The invention relates to an isolated genetically modified microorganism in which the gene IDH1 and at least one of the genes SDH2 and DIC1 are under the control of a first promoter that is repressed to a growth culture medium by means of a cultivation additive and is active in the absence of the cultivation additive. The genes that are part of the group comprising “PYC1, ACS1, CIT1, ACO1, ICL1, MSL1, and CIT2, optionally also MDH3” are constitutively active. The invention further relates to uses of such a microorganism, especially for producing succinic acid.