Journal of Microbiology

Journal Article

Phenotypic and genotypic correlates of daptomycin-resistant methicillin-susceptible Staphylococcus aureus clinical isolates: Kyoung-Mi Kang , Nagendra N. Mishra , Kun Taek Park , Gi-Yong Lee , Yong Ho Park , Arnold S. Bayer , Soo-Jin Yang; J. Microbiol. 2017;55(2):153-159. Published online January 26, 2017; DOI: https://doi.org/10.1007/s12275-017-6509-1

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Abstract: Daptomycin (DAP) has potent activity in vitro and in vivo against both methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains. DAP-resistance (DAP-R) in S. aureus has been mainly observed in MRSA strains, and has been linked to single nucleotide polymorphisms (SNPs) within the mprF gene leading to altered cell membrane (CM) phospholipid (PL) profiles, enhanced positive surface charge, and changes in CM fluidity. The current study was designed to delineate whether these same genotypic and phenotypic perturbations are demonstrated in clinically-derived DAP-R MSSA strains. We used three isogenic DAP-susceptible (DAP-S)/DAP-R strainpairs and compared: (i) presence of mprF SNPs, (ii) temporal expression profiles of the two key determinants (mprF and dltABCD) of net positive surface charge, (iii) increased production of mprF-dependent lysinylated-phosphatidylglycerol (L-PG), (iv) positive surface charge assays, and (v) susceptibility to cationic host defense peptides (HDPs) of neutrophil and platelet origins. Similar to prior data in MRSA, DAP-R (vs DAP-S) MSSA strains exhibited hallmark hot-spot SNPs in mprF, enhanced and dysregulated expression of both mprF and dltA, L-PG overproduction, HDP resistance and enhanced positive surface charge profiles. However, in contrast to most DAP-R MRSA strains, there were no changes in CM fluidity seen. Thus, charge repulsion via mprF- and dlt-mediated enhancement of positive surface charge may be the main mechanism to explain DAP-R in MSSA strains.

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

NOTE] Next-Generation Sequencing-Based Genome-Wide Mutation Analysis of L-Lysine-Producing Corynebacterium glutamicum ATCC 21300 Strain: Chang-Soo Lee , Jae-Young Nam , Eun-Suk Son , O-chul Kwon , Woorijarang Han , Jae-Yong Cho , Young-Jin Park; J. Microbiol. 2012;50(5):860-863. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2109-2

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Abstract: In order to identify single nucleotide polymorphism and insertion/deletion mutations, we performed whole-genome re-sequencing of the enhanced L-lysine-producing Corynebacterium glutamicum ATCC 21300 strain. In total, 142 single nucleotide polymorphisms and 477 insertion/deletion mutations were identified in the ATCC 21300 strain when compared to 3,434 predicted genes of the wild-type C. glutamicum ATCC 13032 strain. Among them, 110 transitions and 29 transversions of single nucleotide polymorphisms were found from genes of the ATCC 21300 strain. In addition, 11 genes, involved in the L-lysine biosynthetic pathway and central carbohydrate metabolism, contained mutations including single nucleotide polymorphisms and insertions/deletions. Interestingly, RT-PCR analysis of these 11 genes indicated that they were normally expressed in the ATCC 21300 strain. This information of genome-wide gene-associated variations will be useful for genome breeding of C. glutamicum in order to develop an industrial amino acidproducing strain with minimal mutation.

Characterization of a Baculovirus Newly Isolated from the Tea Slug Moth, Iragoidae fasciata: Li-Rong Yang , Xiao Qiang , Bao-Qin Zhang , Mei-Jun Tang , Chuan-Xi Zhang; J. Microbiol. 2009;47(2):208-213. Published online May 2, 2009; DOI: https://doi.org/10.1007/s12275-008-0253-5

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Abstract: The tea slug moth Iragoidae fasciata (Lepidoptera, Eucleidae) is one of the main insect pests that attack tea bushes. A new nucleopolyhedrovirus (NPV) called Iragoidae fasciata NPV (IrfaNPV) was recently isolated from diseased larvae. An 11,626 bp fragment of the viral genomic DNA containing the polyhedrin gene and other 12 genes was cloned and sequenced. Gene comparison and phylogenetic analysis showed that IrfaNPV is a member of the Group I NPVs. However, the genomic organization of IrfaNPV is highly distinct. In addition, electron microscopy analysis showed that IrfaNPV is a single nucleocapsid NPV (SNPV). An inoculation assay showed that IrfaNPV is semi-permissive in the Trichoplusia ni cell line Tn-5B1-4. Bioassays on lethal concentration (LC50) and lethal time (LT50) were conducted to test the susceptibility of I. fasciata larvae to the virus.

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