Biological characteristics and preliminary genome analysis of Acinetobacter baumannii bacteriophage SWH-Ab-3

Abstract

Objective To investigate the biological characteristics and basic genomic information of Acinetobacter baumannii (A. baumannii) lytic bacteriophage isolated from hospital sewage. Methods Bacteriophage was isolated and purified with indicator of A. baumannii by double-layer agar plate method, and plaque characteristics of the phage were observed. The structure of purified phage was observed with transmission electron microscopy. The host spectrum was determined by point plate test, and optimal multiplicity of infection (MOI), one-step growth curve, temperature and pH stability of the phage were investigated. The whole genome DNA of phage was extracted and sequenced by Illumina Hiseq2000 high-throughput sequencing technology, and then the genome sequence was annotated and analyzed by alignment. Results A strain of lytic bacteriophage against the A. baumannii, named SWH-Ab-3, was isolated from sewage. The phage had a head of about 70 nm in diameter and a tail of about 80 nm in length. SWH-Ab-3 was identified to belong to Myoviridae family. The bacteriophage had a narrower lytic spectrum of A. baumannii (6/42), optimal MOI of 0.1, latent period of 40 min and burst period of 50 min, and the burst size about 31.4 PFU/cell, and could stand the temperature up to 60 ℃ and keep stable titer under acid or alkali environment. Its genome size was 41 730 bp with G+C content of 39.38%. There were 53 ORF encoded, of which 33 were known functional genes and 20 were hypothetical proteins. The BLASTn alignment found that SWH-Ab-3 had the highest homology with Abp1 and vB_AbaP_B3 (> 94%), but the length of the genome, the G+C% content and the morphological characteristics of the phage were significant. Conclusion SWH-Ab-3 is a new lytic phage of A. baumannii, belonging to the Myoviridae family. It is tolerant to heat, acid and alkali. It may lyse the host bacteria through "two-element lysis system", composed of holin and lyase. It has stronger lytic ability, but narrower lytic spectrum.

Keywords

• acinetobacter baumannii
• bacteriophage
• biological characteristics
• whole genome analysis