BackgroundIncreasing multidrug-resistance in bacteria resulted in a greater need to find alternative antimicrobial substances that can be used for clinical applications or preservation of food and dairy products. Research on antimicrobial peptides including lipopeptides exhibiting both narrow and broad spectrum inhibition activities is increasing in the recent past. Therefore, the present study was aimed at isolation and characterization of antimicrobial lipopeptide producing bacterial strains from fecal contaminated soil sample.ResultsThe phenotypic and 16S rRNA gene sequence analysis of all isolates identified them as different species of Gram-negative genera Citrobacter and Enterobacter. They exhibited common phenotypic traits like citrate utilization, oxidase negative and facultative anaerobic growth. The HPLC analysis of solvent extracts obtained from cell free fermented broth revealed the presence of multiple antimicrobial lipopeptides. The comprehensive mass spectral analysis (MALDI-TOF MS and GC-MS) of HPLC purified fractions of different isolates revealed that the lipopeptides varied in their molecular weight between (m/z) 607.21 to 1536.16 Da. Isomers of mass ion m/z 984/985 Da was produced by all strains. The 1495 Da lipopeptides produced by strains S-3 and S-11 were fengycin analogues and most active against all strains. While amino acid analysis of lipopeptides suggested most of them had similar composition as in iturins, fengycins, kurstakins and surfactins, differences in their β-hydroxy fatty acid content proposed them to be isoforms of these lipopeptides.ConclusionAlthough antimicrobial producing strains can be used as biocontrol agents in food preservation, strains with ability to produce multiple antimicrobial lipopeptides have potential applications in biotechnology sectors such as pharmaceutical and cosmetic industry. This is the first report on antibacterial lipopeptides production by strains of Citrobacter and Enterobacter.

The growing emergence of antibiotic-resistant bacteria has led to the exploration of naturally occurring defense peptides as antimicrobials. In this study, we found that laterosporulin (LS), a class IId bacteriocin, effectively kills active and nonmultiplying cells of both Gram-positive and Gram-negative bacteria. Fluorescence and electron microscopy suggest that growth inhibition occurs because of increased membrane permeability. The crystal structure of LS at 2.0A resolution reveals an all-b conformation of this peptide, with four b-strands forming a twisted b-sheet. All six intrinsic cysteines are intramolecularly disulfide-bonded, with two disulfides constraining the N terminus of the peptide and the third disulfide crosslinking the extreme C terminus, resulting in the formation of a closed structure. The significance of disulfides in maintaining the in-solution peptide structure was confirmed by CD and fluorescence analyses. Despite a low overall sequence similarity, LS has disulfide connectivity [C I -C V , C II -C IV, and C III -C VI ] like that of b-defensins and a striking architectural similarity with a-defensins. Therefore LS presents a missing link between bacteriocins and mammalian defensins, and is also a potential antimicrobial lead, in particular against nonmultiplying bacteria. DatabaseThe atomic coordinates and the structure factors have been deposited in the Protein Data Bank under accession number 4OZK

Purpose Efficient ethanol production through lignocellulosic biomass hydrolysates could solve energy crisis as it is economically sustainable and ecofriendly. Saccharomyces cerevisiae is the work horse for lignocellulosic bioethanol production at industrial level. But its inability to ferment and utilize xylose limits the overall efficacy of the process. Method Data for the review was selected using different sources, such as Biofuels digest, Statista, International energy agency (IEA). Google scholar was used as a search engine to search literature for yeast metabolic engineering approaches. Keywords used were metabolic engineering of yeast for bioethanol production from lignocellulosic biomass. Result Through these approaches, interconnected pathways can be targeted randomly. Moreover, the improved strains genetic makeup can help us understand the mechanisms involved for this purpose. Conclusion This review discusses all possible approaches for metabolic engineering of yeast. These approaches may reveal unknown hidden mechanisms and construct ways for the researchers to produce novel and modified strains.

A novel, Gram-staining-negative, yellow-coloured, rod-shaped, obligately aerobic, non-motile bacterium, designated strain AK7 T , was isolated from seawater collected on the coast at Visakhapatnam, Andhra Pradesh, India. The predominant fatty acids of the novel strain were iso-C 15 : 0 , iso-C 15 : 0 3-OH, C 16 : 1 v5c, iso-C 17 : 0 3-OH and summed features 3 (C 16 : 1 v7c and/or iso-C 15 : 0 2-OH) and 4 (iso-C 17 : 1 I and/or anteiso-C 17 : 1 B). The major respiratory quinone was MK-7 and the polar lipid profile comprised phosphatidylethanolamine, two unidentified aminolipids and four other unidentified lipids. In phylogenetic analysis based on 16S rRNA gene sequences, strain AK7 T appeared most closely related to Fulvivirga kasyanovii KMM 6220 T (95.9 % sequence similarity), a member of the family Flammeovirgaceae in the phylum Bacteroidetes. The genomic DNA G+C content of strain AK7 T was 55.1 mol%. Based on the morphological, biochemical, physiological, chemotaxonomic and phylogenetic evidence, strain AK7 T represents a novel species of the genus Fulvivirga for which the name Fulvivirga imtechensis sp. nov. is proposed. The type strain is AK7 T (5MTCC 11053 T 5JCM 17390 T ).

BackgroundSpecies of the genus Pediococcus are known to produce antimicrobial peptides such as pediocin-like bacteriocins that contain YGNGVXC as a conserved motif at their N-terminus. Until now, the molecular weight of various bacteriocins produced by different strains of the genus Pediococcus have been found to vary between 2.7 to 4.6 kD. In the present study, we characterized an antimicrobial peptide produced by P. pentosaceus strain IE-3.ResultsAntimicrobial peptide was isolated and purified from the supernatant of P. pentosaceus strain IE-3 grown for 48 h using cation exchange chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC) techniques. While MALDI-TOF MS experiments determined the precise molecular mass of the peptide to be 1701.00 Da, the de novo sequence (APVPFSCTRGCLTHLV) of the peptide revealed no similarity with reported pediocins and did not contain the YGNGVXC conserved motif. Unlike pediocin-like bacteriocins, the low molecular weight peptide (LMW) showed resistance to different proteases. Moreover, peptide treated with reducing agent like dithiothreitol (DTT) exhibited increased activity against both Gram-positive and Gram-negative test strains in comparison to native peptide. However, peptide treated with oxidizing agent such as hydrogen peroxide (H2O2) did not show any antimicrobial activity.ConclusionTo our knowledge this is the lowest molecular weight peptide produced by members of the genus Pediococcus. The low molecular weight peptide shared amino acid arrangement with N-terminal sequence of Class IIa, pediocin-like bacteriocins and showed increased activity under reducing conditions. Antimicrobial peptides active under reduced conditions are valuable for the preservation of processed foods like meat, dairy and canned foods where low redox potential prevails.

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