RESUMO
The genomes of six Listeria bacteriophages were sequenced and analyzed. Phages A006, A500, B025, P35, and P40 are members of the Siphoviridae and contain double-stranded DNA genomes of between 35.6 kb and 42.7 kb. Phage B054 is a unique myovirus and features a 48.2-kb genome. Phage B025 features 3' overlapping single-stranded genome ends, whereas the other viruses contain collections of terminally redundant, circularly permuted DNA molecules. Phages P35 and P40 have a broad host range and lack lysogeny functions, correlating with their virulent lifestyle. Phages A500, A006, and B025 integrate into bacterial tRNA genes, whereas B054 targets the 3' end of translation elongation factor gene tsf. This is the first reported case of phage integration into such an evolutionarily conserved genetic element. Peptide fingerprinting of viral proteins revealed that both A118 and A500 utilize +1 and -1 programmed translational frameshifting for generating major capsid and tail shaft proteins with C termini of different lengths. In both cases, the unusual +1 frameshift at the 3' ends of the tsh coding sequences is induced by overlapping proline codons and cis-acting shifty stops. Although Listeria phage genomes feature a conserved organization, they also show extensive mosaicism within the genome building blocks. Of particular interest is B025, which harbors a collection of modules and sequences with relatedness not only to other Listeria phages but also to viruses infecting other members of the Firmicutes. In conclusion, our results yield insights into the composition and diversity of Listeria phages and provide new information on their function, genome adaptation, and evolution.
Assuntos
Bacteriófagos/genética , Bacteriófagos/ultraestrutura , Mudança da Fase de Leitura do Gene Ribossômico/genética , Genoma Viral/genética , Genômica , Listeria/virologia , Prófagos/genética , Sequência de Aminoácidos , Bacteriófagos/classificação , Bacteriófagos/metabolismo , Sequência de Bases , Microscopia Eletrônica , Modelos Genéticos , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Filogenia , Alinhamento de Sequência , Homologia de Sequência do Ácido Nucleico , Proteínas Virais/química , Proteínas Virais/genéticaRESUMO
Only little information on a particular class of myoviruses, the SPO1-like bacteriophages infecting low-G+C-content, gram-positive host bacteria (Firmicutes), is available. We present the genome analysis and molecular characterization of the large, virulent, broad-host-range Listeria phage A511. A511 contains a unit (informational) genome of 134,494 bp, encompassing 190 putative open reading frames (ORFs) and 16 tRNA genes, organized in a modular fashion common among the Caudovirales. Electron microscopy, enzymatic fragmentation analyses, and sequencing revealed that the A511 DNA molecule contains linear terminal repeats of a total of 3,125 bp, encompassing nine small putative ORFs. This particular genome structure explains why A511 is unable to perform general transduction. A511 features significant sequence homologies to Listeria phage P100 and other morphologically related phages infecting Firmicutes such as Staphylococcus phage K and Lactobacillus phage LP65. Equivalent but more-extensive terminal repeats also exist in phages P100 (approximately 6 kb) and K (approximately 20 kb). High-resolution electron microscopy revealed, for the first time, the presence of long tail fibers organized in a sixfold symmetry in these viruses. Mass spectrometry-based peptide fingerprinting permitted assignment of individual proteins to A511 structural components. On the basis of the data available for A511 and relatives, we propose that SPO1-like myoviruses are characterized by (i) their infection of gram-positive, low-G+C-content bacteria; (ii) a wide host range within the host bacterial genus and a strictly virulent lifestyle; (iii) similar morphology, sequence relatedness, and collinearity of the phage genome organization; and (iv) large double-stranded DNA genomes featuring nonpermuted terminal repeats of various sizes.
Assuntos
Genoma Viral , Bactérias Gram-Positivas/virologia , Myoviridae/genética , DNA Viral/química , DNA Viral/genética , Eletroforese em Gel de Poliacrilamida , Espectrometria de Massas , Microscopia Eletrônica , Modelos Genéticos , Dados de Sequência Molecular , Myoviridae/ultraestrutura , Fases de Leitura Aberta/genética , Análise de Sequência de DNARESUMO
This review provides an overview of recent progress in the exploration of genomic, transcriptomic, and proteomic data in Listeria spp. to understand genome evolution and diversity, as well as physiological aspects of metabolism utilized by the bacteria when growing in diverse and varied environments.
