Genomic Characterization of a Novel Freshwater Cyanophage Reveals a New Lineage of Cyanopodovirus

A GH19 lysozyme and peptidase from Myoviridae cyanophages lacking the typical holin-endolysin system exhibit lytic activity

Most of the dsDNA cyanophages employ holin-endolysin lysis systems to damage the host cells. This study aimed to elucidate the lytic activity of ORF91 and ORF117 in the cyanophage MaMV-DH01, which lacked a conventional cholinesterase system. These two proteins contained Lyz-like superfamily domains and were annotated as a member of GH family 19 (named DHGH19) and peptidase (named DHpeptidase), respectively. Overexpression of DHGH19 in E. coli over a 5 h course demonstrated potent bactericidal activity, evident from significant growth inhibition, membrane damage, and leakage of intracellular enzymes of E. coli cells. However, the lytic activity of DHpeptidase was relatively weaker, exhibiting a bacteriostatic effect. It was important to highlight that the specific mutation of enzyme-catalyzed residues in DHGH19 (E122 and E131) showed that these were the essential amino acids for DHGH19 to exert its bactericidal activity. Furthermore, the lytic function of DHGH19 and DHpeptidase on cyanobacteria cells was confirmed by their overexpression in the cyanobacterium Synechocystis sp. PCC6803. Overall, this study provides novel insights into the lytic mechanism of Myoviridae cyanophage, offering potential alternatives for the development of GH19 and peptidase as new antibacterial agents in the future.

The Impact of Viral Infection on the Chemistries of the Earth's Most Abundant Photosynthesizes: Metabolically Talented Aquatic Cyanobacteria

Cyanobacteria are the most abundant photosynthesizers on earth, and as such, they play a central role in marine metabolite generation, ocean nutrient cycling, and the control of planetary oxygen generation. Cyanobacteriophage infection exerts control on all of these critical processes of the planet, with the phage-ported homologs of genes linked to photosynthesis, catabolism, and secondary metabolism (marine metabolite generation). Here, we analyze the 153 fully sequenced cyanophages from the National Center for Biotechnology Information (NCBI) database and the 45 auxiliary metabolic genes (AMGs) that they deliver into their hosts. Most of these AMGs are homologs of those found within cyanobacteria and play a key role in cyanobacterial metabolism-encoding proteins involved in photosynthesis, central carbon metabolism, phosphate metabolism, methylation, and cellular regulation. A greater understanding of cyanobacteriophage infection will pave the way to a better understanding of carbon fixation and nutrient cycling, as well as provide new tools for synthetic biology and alternative approaches for the use of cyanobacteria in biotechnology and sustainable manufacturing.

Sequencing the genomes of LPP-1, the first isolated cyanophage, and its relative LPP-2 reveal different integration mechanisms in closely related phages

In the early 1960s, the first cyanophage was isolated. The description of this phage, named LPP-1, led to the extensive investigation of various cyanophages and to the study of their interactions with their cyanobacterial hosts towards controlling blooms. Here, the genomes of LPP-1 and its putative relative, LPP-2 were sequenced. Sequencing these genomes revealed that LPP-1 and LPP-2 are members of a group of short-tailed cyanophages, which are distantly related to the T7-like cyanophages. Most of the phages in this group have the ability to lysogenize their hosts. Their ability to switch between lytic and lysogenic infection may explain the formation of cyanobacterial blooms despite the persistence of their phages. This lysogenic capacity of the LPP-1-like phages occurs despite the lack of an obvious integrase gene within their genomes. Interestingly, we show that LPP-2 integrates into the host genome through an integration site in high proximity to a recombination endonuclease that may have integrase activity. Further understanding of cyanobacterial-phage relationships may provide insight into their population dynamics and suggest novel approaches for control of destructive cyanobacterial blooms.

