Copper oxide (CuO) nanosheets synthesized in polyvinylpyrrolidone (PVP) were characterized with respect to antimicrobial activity by quick precipitation method. Different sizes and shapes of CuO nanosheets were obtained by simple variations of PVP concentrations. The x-ray diffraction results revealed the formation of pure-phase CuO with monoclinic structure. Transmission electron microscopy analysis showed that the average ratio of length to width of these nanosheets increased with increasing PVP concentrations. Due to the quantum size effect, CuO nanosheets exhibit a blue shift in the ultraviolet-visible spectra. Field emission scanning electron microscopy results showed that as the concentration of PVP increased, well-defined morphologies were formed on the surface of the products. Energy dispersive analysis of x-ray clearly confirmed the presence of Cu and O with an atomic ratio of 1:1. Fourier transform infrared spectroscopy results showed that C5O in PVP coordinated with CuO and formed a protective layer. The mechanism of the reaction was also discussed. CuO nanosheets in suspension showed activity against a range of bacterial pathogens and fungi with minimum bactericidal concentrations (MBCs) ranging from 100 to 5000 lg/mL. The extent of the inhibition zones and the MBCs was found to be size-dependent.

This study was undertaken to investigate the influence of culture conditions and medium components on production of antibacterial compounds by Serratia sp. WPRA3 (JX020764) which was isolated from marine water of Port Dickson, Malaysia. Biochemical, morphological, and molecular characteristics suggested that the isolate is a new candidate of the Serratia sp. The isolate showed strong antimicrobial activity against fungi, Gram-negative and Gram-positive bacteria. This bacterium exhibited optimum antibacterial compounds production at 28°C, pH 7 and 200 rev/min aeration during 72 h of incubation period. Highest antibacterial activity was obtained when sodium chloride (2%), yeast extract (0.5%), and glucose concentration (0.75%) were used as salt, nitrogen, and carbon sources respectively. Different active fractions were obtained by Thin-Layer Chromatography (TLC) and Flash Column Chromatography (FCC) from ethyl acetate crude extracts namely OCE and RCE in different culture conditions, OCE (pH 5, 200 rev/min) and RCE (pH 7/without aeration). In conclusion, the results suggested different culture conditions have a significant impact on the types of secondary metabolites produced by the bacterium.

The bacteriocin-producing strain Bacillus sp., Sh10, isolated from the marine environment, exhibited a broad spectrum of antimicrobial activity against different food spoilage and human pathogens, with a maximum inhibitory activity against Candida albicans. The inhibitory compound was sensitive to trypsin but resistant to proteinase K, lysozyme, lipase and α-amylase. It was heat-stable and remained its activity after autoclaving. In addition, the antimicrobial substance demonstrated striking stability at low temperatures (4 and -20°C) for up to one year and retained its activity in a wide pH range from 2 to 11. It was also stable and active in the presence of different surfactants, solvents and heavy metals. Analysis of the partially purified bacteriocin by SDS-PAGE showed an apparent molecular weight of ~11 KDa. This study reveals a remarkable potential of this bacteriocin to be used as a food preservative.

Background and Objectives: Biofilm formed by Proteus mirabilis strains is one of the most important medical prob- lems especially in the case of device-related urinary tract infections. This study was conducted to evaluate the bacte- riocin produced by a marine isolate of Bacillus sp. Sh10, for it's in vitro inhibitory activity against pre-formed biofilm and in interference with the biofilm-forming of two biofilm-producing bacteria (P. mirabilis UCa4 and P. mirabilis UCe1). Materials and Methods: Sensitivity of two biofilm-producing bacteria (P. mirabilis UCa4 and P. mirabilis UCe1) to bac- teriocin, was investigated in planktonic and biofilm states by cell viability and crystal violet assay, respectively. Scanning electron microscopy (SEM) was also performed to determine the effect of bacteriocin on the morphology of the cells asso- ciated with biofilm. Results: It was found that bacteriocin possessed bactericidal activity to biofilm-forming isolates in the planktonic state. However, bacteriocin interferes with the formation of biofilms and disrupts established biofilms. Bacteriocin reduced biofilm   50   50   formation in the isolates of P. mirabilis UCa4 and P. mirabilis UCe1 with SMIC   of 32 and 128 μg/mL, desirable SMIC   of   bacteriocin for biofilm disruption were 128 and 256 μg/mL, respectively. The SEM results indicated that bacteriocin affected the cell morphology of biofilm-associated cells. Conclusion: The present findings indicated that bacteriocin from Bacillus sp. Sh10 has bactericidal properties against bio- film-forming isolates of P. mirabilis UCa4 and P. mirabilis UCe1 and has the ability to inhibit the formation of biofilm and disrupt established biofilm.

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