Two Distinct Modes of Lysis Regulation in Campylobacter Fletchervirus and Firehammervirus Phages

Abstract

Campylobacter phages are divided into two genera; Fletchervirus and Firehammervirus, showing only limited intergenus homology. Here, we aim to identify the lytic genes of both genera using two representative phages (F352 and F379) from our collection. We performed a detailed in silico analysis searching for conserved protein domains and found that the predicted lytic genes are not organized into lysis cassettes but are conserved within each genus. To verify the function of selected lytic genes, the proteins were expressed in E. coli, followed by lytic assays. Our results show that Fletchervirus phages encode a typical signal peptide (SP) endolysin dependent on the Sec-pathway for translocation and a holin for activation. In contrast, Firehammervirus phages encode a novel endolysin that does not belong to currently described endolysin groups. This endolysin also uses the Sec-pathway for translocation but induces lysis of E. coli after overexpression. Interestingly, co-expression of this endolysin with an overlapping gene delayed and limited cell lysis, suggesting that this gene functions as a lysis inhibitor. These results indicate that Firehammervirus phages regulate lysis timing by a yet undescribed mechanism. In conclusion, we found that the two Campylobacter phage genera control lysis by two distinct mechanisms.

Campylobacter phages use hypermutable polyG tracts to create phenotypic diversity and evade bacterial resistance

“…We looked specifically for regions with varying gene content or genes with different C-terminal regions because this is a common feature of many RBPs that recognize diverse hosts. Our analysis identified a region with varying gene content consisting of two to five conserved open reading frames (ORFs) of unknown function located between a putative antiholin (Zampara et al, 2020) and a putative recombination endonuclease (Figure 1A). Interestingly, two of these open reading frames (ORFs) contained polyG tracts in their N-terminal with lengths ranging from 6 to 42 polyGs in different phages.…”

Distribution of CRISPR Types in Fluoroquinolone-Resistant Campylobacter jejuni Isolates

“…Campylobacter phages are classified into three different groups (I, II, and III) based on the morphology and genome size [ 35 , 46 , 47 ]. In general, phages within a group share high genomic homology, but the overall homology among the different groups may be quite low [ 48 ]. Even though a few open reading frames (ORFs) of phage DA10 (a novel class of Campylobacter phage) have homologs in other Campylobacter phages, including CP39 (a class III Campylobacter phage) and the prophage CJIE4-5 [ 49 ], the likelihood of these shared ORFs in the induction of cross-immunity among different phage groups is expected to be minimal.…”

Functional Analysis of the Endopeptidase and Holin From Planktothrix agardhii Cyanophage PaV-LD

“…The functions of endopeptidases and holins derived from many phages have been extensively studied ( Bavda and Jain, 2020 ; Głowacka-Rutkowska et al, 2020 ; Zampara et al, 2020 ). However, few studies focused on their homologs in cyanophages.…”