The smallest ssDNA phage infecting a marine bacterium

Area of Science:

• Marine microbiology
• Virology
• Genomics

Background:

• Limited isolation and characterization of lytic single-stranded DNA (ssDNA) phages in marine environments.
• Metagenomic studies reveal diverse ssDNA bacteriophages, contrasting with limited isolates.

Purpose of the Study:

• Isolate and characterize a novel ssDNA phage from a marine bacterium.
• Determine the genomic features and phylogenetic placement of the new phage.
• Assess the diversity and distribution of related phages in the environment.

Main Methods:

• Isolation and characterization of ssDNA phage vB_RpoMi-Mini from Ruegeria pomeroyi DSS-3.
• Genome sequencing and analysis, including open reading frame (ORF) identification.
• Phylogenetic analysis and comparison with known ssDNA phages.
• Metagenomic analysis to assess environmental distribution.

Main Results:

• Isolation of vB_RpoMi-Mini, an ssDNA phage with a 4248 bp genome and only four ORFs, making it the smallest known isolate.
• Phylogenetic analysis places bacteriophage Mini as distantly related to known ssDNA phages, within an unclassified group of the Microviridae family.
• Identification of a peptidase gene, suggesting horizontal gene transfer in ssDNA phage evolution.
• Absence of a spike protein, indicating greater ssDNA phage diversity than previously recognized.
• Metagenomic data reveal widespread distribution of Mini-like phages globally.

Conclusions:

• The discovery of vB_RpoMi-Mini expands the known diversity of marine ssDNA phages.
• The phage's unique genomic features challenge existing classifications and highlight evolutionary mechanisms like horizontal gene transfer.
• The widespread presence of Mini-like phages underscores the need for further research into marine ssDNA phage ecology and evolution.