Migration of Polyphosphate Granules in <b><i>Agrobacterium tumefaciens</i></b>

Abstract

&lt;i&gt;Agrobacterium tumefaciens&lt;/i&gt; has two polyphosphate (polyP) kinases, one of which (PPK1&lt;sub&gt;AT&lt;/sub&gt;) is responsible for the formation of polyP granules, while the other (PPK2&lt;sub&gt;AT&lt;/sub&gt;) is used for replenishing the NTP pools by using polyP as a phosphate donor to phosphorylate nucleoside diphosphates. Fusions of eYFP with PPK2&lt;sub&gt;AT&lt;/sub&gt; or of the polyP granule-associated phosin PptA from &lt;i&gt;Ralstonia eutropha&lt;/i&gt; always co-localized with polyP granules in &lt;i&gt;A. tumefaciens&lt;/i&gt; and allowed the tracking of polyP granules in time-lapse microscopy experiments without the necessity to label the cells with the toxic dye DAPI. Fusions of PPK1&lt;sub&gt;AT&lt;/sub&gt; with mCherry formed fluorescent signals often attached to, but not completely co-localizing with, polyP granules in wild-type cells. Time-lapse microscopy revealed that polyP granules in about one-third of a cell population migrated from the old pole to the new cell pole shortly before or during cell division. Many cells de novo formed a second (nonmigrating) polyP granule at the opposite cell pole before cell division was completed, resulting in two daughter cells each having a polyP granule at the old pole after septum formation. Migration of polyP granules was disordered in mitomycin C-treated or in PopZ-depleted cells, suggesting that polyP granules can associate with DNA or with other molecules that are segregated during the cell cycle.

Reentrant DNA shells tune polyphosphate condensate size

“…A major challenge to determining its molecular function has long been identifying and validating molecular interaction partners. While lacking known specificity epitopes at the primary level of organization, the polymer forms membraneless condensates in many bacteria that are spatially and temporally organized [7][8][9][10][11] .…”