TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation: No preparation method is given. Preferred Components: The cells further comprises: at least one introduced nucleic acid encoding at least one deoxyxylulose-5-phosphate (DXP) pathway polypeptide(s), where the DXP pathway polypeptide(s) have increased expression as compared to the cells without the introduced nucleic acids encoding DXP pathway polypeptide(s), and the DXP pathway peptide is 1-deoxy-D-xylulose-5-phosphate synthase (EC 2.2.1.7); and at least one introduced nucleic acid encoding mevalonic acid pathway polypeptide(s) having acetyl-coenzyme-A acetyltransferase, 3-hydroxy-3-methylglutaryl-coenzyme-A (HMGCoA) reductase, HMGCoA synthase, mevalonate kinase, phosphomevalonate kinase or diphosphomevalonate decarboxylase activity. The cells are Clostridium ljungdahlii (preferred), Clostridium aceticum, Moorella thermoacetica, Clostridium autoethanogenum, Eubacterium limosum, Clostridium carboxidivorans, Peptostreptococcus productus, Rhodospirillum rubrum, Desulfitobacterium hafniense, Acetoanaerobium noterae, Butyribacterium methylotrophicum, Thermoanaerobacter kivui, or Acetobacterium woodii. The isoprene synthase polypeptide is a variant of a naturally occurring isoprene synthase polypeptide (EC 42.3.27), where the variant isoprene synthase polypeptide has an improvement which includes improved catalytic activity, improved solubility, increased resistance to degradation and/or increased resistance to cleavage, as compared to the naturally occurring isoprene synthase polypeptide. The variant isoprene synthase polypeptide comprises at least one modification comprising substitution, addition, deletion, or truncation. The variant comprises a truncation of the native N-terminus and an addition of a heterologous oligopeptide in the N-terminal end. The variant is of a plant isoprene synthase polypeptide. The plant is Pueraria, Populus or a Populus alba x Populus tremula hybrid. The promoter is from a cell of Clostridium. The isopentenyl diphosphate isomerase polypeptide belongs to the group EC 13.3.2, where the isopentenyl diphosphate isomerase polypeptide is from a yeast. The introduced nucleic acids comprise coding regions of mevalonic acid-E or mevalonic acid-S. The heterologous nucleic acids are present on a plasmid comprising a gram positive origin of replication isolated from a plasmid isolated from Clostridium butyricum or from a plasmid isolated from Clostridium botulinum. The cells comprise at least one genetic modification resulting in the disruption or down regulation of the genes encoding at least one of the pathways for production of lactate, acetate, ethanol, succinate, or glycerol. The cells are adapted for growth on syngas. In the cells: the isoprene synthase polypeptide is a truncated Populus alba isoprene synthase, where the polypeptide has a histidine-tag at the N-terminus; the isopentenyl diphosphate isomerase polypeptide is from Saccharomyces cerevisiae; the promoter is pFdx from Clostridium sporogenes; and the heterologous nucleic acids are in a plasmid having a gram positive origin of replication isolated from a plasmid isolated from Clostridium butyricum or Clostridium botulinum. In the recombinant obligate anaerobic bacterial acetogen cells, the polypeptides are encoded by mevalonic acid-E or mevalonic acid-S. In the cells (C3), the acetyl-CoA derived product is 2-keto acids, malonyl-CoA, acetoacetyl-CoA and/or ethanol. The cells (C3) further comprises: at least one heterologous nucleic acid encoding a polypeptide capable of converting a 2-keto acid into a non-fermentative alcohol; at least one heterologous nucleic acid encoding a polypeptides capable of converting malonyl-CoA into a fatty acid-derived hydrocarbon; or at least one heterologous nucleic acid encoding a polypeptides capable of converting acetoacetyl-CoA into a fermentative alcohol. The non-fermentative alcohol is 1-propanol, 1-butanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-1-pentanol, 4-methtyl-1-pentanol or 1-hexanol. The fatty acid-derived hydrocarbon is fatty alcohols, fatty esters, olefins or alkanes. EXAMPLE - No suitable example given.