Part:BBa_K2387068
T4 Holin lytic mechanism controlled by inducible araC/pBAD promoter
Host cell lysis is strictly regulated and controlled by the help and action of T4 Holin (BBa_K112000). T4 Holin constitutes a second component of a lysis cassette of phages together with T4 Endolysin. Holins oligomerize and create holes in the cytoplasmic membrane allowing the cytoplasm accumulated endolysins to degrade PG substrate [1].
Four different lytic mechanisms (Colicin E7 system, T4 Endolysin, T4 Holin and T4 Endolysin + T4 Holin cassette) were assessed in two backbones (pSB1C3 and pSB4K5). All the mechanisms are expressed under the pBAD promoter (Figure 2) and therefore all the mechanisms were induced at different arabinose concentrations. The figure (Figure 1) depicts the OD after 20 hours of arabinose induction. Based on the results, it was concluded that already low inductions of L-arabinose are able to induce a complete lysis of the bacterial cells (Figure 1).
From the assessment it was concluded that T4 Holin and T4 Endolysin + T4 Holin were successfully achieving bacterial cell lysis.T4 Endolysin alone was not able to trigger the lysis of bacterial cells. However, when combined with T4 Holin, the lytic effect achieved was even higher than the one achieved with T4 Holin alone (Figure 2). The observed lytic function of T4 Endolysin when acting together with T4 Holin in the double lysis gene cassette is understandable as it requires the action of T4 Holin to make the initial holes in the membrane [7]. T4 Holin starts the membrane degradation process and after holes are made in the membrane, T4 Endolysin is able to further increase bacterial membrane lysis (Figure 2).
References
[1] L. H. Burch, L. Zhang, F. G. Chao, H. Xu, and J. W. Drake, “The bacteriophage T4 rapid-lysis genes and their mutational proclivities.,” J. Bacteriol., vol. 193, no. 14, pp. 3537–45, Jul. 2011.
Sequence and Features| None |