Biomedical subjects

Carlos Canchaya

Publications and source records attributed to Carlos Canchaya.

27 records · Page 2Linked to original sources

PubMed2003

The prophage sequences of Lactobacillus plantarum strain WCFS1.

The Lactobacillus plantarum commensal WCFS1 contains four prophage elements in its genome. Lp1 and Lp2 are two about 40-kb-long uninducible prophages that share closely related DNA packaging, head and tail genes defining a second lineage of pac-site Siphoviridae in L. plantarum, distinct from L. plantarum phage phig1e, but related to Bacillus phage SPP1 and Lactococcus phage TP901-1. Northern analysis revealed transcribed prophage genes exclusively near both attachment sites. Comparative genomics identified candidate lysogenic conversion genes (LCG) downstream of the lysis cassette and within the lysogeny module. Notable are genes with sequence similarities to putative LCG from Streptococcus pyogenes prophages and to a Bacillus plasmid. Both prophages harbored tRNA genes. R-Lp3 and R-Lp4 represent short prophage remnants; R-Lp3 abuts Lp2 and displays sequence links to cos-site Siphoviridae.

Base Sequence↗

PubMed2003

Phage as agents of lateral gene transfer.

When establishing lysogeny, temperate phages integrate their genome as a prophage into the bacterial chromosome. Prophages thus constitute in many bacteria a substantial part of laterally acquired DNA. Some prophages contribute lysogenic conversion genes that are of selective advantage to the bacterial host. Occasionally, phages are also involved in the lateral transfer of other mobile DNA elements or bacterial DNA. Recent advances in the field of genomics have revealed a major impact by phages on bacterial chromosome evolution.

Bacteria↗

PubMed2003

Analysis, characterization, and loci of the tuf genes in lactobacillus and bifidobacterium species and their direct application for species identification.

We analyzed the tuf gene, encoding elongation factor Tu, from 33 strains representing 17 Lactobacillus species and 8 Bifidobacterium species. The tuf sequences were aligned and used to infer phylogenesis among species of lactobacilli and bifidobacteria. We demonstrated that the synonymous substitution affecting this gene renders elongation factor Tu a reliable molecular clock for investigating evolutionary distances of lactobacilli and bifidobacteria. In fact, the phylogeny generated by these tuf sequences is consistent with that derived from 16S rRNA analysis. The investigation of a multiple alignment of tuf sequences revealed regions conserved among strains belonging to the same species but distinct from those of other species. PCR primers complementary to these regions allowed species-specific identification of closely related species, such as Lactobacillus casei group members. These tuf gene-based assays developed in this study provide an alternative to present methods for the identification for lactic acid bacterial species. Since a variable number of tuf genes have been described for bacteria, the presence of multiple genes was examined. Southern analysis revealed one tuf gene in the genomes of lactobacilli and bifidobacteria, but the tuf gene was arranged differently in the genomes of these two taxa. Our results revealed that the tuf gene in bifidobacteria is flanked by the same gene constellation as the str operon, as originally reported for Escherichia coli. In contrast, bioinformatic and transcriptional analyses of the DNA region flanking the tuf gene in four Lactobacillus species indicated the same four-gene unit and suggested a novel tuf operon specific for the genus Lactobacillus.

Adult↗

PubMed2003

Integration and distribution of Lactobacillus johnsonii prophages.

In Lactobacillus johnsonii strain NCC533, two prophages were integrated into tRNA genes and one was disrupted by integration. In a survey, the prophages were restricted to strains sharing an essentially identical restriction pattern. Microarray analysis showed that the prophage DNA represents about 50% of the NCC533 strain-specific DNA.

Animals↗

PubMed2003

Prophage genomics.

The majority of the bacterial genome sequences deposited in the National Center for Biotechnology Information database contain prophage sequences. Analysis of the prophages suggested that after being integrated into bacterial genomes, they undergo a complex decay process consisting of inactivating point mutations, genome rearrangements, modular exchanges, invasion by further mobile DNA elements, and massive DNA deletion. We review the technical difficulties in defining such altered prophage sequences in bacterial genomes and discuss theoretical frameworks for the phage-bacterium interaction at the genomic level. The published genome sequences from three groups of eubacteria (low- and high-G+C gram-positive bacteria and gamma-proteobacteria) were screened for prophage sequences. The prophages from Streptococcus pyogenes served as test case for theoretical predictions of the role of prophages in the evolution of pathogenic bacteria. The genomes from further human, animal, and plant pathogens, as well as commensal and free-living bacteria, were included in the analysis to see whether the same principles of prophage genomics apply for bacteria living in different ecological niches and coming from distinct phylogenetical affinities. The effect of selection pressure on the host bacterium is apparently an important force shaping the prophage genomes in low-G+C gram-positive bacteria and gamma-proteobacteria.

Actinobacteria↗

PubMed2002

Genome analysis of an inducible prophage and prophage remnants integrated in the Streptococcus pyogenes strain SF370.

