Genome organisation of the Acinetobacter lytic phage ZZ1 and comparison with other T4-like Acinetobacter phages.

BACKGROUND: Phage ZZ1, which efficiently infects pathogenic Acinetobacter baumannii strains, is the fifth completely sequenced T4-like Acinetobacter phage to date. To gain a better understanding of the genetic characteristics of ZZ1, bioinformatics and comparative genomic analyses of the T4 phages were performed. RESULTS: The 166,687-bp double-stranded DNA genome of ZZ1 has the lowest GC content (34.4%) of the sequenced T4-like Acinetobacter phages. A total of 256 protein-coding genes and 8 tRNA genes were predicted. Forty-three percent of the predicted ZZ1 proteins share up to 73% amino acid identity with T4 proteins, and the homologous genes generally retained the same order and transcriptional direction. Beyond the conserved structural and DNA replication modules, T4 and ZZ1 have diverged substantially by the acquisition and deletion of large blocks of unrelated genes, especially in the first halves of their genomes. In addition, ZZ1 and the four other T4-like Acinetobacter phage genomes (Acj9, Acj61, 133, and Ac42) share a well-organised and highly conserved core genome, particularly in the regions encoding DNA replication and virion structural proteins. Of the ZZ1 proteins, 70, 64, 61, and 56% share up to 86, 85, 81, and 83% amino acid identity with Acj9, Acj61, 133, and Ac42 proteins, respectively. ZZ1 has a different number and types of tRNAs than the other 4 Acinetobacter phages, although some of the ZZ1-encoded tRNAs share high sequence similarity with the tRNAs from these phages. Over half of ZZ1-encoded tRNAs (5 out of 8) are related to optimal codon usage for ZZ1 proteins. However, this correlation was not present in any of the other 4 Acinetobacter phages. CONCLUSIONS: The comparative genomic analysis of these phages provided some new insights into the evolution and diversity of Acinetobacter phages, which might elucidate the evolutionary origin and host-specific adaptation of these phages.

[Determination of meconium lead level of newborn by graphite furnace atomic absorption spectrometry].

UNLABELLED: To establish a method for the determination of lead in meconium from 144 samples of newborn through nitric acid digestion by means of graphite furnace atomic absorption spectrometry. METHODS: after being baked for at least 12 h at 60 degrees C, 0.3 g of meconium was digested by nitric acid and hydrogen peroxide in turn at 80 degrees C under water-bath condition for 1h and then metered to the whole volume of to 2 mL. After correcting the background with D2 lamp, specimen basal corpuscle matched standard curve was used to detect the lead content. RESULTS: The mean lead content of 93 experimental samples was 1.934 microg x g(-1) with the standard deviation (SD) of 1.551, and that of the 51 control samples was 1.012 microg x g(-1), with the SD of 1.084. There was a significant difference in lead levels of in meconnt between the experimental group and control group (p = 0.000). CONCLUSION: The lead content of the experimental was significantly higher than that of the control group detected by this method. This method was stable and efficient.