Mycobacterium tuberculosis and Clostridium difficille interactomes: demonstration of rapid development of computational system for bacterial interactome prediction

Table 2 Known and estimated sizes of interactomes

Organism	Number of proteins	number of pairs	Upper estimate of number of interactions	Lower estimate of number of interactions	Currently known interactions	% relative to larger estimate of interactome size	% relative to smaller estimate of interactome size
Mtb	4,020	8,078,190	16,156	5,385	3,439*	21	62
CD	4,147	8,598,804	17,197	5,732	3,414*	20	60
Yeast	6,717	22,555,686	45,111	15,037	37,000 [34]	82	246
Human	22,500	253,113,750	506,228	168,743	38,000 [35]	8	23

Number of proteins and the size of the interactome are shown for human, yeast, Clostridium difficile and Mycobacterium tuberculosis. Upper estimate of interactome size is obtained by considering that one in 500 random pairs is an interacting pair, and lower estimate is obtained by considering that one in 1500 random pairs is an interacting pair. *These numbers are determined from nonzero STRING experimental scores