1,721,036 research outputs found
Growth parameters influencing the production of Lactobacillus rhamnosus bacteriocins ST461BZ and ST462BZ
No full textBacteriocins ST461BZ (2.8 kDa) and ST462BZ (8.0 kDa), produced by two strains of Lactobacillus rhamnosus isolated from boza, a beverage produced from different cereals by yeast and lactic acid bacteria, inhibits the growth of Lactobacillus casei, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa. Maximum bacteriocin activity (12 800 AU/ml) was recorded after 15 h in MRS broth. No increase in the production of the two bacteriocins was recorded in MRS broth supplemented with tryptone (20 g/l), D-glucose (20 g/l) and sucrose (20 g/l). Glycerol at 1 g/l and higher inhibited the production of both bacteriocins. Bacteriocin ST461BZ production increased to 25 600 AU/ml in MRS broth supplemented with 20 g/l or 50 g/l K2HPO4. Bacteriocin ST462BZ activity increased to 51 200 AU/ml in MRS broth supplemented with 20 g/l to 100 g/l KH2PO4.Articl
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mode of action of lipid II-targeting lantibiotics
No full textThe antimicrobial action of bacteriocins from Gram-positive bacteria is based on interaction with the cytoplasmic membrane of sensitive bacteria. Models based on studies with artificial membrane systems propose that nisin forms wedge-like poration complexes in the membrane by electrostatic interaction between the positively charged C terminus of the peptide and anionic membrane phospholipids. Nisin can also permeabilise membranes via a targeted mechanism by using lipid II, the bactoprenol-bound precursor of the bacterial cell wall, as a docking molecule. Another consequence of binding with lipid II is the inhibition of peptidoglycan biosynthesis. Mersacidine and actagardine also form a complex with lipid II, but binding only blocks the incorporation of lipid II into peptidoglycan, resulting in slow cell lysis rather than pore formation. Both peptides share a conserved sequence motif with plantaricin C and pediocin PD-1, which is most probably involved in the binding of these bacteriocins to lipid II. Although pediocin PD-1 and plantaricin C may inhibit peptidoglycan biosynthesis, pore formation is rather due to electrostatic interaction between the positively charged unbridged N-terminus and anionic phospholipids in the cytoplasmic membrane of sensitive cells. In the light of increased antibiotic resistance, this review focuses on the mode of action of lantibiotics that involve lipid II, possible candidates for the development of new-generation novel antibiotic drugs. © 2005 Elsevier B.V. All rights reserved.Revie
Effect of modified MRS medium on production and purification of antimicrobial peptide ST4SA produced by Enterococcus mundtii
No full textPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]
Evaluation of lactic acid bacteria from kefir, molasses and olive brine as possible probiotics based on physiological properties
No full textA combination of eight strains comprising of Lactobacillus plantarum, Enterococcus faecium and Leuconostoc mesenteroides subsp. mesenteroides isolated from molasses, olives, beer and kefir were studied for growth at low pH and ox-bile resistance. pH neutralised cell-free supernatants from 24-h-old cultures inhibited the growth of Enterococcus faecium, Lactobacillus sakei, Lactococcus lactis subsp. lactis, Listeria innocua and Listeria ivanovii subsp. ivanovii. Good growth was recorded in MRS broth supplemented with 0.3% (w/v) ox-bile. Lactobacillus plantarum ST28MS and ST26MS, Enterococcus faecium ST311LD and Leuconostoc mesenteroides subsp. mesenteroides ST33LD grew well in the presence of 0.6% (w/v) ox-bile. All eight strains grew well in MRS broth adjusted to pH 7.0. Good growth of Enterococcus faecium ST311LD, Leuconostoc mesenteroides subsp. mesenteroides ST33LD and Lactobacillus plantarum 423 was recorded in MRS broth with an initial pH of 4.0. Auto cell-aggregation ranged from 74.3% for Lactobacillus plantarum ST23LD to 95.4% for Lactobacillus plantarum ST28MS. Different levels of co-aggregation were recorded between the eight strains and Enterococcus faecium HKLHS, Lactobacillus sakei DSM 20017, Lactococcus lactis subsp. lactis HV219, Listeria innocua LMG 13568 and UWC N27, and Listeria ivanovii subsp. ivanovii ATCC 19119. Growth of the eight strains was inhibited by several antibiotics and anti-inflammatory medicaments containing ibuprofen, hydrochlorothiaziden and thioridazine hydrochlorid. Sodium diclofenac inhibited the growth of Lactobacillus plantarum ST8KF and ST341LD, Enterococcus faecium ST311LD and Leuconostoc mesenteroides subsp. mesenteroides ST33LD. Dimenhydrinate inhibited the growth of only Lactobacillus plantarum ST8KF. Adherence to Caco-2 cells ranged from 8.0 to 1.3%. All eight strains contain the Mub, MapA and EF-Tu genes, as determined by amplification with gene-specific primers.Articl
