Identifying the components of the Shewanella phage LambdaSo lysis system

Double-strand DNA bacteriophages usually disrupt their hosts" envelope with a set of lysis proteins characterized by a holin, an endopeptidase and a spanin system. By a combination of mutant screening, protein structure predictions and microscopy, we found that Shewanella oneidensis prophage LambdaSo uses a pinholin/signal-anchor-release (SAR) endolysin system to induce proton-leakage and degradation of the cell wall. Further insight into the lysis cassette of LambdaSo lead to the identification of a two-component spanin modul encoded by two extensively nested open reading frames. In addition, we discovered another small transmembrane protein strictly required for LambdaSo-induced cell lysis, potentially acting at the level of the pinholin. Thus, LambdaSo-mediated cell lysis requires at least four protein factors (pinholin, SAR-endolysin, spanin, Lcc6).