Introduction: Application of lactic acid bacteria for synthesis of silver (AG) nanoparticles (NPs) could be a good ecological friendly alternative to chemical and physical methods. The objective of this study was to investigate the biosynthesis of silver NPs using Lactobacillus strains and to compare their monosaccharide composition of capsular exopolysaccharides and the antibacterial activity of synthesized nanoparticles. Methods: The washed cells of 22 Lactobacillus strains were used for in vitro silver nanoparticle biosynthesis from silver nitrate solution. The NPs formation was confirmed by UV-visible spectroscopy and transmission electron microscopy (TEM) analysis. TEM micrographs were used for the evaluation of NPs size. The monosaccharide composition of capsular exopolysaccharides was determined using GC/MS analysis. The antimicrobial activity was determined by agar well diffusion assay. Results: The capsular layers of Lactobacillus strains contained heteropolysaccharides that were composed mostly of glucose, mannose, galactose and rhamnose in a different molar ratio. It was found that Ag NPs with large size (30.65 ± 5.81 nm) obtained from L. acidophilus 58p were more active against S. epidermidis, E. coli, K. pneumonia,S. flexneri and S. sonnei compared with Ag NPs from L. plantarum 92T (19.92 ± 3.4 nm). Conclusion: The size and antibacterial activities of Ag NPs were strain-dependent and such characteristics may be due to the capsular biopolymer composition of Lactobacillus strains used for Ag NPs synthesis.

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RB43-related bacteriophages have a specific genome type that clearly distinguishes them from other T4-like viruses. Here, we present the complete genome sequence of a new virulent phage, Lw1, isolated as an Escherichia coli BL21(DE3) contaminant. Lw1 shares an RB43-like genome organization, but it does not contain putative AP2-domain endonuclease genes.

Short-chain fatty acids (SCFAs) T he interchange of low molecular weight metabolites between gut microorganisms and macroorganism have attracted a lot of attention during last years [1][2][3]. The gut microbiota affects predominantly host physiology by the production of short-chain fatty acids (SCFAs). SCFAs are saturated aliphatic organic acids that consist of one to six carbons of which acetate (C2), propionate (C3), and butyrate (C4) are most abundant (≥95%). Acetate, propionate, and butyrate are present in an approximate molar ratio of 60:20:20 in the colon and stool [4]. Depending on the diet, the total maximum concentration of SCFAs decreases from 70 to 140 mM in the proximal colon from 20 to 70 mM in the distal colon [5].These metabolites, especially butyrate, serve as an important source of energy for the intestinal epithelial cells, providing about 60-70% of their ener gy demand. Colonocytes from germ-free mice are in an energy-deprived state and exhibit decreased expression of enzymes that catalyze key steps in intermediary metabolism including the tricarboxylic acid cycle. Consequently, there is a marked decrease in NADH/NAD + , oxidative phosphorylation, and ATP levels, that results in AMP-activated protein kinase activation, cyclin-dependent kinase inhibitor 1B phosphorylation and autophagy. When butyrate is added to germ-free colonocytes, it rescues their deficit in mitochondrial respiration and prevents them from undergoing autophagy [6].

The phenotypic, chemotaxonomic and genetic peculiarities of 5 deep strains of Alteromonas macleodii (isolated from Adriatic and Ionian Sea water from a depth of 1,000-3,500 m) and 5 strains of the same species isolated from the surface layer of Aegean, Andaman, Black Sea and Atlantic Ocean water near the British shore have been studied. Electron microscopy has shown that the deep strains' cells were, on average, two times longer (2.1±0.2×0.7±0.1 µm) than the surface strains' (1.1±0.1×0.6±0.1 µm). Using fatty acid analysis (particularly the mono-unsaturated C16:1 and C18:1 fatty acids contents) the deep and surface isolates were clearly separated into two clusters. Distinctions between them were also found in different lectin binding capacity, which is probably determined by the structure of their extracellular polysaccharide matrix. Analysis of the results of PCR with primers to repeated nucleotide sequences revealed a higher level of genetic polymorphism in surface strains in comparison with the deep isolates. This division was confirmed by the cluster analysis method though it was not as clear as in the fatty acids analysis. The described peculiarities are probably reflective of specific conditions in which A. macleodii strains live on the surface or in the depth of the world's oceans.

The methodological procedure provides the detection of the relatively high Na

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