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Isolation and molecular characterisation of Achromobacter phage phiAxp-3, an N4-like bacteriophage.

Ma Y, Li E, Qi Z, Li H, Wei X, Lin W, Zhao R, Jiang A, Yang H, Yin Z, Yuan J, Zhao X - Sci Rep (2016)

Bottom Line: Using proteomics, we identified 25 viral proteins from purified phiAxp-3 particles.Notably, investigation of the phage phiAxp-3 receptor on the surface of the host cell revealed that lipopolysaccharide serves as the receptor for the adsorption of phage phiAxp-3.Our findings advance current knowledge about A. xylosoxidans phages in an age where alternative therapies to combat antibiotic-resistant bacteria are urgently needed.

View Article: PubMed Central - PubMed

Affiliation: College of Food Science, Henan Institute of Science and Technology, Xinxiang, 453003, China.

ABSTRACT
Achromobacter xylosoxidans, an opportunistic pathogen, is responsible for various nosocomial and community-acquired infections. We isolated phiAxp-3, an N4-like bacteriophage that infects A. xylosoxidans, from hospital waste and studied its genomic and biological properties. Transmission electron microscopy revealed that, with a 67-nm diameter icosahedral head and a 20-nm non-contractile tail, phiAxp-3 has features characteristic of Podoviridae bacteriophages (order Caudovirales). With a burst size of 9000 plaque-forming units and a latent period of 80 min, phiAxp-3 had a host range limited to only four A. xylosoxidans strains of the 35 strains that were tested. The 72,825 bp phiAxp-3 DNA genome, with 416-bp terminal redundant ends, contains 80 predicted open reading frames, none of which are related to virulence or drug resistance. Genome sequence comparisons place phiAxp-3 more closely with JWAlpha and JWDelta Achromobacter phages than with other N4 viruses. Using proteomics, we identified 25 viral proteins from purified phiAxp-3 particles. Notably, investigation of the phage phiAxp-3 receptor on the surface of the host cell revealed that lipopolysaccharide serves as the receptor for the adsorption of phage phiAxp-3. Our findings advance current knowledge about A. xylosoxidans phages in an age where alternative therapies to combat antibiotic-resistant bacteria are urgently needed.

No MeSH data available.


Related in: MedlinePlus

Multiple genome alignment generated by Mauve software (http://asap.ahabs.wisc.edu/mauve/), and the chromosomes of Achromobacter phages phiAxp-3, JWAlpha and JWDelta and the Enterobacter phage, N4.Genome similarity is represented by the height of the bars, which correspond to the average level of conservation in that region of the genome sequence. Completely white regions represent fragments that were not aligned or contained sequence elements specific to a particular genome.
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f3: Multiple genome alignment generated by Mauve software (http://asap.ahabs.wisc.edu/mauve/), and the chromosomes of Achromobacter phages phiAxp-3, JWAlpha and JWDelta and the Enterobacter phage, N4.Genome similarity is represented by the height of the bars, which correspond to the average level of conservation in that region of the genome sequence. Completely white regions represent fragments that were not aligned or contained sequence elements specific to a particular genome.

