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Antimicrobial peptides are components of both vertebrate and invertebrate innate immune systems that are expressed in response to exposure to bacterial antigens. Naturally occurring antimicrobial peptides from evolutionarily ancient species have been extensively studied and are being developed as potential therapeutics against antibiotic resistant microorganisms. In this study, a putative Cimex lectularius (bedbug, CL) defensin is characterized for its effectiveness against human skin flora including Gram-negative and Gram-positive bacteria. The bedbug defensin (CL-defensin), belonging to family of insect defensins, is predicted to have a characteristic N-terminal loop, an α-helix, and an antiparallel β-sheet, which was supported by circular dichroism spectroscopy. The defensin was shown to be antimicrobial against Gram-positive bacteria commonly found on human skin (Micrococcus luteus, Corynebacterium renale, Staphylococcus aureus and Staphylococcus epidermidis); however, it was ineffective against common skin Gram-negative bacteria (Pseudomonas aeruginosa and Acinetobacter baumannii) under low-salt conditions. CL-defensin was also effective against M. luteus and C. renale in high-salt (MIC) conditions. Our studies indicate that CL-defensin functions by depolarization and pore-formation in the bacterial cytoplasmic membrane.

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7Our long-term goal is to identify new antimicrobial peptides that might be effective 8 against pneumonic Francisella infection in mice. Previously, our group searched the peptidome 9 of the American alligator for novel cationic antimicrobial peptides and identified a naturally-10 occurring C-terminal fragment of apolipoprotein C-1, which we called Apo6. This peptide was 11 found to have antibacterial activity against the ESKAPE pathogens, including those exhibiting 12 multi-drug resistance. In this work, we tested Apo6 and synthetic derivatives for antibacterial 13 activity against Francisella tularensis including the virulent strain F. tularensis SchuS4.14 Francisella is inherently highly resistant to the cyclic peptide polymyxin antibiotics and beta-15 lactam antibiotics. We found that our synthetic peptide derivatives (called GATR peptides), 16 designed with increased hydrophobicity and charge, had generally stronger in vitro antimicrobial 17 activity against Francisella than the parent peptide Apo6. The GATR peptides had a greater 18 effect on the bacterial membrane than the Apo6 peptide and were able to bind Francisella LPS, 19 suggesting their mechanism of action against Francisella. Cytotoxicity experiments showed low 20 cytotoxicity for most of the GATR peptides, and whole organism toxicity studies in the 21 waxworm allowed us to down-select to two our lead peptides, GATR-3 and GATR-6. These 22 peptides were tested in a murine pulmonary tularemia model. We found that the GATR-3 peptide 23 rescued 50-60% of mice from lethal tularemia infection when administered systemically through 24 2 the intraperitoneal route. This peptide is a candidate for further pre-clinical studies for a potential 25 peptide-based approach to tularemia. 26

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In today's communication world, data sharing and transfer is increasing exponentially. The threat of an attacker accessing secret information has been an ever existing concern for the data communication experts. Cryptography and steganography are the most widely used techniques to overcome this threat. Steganography is the art of hiding the existence of the communication message before sending it to the receiver. In this paper it is proposed to use Discrete Fractional Fourier transform (DFrFT) as basic tool in image processing for data hiding technique called steganography. A comparative study of steganography in spatial domain and frequency domain based on Discrete Fourier transform (DFT), Discrete cosine transform (DCT), Discrete Fractional Fourier transform (DFrFT) is made. Peak signal to noise ratio (PSNR) and Mean square error (MSE) of cover image and stego image are used as performance index and it is found that among three frequency domain methods DFrFT based steganography gives better results in terms of PSNR and MSE and also provide more security for communication. MATLAB platform is used for simulation, results show that the proposed technique provides more security, better PSNR and lower MSE of cover image and stego image. General TermsImage, Peak signal to noise ratio, Mean square error.