Suicin 90-1330 from a Nonvirulent Strain of Streptococcus suis: a Nisin-Related Lantibiotic Active on Gram-Positive Swine Pathogens

Streptococcus suis serotype 2 is known to cause severe infections (meningitis, endocarditis, and septicemia) in pigs and is considered an emerging zoonotic agent. Antibiotics have long been used in the swine industry for disease treatment/prevention and growth promoters. This pattern of utilization resulted in the spread of antibiotic resistance in S. suis worldwide. Interestingly, pigs may harbor S. suis in their tonsils without developing diseases, while North American strains belonging to the sequence type 28 (ST28) are nonvirulent in animal models. Consequently, the aim of this study was to purify and characterize a bacteriocin produced by a nonvirulent strain of S. suis serotype 2, with a view to a potential therapeutic and preventive application. S. suis 90-1330 belonging to ST28 and previously shown to be nonvirulent in an animal model exhibited antibacterial activity toward all S. suis pathogenic isolates tested. The bacteriocin produced by this strain was purified to homogeneity by cationic exchange and reversed-phase fast protein liquid chromatography. Given its properties (molecular mass of <4 kDa, heat, pH and protease stability, and the presence of modified amino acids), the bacteriocin, named suicin 90-1330, belongs to the lantibiotic class. Using a DNA-binding fluorophore, the bacteriocin was found to possess a membrane permeabilization activity. When tested on other swine pathogens, the suicin showed activity against Staphylococcus hyicus and Staphylococcus aureus, whereas it was inactive against all Gram-negative bacteria tested. Amino acid sequencing of the purified bacteriocin showed homology (90.9% identity) with nisin U produced by Streptococcus uberis. The putative gene cluster involved in suicin production was amplified by PCR and sequence analysis revealed the presence of 11 open reading frames, including the structural gene and those required for the modification of amino acids, export, regulation, and immunity. Further studies will evaluate the ability of suicin 90-1330 or the producing strain to prevent experimental S. suis infections in pigs.     

Molecular Variability and Evolution of the Pectate Lyase (<Emphasis Type="Italic">pel</Emphasis>-2) Parasitism Gene in Cyst Nematodes Parasitizing Different <Emphasis Type="Italic">Solanaceous</Emphasis> Plants

While pectate lyases are major parasitism factors in plant-parasitic nematodes, there is little information on the variability of these genes within species and their utility as pathotype or host range molecular markers. We have analysed polymorphisms of pectate lyase 2 (pel-2) gene, which degrades the unesterified polygalacturonate (pectate) of the host cell-wall, in the genus Globodera. Molecular variability of the pel-2 gene and the predicted protein was evaluated in populations of G. rostochiensis, G. pallida, G. “mexicana” and G. tabacum. Seventy eight pel-2 sequences were obtained and aligned. Point mutations were observed at 373 positions, 57% of these affect the coding part of the gene and produce 129 aa replacements. The observed polymorphism does not correlate either to the pathotypes proposed in potato cyst nematodes (PCN) or the subspecies described in tobacco cyst nematodes. The trees reveal a topology different from the admitted species topology as G. rostochiensis and G. pallida sequences are more similar to each other than to G. tabacum. Species-specific sites, potentially applicable for identification, and sites distinguishing PCN from tobacco cyst nematodes, were identified. As both G. rostochiensis and G. pallida display the same host range, but distinct from G. tabacum, which cannot parasitize potato plants, it is tempting to speculate that pel-2 genes polymorphism may be implicated in this adaptation, a view supported by the fact that no active pectate lyase 2 was found in G. “mexicana”, a close relative of G. pallida that is unable to develop on cultivated potato varieties.     

Genetic Improvement of Willow for Bioenergy and Biofuels

Willows (Salix spp.) are a very diverse group of catkin-bearing trees and shrubs that are widely distributed across temperate regions of the globe.Some species respond well to being grown in short rotation coppice (SRC) cycles,which are much shorter than conventional forestry.Coppicing reinvigorates growth and the biomass rapidly accumulated can be used as a source of renewable carbon for bioenergy and biofuels.As SRC willows re-distribute nutrients during the perennial cycle they require only minimal nitro...     

Assessment of genetic diversity in three subsets constituted from the ICRISAT sorghum collection using random vs non-random sampling procedures A. Using morpho-agronomical and passport data

A large collection, such as the sorghum [Sorghum bicolor (L.) Moench] landrace collection held at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), represents a challenge for the maintenance of both the accessions of and the information documented for the germplasm collection. The accessibility and knowledge of the landrace collection are the essential factors for an efficient utilization of the genetic resources by both breeders and farmers. Different sampling strategies, either random or non-random, were proposed to obtain subsets of reduced size (core collection). Three subsets were established; a random sampling within a stratified collection (logarithmic strategy: L); a sample based upon morpho-agronomic diversity (principal component score strategy: PCS); and a sample based upon an empirical knowledge of sorghum (taxonomic strategy: T). Comparisons of these three samples for morpho-agronomic characterization and passport information were assessed to determine their impact on phenotypic diversity. For their overall diversity, the three subsets did not differ, as shown with the two-dimensional representation of the morpho-agronomic diversity and the Shannon-Weaver diversity indices. When comparisons for morpho-agronomic and passport data were considered, the PCS subset looked similar to the entire landrace collection. The L subset showed differences for characters associated with the photoperiod reaction that was considered in the stratification of the collection. The T subset was the most distinct from the entire landrace collection as it over-represented the landraces selected by farmers for specific uses and covered the widest range of geographical adaptation and morpho-agronomic characteristics. Received: 5 October 1999 / Accepted: 3 November 1999     

