The rapid response of a smart material surface to external stimuli is critical for application to cell-based biochips. The sharp and controllable phase transition of elastin-like polypeptide (ELP) enabled reversible cell adhesion on the surface by changing the temperature or salt concentration in the system. First, ELP micropatterns were prepared on a glass surface modified into aldehyde. The lysine-containing ELP (ELP-K) was genetically synthesized from E. coli for conjugation with the aldehyde on the glass surface. The phase transition of ELP was monitored in PBS and cell culture media using UV-visible spectroscopy, and a significant difference in transition temperature (Tt) was observed between the two solution systems. The micropatterning of ELP on the glass surface was performed by microcontact printing a removable polymeric template on the aldehyde-glass followed by incubation in ELP-K aqueous solution. The ELP micropatterns were imaged with atomic force microscopy and showed a monolayer thickness of approximately 4 nm. Imaging from time-of-flight secondary ion mass spectroscopy confirmed that the ELP molecules were successfully immobilized on the highly resolved micropatterns. Cell attachment and detachment could be reversibly controlled on the ELP surfaces by external stimuli. The hydrophobic phase above Tt resulted in the adhesion of fibroblasts, while the detachment of cells was induced by lowering the incubation temperature below Tt. The smart properties of ELP were reliable and reproducible, demonstrating potential applications in cell-based microdevices.

We characterized two new streptogramin A resistance genes from quinupristin-dalfopristin-resistant Enterococcus faecium JS79, which was selected from 79 E. faecium isolates lacking known genes encoding streptogramin A acetyltransferase. A 5,650-bp fragment of HindIII-digested plasmid DNA from E. faecium JS79 was cloned and sequenced. The fragment contained two open reading frames carrying resistance genes related to streptogramin A, namely, genes for an acetyltransferase and an ATP efflux pump. The first open reading frame comprised 648 bp encoding 216 amino acids with a predicted left-handed parallel ␤-helix domain structure; this new gene was designated vatG. The second open reading frame consisted of 1,575 bp encoding 525 amino acids with two predicted ATPase binding cassette transporters comprised of Walker A, Walker B, and LSSG motifs; this gene was designated vgaD. vgaD is located 65 bp upstream from vatG, was detected together with vatG in 12 of 179 quinupristin-dalfopristin-resistant E. faecium isolates, and was located on the same plasmid. Also, the 5.6-kb HindIII-digested fragment which was observed in JS79 was detected in nine vgaD-and vatG-containing E. faecium isolates by Southern hybridization. Therefore, it was expected that these two genes were strongly correlated with each other and that they may be composed of a transposon. Importantly, vgaD is the first identified ABC transporter conferring resistance to streptogramin A in E. faecium. Pulsed-field gel electrophoresis patterns and sequence types of vgaD-and vatG-containing E. faecium isolates differed for isolates from humans and nonhumans.

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