Before revision:  In this work we investigate how gene conservation, essentiality and functional repertoire are reflected in the connectivity k of the corresponding proteins in the PPI networks  of 42 evolutionarily unrelated bacterial species . We investigate three issues: i) the degree distribution and densities of the PPI subnetworks of essential and nonessential genes;
After revision:  In this work we investigate how gene conservation, essentiality and functional repertoire are reflected in the connectivity k of the corresponding proteins in the PPI networks of 42 bacterial species with reasonably separated evolutionary trajectories, we investigate three issues: i) the degree distribution and densities of the PPI subnetworks of essential and nonessential genes;