RESUMO
AIMS: Sequences related to Lactobacillus delbrueckii phage JCL1032 genome integration, the maintenance of lysogeny and putative immunity genes were characterized. Phenotypic changes of the JCL1032 lysogens were investigated. METHODS AND RESULTS: Integration of JCL1032 DNA into the host genome and the location of phage and bacterial attachment sites were studied by standard molecular methods. The frequency of lysogenization was 10(-7), and stable lysogeny was an even rarer phenomenon. JCL1032 integrates its genome into two distinct host genes of unknown functions. According to EOP (efficiency of plating) and adsorption tests JCL1032 lysogens showed resistance against several virulent and temperate Lactobacillus phages at different steps of phage infection. CONCLUSIONS: Temperate JCL1032 integrates its genome into bacterial DNA with exceptionally low frequency. JCL1032 lysogens express a complex phage resistance against several Lact. delbrueckii phages. An antagonistic arms race between the temperate phage and its host is proposed. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that the genome integration of a group c Lact. delbrueckii phage has been described. The characterized lysogens could facilitate studies on Lact. delbrueckii phage receptors and phage resistance mechanisms. The genetic information gained from this study benefits the development of integration vectors and phage resistant starters.
Assuntos
Queijo , Microbiologia de Alimentos , Microbiologia Industrial , Lactobacillus delbrueckii/imunologia , Lisogenia/genética , Prófagos/fisiologia , Sequência de Bases , Clonagem Molecular , DNA Bacteriano/análise , DNA Viral/análise , Lactobacillus delbrueckii/virologia , Dados de Sequência Molecular , Prófagos/genética , Prófagos/isolamento & purificação , Análise de Sequência de DNARESUMO
The complete 36,466-bp genome sequence of the virulent phage Lc-Nu of probiotic Lactobacillus rhamnosus was determined. The linear dsDNA with a GC-content of 44.2% contained 3' single-stranded cohesive ends of 12 nucleotides. A total of 51 putative open reading frames (orfs) were predicted. Lc-Nu showed to be evolutionary closely related to the temperate Lactobacillus casei phages phi AT3 and A2. High DNA homology with phi AT3 was shared over the late transcribed genes, and the highest homology with A2 was within the genetic switch region. The truncated cI-like repressor was the only lysogeny related gene left, which strongly suggested Lc-Nu to be recently evolved from a temperate origin. Three putative methylases and endonucleases were detected from the region of early-transcribed genes. The putative origin of replication within the putative gene orf34 homologous to replisome organizers resembled to that of lambdoid phages. The present study suggested Lc-Nu to be a new candidate for the proposed Sfi21-like species.
Assuntos
DNA Viral/genética , Genoma Viral , Lacticaseibacillus rhamnosus/virologia , Siphoviridae/genética , Composição de Bases , Sequência de Bases , DNA Viral/química , Endonucleases/genética , Evolução Molecular , Ordem dos Genes , Lacticaseibacillus casei/virologia , Metiltransferases/genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Origem de Replicação/genética , Proteínas Repressoras/genética , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , SinteniaRESUMO
Two group I introns were detected from the late gene region of the prolate-headed phage JCL1032 of Lactobacillus delbrueckii. Introns JCL-I1 and JCL-I2 interrupt orf602 and orf1868 encoding a phage terminase large subunit (TerL, 69.7 kDa) and a putative tape measure protein (TMP, 202 kDa), respectively. The introns JCL-I1 (226 bp) and JCL-I2 (322 bp) were efficiently self-spliced in vivo. Both introns were classified to the subgroup IA1 having all the conserved structures necessary for splicing, but lacking the ability to encode endonucleases or other gene products. The introns JCL-I1 and JCL-I2 shared restricted nucleotide sequence similarity with each other and with the group I terL intron of Lb. delbrueckii phage LL-H. No match was found for JCL-I1 in the homology searches. Instead, the primary sequence from the joining region of P8 and P7 to P9 of the intron JCL-I2 was homologous to the group I intron of Bacillus mojavensis; the orf142 introns I1, I2 and I3 of Staphylococcus aureus phage Twort; the group I intron of phage Bastille (Bacillus thuringiensis); and to the group IA3 intron of Monomastix species.
Assuntos
Bacteriófagos/genética , Genes Virais , Íntrons , Lactobacillus delbrueckii/virologia , Splicing de RNA , Sequência de Aminoácidos , Fagos Bacilares/genética , Sequência de Bases , DNA Viral/química , DNA Viral/isolamento & purificação , Endodesoxirribonucleases/genética , Modelos Moleculares , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Fases de Leitura Aberta , RNA Catalítico/genética , Análise de Sequência de DNA , Homologia de Sequência , Fagos de Staphylococcus/genética , Transcrição Gênica , Proteínas Virais/genéticaRESUMO
cagA, vacA s and m genotypes and iceA alleles were analyzed from Helicobacter pylori strains isolated from 17 Finnish children and 32 children of non-Finnish origin living in Finland. Twelve children in the latter group were eastern European and 15 were of African origin. Only three children of non-Finnish origin were born in Finland. The vacA sla subtype was more prevalent in the isolates from Finnish children than African children (76% vs. 7%, P<0.001); vacA s1b frequencies were 5% and 67%, respectively (P<0.001). The iceA1 allele was significantly more prevalent in African than Finnish isolates (93% vs. 35%, P< 0.01). Considerable variation was noted in the frequency of vacA s1 subtypes and iceA alleles in children originating from different geographic regions, but the geographic variation of s1 subtypes resembled that described in other reports.