The mitomycin C inducible prophage SF370.1 from the highly pathogenic M1 serotype Streptococcus pyogenes isolate SF370 showed a 41-kb-long genome whose genetic organization resembled that of SF11-like pac-site Siphoviridae. Its closest relative was prophage NIH1.1 from an M3 serotype S. pyogenes strain, followed by S. pneumoniae phage MM1 and Lactobacillus phage phig1e, Listeria phage A118, and Bacillus phage SPP1 in a gradient of relatedness. Sequence similarity with the previously described prophages SF370.2 and SF370.3 from the same polylysogenic SF370 strain were mainly limited to the tail fiber genes. As in these two other prophages, SF370.1 encoded likely lysogenic conversion genes between the phage lysin and the right attachment site. The genes encoded the pyrogenic exotoxin C of S. pyogenes and a protein sharing sequence similarity with both DNases and mitogenic factors. The screening of the SF370 genome revealed further prophage-like elements. A 13-kb-long phage remnant SF370.4 encoded lysogeny and DNA replication genes. A closely related prophage remnant was identified in S. pyogenes strain Manfredo at a corresponding genome position. The two prophages differed by internal indels and gene replacements. Four phage-like integrases were detected; three were still accompanied by likely repressor genes. All prophage elements were integrated into coding sequences. The phage sequences complemented the coding sequences in all cases. The DNA repair genes mutL and mutS were separated by the prophage remnant SF370.4; prophage SF370.1 and S. pneumoniae phage MM1 integrated into homologous chromosomal locations. The prophage sequences were interpreted with a hypothesis that predicts elements of cooperation and an arms race between phage and host genomes.

Attachment Sites, Microbiological↗

PubMed2002

Transcription analysis of Streptococcus thermophilus phages in the lysogenic state.

The transcription of prophage genes was studied in two lysogenic Streptococcus thermophilus cells by Northern blot and primer-extension experiments. In the lysogen containing the cos-site phage Sfi21 only two gene regions of the prophage were transcribed. Within the lysogeny module an 1.6-kb-long mRNA started at the promoter of the phage repressor gene and covered also the next two genes, including a superinfection exclusion (sie) gene. A second, quantitatively more prominent 1-kb-long transcript was initiated at the promoter of the sie gene. Another prophage transcript of 1.6-kb length covered a group of genes without database matches that were located between the lysin gene and the right attachment site. The rest of the prophage genome was transcriptionally silent. A very similar transcription pattern was observed for a S. thermophilus lysogen containing the pac-site phage O1205 as a prophage. Prophages from pathogenic streptococci encode virulence genes downstream of the lysin gene. We speculate that temperate phages from lactic streptococci also encode nonessential phage genes ("lysogenic conversion genes") in this region that increase the ecological fitness of the lysogen to further their own evolutionary success. A comparative genome analysis revealed that many temperate phages from low GC content Gram-positive bacteria encode a variable number of genes in that region and none was linked to known phage-related function. Prophages from pathogenic streptococci encode toxin genes in this region. In accordance with theoretical predictions on prophage-host genome interactions a prophage remnant was detected in S. thermophilus that had lost most of the prophage DNA while transcribed prophage genes were spared from the deletion process.

Base Sequence↗

PubMed2002

Transcription mapping as a tool in phage genomics: the case of the temperate Streptococcus thermophilus phage Sfi21.

For the lytic growth cycle of the temperate cos-site Streptococcus thermophilus phage Sfi21 a transcription map was developed on the basis of systematic Northern blot hybridizations. All deduced 5' ends were confirmed by primer extension analysis. Three time classes of transcripts were observed. Early transcripts were identified in four different genome regions. One prominent early mRNA of 4.8 kb length covered a group of 12 genes located between the origin of replication and the cos-site. Two short early mRNAs represented a single gene from the direct vicinity of the cos-site and the superinfection immunity gene from the lysogeny module, respectively. A fourth early transcript covered a group of four genes located between the lysin and the integrase gene. Middle transcripts of 2.1 and 5.8 kb length covered cro-like and ant-like repressor genes and the DNA replication module, respectively. Four types of late transcripts were identified. The transcripts covered the likely DNA packaging genes, the head morphogenesis module plus the major tail gene, the remainder of the tail genes, and the putative tail fiber plus lysis genes, respectively. Only the transcript from the head morphogenesis genes yielded defined late mRNA species. The transcription map concurred with most of the in silico predictions for the genome organization of phage Sfi21 except for the separation of the DNA replication module from a possible transcription regulation module. Most 5' ends of the transcripts determined in primer-extension experiments were not preceded by a consensus promoter sequence. The involvement of phage-encoded regulators for middle and late transcription was suggested by chloramphenicol-inhibition experiments.

5' Untranslated Regions↗

PubMed2002

Comparative genomics of phages and prophages in lactic acid bacteria.

Comparative phage genomics has become possible due to the availability of more than 100 complete phage genome sequences and the development of powerful bioinformatics tools. This technology, profiting from classical molecular-biology knowledge, has opened avenues of research for topics, which were difficult to address in the past. Now, it is possible to retrace part of the evolutionary history of phage modules by comparative genomics. The diagnosis of relatedness is hereby not uniquely based on sequence similarity alone, but includes topological considerations of genome organization. Detailed transcription maps have allowed in silico predictions of genome organization to be verified and refined. This comparative knowledge is providing the basis for a new taxonomic classification concept for bacteriophages infecting low G + C-content Gram-positive bacteria based on the genetic organization of the structural gene module. An Sfi21-like and an Sfi11-like genus of Siphoviridae is proposed. The gene maps of many phages show remarkable synteny in their structural genes defining a lambda super-group within Siphoviridae. A hierarchy of relatedness within the lambda super-group suggests elements of vertical evolution in Siphoviridae. Tailed phages are the result of both vertical and horizontal evolution and are thus fascinating objects for the study of molecular evolution. Prophage sequences integrated into the genomes of their bacterial host present theoretical challenges for evolutionary biologists. Prophages represent up to 10% of the genome in some LAB. In pathogenic streptococci prophages confer genes of selective value for the lysogenic cell. The lysogenic conversion genes are located between the lysin gene and the right phage attachment site. Non-attributed genes were found at the same genome position of prophages from lactic streptococci. These genes belong to the few prophage genes transcribed in the lysogen. Prophages from dairy bacteria might therefore also contribute to the evolutionary fitness of non-pathogenic LAB.

Bacteriophages↗