Functions of the Essential Gene mraY in Cellular Morphogenesis and Development of the Filamentous Cyanobacterium Anabaena PCC 7120

Abstract

Bacterial cell shape is determined by the peptidoglycan (PG) layer. The cyanobacterium Anabaena sp. PCC 7120 (Anabaena) is a filamentous strain with ovoid-shaped cells connected together with incomplete cell constriction. When deprived of combined nitrogen in the growth medium, about 5–10% of the cells differentiate into heterocysts, cells devoted to nitrogen fixation. It has been shown that PG synthesis is modulated during heterocyst development and some penicillin-binding proteins (PBPs) participating in PG synthesis are required for heterocyst morphogenesis or functioning. Anabaena has multiple PBPs with functional redundancy. In this study, in order to examine the function of PG synthesis and its relationship with heterocyst development, we created a conditional mutant of mraY, a gene necessary for the synthesis of the PG precursor, lipid I. We show that mraY is required for cell and filament integrity. Furthermore, when mraY expression was being limited, persistent septal PG synthetic activity was observed, resulting in increase in cell width. Under non-permissive conditions, filaments and cells were rapidly lysed, and no sign of heterocyst development within the time window allowed was detected after nitrogen starvation. When mraY expression was being limited, a high percentage of heterocyst doublets were found. These doublets are formed likely as a consequence of delayed cell division and persistent septal PG synthesis. MraY interacts with components of both the elongasome and the divisome, in particular those directly involved in PG synthesis, including HetF, which is required for both cell division and heterocyst formation.

Development of a natural product optimization strategy for inhibitors against MraY, a promising antibacterial target

“…These results indicate that 2 exhibits bactericidal activity against both S. aureus and E. coli . The bactericidal effect of 2 is consistent with the known essentiality of the MraY enzyme, whose depletion using a conditional mutant has been shown to result in rapid cell lysis 5 , 46 . Moreover, the MIC of 2 increased only 2-fold over 30 days of continuous exposure at 1/2×MIC, which indicates that resistant strains are unlikely to emerge (Fig.…”

Development of a Natural Product Optimization Strategy for inhibitors against the cell wall synthesis enzyme MraY, a promising antibacterial target

“…The bactericidal effect of 2 is consistent with the known essentiality of the MraY enzyme, whose depletion using a conditional mutant has been shown to result in rapid cell lysis. 22,53 Moreover, the MIC of 2 increased only 2-fold over 30 days of continuous exposure at 1/2×MIC, which indicates that resistant strains are unlikely to emerge (Fig. 4c).…”

Bacteria evolve macroscopic multicellularity by the genetic assimilation of phenotypically plastic cell clustering

“…Moreover, MreB, which is the bacterial analog of actin, is an essential protein that forms a scaffold which interacts with several other peptidoglycan biosynthesis proteins and plays key role in cellular elongation 52 . Finally, MraY has been shown to affect both the cell shape and adhesion in the multicellular cyanobacterium Anabaena 56 . This suggests that the mutations observed in the clones that successfully assimilated multicellular clustering can also be linked to the evolutionary changes in cell shape plasticity (Fig.…”