Purification and partial characterization of bacillocin 490, a novel bacteriocin produced by a thermophilic strain of Bacillus licheniformis

BACKGROUND: Applications of bacteriocins as food preservatives have been so far limited, principally because of their low antimicrobial activity in foods. Nisin is the only bacteriocin of significant use, but applications are restricted principally because of its very low activity at neutral or alkaline pH. Thus the isolation of new bacteriocins active in foods is desirable. RESULTS: We isolated a Bacillus licheniformis thermophilic strain producing a bacteriocin with some novel features, named here bacillocin 490. This bacteriocin was inactivated by pronase E and proteinase K and was active against closely related Bacillus spp. both in aerobic and in anaerobic conditions. Bactericidal activity was kept during storage at 4°C and was remarkably stable in a wide pH range. The bacteriocin was partially purified by elution after adhesion to cells of the food-isolated strain Bacillus smithii and had a rather low mass (2 KDa). Antimicrobial activity against B. smithii was observed also when this organism was grown in water buffalo milk. CONCLUSIONS: Bacillocin 490 is a novel candidate as a food anti-microbial agent since it displays its activity in milk, is stable to heat treatment and during storage, is active in a wide pH range and has bactericidal activity also at high temperature. These features may allow the use of bacillocin 490 during processes performed at high temperature and as a complementary antimicrobial agent of nisin against some Bacillus spp. in non-acidic foods. The small size suggests its use on solid foods

Transcriptional analysis of the recA gene of Streptococcus thermophilus

BACKGROUND: RecA is a highly conserved prokaryotic protein that not only plays several important roles connected to DNA metabolism but also affects the cell response to various stress conditions. While RecA is highly conserved, the mechanism of transcriptional regulation of its structural gene is less conserved. In Escherichia coli the LexA protein acts as a recA repressor and is able, in response to DNA damage, of RecA-promoted self-cleavage, thus allowing recA transcription. The LexA paradigm, although confirmed in a wide number of cases, is not universally valid. In some cases LexA does not control recA transcription while in other RecA-containing bacteria a LexA homologue is not present. RESULTS: We have studied the recA transcriptional regulation in S. thermophilus, a bacterium that does not contain a LexA homologue. We have characterized the promoter region of the gene and observed that its expression is strongly induced by DNA damage. The analysis of deletion mutants and of translational gene fusions showed that a DNA region of 83 base pairs, containg the recA promoter and the transcriptional start site, is sufficient to ensure normal expression of the gene. Unlike LexA of E. coli, the factor controlling recA expression in S. thermophilus acts in a RecA-independent way since recA induction was observed in a strain carrying a recA null mutation. CONCLUSION: In S. thermophilus, as in many other bacteria,recA expression is strongly induced by DNA damage, however, in this organism expression of the gene is controlled by a factor different from those well characterized in other bacteria. A small DNA region extending from 62 base pairs upstream of the recA transcriptional start site to 21 base pairs downstream of it carries all the information needed for normal regulation of the S. thermophilus recA gene

Expression of the heat shock gene clpL of Streptococcus thermophilus is induced by both heat and cold shock

BACKGROUND: Heat and cold shock response are normally considered as independent phenomena. A small amount of evidence suggests instead that interactions may exist between them in two Lactococcus strains. RESULTS: We show the occurrence of molecular relationships between the mechanisms of cold and heat adaptations in Streptococcus thermophilus, a lactic acid bacterium widely used in dairy fermentation, where it undergoes both types of stress. We observed that cryotolerance is increased when cells are pre-incubated at high temperature. In addition, the production of a protein, identified as ClpL, a member of the heat-shock ATPase family Clp A/B, is induced at both high and low temperature. A knock-out clpL mutant is deficient in both heat and cold tolerance. However lack of production of this protein does not abolish the positive effect of heat pre-treatment towards cryotolerance. CONCLUSION: Dual induction of ClpL by cold and heat exposure of cells and reduced tolerance to both temperature shocks in a clpL mutant indicates that the two stress responses are correlated in S. thermophilus. However this protein is not responsible by itself for cryotolerance of cells pre-treated at high temperature, indicating that ClpL is necessary for the two phenomena, but does not account by itself for the relationships between them

