English: Observation and functional assay of the chronic bacteriophage induced by NO₃⁻ or NH₄⁺ from Poriferisphaera heterotrophicis ZRK32 (NCBI taxID 2881018).
(A) TEM observation of phages extracted from the cell suspensions of ZRK32 strains that cultured in either the rich medium alone, or rich medium supplemented with 20 mM of either NO₃⁻ or NH₄⁺. (A, Panel I) No phage-like particles were observed in the cell suspensions from the ZRK32 strain cultured in the rich medium. (A, Panels II and III) Hexagonal phages (indicated with yellow arrows) observed in the cell suspensions from the ZRK32 strains cultured in the rich medium supplemented with 20 mM of either NO₃⁻ or NH₄⁺. The scale bar is 200 nm. (B) A diagram showing the genomic composition of Phage-ZRK32 (NCBI Tax ID 2989513). The arrows represent different ORFs and the direction of transcription. The main putative gene products of this phage are shown, and the numbers in brackets indicate the numbers of amino acids. Hypothetical proteins are indicated by gray arrows, structural modules are indicated by green arrows, nucleotide metabolism is indicated by blue-gray arrows, the replication module is indicated by gold arrows, and AMGs are indicated by red arrows. The size of the phage genome is shown beside the gene cluster. (C) Bacterial growth curve showing the growth rate of strains of aerobic marine bacterium Pseudomonas stutzeri 273 cultivated in either oligotrophic medium, oligotrophic medium supplemented with Phage-ZRK32, oligotrophic medium supplemented with 20 mM NO₃⁻, or oligotrophic medium supplemented with 20 mM NO₃⁻ and Phage-ZRK32. (D) Bacterial growth curve showing the growth rate of strains of Pseudomonas stutzeri 273 cultivated in either oligotrophic medium, oligotrophic medium supplemented with Phage-ZRK32, oligotrophic medium supplemented with 20 mM NH₄⁺, or oligotrophic medium supplemented with 20 mM NH₄⁺ and Phage-ZRK32. “Oligo” indicates oligotrophic medium.