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Uptake of dissolved inorganic carbon (bicarbonate and carbon dioxide) from the environment is the first step in the synthesis of organic carbon by autotrophic, carbon dioxide-fixing microorganisms. Despite the importance of this first step and the presence of autotrophs in numerous phyla, uptake of dissolved inorganic carbon has been characterized only in cyanobacteria. Mangiapia et al. (e00871-16) identify a likely dissolved inorganic carbon transporter in the deep-sea chemolithoautotroph Thiomicrospira crunogena. Homologs of this transporter are present in 14 phyla and are often colocated on genomes with carboxylases, suggesting that their role as dissolved inorganic carbon transporters is broadly distributed.
ToxT is the master regulator of virulence in Vibrio cholerae. Kovacikova et al. (e00762-16) have identified a new link between fatty acid (FA) metabolism and virulence in the El Tor biotype by showing that FadR, the transcription factor that controls FA degradation and biosynthesis in enteric bacteria, influences both the transcription and posttranslational regulation of ToxT. FadR appears to control these processes indirectly. Interestingly, preventing activation of one of its target genes, fabA, encoding an enzyme essential for unsaturated FA biosynthesis, decreased ToxT posttranslationally but had no effect on its transcription. Thus, FadR influences ToxT via two distinct mechanisms.