The invention provides a non-naturally occurring microbial 
organism having an acetyl-CoA pathway and the capability of utilizing 
syngas or 
syngas and 
methanol. In one embodiment, the invention provides a non-naturally occurring 
microorganism, comprising one or more exogenous proteins conferring to the 
microorganism a pathway to convert CO, CO2 and / or H2 to acetyl-
coenzyme A (acetyl-CoA), methyl tetrahydrofolate (methyl-THF) or other desired products, wherein the 
microorganism lacks the ability to convert CO or CO2 and H2 to acetyl-CoA or methyl-THF in the absence of the one or more exogenous proteins. For example, the microbial 
organism can contain at least one exogenous 
nucleic acid encoding an 
enzyme or 
protein in an acetyl-CoA pathway. The microbial 
organism is capable of utilizing synthesis gases comprising CO, CO2 and / or H2, alone or in combination with 
methanol, to produce acetyl-CoA. The invention additionally provides a method for producing acetyl-CoA, for example, by culturing an acetyl-CoA producing microbial organism, where the microbial organism expresses at least one exogenous 
nucleic acid encoding an acetyl-CoA pathway 
enzyme or 
protein in a sufficient amount to produce acetyl-CoA, under conditions and for a sufficient period of time to produce acetyl-CoA.