Mentions: Analysis of a bacteriophage’s genome is an important preliminary step towards the development of phage therapy19. Whole-genome sequencing and assembling of the phiAxp-3 genome generated a circular molecule of 72,409 bp in size. The assembly was terminally permuted but not redundant after the original sequencing was completed. An initial whole genome Basic Local Alignment Search Tool (BLAST) analysis of phiAxp-3 against the National Center for Biotechnology Information database and multiple genome alignments showed that phiAxp-3 is related to two N4-like viruses (i.e., JWAlpha and JWDelta), indicating that phiAxp-3 is an N4-like phage (Fig. 3). It is well-known that N4-like phages have linear genomes and terminal repeats, but the terminal repeats are usually not identical20. Additionally, it is important to verify experimentally the ends of the phage genome rather than relying on genome assembly programs21. Therefore, to determine whether the phiAxp-3 genome is linear or circularly permuted and whether the ends are fixed or variable, restriction enzyme analyses were performed. BlpI restriction enzyme digestion of phiAxp-3 DNA produced two distinct fragments, thereby indicating the presence of a single recognition site in the viral DNA, and four distinct fragments when cut with EagI, thereby indicating the presence of three sites in the viral DNA (Supplementary Figure 1a). These findings clearly indicate that phiAxp-3 has a fixed linear genome structure without circular permutation. Terminal restriction enzyme fragments and primer walking experiments were used to determine the sequence of the phiAxp-3 genomic ends. The 5′ genomic end was predicted to be contained within a 3.5 kb BlpI fragment (Supplementary Figure 1b); hence, the gel-purified BlpI fragment was used as a template for sequencing reactions. Primer (P1), which was designed to read off the 5′ end of the genome, exhibited a detectable drop in signal intensity, indicating that the likely 5′ genome end had been reached. Sequencing from the predicted 3′ end, using the 3′ 5.4 kb EagI fragment and primer P2 (Supplementary Figure 1b), produced the repeat region at the 3′ end. Therefore, the phiAxp-3 genome has direct terminal repeats of 416 bp and possesses no cohesive ends; this result is consistent with those described previously for JWAlpha and JWDelta phages14. An alignment of the direct terminal repeats of phiAxp-3 is very similar to those for JWAlpha and JWDelta (Supplementary Figure 2). The terminal repeats in phiAxp-3 are 51 bp longer than that of JWAlpha (365 bp) and 4 bp shorter than that of JWDelta (420 bp). When the non-consecutive indels were removed, we found that they shared about 77% identity with those of JWAlpha and JWDelta. The additional 416-bp repeat means that the genome is 72,825-bp-long (GC content, 55.2%), rather than 72,409-bp-long (Supplementary Figure 1c).


Isolation and molecular characterisation of Achromobacter phage phiAxp-3, an N4-like bacteriophage.

Ma Y, Li E, Qi Z, Li H, Wei X, Lin W, Zhao R, Jiang A, Yang H, Yin Z, Yuan J, Zhao X - Sci Rep (2016)

Multiple genome alignment generated by Mauve software (http://asap.ahabs.wisc.edu/mauve/), and the chromosomes of Achromobacter phages phiAxp-3, JWAlpha and JWDelta and the Enterobacter phage, N4.Genome similarity is represented by the height of the bars, which correspond to the average level of conservation in that region of the genome sequence. Completely white regions represent fragments that were not aligned or contained sequence elements specific to a particular genome.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837373&req=5

