Broad Environmental Tolerance for a Salicola Host-Phage Pair Isolated from the Cargill Solar Saltworks, Newark, CA, USA

Exploring the Microbial Ecology of Water in Sub-Saharan Africa and the Potential of Bacteriophages in Water Quality Monitoring and Treatment to Improve Its Safety

Access to safe water and food is a critical issue in sub-Saharan Africa, where microbial contamination poses significant health risks. Conventional water treatment and food preservation methods have limitations in addressing water safety, particularly for antibiotic-resistant bacteria and other pathogenic microorganisms. This review explores the potential application of bacteriophages as an innovative solution for water treatment and food safety in the region. Bacteriophages specifically infect bacteria and offer a targeted approach to reducing bacterial load, including multidrug-resistant strains, without the drawbacks of chemical disinfectants. This review also highlights the advantages of phage bioremediation, including its specificity, adaptability, and minimal environmental impact. It also discusses various case studies demonstrating its efficacy in different water systems. Additionally, we underscore the need for further research and the development of region-specific phage applications to improve water quality and public health outcomes in sub-Saharan Africa. By integrating bacteriophage strategies into water treatment and food production, the region can address critical microbial threats, mitigate the spread of antimicrobial resistance, and advance global efforts toward ensuring safe water for all.

Soil Giant Phage: Genome and Biological Characteristics of Sinorhizobium Jumbo Phage

This paper presents the first in-depth research on the biological and genomic properties of lytic rhizobiophage AP-J-162 isolated from the soils of the mountainous region of Dagestan (North Caucasus), which belongs to the centers of origin of cultivated plants, according to Vavilov N.I. The rhizobiophage host strains are nitrogen-fixing bacteria of the genus Sinorhizobium spp., symbionts of leguminous forage grasses. The phage particles have a myovirus virion structure. The genome of rhizobiophage AP-J-162 is double-stranded DNA of 471.5 kb in length; 711 ORFs are annotated and 41 types of tRNAs are detected. The closest phylogenetic relative of phage AP-J-162 is Agrobacterium phage Atu-ph07, but no rhizobiophages are known. The replicative machinery, capsid, and baseplate proteins of phage AP-J-162 are structurally similar to those of Escherichia phage T4, but there is no similarity between their tail protein subunits. Amino acid sequence analysis shows that 339 of the ORFs encode hypothetical or functionally relevant products, while the remaining 304 ORFs are unique. Additionally, 153 ORFs are similar to those of Atu_ph07, with one-third of the ORFs encoding different enzymes. The biological properties and genomic characteristics of phage AP-J-162 distinguish it as a unique model for exploring phage-microbe interactions with nitrogen-fixing symbiotic microorganisms.

Isolation of phages against Streptococcus species in the oral cavity for potential control of dental diseases and associated systemic complications

Dental infections and systemic complications caused by Streptococcus species in the oral cavity are increasingly exhibiting resistance to commonly used antibiotics, posing a potential threat to global public health. Phage therapy may offer a superior alternative, given that bacteriophages can be easily isolated and rapidly replicate in large numbers. In this study, six Streptococcus species from the oral cavity were characterized. Bacteriophages isolated from wastewater using five of these species as hosts produced plaques ranging from 0.2 to 2.4 mm in size. The phages demonstrated stability within a temperature range of 4 ℃ to 37 ℃. However, at temperatures exceeding 45 ℃, a noticeable reduction in bacteriophage titer was observed. Similarly, the phages showed greater stability within a pH range of 5 to 10. The isolated phages exhibited latency periods ranging from 15 to 20 min and had burst sizes varying from 10 to 200 viral particles. This study supports the potential use of bacteriophages in controlling infections caused by Streptococcus species.

