Mobile elements account for 16% of the P. lutzii genome and 7.7% and 9.2% of the genomes of P. brasiliensis isolates Pb03 and Pb18, respectively.
To explore the reasons underlying the observation that NT had highly variable PFGE profiles in contrast to relatively conserved STs, we assessed whether the presence of prophages or other mobile elements could account for these observations.
A remarkable feature of primate genomes is the proportion of retroposed insertions involving LINEs, short interspersed nuclear elements (SINEs) and other mobile elements, which account for up to approximately 45% of the genomes of humans (Lander et al. 2001; Venter et al. 2001), chimpanzees (Chimpanzee Sequencing and Analysis Consortium 2005), and gorillas (Scally et al. 2012).
The two most significant classes of human mobile elements are long interspersed elements (LINEs) and short interspersed elements (SINEs), and together, these elements account for at least 38% of genomic content [ 2, 3].
It is the most successfully integrated mobile element and accounts for about 18% of the human genome [ 6].
It is worth noticing that mobile elements and their remnants account for large proportions of most eukaryotic genomes, in which they have had central roles in genome evolution and hypervariation.
Moreover, whereas in the human genome, mainly SINEs (Alu) and LINEs (L1) are involved, diverse mobile elements were found to account for polymorphic insertions in S. cephaloptera, with several known classes of retrotransposons (Gypsy, Bel/Pao, and Penelope) and DNA transposon (Tc1/mariner).
The homology of exons -2aM, -3aH and -3bH with various SINE/ALU repeated sequences (data not shown) suggests they are part of mobile elements, an observation which may account for their lack of evolutionary conservation.
More recently, mobile elements have been found to account for about half of the genome size also in the phytopathogenic oomycete Phytophthora infestans and the truffle fungus Tuber melanosporum[ 12].
To define orthologous chromosomal genes among the different L. pneumophila strains, pseudogenes and mobile elements were not taken into account due to the difficulty of ortholog assignment for these genes.
