AUTHOR=Huang Lixin , Han Guangjie , Crickmore Neil , Li Chuanming , Xia Yang , Song Fuping , Xu Jian 

TITLE=Characterization of a novel cell wall hydrolase CwlE involved in Bacillus thuringiensis subsp. israelensis mother cell lysis

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1250542

DOI=10.3389/fmicb.2023.1250542

ISSN=1664-302X

ABSTRACT=<p>Cell wall hydrolases are ubiquitous among spore-form bacteria and essential for mother cell lysis. In this study, a novel cell wall hydrolase gene <italic>cwlE</italic> involved in mother cell lysis was characterized from <italic>Bacillus thuringiensis</italic> subsp<italic>. israelensis</italic> (Bti) strain Bt-59. <italic>cwlE</italic> was specifically expressed in Bti and located in the large plasmid carrying the insecticidal genes. The encoded CwlE protein consists of a Mur<italic>N</italic>Ac-LAA domain and two highly conserved catalytic residues (E26 and E151). The recombinant CwlE-His protein was able to digest the cell wall of Bti, indicating that CwlE is an <italic>N</italic>-acetylmuramoyl-<sub>L</sub>-alanine amidase. Transcriptional analysis indicated that <italic>cwlE</italic> began to express at the early stage of stationary phase and was controlled by SigE. Single mutation of <italic>cwlE</italic> gene delayed Bti mother cell lysis, while double mutation of <italic>cwlE</italic> and <italic>sigK</italic> completely blocked Bti mother cell lysis. After exposure to UV light to deactivate the crystal proteins, the level of decrease of insecticidal activity against mosquito larvae of Bt-59 (Δ<italic>cwlE-sigK</italic>) was less than that observed for Bt-59. This study elucidates the mechanism of Bti mother cell lysis and provides an effective strategy for mosquito control using Bt products with increased persistence.</p>