DivIVA Controls Progeny Morphology and Diverse ParA Proteins Regulate Cell Division or Gliding Motility in Bdellovibrio bacteriovorus

Abstract

The predatory bacterium B. bacteriovorus grows and divides inside the periplasm of Gram-negative bacteria, forming a structure known as a bdelloplast. Cell division of predators inside the dead prey cell is not by binary fission but instead by synchronous division of a single elongated filamentous cell into odd or even numbers of progeny cells. Bdellovibrio replication and cell division processes are dependent on the finite level of nutrients available from inside the prey bacterium. The filamentous growth and division process of the predator maximizes the number of progeny produced by the finite nutrients in a way that binary fission could not. To learn more about such an unusual growth profile, we studied the role of DivIVA in the growing Bdellovibrio cell. This protein is well known for its link to polar cell growth and spore formation in Gram-positive bacteria, but little is known about its function in a predatory growth context. We show that DivIVA is expressed in the growing B. bacteriovorus cell and controls cell morphology during filamentous cell division, but not the number of progeny produced. Bacterial Two Hybrid (BTH) analysis shows DivIVA may interact with proteins that respond to metabolic indicators of amino-acid biosynthesis or changes in redox state. Such changes may be relevant signals to the predator, indicating the consumption of prey nutrients within the sealed bdelloplast environment. ParA, a chromosome segregation protein, also contributes to bacterial septation in many species. The B. bacteriovorus genome contains three ParA homologs; we identify a canonical ParAB pair required for predatory cell division and show a BTH interaction between a gene product encoded from the same operon as DivIVA with the canonical ParA. The remaining ParA proteins are both expressed in Bdellovibrio but are not required for predator cell division. Instead, one of these ParA proteins coordinates gliding motility, changing the frequency at which the cells reverse direction. Our work will prime further studies into how one bacterium can coordinate its cell division with the destruction of another bacterium that it dwells within.

Chromosome choreography during the non-binary cell cycle of a predatory bacterium

“…To further investigate segregation dynamics, we turned to the endogenous ParB (here named ParB Bb ) to mark the native centromeric parS Bb site located next to ori ( Figure S1 A). Consistent with the reported biphasic expression pattern of the corresponding operon, 70 , 71 we could only detect weak fluorescent signal in G1 cells of a strain in which parB Bb was replaced by parB Bb -mcherry ( Figure S5 C). Nevertheless, although no detectable foci could be observed in the G1 phase (see below), ParB Bb -mCherry always formed a focus that colocalized with the first DnaN-msfGFP-labeled replisome ( Figure S5 D).…”

“…It would be tempting to speculate that the accessibility of parS Bb may vary during the cell cycle depending on the level of nucleoid compaction; however, the heterologous parS PMT1 inserted near endogenous parS Bb sites remained accessible to ParB PMT1 at all times. To the best of our knowledge, this is the first example of a ParB homolog that does not permanently localize at the chromosomal centromere, regardless of protein levels, hinting that beside transcriptional modulation 70,71 , ParB Bb function could be subjected to novel cell-cycle-dependent regulation. Detailed mechanistic investigation of the ParABS system in Bdellovibrio, including the analysis of ParA subcellular dynamics, should reveal interesting features of this highly conserved partitioning machinery.…”

Predatory bacteria as living antibiotics – where are we now?

“… B. bacteriovorus consumes its Gram-negative bacterial prey in a process that typically lasts 3–4 h. This predatory lifecycle is a complex process that is beginning to be understood at the molecular level [26–33]. Initially, B.…”

“…B. bacteriovorus consumes its Gram-negative bacterial prey in a process that typically lasts 3-4 h. This predatory lifecycle is a complex process that is beginning to be understood at the molecular level [26][27][28][29][30][31][32][33]. Initially, B. bacteriovorus recognizes, attaches to [34] and enters the prey cell, reinforcing, traversing and re-sealing its entry port [35].…”

The unusual cell wall of the Lyme disease spirochaete Borrelia burgdorferi is shaped by a tick sugar

“…5a). Morphometric, single-cell analysis between each population was determined by measuring the Roundness 27 or the collective area required to enclose an object in an ellipse, corrected by aspect ratio 28,29 . Roundness provides a normalized assessment of deviations from the typical flat-wave morphology by estimating collective differences in helical trough depth.…”