A genomic approach to understand interactions between Streptococcus pneumoniae and its bacteriophages

Background: Bacteriophage replication depends on bacterial proteins and inactivation of genes coding for such host factors should interfere with phage infection. To gain further insights into the interactions between S. pneumoniae and its pneumophages, we characterized S. pneumoniae mutants selected for resistance to the virulent phages SOCP or Dp-1. Results: S. pneumoniae R6-SOCPR and R6-DP1R were highly resistant to the phage used for their selection and no cross-resistance between the two phages was detected. Adsorption of SOCP to R6-SOCPR was partly reduced whereas no difference in Dp-1 adsorption was noted on R6-DP1R . The replication of SOCP was completely inhibited in R6-SOCPR while Dp-1 was severely impaired in R6-DP1R . Genome sequencing identified 8 and 2 genes mutated in R6-SOCPR and R6-DP1R , respectively. Resistance reconstruction in phage-sensitive S. pneumoniae confirmed that mutations in a GntR-type regulator, in a glycerophosphoryl phosphodiesterase and in a Mur ligase were responsible for resistance to SOCP. The three mutations were additive to increase resistance to SOCP. In contrast, resistance to Dp-1 in R6-DP1R resulted from mutations in a unique gene coding for a type IV restriction endonuclease. Conclusion: The characterization of mutations conferring resistance to pneumophages highlighted that diverse host genes are involved in the replication of phages from different families

CRISPR provides acquired resistance against viruses in prokaryotes

Clustered regularly interspaced short palindromic repeats (CRISPR) are a distinctive feature of the genomes of most Bacteria and Archaea and are thought to be involved in resistance to bacteriophage. We found that following viral challenge, bacteria integrated new spacers derived from phage genomic sequences. Removal or addition of particular spacers modified the phage-resistance phenotype of the cell. Thus, CRISPR, together with associated cas genes, provided resistance against phages, whereby specificity is determined by spacer/phage sequence similarity

Widespread anti-CRISPR proteins in virulent bacteriophages inhibit a range of Cas9 proteins

International audienceCRISPR-Cas systems are bacterial anti-viral systems, and bacterial viruses (bacteriophages, phages) can carry anti-CRISPR (Acr) proteins to evade that immunity. Acrs can also fine-tune the activity of CRISPR-based genome-editing tools. While Acrs are prevalent in phages capable of lying dormant in a CRISPR-carrying host, their orthologs have been observed only infrequently in virulent phages. Here we identify AcrIIA6, an Acr encoded in 33% of virulent Streptococcus thermophilus phage genomes. The X-ray structure of AcrIIA6 displays some features unique to this Acr family. We compare the activity of AcrIIA6 to those of other Acrs, including AcrIIA5 (also from S. thermophilus phages), and characterize their effectiveness against a range of CRISPR-Cas systems. Finally, we demonstrate that both Acr families from S. thermophilus phages inhibit Cas9-mediated genome editing of human cells

Complete genome sequence of Ebrios, a novel T7virus isolated from the Ebrie Lagoon in Abidjan, Côte d’Ivoire

The lytic Escherichia coli phage Ebrios was isolated from a water sample collected in Ebrie Lagoon on the Adiopodoumé River in Abidjan (Republic of Côte d’Ivoire, West Africa). The linear genome of this Podoviridae family member contains 39,752 bp, has a G+C content of 52.9%, is composed of 53 open reading frames, and is related to the Stenotrophomonas maltophilia phage IME15

Functional carbohydrate binding modules identified in evolved Dits from siphophages infecting various Gram-positive bacteria

With increasing numbers of 3D structures of bacteriophage components, combined with powerful in silico predictive tools, it has become possible to decipher the structural assembly and associated functionality of phage adhesion devices. Recently, decorations have been reported in the tail and neck passage structures of members of the so‐called 936 group of lactococcal siphophages. In the current report, using bioinformatic analysis we identified a conserved carbohydrate binding module (CBM) among many of the virion baseplate Dit components, in addition to the CBM present in the ‘classical’ receptor binding proteins (RBPs). We observed that, within these so‐called ‘evolved’ Dit proteins, the identified CBMs have structurally conserved folds, yet can be grouped into four distinct classes. We expressed such modules in fusion with GFP, and demonstrated their binding capability to their specific host using fluorescent binding assays with confocal microscopy. We detected evolved Dits in several phages infecting various Gram‐positive bacterial species, including mycobacteria. The omnipresence of CBM domains in Siphophages indicates their auxiliary role in infection, as they can assist in the specific recognition of and attachment to their host, thus ensuring a highly efficient and specific phage‐host adhesion process as a prelude to DNA injection