Anti-biofilm activity of an exopolysaccharide from a sponge-associated strain of Bacillus licheniformis

<p>Abstract</p> <p>Background</p> <p>Secondary metabolites ranging from furanone to exo-polysaccharides have been suggested to have anti-biofilm activity in various recent studies. Among these, <it>Escherichia coli </it>group II capsular polysaccharides were shown to inhibit biofilm formation of a wide range of organisms and more recently marine <it>Vibrio </it>sp. were found to secrete complex exopolysaccharides having the potential for broad-spectrum biofilm inhibition and disruption.</p> <p>Results</p> <p>In this study we report that a newly identified ca. 1800 kDa polysaccharide having simple monomeric units of α-D-galactopyranosyl-(1→2)-glycerol-phosphate exerts an anti-biofilm activity against a number of both pathogenic and non-pathogenic strains without bactericidal effects. This polysaccharide was extracted from a <it>Bacillus licheniformis </it>strain associated with the marine organism <it>Spongia officinalis</it>. The mechanism of action of this compound is most likely independent from quorum sensing, as its structure is unrelated to any of the so far known quorum sensing molecules. In our experiments we also found that treatment of abiotic surfaces with our polysaccharide reduced the initial adhesion and biofilm development of strains such as <it>Escherichia coli </it>PHL628 and <it>Pseudomonas fluorescens</it>.</p> <p>Conclusion</p> <p>The polysaccharide isolated from sponge-associated <it>B. licheniformis </it>has several features that provide a tool for better exploration of novel anti-biofilm compounds. Inhibiting biofilm formation of a wide range of bacteria without affecting their growth appears to represent a special feature of the polysaccharide described in this report. Further research on such surface-active compounds might help developing new classes of anti-biofilm molecules with broad spectrum activity and more in general will allow exploring of new functions for bacterial polysaccharides in the environment.</p

The scientific impact of microbial cell factories

Abstract in dt. Sprache nicht vorhandenAbstract not available(VLID)90458

Expression and display of UreA of Helicobacter acinonychis on the surface of Bacillus subtilis spores

<p>Abstract</p> <p>Background</p> <p>The bacterial endospore (spore) has recently been proposed as a new surface display system. Antigens and enzymes have been successfully exposed on the surface layers of the <it>Bacillus subtilis </it>spore, but only in a few cases the efficiency of expression and the effective surface display and have been determined. We used this heterologous expression system to produce the A subunit of the urease of the animal pathogen <it>Helicobater acinonychis</it>. Ureases are multi-subunit enzymes with a central role in the virulence of various bacterial pathogens and necessary for colonization of the gastric mucosa by the human pathogen <it>H. pylori</it>. The urease subunit UreA has been recognized as a major antigen, able to induce high levels of protection against challenge infections.</p> <p>Results</p> <p>We expressed UreA from <it>H. acinonychis </it>on the <it>B. subtilis </it>spore coat by using three different spore coat proteins as carriers and compared the efficiency of surface expression and surface display obtained with the three carriers. A combination of western-, dot-blot and immunofluorescence microscopy allowed us to conclude that, when fused to CotB, UreA is displayed on the spore surface (ca. 1 × 10³recombinant molecules per spore), whereas when fused to CotC, although most efficiently expressed (7-15 × 10³recombinant molecules per spore) and located in the coat layer, it is not displayed on the surface. Experiments with CotG gave results similar to those with CotC, but the CotG-UreA recombinant protein appeared to be partially processed.</p> <p>Conclusion</p> <p>UreA was efficiently expressed on the spore coat of <it>B. subtilis </it>when fused to CotB, CotC or CotG. Of these three coat proteins CotC allows the highest efficiency of expression, whereas CotB is the most appropriate for the display of heterologous proteins on the spore surface.</p

Biotecnologia: una grande avventura dell'uomo dalla preistoria ad oggi

Le origini delle biotecnologie, alla luce dei testi scientifici dell'antichità e delle pitture murali delle tomb