Fig. 6.

Correlations in Archaea and Bacteria genomes and their classification: the analysis of the correlation coefficient δ(l) of Archaea (a, b) and Bacteria (c–l) reveals behaviours separable into four major classes, referred to as A, A′, A′′, and B, as revealed by cluster analysis. Members of each class were averaged, respectively (Fig. 10). In general, Archaea and Bacteria are characterized by a first maximum below 10³ bp with decreased height and increased position, influenced by a second maximum. The transition exhibits a minimum or a saddle point also connected to the growing presence of the second maximum. The often extreme degree of correlation is unlike that found in any of the Eukarya. A prime example for Archaea is Archeoglobus fulgidus, for class A Aquifex aeolicus, and for class A′ Campylobacter jejuni. Class A′′ is a mixture of class A and A′ consisting, e.g. of Methanobacterium thermoautotrophicum delta-H and Xylella fastidiosa. Class B consists e.g. of Bacillus halodurans or Clostridium acetobutylicum and is characterized by an extreme degree of correlation and a sharp descent without fluctuations. Sequences from the same Archaea or Bacteria species but different strains show almost identical behaviour