Biological and Genomic Characteristics of MaMV-DH01, a Novel Freshwater Myoviridae Cyanophage Strain

The genomic traits of cyanophages and their potential for metabolic reprogramming of the host cell remain unknown due to the limited number of studies on cyanophage isolates. In the present study, a lytic Microcystis cyanophage, MaMV-DH01, was isolated and identified. MaMV-DH01 has an icosahedral head approximately 100 nm in diameter and a tail 260 nm in length. Its burst size is large, with approximately 145 phage particles/infected cell; it has a latent period of 2 days, and it shows high stability under pH and temperature stresses. Multiple infection (multiplicity of infection [MOI] 0.0001 to 100) results showed that when the MOI was 0.0001, MaMV-DH01 needed a longer time to lyse host cells. Cyanophage MaMV-DH01 has a double-stranded DNA genome of 182,372 bp, with a GC content of 45.35% and 210 predicted open reading frames (ORFs). These ORFs are related to DNA metabolism, structural proteins, lysis, host-derived metabolic genes, and DNA packaging. Phylogenetic trees based on the whole genome and two conserved genes (TerL and capsid) indicate that MaMV-DH01 is clustered with Ma-LMM01 and MaMV-DC, which are independent of other cyanophages. Collinearity analysis showed that the complete genome of MaMV-DH01 was longer than those of Ma-LMM01 and MaMV-DC, with lengths of 20,263 bp and 13,139 bp, respectively. We verified the authenticity of these excess DNA fragments and found that they are involved to various degrees in the MaMV-DH01 transcription process. Map overlays of environmental virus macrogenomic reads onto the MaMV-DH01 genome revealed that viral sequences similar to that of MaMV-DH01 are widespread in the environment. IMPORTANCE A novel freshwater Myoviridae cyanophage strain, MaMV-DH01, was isolated; this strain infects Microcystis aeruginosa FACHB-524, and the biological and genomic characteristics of MaMV-DH01 provide new insights for understanding the mechanism by which cyanophages infect cyanobacterial blooms.

Cyanophage technology in removal of cyanobacteria mediated harmful algal blooms: A novel and eco-friendly method

Cyanophages are highly abundant specific viruses that infect cyanobacterial cells. In recent years, the cyanophages and cyanobacteria interactions drew attention to environmental restoration due to their discovery in marine and freshwater systems. Cyanobacterial harmful algal blooms (cyanoHABs) are increasing throughout the world and contaminating aquatic ecosystems. The blooms cause severe environmental problems including unpleasant odors and cyanotoxin production. Cyanotoxins have been reported to be lethal agents for living beings and can harm animals, people, aquatic species, recreational activities, and drinking water reservoirs. Biological remediation of cyanoHABs in aquatic systems is a sustainable and eco-friendly approach to increasing surface water quality. Therefore, this study compiles the fragmented information with the solution of removal of cyanoHABs using cyanophage therapy techniques. To date, scant information exists in terms of bloom formation, cyanophage occurrence, and mode of action to remediate cyanoHABs. Overall, this study illustrates cyanobacterial toxin production and its impacts on the environment, the mechanisms involved in the cyanophage-cyanobacteria interaction, and the application of cyanophages for the removal of toxic cyanobacterial blooms.

Characterization of Three Novel Virulent Aeromonas Phages Provides Insights into the Diversity of the Autographiviridae Family

In this study, we isolated and characterized three novel virulent Autographiviridae bacteriophages, vB_AspA_Bolek, vB_AspA_Lolek, and vB_AspA_Tola, which infect different Aeromonas strains. These three host-pathogen pairs were derived from the same sampling location-the arsenic-containing microbial mats of the Zloty Stok gold mine. Functional analysis showed they are psychrotolerant (4-25 °C), albeit with a much wider temperature range of propagation for the hosts (≤37 °C). Comparative genomic analyses revealed a high nucleotide and amino acid sequence similarity of vB_AspA_Bolek and vB_AspA_Lolek, with significant differences exclusively in the C-terminal region of their tail fibers, which might explain their host range discrimination. The protein-based phage network, together with a phylogenetic analysis of the marker proteins, allowed us to assign vB_AspA_Bolek and vB_AspA_Lolek to the Beijerinckvirinae and vB_AspA_Tola to the Colwellvirinae subfamilies, but as three novel species, due to their low nucleotide sequence coverage and identity with other known phage genomes. Global comparative analysis showed that the studied phages are also markedly different from most of the 24 Aeromonas autographiviruses known so far. Finally, this study provides in-depth insight into the diversity of the Autographiviridae phages and reveals genomic similarities between selected groups of this family as well as between autographiviruses and their relatives of other Caudoviricetes families.