Involved in biosynthesis of di-myo-inositol phosphate (DIP), a widespread organic solute in microorganisms adapted to hot environments. Catalyzes the condensation of CTP and L-myo-inositol-1-phosphate into CDP-L-myo-inositol, as well as the biosynthesis of di-myo-inositol-1,3'-phosphate-1'-phosphate (DIPP) from CDP-L-myo-inositol and L-myo-inositol-1-phosphate. The cytidylyltransferase is absolutely specific for CTP and L-myo-inositol-1-P. The DIPP synthase uses only L-myoinositol-1-phosphate as an alcohol acceptor, but CDP-glycerol, as well as CDP-L-myo-inositol and CDP-D-myoinositol, are recognized as alcohol donors. 1D-myo-inositol 3-phosphate + CTP + H(+) = CDP-1L-myo-inositol + diphosphate 1D-myo-inositol 3-phosphate + CDP-1L-myo-inositol = bis(1L-myo-inositol) 3,1'-phosphate 1-phosphate + CMP + H(+) Optimum pH is between 6.5 and 7.5. Optimum temperature is between 90 and 95 degrees Celsius. The activity is undetectable at temperatures below 60 degrees Celsius. Forms a mixture of monomers and dimers in solution, with prevalence of the monomeric form. In the N-terminal section; belongs to the MobA family. In the C-terminal section; belongs to the CDP-alcohol phosphatidyltransferase class-I family.