Melittin-induced leakage from phosphatidylcholine vesicles is modulated by cholesterol: a property used for membrane targeting

Melittin, an amphiphathic peptide, affects the permeability of vesicles. This can be demonstrated using the dye release technique. Calcein, a fluorescent marker, is trapped in large unilamellar 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) vesicles and melittin-induced leakage of the dye can be monitored directly by increasing fluorescence intensity. First, we characterized the effect of increasing cholesterol content in the membrane on melittin-induced leakage and our results reveal that cholesterol inhibits the lytic activity of the peptide. Using intrinsic fluorescence of the single tryptophan of melittin and ²H-NMR of headgroup deuterated phosphatidylcholine, we demonstrated that the affinity of melittin for phosphatidylcholine vesicles is reduced in the presence of cholesterol; this is associated with the tighter lipid packing of the cholesterol-containing bilayer. This reduced binding is responsible for the reduced melittin-induced leakage from cholesterol-containing membranes. The pathway of release was determined to be an all-or-none mechanism. Finally, we investigated the possibility of achieving specific membrane targeting with melittin, when vesicles of different lipid composition are simultaneously present. Melittin incubated together with vesicles made of pure POPC and POPC containing 30(mol)% cholesterol can empty nearly all the cholesterol-free vesicles while the cholesterol-containing vesicles remain almost intact. Owing to the preferential interaction of melittin with the pure POPC vesicles, we were able to achieve controlled release of encapsulated material from a specific vesicle population. Received: 8 May 1996 / Accepted: 12 September 1996     

Targeting CoV-2 spike RBD and ACE-2 interaction with flavonoids of Anatolian propolis by in silico and in vitro studies in terms of possible COVID-19 therapeutics

Propolis is a multi-functional bee product rich in polyphenols. In this study, the inhibitory effect of Anatolian propolis against SARS-coronavirus-2 (SARS-CoV-2) was investigated in vitro and in silico. Raw and commercial propolis samples were used, and both samples were found to be rich in caffeic acid, p-coumaric acid, ferulic acid, t-cinnamic acid, hesperetin, chrysin, pinocembrin, and caffeic acid phenethyl ester (CAPE) at HPLC-UV analysis. Ethanolic propolis extracts (EPE) were used in the ELISA screening test against the spike S1 protein (SARS-CoV-2): ACE-2 interaction for in vitro study. The binding energy values of these polyphenols to the SARS-CoV-2 spike and ACE-2 protein were calculated separately with a molecular docking study using the AutoDock 4.2.6 program. In addition, the pharmacokinetics and drug-likeness properties of these eight polyphenols were calculated according to the SwissADME tool. The binding energy value of pinocembrin was highest in both receptors, followed by chrysin, CAPE, and hesperetin. Based on the in silico modeling and ADME (absorption, distribution, metabolism, and excretion) behaviors of the eight polyphenols, the compounds exhibited the potential ability to act effectively as novel drugs. The findings of both studies showed that propolis has a high inhibitory potential against the Covid-19 virus. However, further studies are now needed.     

The LuxS/AI-2 system of Streptococcus suis

Applied Microbiology and Biotechnology - Quorum sensing (QS) is an important protective mechanism that allows bacteria to adapt to its environment. A limited number of signal molecules play the key...     

Determination of aflatoxin levels in peanut butter using HPLC and ELISA procedures: Inter-laboratory comparison

Mycotoxin Research - Six laboratories analyzed portions of the same aqueous acetonitrile extracts of three peanut butters for aflatoxin concentrations by an HPLC procedure (using immunoaffinity...     

Detection of collagenase activity in oral bacteria

Collagenolytic activity of 12 species of oral bacteria was assessed using two methods of detection. Except for two species, all bacterial strains tested were capable of degrading at least one general protein substrate. Results of collagenolytic activity in a growth assay indicate that Bacteroides gingivalis is the only bacterium capable of degrading collagen when the substrate is sterilized using ethylene oxide. However, if the substrate is sterilized by autoclaving, in the presence or absence of the growth medium, other bacterial species could be shown to be collagenolytic. Collagenolytic activity was also demonstrated when whole or broken cells were used in a [14C]collagen assay. Results from this assay and from inhibition studies indicate that collagenolytic activity can either be the result of the combined activities of both a specific collagenase and nonspecific proteases (B. gingivalis) or nonspecific proteases only (other strains in this study), although in the latter case, the time taken to hydrolyze collagen can be 10 times longer than with a specific collagenase.