The growth strategy of the Gram-positive rod

Abstract

Bacteria grow by enlarging their envelope in such a way that osmotic pressure does not normally cause physical rupture. The strategy of Bacillus subtilis for both cylindrical elongation and pole formation is now substantially defined. Side-wall growth takes place by laying down new peptidoglycan, which is then displaced outwards, stretched and discarded; cross walls are laid down in the absence of stress, and then stretched and bulged outward as the septum is split and the pole is formed.

Mechanical Consequences of Cell-Wall Turnover in the Elongation of a Gram-Positive Bacterium

“…To determine whether our model permits a steady-state wall thickness, we performed simulations of the elongation dynamics of a multilayered cell wall for the experimentally motivated synthesis rate k s ¼ 1:2 min À1 , and a hydrolysis rate k h ¼ 0:06 min À1 selected to produce a doubling time of~20 min. To challenge the system to achieve a steady state, we initialized the network with two layers and allowed the network to relax under the applied extensional load of a turgor pressure P ¼ 15 atm (7). The thickness stabilized at a steady-state value of 20 layers on the timescale of doubling, as expected since the spring constant of each layer decreases to zero with a regular time constant proportional to 1=k h .…”

“…The high solute and nutrient concentrations in the cytoplasm of Gram-positive bacteria lead to a relatively high internal osmotic pressure, which can be up to 30 atm (1,7). How bacteria grow and divide in the presence of a high turgor pressure has motivated theoretical (8)(9)(10)(11)(12)(13) and experimental studies (14)(15)(16)(17)(18) of the structure and mechanical properties of the cell envelope.…”

The wall of bacteria serves the roles that mechano-proteins do in eukaryotes

“…Since the seminal work of Jacob, Brenner, and Cuzin [48] the causal dependence of nuclear segregation and cell wall growth and division has been accepted. We have found it necessary to modify their model based on new facts [31,34,49,50]. It is now known that peptidoglycan is added over the cylindrical region and not uniquely in the central region between nucleoids as required by the origined model.…”