Influence of diet on the distribution of nitrogen isotopes in animals

The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

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Publisher Summary Recent advances in the biochemistry of microorganisms have revealed that cell-component analysis can be effectively applied to bacterial systematics, providing the basis of chemotaxonomy. Analyses of cell components are coming to be essential tools not only for bacterial classification but also for identification. The sequence of chromosomal DNA holds the essential genetic information for an organism. Phylogenetic relationships are often examined using data on nucleotide sequences of ribosomal RNA. However, it is still impossible to determine the sequences of large polynucleotides for the number of organisms sufficient for taxonomic purposes. DNA (RNA) homologies, which have been applied to various kinds of bacteria, present useful information on bacterial systematics. Homology indices are values used in comparing microorganisms. DNA homology data contribute to the clarification, not only of the relatedness of two organisms, but also of the evaluation of phenotypic characteristics.

4 Lipid and Cell-Wall Analysis in Bacterial Systematics

Lipid decomposition studies in frozen fish have led to the development of a simple and rapid method for the extraction and purification of lipids from biological materials. The entire procedure can...

E. G. Bligh

Papers

A rapid method of total lipid extraction and purification.