Partial characterisation of two bacteriocins produced by Lactobacillus paracasei subsp. paracasei ST242BZ and ST284BZ and the effect of medium components on their production
No full textThe influence of medium components on production of bacteriocins ST242BZ (10.0 kDa) and ST284BZ (3.5 kDa) by Lactobacillus paracasei subsp. paracasei ST242BZ and ST284BZ have been studied. Growth in MRS broth (pH of 6.5) yielded bacteriocin levels of 12800 AU/ml. Modified MRS with tryptone as the only nitrogen source, MRS supplemented with KH2PO4 (10-100 g/l), or MRS supplemented with thiamine increased bacteriocin ST242BZ production to 25600 AU/ml. Tryptone, combinations of tryptone, meat extract and yeast extract, or thiamine did not increase bacteriocin ST284BZ production. However, MRS supplemented with K2HPO4 (50-100 g/l) increased bacteriocin ST284BZ production up to 25600 AU/ml. Our results suggest that production of bacteriocins ST242BZ and ST284BZ are stimulated by potassium ions.Articl
Production of bacteriocin ST33LD, produced by Leuconostoc mesenteroides subsp. mesenteroides, as recorded in the presence of different medium components
No full textBacteriocin ST33LD, produced by Leuconostoc mesenteroides subsp. mesenteroides, is approximately 2.7 kDa in size and inhibits Enterococcus faecalis, Escherichia coli, Lactobacillus casei and Pseudomonas aeruginosa. Good growth was recorded in the presence of 10% (w/v) soy milk or 10% (w/v) molasses, but there was no bacteriocin production. Growth in MRS broth adjusted to pH 4.5 yielded low bacteriocin levels (800 AU/ml). However, the same medium adjusted to pH 5.0, 5.5 and 6.5, respectively, yielded 3200 AU/ml. Tween 80 decreased bacteriocin production by more than 50%. Growth in the presence of tryptone yielded maximal activity (12,800 AU/ml), whereas different combinations of tryptone, meat extract and yeast extract produced activity levels of 1600 AU/ml and less. Growth in the presence of 2.0% (w/v) sucrose, or maltose, yielded much higher levels of bacteriocin activity (12,800 AU/ml) compared to growth in the presence of 2.0% (w/v) glucose or lactose (6400 AU/ml). Lower yields were also recorded in the presence of fructose and mannose. KH 2PO4 at 10.0% (w/v) stimulated bacteriocin production. Glycerol concentrations of 0.5% (w/v) and higher (up to 5.0%, w/v) repressed bacteriocin production by 50%. The addition of cyanocobalamin, thiamine and L-ascorbic acid to MRS broth (1.0 ppm) yielded 12,800 AU/ml bacteriocin, whereas the addition of DL-6,8-thioctic acid yielded only 6 400 AU/ml. © Springer 2005.Articl
Effect of medium components on bacteriocin production by Lactobacillus pentosus ST151BR, a strain isolated from beer produced by the fermentation of maize, barley and soy flour
No full textLactobacillus pentosus ST151BR, isolated from home-brewed beer, produces a 3.0 kDa antibacterial peptide (bacteriocin ST151BR) active against Lactobacillus casei, Lactobacillus sakei, Pseudomonas aeruginosa, Enterococcus faecalis and Escherichia coli. Treatment with Proteinase K or Pronase resulted in loss of activity. Bacteriocin levels of 6400 AU/ml were recorded in MRSbb (De Man-Rogosa-Sharpe broth without Tween 80) at pH 5.5, 6.0 and 6.5. The same growth conditions at pH 4.5 yielded only 1600 AU/ml bacteriocin. Inclusion of Tween 80 in the growth medium reduced bacteriocin production by more than 50%. Growth in the presence of tryptone or tryptone plus meat extract stimulated bacteriocin production, whereas much lower activity was recorded when the bacteria were grown in the presence of meat extract, yeast extract, tryptone plus yeast extract, meat extract plus yeast extract, or a combination of tryptone, meat extract and yeast extract. MRSbb supplemented with maltose, lactose or mannose (2.0%, w/v) yielded bacteriocin levels of 6400 AU/ml. Sucrose or fructose at these concentrations reduced the activity by 50 and 75%, respectively. Growth in the presence of 4.0% (w/v) glucose resulted in 50% activity loss. Glycerol levels as low as 0.1% (w/v) repressed bacteriocin production. Addition of cyanocobalamin, ascorbic acid, thiamine and thioctic acid (1.0 mg/l) to the growth medium did not lead to an increase in bacteriocin production.Articl
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