RÉSUMÉ
The present study focused on the characterization and genomic sequence of phage PS2 that infects Serratia marcescens clinical isolates.The morphology of phage PS2 was observed with electron microscope.The one-step growth curve,host range,and stability of PS2 were investigated.In addition,Phage DNA was extracted from the purified phage particles using a MiniBEST Viral RNA/DNA Extraction Kit.DNA sample was analyzed by digesting with restriction enzymes.The phage DNA was used for constructing the sequencing library.The library was sequenced on a MiSeqTM platform.The whole genome sequence was obtained by Velvet (version:1.2.08) assembling.Phage PS2 belongs to the Myoviridae family.The linear,circularly permuted,167 266-bp double-stranded DNA genome of PS2 has high similarities to T4-1ike phages.The phage DNA contains 41.7％ GC and 276 ORFs.PS2 exhibited a 21-minute latent period and 70 PFU per cell at burst size when the pathogenic S.marcescens strain S2 served as a host.Further investigation suggested that PS2 is stable in a wide pH range (pH5 to pH10) and at extreme temperatures (50 ℃ and 60 ℃) after incubation alone at different pHs and different temperatures,respectively.The paper focused on the isolation and identification of a novel lytic S.marcescens phage,the biological characteristics,the whole genome sequencing and the preliminary study of bioinformatics,which laid the foundation for deeply analysis to the phage therapy of multi-drug resistant bacteria and the phage biological information.
RÉSUMÉ
The present study focused on the characterization and genomic sequence of phage PS2 that infects Serratia marcescens clinical isolates.The morphology of phage PS2 was observed with electron microscope.The one-step growth curve,host range,and stability of PS2 were investigated.In addition,Phage DNA was extracted from the purified phage particles using a MiniBEST Viral RNA/DNA Extraction Kit.DNA sample was analyzed by digesting with restriction enzymes.The phage DNA was used for constructing the sequencing library.The library was sequenced on a MiSeqTM platform.The whole genome sequence was obtained by Velvet (version:1.2.08) assembling.Phage PS2 belongs to the Myoviridae family.The linear,circularly permuted,167 266-bp double-stranded DNA genome of PS2 has high similarities to T4-1ike phages.The phage DNA contains 41.7％ GC and 276 ORFs.PS2 exhibited a 21-minute latent period and 70 PFU per cell at burst size when the pathogenic S.marcescens strain S2 served as a host.Further investigation suggested that PS2 is stable in a wide pH range (pH5 to pH10) and at extreme temperatures (50 ℃ and 60 ℃) after incubation alone at different pHs and different temperatures,respectively.The paper focused on the isolation and identification of a novel lytic S.marcescens phage,the biological characteristics,the whole genome sequencing and the preliminary study of bioinformatics,which laid the foundation for deeply analysis to the phage therapy of multi-drug resistant bacteria and the phage biological information.
RÉSUMÉ
The performance of internal-loop air-lift nitrifying bioreactor was good with strong tolerance to influent ammonia concentration (78.49 mmol/L), high volume converting rate (163.18 mmol/L.d) and obvious working stability (ammonia removal > 94.42%). During operation of internal-loop air-lift bioreactor, the nitrifying activated sludge was granulated. The nitrifying granular activated sludge began to appear on day 45. Its average diameter was 0.83 mm, settling velocity was 55.53 m/h and specific ammonia removal rate was 0.95 mmol (NH4(+)-N)/g (VS).d. The nitrifying granular activated sludge had the activity for anaerobic ammonia oxidation with ammonia oxidation rate of 0.23 mmol (NH4(+)-N)/g(VS).d and nitrite reduction rate of 0.24 mmol (NO2(-)-N)/g(VS).d.