Fig. 5

A step-wise model of compensatory adaptation to LGT. 1, LGT DNA (green box) inserts into the genome and causes an increase in fitness, fixing in the population. 2, Expression of the gene is hampered by non-optimal codon use. In order to increase the expression of the LGT gene, LGT DNA is duplicated (green boxes) [38, 39], causing an increase in fitness. This comes at the cost of the inefficient use of the translational machinery, here shown by increased use of ribosomes. 3, tRNA genes (orange box) are duplicated, resulting in more efficient translation of the LGT genes, and reduced demand upon the translational machinery. 4, The LGT genes become integrated, adjusting codon use by way of mutational pressure and selection for lower translation error and missense mutation rates [35]. Purple indicates integrated host DNA