Observation of polyphosphate bodies and DNA during the cell division cycle of Synechococcus elongatus PCC 7942

Abstract

Although most cyanobacterial cells contain prominent polyphosphate bodies in the central cytoplasmic area enclosed by the peripheral thylakoid membranes, their roles are not fully understood. Storing phosphate for nucleotide production might be one of their important roles in survival of the cells. As a step towards identifying a possible contribution of the polyphosphate bodies to DNA synthesis, the relationship between polyphosphate bodies and DNA throughout cell division cycle of Synechococcus elongatus PCC 7942 cells cultured under light/dark cycles was investigated with light and electron microscopy. During the dark period, the average size of polyphosphate bodies increased gradually without significant change in their number and distribution. However, during the light period, the number of polyphosphate bodies increased, while the size of each polyphosphate body decreased and cells elongated until the end of the light period, when most cells divided. The ratio of the content of polyphosphate bodies to cell length increased gradually during the dark period and decreased during the light period. Hoechst 33342-stained DNA appeared diffuse during the dark period, but in the light period it became condensed and eventually formed a wavy, rope-like structure prior to cell division. Close association between fibres containing DNA and polyphosphate bodies was demonstrated by TEM using DNA-specific staining and BrdU labelling. These regular coordinated changes of polyphosphate bodies and DNA shape during the cell division cycle, together with their intimate interaction, imply a role of polyphosphate bodies in supplying material for DNA.

Dynamic polyphosphate metabolism in cyanobacteria responding to phosphorus availability

“…This can explain the dramatic decrease of polyP: cell, as cell growth entered exponential phase (Figs , after 7, 9 and 9 days respectively). Recurrent decrease in the polyP level immediately prior to and during nuclear division was commonly observed in other bacteria, suggesting that polyP may be utilized efficiently for nucleic synthesis (Rhee, ; Rao et al, ; Seki et al, ). The high rate of cell division in exponential growth, therefore, may have resulted in the decline of polyP: cell during the transition between the lag and exponential phases (Figs B, B and B), in contrast to polyP accumulation observed during the lag phase with the slow growth rate.…”

The stringent response regulates adaptation to darkness in the cyanobacterium Synechococcus elongatus

“…Increased concentrations of (p)ppGpp, the nucleotide second messengers of the stringent response, cause polyphosphate (polyP)-a linear polymer of orthophosphates-to accumulate in E. coli (12). We hypothesized that increased levels of (p)ppGpp might also be responsible for increased polyP levels recently observed in Synechococcus in the dark (13). Although previous work has shown that (p)ppGpp is synthesized by Synechococcus (8,14), mechanistic explanations for targets of the stringent response and its physiological effects are lacking, which led us to investigate the role of this pathway more broadly in Synechococcus.…”

The ploidy level of Synechocystis sp. PCC 6803 is highly variable and is influenced by growth phase and by chemical and physical external parameters

“…This phosphate storage polymer might well be inorganic polyphosphate, because Synechocystis sp. PCC 6803 has been shown to synthesize polyphosphate (Morohoshi et al, 2002), like many other cyanobacteria (Grillo & Gibson, 1979;Lawrence et al, 1998;Gomez-Garcia et al, 2013;Seki et al, 2014;Zhang et al, 2015). The polyphosphate content during growth in the absence of phosphate was not analysed, because this was beyond the scope of this study.…”