A function of DivIVA in Listeria monocytogenes division site selection

Abstract

SummaryThe cell division protein DivIVA influences protein transport via the accessory SecA2 secretion route in Listeria monocytogenes. In contrast, DivIVA from the closely related bacterium Bacillus subtilis contributes to division site selection via the MinCDJ system. However, no classical min phenotype, i.e. filamentation and minicell production was observed with a listerial ΔdivIVA mutant. This has prompted the speculation that division site selection is DivIVAindependent in L. monocytogenes. We addressed this question with genetic, cytological and bacterial twohybrid experiments and the data obtained correct this view. DivIVA not only binds to MinJ but also directly interacts with MinD. Experiments with fluorescently tagged proteins showed that localization of MinC and MinD was clearly DivIVA-dependent, whereas localization of MinJ was not. An impact of DivIVA on cell division was confirmed by careful comparisons of cell size distributions of divIVA and secA2 mutants. Gene deletion studies and epistasis experiments consistently reinforced these findings, and also revealed that MinJ must have a DivIVA-independent function. The frequency of minicell formation is low in L. monocytogenes min mutants. However, since listerial minicells might be useful as carriers for the introduction of therapeutic compounds into eukaryotic cells, we present a strategy how minicell frequency can be increased.

Genetic Dissection of DivIVA Functions in Listeria monocytogenes

“…In L. monocytogenes, DivIVA affects (i) SecA2-dependent autolysin secretion, required for daughter cell separation (25); (ii) MinCD-dependent control of division site positioning (26), necessary for cell length maintenance; and (iii) swarming (25). Thus, a L. monocytogenes ΔdivIVA mutant forms long chains of unsegregated daughter cells with irregular length that do not swarm on semisolid agar plates.…”

“…In contrast to B. subtilis, where this interaction is mediated through MinJ (10,11), DivIVA of L. monocytogenes seemingly interacts with MinD in a direct fashion, as suggested by bacterial two-hybrid experiments (26). Thus, not only do ΔdivIVA mutant cells form cell chains, but also the individual cells in these chains are considerably elongated (26).…”

“…In addition to these functions, L. monocytogenes DivIVA is also required for precise positioning of the divisional septum in the middle of a dividing cell. This activity is dependent on the septal recruitment of the division-inhibitory MinCD proteins through DivIVA (26). In contrast to B. subtilis, where this interaction is mediated through MinJ (10,11), DivIVA of L. monocytogenes seemingly interacts with MinD in a direct fashion, as suggested by bacterial two-hybrid experiments (26).…”

Minicells, Back in Fashion

“…Alternatively, the overproduction of FtsZ can overwhelm the Min system and produce minicells in an otherwise wild-type strain of E. coli (58). A similar strategy was recently used to overproduce FtsZ and resulted in a 2-fold increase in minicell production of L. monocytogenes (57).…”

“…However, inactivation of the Min system in some bacterial species may not be sufficient for generating high minicell yields. For example, inactivation of the Listeria monocytogenes Min system produces minicells at very low frequency (57), perhaps because of the action of additional Z-ring spatial regulators in this species. Alternatively, the overproduction of FtsZ can overwhelm the Min system and produce minicells in an otherwise wild-type strain of E. coli (58).…”