Genomic Characterization of a Halovirus Representing a Novel Siphoviral Cluster

Salt mines are a special type of hypersaline environment. Current research mainly focuses on prokaryotes, and the understanding of viruses in salt mines remains limited. Understanding viruses in hypersaline environments is of great significance for revealing the formation and maintenance of microbial communities, energy flow and element cycling, and host ecological functions. A phage infecting Halomonas titanicae was isolated from Yipinglang Salt Mine in China, designated Halomonas titanicae phage vB_HtiS_YPHTV-1 (YPHTV-1). Transmission electron microscopy revealed that YPHTV-1 had an icosahedral head with a diameter of 49.12 ± 0.15 nm (n = 5) and a long noncontractile tail with a length of 141.7 ± 0.58 nm (n = 5), indicating that it was a siphovirus. The one-step growth curve showed that the burst size of YPHTV-1 was 69 plaque forming units (PFUs) cell^-1. The genome of YPHTV-1 was 37,980 bp with a GC content of 36.2%. The phylogenetic analysis of the six conserved proteins indicated that YPHTV-1 formed a cluster with Bacillus phages and was separated from phages infecting Halomonas. The average nucleotide identity (ANI), phylogenetic, and network analyses indicated that the phage YPHTV-1 represented a new genus under Caudoviricetes. In total, 57 open reading frames (ORFs) were predicted in the YPHTV-1 genome, 30 of which could be annotated in the database. Notably, several auxiliary metabolic genes were encoded by YPHTV-1, such as ImmA/IrrE family metalloendopeptidase, mannose-binding lectin (MBL) folding metallohydrolase, M15 family of metal peptidases, MazG-like family protein, O antigen ligase, and acyltransferase. These genes potentially enabled the host bacterium to resist ionizing radiation, ultraviolet light (UV), mitomycin C, β-lactam antibiotic, high osmotic pressure, and nutritional deficiencies. These findings highlight the role of haloviruses in the life cycle of halobacteria.

Characterization and genomic analysis of a novel halovirus infecting Chromohalobacter beijerinckii

Bacteriophages function as a regulator of host communities and metabolism. Many phages have been isolated and sequenced in environments such as the ocean, but very little is known about hypersaline environments. Phages infecting members of the genus Chromohalobacter remain poorly understood, and no Chromohalobacter phage genome has been reported. In this study, a halovirus infecting Chromohalobacter sp. F3, YPCBV-1, was isolated from Yipinglang salt mine. YPCBV-1 could only infect host strain F3 with burst size of 6.3 PFU/cell. It could produce progeny in 5%-20% (w/v) NaCl with an optimal concentration of 10% (w/v), but the optimal adsorption NaCl concentration was 5%-8% (w/v). YPCBV-1 is sensitive to pure water and depends on NaCl or KCl solutions to survive. YPCBV-1 stability increased with increasing salinity but decreased in NaCl saturated solutions, and it has a broader salinity adaptation than the host. YPCBV-1 has a double-stranded DNA of 36,002 bp with a G + C content of 67.09% and contains a total of 55 predicted ORFs and no tRNA genes. Phylogenetic analysis and genomic network analysis suggested that YPCBV-1 is a novel Mu-like phage under the class Caudoviricetes. Auxiliary metabolic gene, SUMF1/EgtB/PvdO family non-heme iron enzyme, with possible roles in antioxidant was found in YPCBV-1. Moreover, DGR-associated genes were predicted in YPCBV-1 genome, which potentially produce hypervariable phage tail fiber. These findings shed light on the halovirus-host interaction in hypersaline environments.

Virus-Host Interactions and Genetic Diversity of Antarctic Sea Ice Bacteriophages

Although we know the generally appreciated significant roles of microbes in sea ice and polar waters, detailed studies of virus-host systems from such environments have been so far limited by only a few available isolates. Here, we investigated infectivity under various conditions, infection cycles, and genetic diversity of the following Antarctic sea ice bacteriophages: Paraglaciecola Antarctic GD virus 1 (PANV1), Paraglaciecola Antarctic JLT virus 2 (PANV2), Octadecabacter Antarctic BD virus 1 (OANV1), and Octadecabacter Antarctic DB virus 2 (OANV2). The phages infect common sea ice bacteria belonging to the genera Paraglaciecola or Octadecabacter. Although the phages are marine and cold-active, replicating at 0°C to 5°C, they all survived temporal incubations at ≥30°C and remained infectious without any salts or supplemented only with magnesium, suggesting a robust virion assembly maintaining integrity under a wide range of conditions. Host recognition in the cold proved to be effective, and the release of progeny viruses occurred as a result of cell lysis. The analysis of viral genome sequences showed that nearly one-half of the gene products of each virus are unique, highlighting that sea ice harbors unexplored virus diversity. Based on predicted genes typical for tailed double-stranded DNA phages, we suggest placing the four studied viruses in the class Caudoviricetes. Searching against viral sequences from metagenomic assemblies, we revealed that related viruses are not restricted to Antarctica but are also found in distant marine environments.

