Investigating the Genomic Adaptation of Group B Streptococcus after Maternal Transmission
Group B streptococcus (GBS) is a leading cause of neonatal infections. Almeida et al. (p. 3354–3366) have performed a genomic comparison between 19 pairs of strains from infected newborns and their mothers. In a few cases, they found that this organism undergoes genomic changes in the newborn after maternal transmission. Notably, mutations within a known virulence regulator (CovR) and a promoter of an immunogenic surface protein (Rib) were shown to alter the expression of virulence-associated genes in human blood. These results suggest that mutations selected in the newborn might contribute to the ability of GBS to infect its host.
Differential Relevance of Distinct Cellular Pools of the Second Messenger Cyclic Di-AMP
Many bacteria produce cyclic dinucleotides as second messengers, and often, parallel enzymes are involved in their synthesis and degradation. Gundlach et al. (p. 3265–3274) have now analyzed the control of the synthesis and degradation of cyclic di-AMP (c-di-AMP) in Bacillus subtilis. Although c-di-AMP is known to be essential, the accumulation of c-di-AMP is toxic for the cells. The analysis of suppressor mutants revealed that the pool of the nucleotide synthesized by the membrane-bound diadenylate cyclase CdaA is particularly toxic. Importantly, CdaA is conserved in most Firmicutes and is the only diadenylate cyclase in many Gram-positive pathogens.
Two Regulators for the Control of Pyrimidine Synthesis in Corynebacterium glutamicum
Microorganisms regulate the expression of pyrimidine de novo synthesis genes in response to altered pyrimidine availability. Tanaka et al. (p. 3307–3316) show that simultaneous deletion of the pyrR gene, encoding a homologue of mRNA-binding regulator PyrR, and rho is required for elimination of the uracil response of pyr genes in Corynebacterium glutamicum. These results suggest that expression of the pyrimidine biosynthetic gene cluster in C. glutamicum is controlled by two different mechanisms mediated by PyrR or Rho.
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