176 research outputs found
Identification of lactic acid bacteria isolated from South African brandy based wines
No full textH.W. du Plessis, L.M.T. Dicks, I.S. Pretorius, M.G. Lambrechts, M. du Toi
Probiotics at War Against Viruses: What Is Missing From the Picture?
No full textOur world is now facing a multitude of novel infectious diseases. Bacterial infections are treated with antibiotics, albeit with increasing difficulty as many of the more common causes of infection have now developed broad spectrum antimicrobial resistance. However, there is now an even greater challenge from both old and new viruses capable of causing respiratory, enteric, and urogenital infections. Reports of viruses resistant to frontline therapeutic drugs are steadily increasing and there is an urgent need to develop novel antiviral agents. Although this all makes sense, it seems rather strange that relatively little attention has been given to the antiviral capabilities of probiotics. Over the years, beneficial strains of lactic acid bacteria (LAB) have been successfully used to treat gastrointestinal, oral, and vaginal infections, and some can also effect a reduction in serum cholesterol levels. Some probiotics prevent gastrointestinal dysbiosis and, by doing so, reduce the risk of developing secondary infections. Other probiotics exhibit anti-tumor and immunomodulating properties, and in some studies, antiviral activities have been reported for probiotic bacteria and/or their metabolites. Unfortunately, the mechanistic basis of the observed beneficial effects of probiotics in countering viral infections is sometimes unclear. Interestingly, in COVID-19 patients, a clear decrease has been observed in cell numbers of Lactobacillus and Bifidobacterium spp., both of which are common sources of intestinal probiotics. The present review, specifically motivated by the need to implement effective new counters to SARS-CoV-2, focusses attention on viruses capable of co-infecting humans and other animals and specifically explores the potential of probiotic bacteria and their metabolites to intervene with the process of virus infection. The goal is to help to provide a more informed background for the planning of future probiotic-based antiviral research. © Copyright © 2020 Tiwari, Dicks, Popov, Karaseva, Ermakov, Suvorov, Tagg, Weeks and Chikindas
Biosensors for the detection of Escherichia coli
No full textCITATION: Maas, M. B., Perold, W. J. & Dicks, L. M. T. 2017. Biosensors for the detection of Escherichia coli. Water SA, 43(4):707-721, doi:10.4314/wsa.v43i4.17.The original publication is available at http://www.wrc.org.zaENGLISH ABSTRACT: The supply of safe potable water, free from pathogens and chemicals, requires routine analyses and the application of several diagnostic techniques. Apart from being expensive, many of the detection methods require trained personnel and are often time-consuming. With drastic climate changes, severe droughts, increases in population and pollution of natural water systems, the need to develop ultrasensitive, low-cost and hand-held, point-of-use detection kits to monitor water quality is critical. Although Escherichia coli is still considered the best indicator of water quality, cell numbers may be below detection limits, or the cells may be non-culturable and thus only detected by DNA amplification. A number of different biosensors have been developed to detect viable, dead or non-culturable microbial cells and chemicals in water. This review discusses the differences in these biosensors and evaluates the application of microfluidics in the design of ultra-sensitive nano-biosensors.Publisher's versio
Relatedness of Leuconostoc species of the Leuconostoc sensu stricto Line of Descent, Leuconostoc oenos and Weissella paramesenteroides Revealed by Numerical Analysis of Total Soluble Cell Protein Patterns
No full textTaxonomic Status of Lactic Acid Bacteria in Wine and Key Characteristics to Differentiate Species
No full textOenococcus oeni is the best malolactic bacterium adapted to low pH and the high SO2 and ethanol concentrations inwine. Leuconostoc mesenteroides and Leuconostoc paramesenteroides (now classified as Weissella paramesenteroides)have also been isolated from wine. Pediococcus damnosus is not often found in wine and is considered a contaminantof high pH wines. Pediococcus inopinatus, Pediococcus parvulus and Pediococcus pentosaceus have occasionallybeen isolated from wines. Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus buchneri, Lactobacillushilgardii (previously Lactobacillus vermiforme), Lactobacillus fructivorans (previously Lactobacillus trichoidesand Lactobacillus heterohiochii) and Lactobacillus fermentum have been isolated from most wines. Lactobacillushilgardii and L. fructivorans are resistant to high acid and alcohol and have been isolated from spoiled fortifiedwines. Lactobacillus vini, Lactobacillus lindneri, Lactobacillus nagelii and Lactobacillus kunkeei have been describedmore recently. The latter two species are known to cause sluggish or stuck alcoholic fermentations in wine.Although Lactobacillus collinoides and Lactobacillus mali (previously Lactobacillus yamanashiensis) decarboxylateL-malic acid, they are more often found in cider and fruit juices. Lactobacillus curvatus, Lactobacillus delbrueckii,Lactobacillus diolivorans, Lactobacillus jensenii and Lactobacillus paracasei are seldomly isolated from wines. Somestrains of Lactobacillus casei may be closer related to Lactobacillus paracasei or a distant relative, Lactobacilluszeae. Oenococcus kitaharae, isolated from compost is genetically closely related to Oenococcus oeni, but does notdecarboxylate malate, prefers higher growth pH and is phenotypically well distinguished from O. oeni. This reviewsummarises the current taxonomic status of malolactic bacteria and lists key phenotypic characteristics that maybe used to identify the species
Identification of Lactobacillus spp. Isolated from Different Phases During the Production of a South African Fortified Wine
No full textFortified wines contain a high level of unfermented sugars and are prone to spoilage by alcohol-tolerant lactic acid bacteria. A total of 62 strains were isolated from various production stages of one of the more popular fortified wines produced in South Africa. The strains were identified by using numerical analysis of total soluble cell protein patterns and 16S rRNA sequence analyses. The species most frequently isolated were Lactobacillus vermiforme (24 strains) and Lactobacillus casei subsp. casei (32 strains). Twenty-four of the strains of L. vermiforme, three strains of Lactobacillus buchneri, one strain of Lactobacillus plantarum and two strains of L. casei subsp. casei were isolated from spoiled fortified wine which contained 22% (vol/vol) ethanol. The majority of strains of L. casei subsp. casei (25 of the 32) and two strains of Lactobacillus zeae were isolated from wine before submerged fermentation. Five strains of L. casei subsp. casei were isolated from wine undergoing submerged fermentation, with an alcohol content of 11.92% (vol/vol). No strain was isolated from unbottled wine which underwent the complete fermentation process and with an alcohol content of 17.20% (vol/vol). Three distinct phenotypic groups of L. vermiforme were identified at r ≥ 0. 70, separate from Lactobacillus brevis,' L. buchneri and Lactobacillus hilgardii. Three phenotypic clusters have been identified for L. casei subsp. casei. This is the first report of the presence of L. vermiforme, L. zeae, L. casei subsp. casei and L. plantarum in fortified wines
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
Control of Malolactic Fermentation in Wine. A Review
No full textMalolactic fermentation (MLF) is conducted by lactic acid bacteria (LAB) and refers to the decarboxylation of Lmalate to L-lactate. This secondary fermentation is difficult to control and is mainly driven by Oenococcus oeni. Uncontrolled MLF, especially in wines with a high pH, which are typical of warmer viticultural regions, may render the wine unpalatable or even cause spoilage. In this review we focus on wine compounds and emphasise factors that affect the growth of 0. oeni and MLF, and discuss practical applications. We also explore alternative technologies that may enable better control over MLF
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
- …
