Profile of the Spatial Distribution Patterns of the Human and Bacteriophage Virome in a Wastewater Treatment Plant Located in the South of Spain

In wastewater treatment plants, most microbial characterization has focused on bacterial, archaeal, and fungal populations. Due to the difficult isolation, quantification, and identification of viruses, only a limited number of virome studies associated with wastewater treatment plants have been carried out. However, the virus populations play an important role in the microbial dynamics in wastewater treatment systems and the biosafety of effluents. In this work, the viral members present in influent wastewater, mixed liquor (aerobic bioreactor), excess sludge, and effluent water of a conventional activated sludge system for the treatment of urban wastewater were identified. Viral members were observed by transmission electron microscopy and studied through next-generation sequencing studies. The results showed the dominance of bacteriophages in the viral community in all samples, with the dominant viral phylotype classified as Escherichia coli O157 typing phage 7. Moreover, different human viruses, such as Cynomolgus cytomegalovirus and Gammaherpesvirus, were also detected.

Escherichia coli O157:H7 Typing Phage V7 Is a T4-Like Virus

The complete genome sequence of theEscherichia coliO157:H7 typing phage V7 was determined. Its double-stranded DNA genome is 166,452 bp long, encoding 273 proteins and including 11 tRNAs. This virus belongs to the genus T4-like viruses within the subfamilyTevenvirinae, familyMyoviridae.

The Core Oligosaccharide and Thioredoxin of Vibrio cholerae Are Necessary for Binding and Propagation of Its Typing Phage VP3

ABSTRACT VP3 is a T7-like phage and was used as one of the typing phages in a phage-biotyping scheme that has been used for the typing of Vibrio cholerae O1 biotype El Tor. Here, we studied the receptor and other host genes of V. cholerae necessary for the lytic propagation of VP3. Six mutants resistant to VP3 infection were obtained from the random transposon insertion mutant bank of the sensitive strain N16961. The genes VC0229 and VC0231, which belong to the wav gene cluster encoding the core oligosaccharide (OS) region of lipopolysaccharide, were found to be interrupted by the transposon in five mutants, and the sixth mutant had the transposon inserted between the genes rhlB and trxA, which encode the ATP-dependent RNA helicase RhlB and thioredoxin, respectively. Gene complementation, transcription analysis, and the loss of VP3 sensitivity by the gene deletion mutants confirmed the relationship between VP3 resistance and VC0229, VC0231, and trxA mutation. The product of VP3 gene 44 (gp44) was predicted to be a tail fiber protein. gp44 could bind to the sensitive wild-type strain and the trxA mutant, but not to VC0229 and VC0231 mutants. The results showed that OS is a VP3 receptor on the surface of N16961, thioredoxin of the host strain is involved in the propagation of the phage, and gp44 is the tail fiber protein of VP3. This revealed the first step in the infection mechanism of the T7-like phage VP3 in V. cholerae.

Genetic and Phenotypic Variability among Salmonella enterica Serovar Typhimurium Isolates from California Dairy Cattle and Humans

ABSTRACT Fifty-six human and 24 adult dairy cattle isolates of Salmonella enterica serovar Typhimurium from a single county in California were compared using ribotyping, insertion sequence typing (IS200), pulsed-field gel electrophoresis, plasmid typing, phage typing, and antimicrobial resistance testing. The majority of the isolates fell into one of two groups which were phage types DT104 and DT193. Combining the information from all typing methods, a total of 45 different “clusters” were defined, with 35 of those including only a single isolate. The library of isolates had a high degree of variability, but antibiotic resistance and plasmid typing each defined single clusters in which human or bovine isolates predominated (χ2, P < 0.05).