic acids (quinone) followed with aromatic ring condensation. 

Table 4 shows the metals contents for catalyst B samples on different locations inside the catalytic system. Since metal levels in the second reactor are too low if compared with the real capacity to assimilate metals shown in the first reactor, then it is concluded that the exhaustion is produced by coke deposition either in quantity or quality. In this case these deposits are... 

---