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Isolation and characterization of an autoinducer synthase from Acinetobacter baumannii.

ABSTRACT: The opportunistic human pathogen Acinetobacter baumannii strain M2 was found to produce distinct acyl-homoserine lactone (AHL) signals based on the use of an Agrobacterium tumefaciens traG-lacZ biosensor. An A. baumannii gene, designated abaI, was cloned and directed AHL production in recombinant Escherichia coli. The AbaI protein was similar to members of the LuxI family of autoinducer synthases and was predicted to be the only autoinducer synthase encoded by A. baumannii. The primary AHL signal directed by AbaI was identified by mass spectrometry as being N-(3-hydroxydodecanoyl)-L-HSL (3-hydroxy-C(12)-HSL). Minor amounts of at least five additional AHLs were also identified. The expression of abaI at the transcriptional level was activated by ethyl acetate extracts of culture supernatants or by synthetic 3-hydroxy-C(12)-HSL. An abaI::Km mutant failed to produce any detectable AHL signals and was impaired in biofilm development.

SUBMITTER: Niu C

PROVIDER: S-EPMC2347373 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Isolation and characterization of an autoinducer synthase from Acinetobacter baumannii.

Niu Chen C Clemmer Katy M KM Bonomo Robert A RA Rather Philip N PN

Journal of bacteriology 20080215 9

The opportunistic human pathogen Acinetobacter baumannii strain M2 was found to produce distinct acyl-homoserine lactone (AHL) signals based on the use of an Agrobacterium tumefaciens traG-lacZ biosensor. An A. baumannii gene, designated abaI, was cloned and directed AHL production in recombinant Escherichia coli. The AbaI protein was similar to members of the LuxI family of autoinducer synthases and was predicted to be the only autoinducer synthase encoded by A. baumannii. The primary AHL signa ...[more]

PMID: 18281398

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Project description:BACKGROUND: Acinetobacter baumannii is an emerging nosocomial pathogen worldwide with increasing prevalence of multi-drug and pan-drug resistance. A. baumannii exists widely in natural environment, especially in health care settings, and has been shown difficult to be eradicated. Bacteriophages are often considered alternative agent for controlling bacterial infection and contamination. In this study, we described the isolation and characterization of one virulent bacteriophage AB1 capable of specifically infecting A. baumannii. RESULTS: A virulent bacteriophage AB1, specific for infecting a clinical strain A. baumannii KD311, was first isolated from marine sediment sample. Restriction analysis indicated that phage AB1 was a dsDNA virus with an approximate genome size of 45.2 kb to 46.9 kb. Transmission electron microscopy showed that phage AB1 had an icosahedral head with a non-contractile tail and collar or whisker structures, and might be tentatively classified as a member of the Siphoviridae family. Proteomic pattern of phage AB1, generated by SDS-PAGE using purified phage particles, revealed five major bands and six minor bands with molecular weight ranging from 14 to 80 kilo-dalton. Also determined was the adsorption rate of phage AB1 to the host bacterium, which was significantly enhanced by addition of 10 mM CaCl2. In a single step growth test, phage AB1 was shown having a latent period of 18 minutes and a burst size of 409. Moreover, pH and thermal stability of phage AB1 were also investigated. At the optimal pH 6.0, 73.2% of phages survived after 60 min incubation at 50 degrees C. When phage AB1 was used to infect four additional clinical isolates of A. baumannii, one clinical isolate of Stenotrophomonas maltophilia, and Pseudomonas aeruginosa lab strains PAK and PAO1, none of the tested strains was found susceptible, indicating a relatively narrow host range for phage AB1. CONCLUSION: Phage AB1 was capable of eliciting efficient lysis of A. baumannii, revealing its potential as a non-toxic sanitizer for controlling A. baumannii infection and contamination in both hospital and other public environments.

Project description:BACKGROUND: Acinetobacter baumannii, a significant nosocomial pathogen, has evolved resistance to almost all conventional antimicrobial drugs. Bacteriophage therapy is a potential alternative treatment for multidrug-resistant bacterial infections. In this study, one lytic bacteriophage, ZZ1, which infects A. baumannii and has a broad host range, was selected for characterization. RESULTS: Phage ZZ1 and 3 of its natural hosts, A. baumanni clinical isolates AB09V, AB0902, and AB0901, are described in this study. The 3 strains have different sensitivities to ZZ1, but they have the same sensitivity to antibiotics. They are resistant to almost all of the antibiotics tested, except for polymyxin. Several aspects of the life cycle of ZZ1 were investigated using the sensitive strain AB09V under optimal growth conditions. ZZ1 is highly infectious with a short latent period (9 min) and a large burst size (200 PFU/cell). It exhibited the most powerful antibacterial activity at temperatures ranging from 35°C to 39°C. Moreover, when ZZ1 alone was incubated at different pHs and different temperatures, the phage was stable over a wide pH range (4 to 9) and at extreme temperatures (between 50°C and 60°C). ZZ1 possesses a 100-nm icosahedral head containing double-stranded DNA with a total length of 166,682 bp and a 120-nm long contractile tail. Morphologically, it could be classified as a member of the Myoviridae family and the Caudovirales order. Bioinformatic analysis of the phage whole genome sequence further suggested that ZZ1 was more likely to be a new member of the Myoviridae phages. Most of the predicted ORFs of the phage were similar to the predicted ORFs from other Acinetobacter phages. CONCLUSION: The phage ZZ1 has a relatively broad lytic spectrum, high pH stability, strong heat resistance, and efficient antibacterial potential at body temperature. These characteristics greatly increase the utility of this phage as an antibacterial agent; thus, it should be further investigated.

Dataset Information

Isolation and characterization of an autoinducer synthase from Acinetobacter baumannii.

Publications

Isolation and characterization of an autoinducer synthase from Acinetobacter baumannii.

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