Temporal Dynamics of Soil Virus and Bacterial Populations in Agricultural and Early Plant Successional Soils

As reported in many aquatic environments, recent studies in terrestrial ecosystems implicate a role for viruses in shaping the structure, function, and evolution of prokaryotic soil communities. However, given the heterogeneity of soil and the physical constraints (i.e., pore-scale hydrology and solid-phase adsorption of phage and host cells) on the mobility of viruses and bacteria, phage-host interactions likely differ from those in aquatic systems. In this study, temporal changes in the population dynamics of viruses and bacteria in soils under different land management practices were examined. The results showed that bacterial abundance was significantly and positively correlated to both virus and inducible prophage abundance. Bacterial and viral abundance were also correlated with soil organic carbon and nitrogen content as well as with C:N ratio. The seasonal variability in viral abundance increased with soil organic carbon content. The prokaryotic community structure was influenced more by land use than by seasonal variation though considerable variation was evident in the early plant successional and grassland sites. The free extracellular viral communities were also separated by land use, and the forest soil viral assemblage exhibiting the most seasonal variability was more distinct from the other sites. Viral assemblages from the agricultural soils exhibited the least seasonal variability. Similar patterns were observed for inducible prophage viral assemblages. Seasonal variability of viral assemblages was greater in mitomycin-C (mitC) induced prophages than in extracellular viruses irrespective of land use and management. Taken together, the data suggest that soil viral production and decay are likely balanced but there was clear evidence that the structure of viral assemblages is influenced by land use and by season.

Isolation and Characterization of a Novel Phage for Controlling Multidrug-Resistant Klebsiella pneumoniae

The emergence of multidrug-resistant bacterial pathogens has severely threatened global health. A phage with the ability to efficiently and specifically lyse bacteria is considered an alternative for controlling multidrug-resistant bacterial pathogens. The discovery of novel agents for controlling the infections caused by K. pneumoniae is urgent due to the broad multidrug-resistance of K. pneumoniae. Only a few phage isolates have been reported to infect multidrug-resistant K. pneumoniae. In this study, by using the multidrug-resistant K. pneumoniae strain as an indicator, a novel phage called vB_KleS-HSE3, which maintains high antibacterial activity and high physical stability, was isolated from hospital sewage. This phage infected one of four tested multidrug-resistant K. pneumoniae strains. This phage belongs to the Siphoviridae family and a comparative genomic analysis showed that this phage is part of a novel phage lineage among the Siphoviridae family of phages that infect strains of Klebsiella. Based on its features, the vB_KleS-HSE3 phage has potential for controlling infections caused by multidrug-resistant K. pneumoniae.

Characterization of the Three New Kayviruses and Their Lytic Activity Against Multidrug-Resistant Staphylococcus aureus

The development of antimicrobial resistance has become a global concern. One approach to overcome the problem of drug resistance is the application of bacteriophages. This study aimed at characterizing three phages isolated from sewage, which show lytic activity against clinical isolates of multidrug-resistant Staphylococcus aureus. Morphology, genetics and biological properties, including host range, adsorption rate, latent time, phage burst size and lysis profiles, were studied in all three phages. As analyzed by transmission electron microscopy (TEM), phages vB_SauM-A, vB_SauM-C, vB_SauM-D have a myovirion morphology. One of the tested phages, vB_SauM-A, has relatively rapid adsorption (86% in 17.5 min), short latent period (25 min) and extremely large burst size (~500 plaque-forming units (PFU) per infected cell). The genomic analysis revealed that vB_SauM-A, vB_SauM-C, vB_SauM-D possess large genomes (vB_SauM-A 139,031 bp, vB_SauM-C 140,086 bp, vB_SauM-D 139,088 bp) with low G+C content (~30.4%) and are very closely related to the phage K (95-97% similarity). The isolated bacteriophages demonstrate broad host range against MDR S. aureus strains, high lytic activity corresponding to strictly virulent life cycle, suggesting their potential to treat S. aureus infections.