Before revision:  Noteworthy, a phase transition is observed such that, for  k\ge40, bacterial PPI network are mostly populated by genes that are conserved, essential and which, in most cases, belong to the COG J, a category of genes which is related to ribosomal functions and to the processing of genetic information.
After revision:  Noteworthy, a phase transition is observed such that, for k\ge40, bacterial PPI network are mostly populated by genes that are conserved, essential and which, in most cases, belong to the COG cluster J, related to ribosomal functions and to the processing of genetic information.