Characterization and complete genomic sequence of a novel phage BUCT805 infecting Serratia marcescens and its anti-biofilm activities

ABSTRACT Serratia marcescens ( S. marcescens ) is an opportunistic pathogen commonly found in the environment and is capable of causing nosocomial and various severe infections. Bacteriophages (phages), as safe and eco-friendly natural antibacterial agents, hold promise for eradicating S. marcescens and its biofilms in hospital settings. In this study, we report a novel phage, BUCT805, isolated from wastewater, which effectively lysed S. marcescens , and we provide a detailed analysis of its physiological properties and genomic characteristics. BUCT805 was classified within the kingdom Heunggongvirae and the phylum Uroviricota . It formed clear plaques with a diameter of approximately 3.36 ± 0.63 mm, featuring a transparent center surrounded by a halo. The optimal multiplicity of infection for BUCT805 was 0.1, with a burst size of 338 ± 17 PFU per infected cell ( n = 3), and the phage exhibited robust stability across a wide range of temperatures and pH levels. The genome of phage BUCT805 was composed of double-stranded DNA with a total length of 42,067 bp and a G+C content of 47%, exhibiting the highest sequence similarity to Serratia phage vB_SmaS_Serratianator with a query coverage of 88%. Importantly, no known antibiotic resistance or virulence genes were identified in the genome, and 40.32% of its open reading frames were annotated as functional proteins. Although the efficiency of biofilm removal by BUCT805 varied among different bacterial strains, it demonstrated significant biofilm eradication effects at high titers (10 9 PFU/mL) against all tested strains. Overall, our findings supported the potential of phage BUCT805 as a promising candidate for the removal of S. marcescens biofilms from environmental settings. IMPORTANCE Hospital surfaces could harbor Serratia marcescens , a resilient bacterium that forms protective biofilms and causes hospital-acquired infections (HAIs). We isolated and fully characterized BUCT805, a novel phage that specifically targeted S. marcescens and effectively removed its biofilms on plastic surfaces. BUCT805 was highly stable across a broad range of temperatures and pH, exhibited a high burst size, and carried no known antibiotic-resistance or toxin genes, supporting its safety for environmental applications. Phage BUCT805 had the potential to remove biofilms in the environment, thereby reducing the risk of HAI and providing an additional option for controlling S. marcescens and its biofilms in clinical settings.