Browsing by Subject "Antimicrobial"

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Characterization of Bacillus velezensis UTB96, demonstrating improved lipopeptide production compared to the strain B. velezensis FZB42
(2022) Vahidinasab, Maliheh; Adiek, Isabel; Hosseini, Behnoush; Akintayo, Stephen Olusanmi; Abrishamchi, Bahar; Pfannstiel, Jens; Henkel, Marius; Lilge, Lars; Vögele, Ralf ; Hausmann, Rudolf
Bacillus strains can produce various lipopeptides, known for their antifungal properties. This makes them attractive metabolites for applications in agriculture. Therefore, identification of productive wild-type strains is essential for the development of biopesticides. Bacillus velezensis FZB42 is a well-established strain for biocontrol of plant pathogens in agriculture. Here, we characterized an alternative strain, B. velezensis UTB96, that can produce higher amounts of all three major lipopeptide families, namely surfactin, fengycin, and iturin. UTB96 produces iturin A. Furthermore, UTB96 showed superior antifungal activity towards the soybean fungal pathogen Diaporthe longicolla compared to FZB42. Moreover, the additional provision of different amino acids for lipopeptide production in UTB96 was investigated. Lysine and alanine had stimulatory effects on the production of all three lipopeptide families, while supplementation of leucine, valine and isoleucine decreased the lipopeptide bioproduction. Using a 45-litre bioreactor system for upscaling in batch culture, lipopeptide titers of about 140 mg/L surfactin, 620 mg/L iturin A, and 45 mg/L fengycin were achieved. In conclusion, it becomes clear that B. velezensis UTB96 is a promising strain for further research application in the field of agricultural biological controls of fungal diseases.
Charakterisierung der antimikrobiellen Aktivität von High-mobility group box 2
(2013) Küchler, Robert; Wehkamp, Jan
The human body is continuously exposed to an enormous amount of microbes. Especially surfaces like the skin or the gastrointestinal mucosa are in close contact with large numbers of microorganisms, including bacteria, fungi and viruses. A very effective innate immune system protects the intestinal mucosa from an overgrowth of commensal bacteria and penetration by pathogenic microbes. Besides an efficient layer of thick mucus, antimicrobial peptides and proteins (AMPs) which can inhibit the growth of microorganisms or even destroy them are an essential part of the epithelial barrier. In 2009, as a part of my diploma thesis, I could show that high-mobility group box 2 (HMGB2) exhibits antimicrobial activity against E. coli. The aim of this PhD thesis was to characterize and further clarify this new function. HMGB2 was recombinantly expressed and systematically analyzed for antimicrobial activity. Notably, several gram-negative and gram-positive bacteria of the normal gut flora were critically affected by HMGB2. In addition, bactericidal properties against the pathogenic bacterial strain Staphylococcus aureus were detected via electron microscopic analysis. Furthermore potential influences of intestinal environmental conditions on the activity of HMGB2 were investigated. Changes in the pH or the generation of a reducing environment altered the activity of the protein only to a small amount. To localize the part of HMGB2 which is essential for its antimicrobial activity, three peptides which represent three regions of the protein were recombinantly expressed. An activity screening with the three peptides showed that the two DNA-binding-domains HMG-Box A and B are crucial for the antimicrobial effects. An expression study showed that HMGB2 is present in all analyzed stomach and intestinal sections. In addition, the expression in patients with inflammatory bowel disease (IBD) was studied. No significant differences between patients with Crohn?s disease, ulcerative colitis and unaffected controls were detected. However, the examination of stool from individuals of these three groups suggests that HMGB2 might be useful as a new marker for intestinal inflammation. In summary, HMGB2 exhibits antimicrobial activity against various commensal bacteria of the normal gut flora and is expressed in all analyzed gastrointestinal tract sections. HMGB2 is part of the intestinal barrier and protects, together with other AMPs, the intestine from microorganisms.