Figure 8. Disrupting components of histidine biosynthesis produces a filamentation response.

(A) Histidine biosynthetic genes are located throughout the chromosome. (B) Histidine is synthesized through a multi-step pathway (KEGG). (C) Cluster analysis demonstrated a consistent filamentation phenotype associated with genes involved in histidine synthesis. (D) Growth could be rescued with histidine supplementation (normalized to non-induced mutants). As HisA has an additional role in tryptophan synthesis, full rescue required simultaneous tryptophan supplementation (50 µg/ml). (E) The addition of histidine to ATc-containing growth media rescued the filamentation phenotype in all mutants other than hisS.

Figure 8—figure supplement 1. Absence of septum formation on histidine depletion.

Following CRISPRi-mediated silencing of hisG, cells were stained with the D-alanine analogue, NADA, for visualization of peptidoglycan (Botella et al., 2017). While staining was uneven, no clear septa were detected in any cells imaged (n = 35).