In addition, several base-excision-repair enzymes have also been identified and shown to be required for in vivo, but not in vitro, growth of M. tuberculosis. LY2835219 Moreover, mutations in uvrD1, thought to be part of the nucleotide-excision-repair pathway as well as replication restart and recombination, result in RNS susceptibility in vitro and reduced capacity to resist ROS and RNS in vivo. Elimination of uvrD1 significantly affects the chronic stage of infection and impacts the ability of Mtb to replicate and persist in a mouse model of infection. On the other hand, Mtb defective for UvrA, mediating the initial step of NER, are not attenuated in MØs, suggesting that NER is not required under these conditions. Mtb defective for UvrB, the other NER component, exhibit a slightly reduced ability to survive in bone marrow-derived MØs and show modestly attenuated infection in mice as well as in primate lungs. Little is known about the role of DSB repair pathways during infection. A recA mutant of the M. bovis BCG strain causes no detectable phenotype in mice for up to 80 days after infection, possibly indicating that nitrosative or oxidative stresses do not induce cytotoxic DNA damage in the murine model. However, the possibility that the attenuated phenotype of BCG may have masked a recA deficiency cannot be excluded. The attenuation of recA mutants during infection has been described for other bacteria, including Burkholderia spp., Salmonella enterica and Acinetobacter baumannii, but not Porphyromonas gingivalis. In our study, the recA mutant appeared to be sensitive to the DNA-damaging agent UV in vitro, but was not attenuated in THP1-derived MØs. Inactivation of NHEJ did not result in a detectable phenotype either in vitro or inside MØs. It was previously found that the absence of NHEJ sensitizes fast-growing mycobacteria to desiccation and IR during the stationary phase of growth, but not to mitomycin C or UV. In the current study, Mtb were only clearly attenuated in MØs if both DSB repair pathways were disrupted. Moreover, virulence was restored by complementation of either pathway. We conclude that intracellular exposure of Mtb to RNS and ROS results in the formation of DSBs, which must be repaired by HR or NHEJ— notwithstanding the fact that Mtb expression profiles suggest that HR genes, but not ligD and ku, are regulated during infection. NHEJ may nevertheless be important for Mtb survival within MØs, where they are continually exposed to the genotoxic defense mechanisms of host cells. Moreover, in some cells it become an only DSB repair pathway available during latency or reactivation from latency in cases where no daughter chromatid for HR is present. Methods for engineering cell metabolism have enabled the production of high-value chemical compounds in large quantities. A single cell can be engineered to convert various carbon sources into valuable biochemical products such as lactate, butadiene, succinate, and 2,3-butanediol.