Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Genetic Organization and Conjugal Plasmid DNA Transfer of pHP69, a Plasmid from a Korean Isolate of Helicobacter pylori: Jung-Soo Joo , Jae-Young Song , Seung-Chul Baik , Woo-Kon Lee , Myung-Je Cho , Kon-Ho Lee , Hee-Shang Youn , Ji-Hyun Seo , Kwang-Ho Rhee , Hyung-Lyun Kang; J. Microbiol. 2012;50(6):955-961. Published online December 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2580-9

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Abstract: We isolated pHP69, a 9,153 bp plasmid from Helicobacter pylori with a 33.98% (G+C) content. We identified 11 open reading frames (ORFs), including replication initiation protein A (repA), fic (cAMP-induced filamentation protein), mccC, mccB, mobA, mobD, mobB, and mobC, as well as four 22 bp tandem repeat sequences. The nucleic acid and predicted amino acid sequences of these ORFs exhibited significant homology to those of other H. pylori plasmids. pHP69 repA encodes a replication initiation protein and its amino acid sequence is similar to those of replicase proteins from theta-type plasmids. pHP69 contains two types of repeat sequences (R1 and R2), a MOBHEN family mobilization region comprising mobC, mobA, mobB, and mobD, and genes encoding microcin B and C. Among the 36 H. pylori strains containing plasmids, mobA or mccBC are present in 12 or 6, respectively and 3 contain both genes. To examine intrinsic capability of H. pylori for conjugative plasmid transfer, a shuttle vector pBHP69KH containing pHP69 and replication origin of pBR322 was constructed. It was shown that this vector could stably replicate and be mobilized among clinical H. pylori strains and demonstrated to gene transfer by natural plasmid.

In Vitro Development and Transfer of Resistance to Chlortetracycline in Bacillus subtilis: Menghong Dai , Junjie Lu , Yulian Wang , Zhenli Liu , Zonghui Yuan; J. Microbiol. 2012;50(5):807-812. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-1454-5

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Abstract: The present criteria and rules controlling the approval of the use of probiotics are limited to antibiotic resistance patterns and the presence of antibiotic resistance genes in bacteria. There is little information available in the literature regarding the risk of the usage of probiotics in the presence of antibiotic pressure. In this study we investigated the development and transfer of antibiotic resistance in Bacillus subtilis selected in vitro by chlortetracycline in a stepwise manner. Bacillus subtilis was exposed to increasing concentrations of chlortetracyclineto induce in vitro resistance to chlortetracycline, and the minimal inhibitory concentrations were determinedfor the mutants. Resistant B. subtilis were conjugated with Escherichia coli NK5449 and Enterococcus faecalis JH2-2 using the filter mating. Three B. subtilis tetracycline resistant mutants (namely, BS-1, BS-2, and BS-3) were derived in vitro. A tetracycline resistant gene, tet (K), was found in the plasmids of BS-1 and BS-2. Three conjugates (BS-1N, BS-2N, and BS-3N) were obtained when the resistant B. subtilis was conjugated with E. coli NK5449. The conjugation frequencies for the BS-1N, BS-2N, and BS-3N conjugates were 4.57×10-7, 1.4×10-7, and 1.3×10-8, respectively. The tet(K) gene was found only in the plasmids of BS-1N. These results indicate that long-term use of probiotics under antibiotic selection pressure could cause antibiotic resistance, and the resistance gene could be transferred to other bacteria. The risk arising from the use of probiotics under antibiotic pressure should be considered in the criteria and rules for the safety assessment of probiotics.

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