Lysis cassette-mediated exoprotein release inYersinia entomophagais controlled by a PhoB- like regulator

Abstract

Secretion of exoproteins is a key component of bacterial virulence and is tightly regulated in response to environmental stimuli and host-dependent signals. The entomopathogenic bacterium Yersinia entomophaga MH96 produces a wide range of exoproteins including its main virulence factor, the 2.46 MDa insecticidal Yen-Tc toxin complex. Previously, a high-throughput transposon-based screening assay identified the region of exoprotein release (YeRER) as essential to exoprotein release in MH96. The current study defines the role of the YeRER-associated ambiguous holin/endolysin-based lysis cluster (ALC) and the novel RoeA regulator in the regulation and release of exoproteins in MH96. A mutation in the ALC region abolished exoprotein release and caused cell elongation, a phenotype able to be restored through trans-complementation with an intact ALC region. Endogenous ALC did not impact cell growth of the wild type, while artificial expression of an optimised ALC caused cell lysis. Using HolA-sfGFP and Rz1-sfGFP reporter, Rz1 expression was observed in all cells while HolA expression was limited to a small proportion of cells, which increased over time. Transcriptomic assessments found expression of the genes encoding the prominent exoproteins, including the Yen-Tc, was reduced in the roeA mutant and identified a 220 ncRNA of the YeRER intergenic that, when trans complemented in the wildtype, abolished exoprotein release. A model for Y. entomophaga mediated exoprotein regulation and release is proposed.

Serratia‐based toxin cluster elements are associated with a type I fimbria

“…The leading hypothesis was that Sef somehow proliferates the plasmid through aiding conjugation, allowing more cells to produce Tcs; however, conjugation rate experiments have shown no such effect. Recent data have found that Yersinia Holin (lysis cassette), which is associated with secreting Tcs, is only expressed in a subset of the population (<10%) (Schoof et al, 2023). Through TEM, it was established that only ~10% of WT S. entomophila A1MO2 cells were observed to be fimbriated.…”