Background Acinetobacter baumannii is known for its ability to develop resistance to the major groups of antibiotics, form biofilms, and survive for long periods in hospital environments. The prevalence of infections caused by multidrug-resistant A. baumannii is a significant problem for the modern health care system, and application of lytic bacteriophages for controlling this pathogen may become a solution.Methodology/Principal FindingsIn this study, using atomic force microscopy (AFM) and microbiological assessment we have investigated A. baumannii bacteriophage AP22, which has been recently described. AFM has revealed the morphology of bacteriophage AP22, adsorbed on the surfaces of mica, graphite and host bacterial cells. Besides, morphological changes of bacteriophage AP22-infected A. baumannii cells were characterized at different stages of the lytic cycle, from phage adsorption to the cell lysis. The phage latent period, estimated from AFM was in good agreement with that obtained by microbiological methods (40 min). Bacteriophage AP22, whose head diameter is 62±1 nm and tail length is 88±9 nm, was shown to disperse A. baumannii aggregates and adsorb to the bacterial surface right from the first minute of their mutual incubation at 37°C.Conclusions/SignificanceHigh rate of bacteriophage AP22 specific adsorption and its ability to disperse bacterial aggregates make this phage very promising for biomedical antimicrobial applications. Complementing microbiological results with AFM data, we demonstrate an effective approach, which allows not only comparing independently obtained characteristics of the lytic cycle but also visualizing the infection process.

Morphological changes in an experimental purulent wound in a rat model is studied for application of surgical gauze with immobilized enzymes: trypsin, lysozyme, coUitin, or co-immobilized trypsin and lysozyme. Comparison of the times of wound cleansing and healing shows that immobilized enzymes are more effective than native preparations, and the therapeutic effect of gauze with the enzyme complex is higher than that of gauze with individually immobilized enzymes. Morphological studies confirm that immobilized trypsin-lysozyme complex and coilitin are the most efficient in hastening and potentiating reparative processes in a purulent wound.

No abstract

Atomic force microscopy (AFM) and single molecule force spectroscopy (SMFS) have been used to characterize the structure and interactions of clathrin triskelia, which are principal components of the protein coats surrounding certain plasma-membrane-derived vesicles involved in receptor-mediated endocytosis. Time sequence AFM images of wet triskelia resting on mica surfaces clearly demonstrate conformational fluctuations within individual triskelia, further strengthening indirect inferences from earlier AFM and electron microscopy of dried protein samples. Related studies using SMFS reveal a series of internal energetic barriers that characterize triskelion heavy chain domain unfolding. Protein sequence and force spectrum alignment analyses suggest that these features correspond to the unfolding of numerous alpha-helix hairpins of ca. 30 amino acid residues and cooperative unraveling of several hairpin domains up to the size of the known repeating motif of ca.145 amino acid residues. The dynamic domain rupture forces range from 10s of pN to over 500 pN, increasing continuously as the stretching loading rate increases, in accordance with the Bell model. To further understand the molecular functionality of clathrin, specific clathrin-substrate and clathrin-tip attachments via antibodies are being explored in ongoing investigations.

No abstract