f3: Multiple genome alignment generated by Mauve software (http://asap.ahabs.wisc.edu/mauve/), and the chromosomes of Achromobacter phages phiAxp-3, JWAlpha and JWDelta and the Enterobacter phage, N4.Genome similarity is represented by the height of the bars, which correspond to the average level of conservation in that region of the genome sequence. Completely white regions represent fragments that were not aligned or contained sequence elements specific to a particular genome.
Mentions: Analysis of a bacteriophage’s genome is an important preliminary step towards the development of phage therapy19. Whole-genome sequencing and assembling of the phiAxp-3 genome generated a circular molecule of 72,409 bp in size. The assembly was terminally permuted but not redundant after the original sequencing was completed. An initial whole genome Basic Local Alignment Search Tool (BLAST) analysis of phiAxp-3 against the National Center for Biotechnology Information database and multiple genome alignments showed that phiAxp-3 is related to two N4-like viruses (i.e., JWAlpha and JWDelta), indicating that phiAxp-3 is an N4-like phage (Fig. 3). It is well-known that N4-like phages have linear genomes and terminal repeats, but the terminal repeats are usually not identical20. Additionally, it is important to verify experimentally the ends of the phage genome rather than relying on genome assembly programs21. Therefore, to determine whether the phiAxp-3 genome is linear or circularly permuted and whether the ends are fixed or variable, restriction enzyme analyses were performed. BlpI restriction enzyme digestion of phiAxp-3 DNA produced two distinct fragments, thereby indicating the presence of a single recognition site in the viral DNA, and four distinct fragments when cut with EagI, thereby indicating the presence of three sites in the viral DNA (Supplementary Figure 1a). These findings clearly indicate that phiAxp-3 has a fixed linear genome structure without circular permutation. Terminal restriction enzyme fragments and primer walking experiments were used to determine the sequence of the phiAxp-3 genomic ends. The 5′ genomic end was predicted to be contained within a 3.5 kb BlpI fragment (Supplementary Figure 1b); hence, the gel-purified BlpI fragment was used as a template for sequencing reactions. Primer (P1), which was designed to read off the 5′ end of the genome, exhibited a detectable drop in signal intensity, indicating that the likely 5′ genome end had been reached. Sequencing from the predicted 3′ end, using the 3′ 5.4 kb EagI fragment and primer P2 (Supplementary Figure 1b), produced the repeat region at the 3′ end. Therefore, the phiAxp-3 genome has direct terminal repeats of 416 bp and possesses no cohesive ends; this result is consistent with those described previously for JWAlpha and JWDelta phages14. An alignment of the direct terminal repeats of phiAxp-3 is very similar to those for JWAlpha and JWDelta (Supplementary Figure 2). The terminal repeats in phiAxp-3 are 51 bp longer than that of JWAlpha (365 bp) and 4 bp shorter than that of JWDelta (420 bp). When the non-consecutive indels were removed, we found that they shared about 77% identity with those of JWAlpha and JWDelta. The additional 416-bp repeat means that the genome is 72,825-bp-long (GC content, 55.2%), rather than 72,409-bp-long (Supplementary Figure 1c).

Bottom Line: Using proteomics, we identified 25 viral proteins from purified phiAxp-3 particles.Notably, investigation of the phage phiAxp-3 receptor on the surface of the host cell revealed that lipopolysaccharide serves as the receptor for the adsorption of phage phiAxp-3.Our findings advance current knowledge about A. xylosoxidans phages in an age where alternative therapies to combat antibiotic-resistant bacteria are urgently needed.

View Article: PubMed Central - PubMed

Affiliation: College of Food Science, Henan Institute of Science and Technology, Xinxiang, 453003, China.

ABSTRACT
Achromobacter xylosoxidans, an opportunistic pathogen, is responsible for various nosocomial and community-acquired infections. We isolated phiAxp-3, an N4-like bacteriophage that infects A. xylosoxidans, from hospital waste and studied its genomic and biological properties. Transmission electron microscopy revealed that, with a 67-nm diameter icosahedral head and a 20-nm non-contractile tail, phiAxp-3 has features characteristic of Podoviridae bacteriophages (order Caudovirales). With a burst size of 9000 plaque-forming units and a latent period of 80 min, phiAxp-3 had a host range limited to only four A. xylosoxidans strains of the 35 strains that were tested. The 72,825 bp phiAxp-3 DNA genome, with 416-bp terminal redundant ends, contains 80 predicted open reading frames, none of which are related to virulence or drug resistance. Genome sequence comparisons place phiAxp-3 more closely with JWAlpha and JWDelta Achromobacter phages than with other N4 viruses. Using proteomics, we identified 25 viral proteins from purified phiAxp-3 particles. Notably, investigation of the phage phiAxp-3 receptor on the surface of the host cell revealed that lipopolysaccharide serves as the receptor for the adsorption of phage phiAxp-3. Our findings advance current knowledge about A. xylosoxidans phages in an age where alternative therapies to combat antibiotic-resistant bacteria are urgently needed.

No MeSH data available.


Related in: MedlinePlus