Replications of Two Closely Related Groups of Jumbo Phages Show Different Level of Dependence on Host-encoded RNA Polymerase.

Takeru Matsui,Hiroyuki Ogata,Takeru Kawasaki,Genki Yoshikawa,Makoto Fujie,Tomoko Mihara,Takashi Yamada,Orawan Chatchawankanphanich,Miyako Nakano

doi:10.3389/fmicb.2017.01010

Abstract

Ralstonia solanacearum phages ΦRP12 and ΦRP31 are jumbo phages isolated in Thailand. Here we show that they exhibit similar virion morphology, genome organization and host range. Genome comparisons as well as phylogenetic and proteomic tree analyses support that they belong to the group of ΦKZ-related phages, with their closest relatives being R. solanacearum phages ΦRSL2 and ΦRSF1. Compared with ΦRSL2 and ΦRSF1, ΦRP12 and ΦRP31 possess larger genomes (ca. 280 kbp, 25% larger). The replication of ΦRP12 and ΦRP31 was not affected by rifampicin treatment (20 μg/ml), suggesting that phage-encoded RNAPs function to start and complete the infection cycle of these phages without the need of host-encoded RNAPs. In contrast, ΦRSL2 and ΦRSF1, encoding the same set of RNAPs, did not produce progeny phages in the presence of rifampicin (5 μg/ml). This observation opens the possibility that some ΦRP12/ΦRP31 factors that are absent in ΦRSL2 and ΦRSF1 are involved in their host-independent transcription.

Highlights

SMA5 (250 kbp, Chang et al, 2005), Vibrio parahaemolyticus phage KVP40 (386 kbp, Miller et al, 2003), Yersinia enterocolitica phage R1-37 (270 kbp, Kiljunen et al, 2005), Klebsiella phage vB_KleM-RaK2 (346 kbp, Simoliunas et al, 2013), and Bacillus phage AR9 (251 kbp, Lavysh et al, 2016)
We show that two newly isolated jumbo phages infecting R. solanacearum are closely related to RSL2/ RSF1 but their infection is resistant to rifampicin treatment
The jumbo phage nature of RP12 and RP31 was recognized by their large genome size and morphology

Summary

Introduction

SMA5 (250 kbp, Chang et al, 2005), Vibrio parahaemolyticus phage KVP40 (386 kbp, Miller et al, 2003), Yersinia enterocolitica phage R1-37 (270 kbp, Kiljunen et al, 2005), Klebsiella phage vB_KleM-RaK2 (346 kbp, Simoliunas et al, 2013), and Bacillus phage AR9 (251 kbp, Lavysh et al, 2016). One of the notable features of KZrelated phages is the independence of their replication from the host transcriptional machinery This property is attributed to two sets of phage-encoded multisubunit RNA polymerase (RNAP) subunits (β- and β′- subunits) (Ceyssens et al, 2014; Yukunina et al, 2015; Lavysh et al, 2016). In contrast to KZ and AR9, the replication of both RSL2 and RSF1 were inhibited by rifampicin (Bhunchoth et al, 2016) These results suggest functional variations of the phage-encoded multisubunit RNAPs among different KZ-related phages. We show that two newly isolated jumbo phages infecting R. solanacearum are closely related to RSL2/ RSF1 but their infection is resistant to rifampicin treatment

Methods

Results

Conclusion