Effect of Growth Medium on Bacteriocin Production by Lactobacillus plantarum ST194BZ, a Strain Isolated from Boza

The cell-free supernatant containing bacteriocin ST194BZ, produced by Lactobacillus plantarum ST194BZ, inhibits the growth of Lactobacillus casei, Lactobacillus sakei, Lactobacillus delbrueckii subsp. bulgaricus, Enterococcus faecalis, Escherichia coli, Enterobacter cloacae and Pseudomonas aeruginosa. Strain ST194BZ produces two bacteriocins, viz. ST194BZ(a) of 3.3 kDa and ST194BZ(b) of 14.0 kDa, based on tricine-SDS-PAGE. Reduction in bacteriocin activity was observed after treatment with proteinase K, trypsin and pronase, but not with catalase and a-amylase. A maximum total bacteriocin activity of 12 800 AU/mL was recorded after 14 h in MRS broth. In MRS broth adjusted to pH=5.5, 6.0 or 6.5, an equal level of bacteriocin production of 12 800 AU/mL was recorded. Optimal production (12 800 AU/ mL) was recorded in the presence of tryptone (20 g/L), a combination of tryptone and meat extract (1:0.6), or tryptone and yeast extract (1:0.6). Growth of strain ST194BZ in the presence of 10 or 20 g/L of D-mannose yielded bacteriocin levels of 12 800 AU/mL. In the presence of 30 or 40 g/L of mannose the activity levels doubled to 25 600 AU/mL. No difference in antibacterial activity was recorded when strain ST194BZ was grown in the presence of 2 g/L of K2HPO4 and 2 g/L of KH2PO4. Concentrations of 10, 20 and 50 g/L of KH2PO4 yielded double activity (25 600 AU/mL). Supplementing MRS with 1 g/L or more glycerol inhibited the production of bacteriocin. Growth in the presence of vitamins did not stimulate bacteriocin production. No plasmids were recorded for strain ST194BZ, suggesting that the genes encoding bacteriocin production are located on the genome

A taxonomic study of Leuconostoc oenos

Thesis (Ph. D.) -- University of Stellenbosch, 1989.Full text to be digitised and attached to bibliographic record

Taxonomy and physiology of heterofermentative Lactobacillus species including isolates from South African red wines

Thesis (M. Sc.) -- University of Stellenbosch, 1985.Full text to be digitised and attached to bibliographic record

Lactic acid bacteria : taxonomy antimicrobial characteristics and probiotics

10 A4 digitized pages in pdf.Inaugural address delivered by Prof Leon Milner Theodore Dicks during 2002, Stellenbosch University.NRF, THRIP, Dow Chemicals (previously Sentrachem), Industrial Development Corporation, Winetech, Red Meat Research Development Trust, Medical Research Council, Stellenbosch Universit

Heterologous expression of the class IIa bacteriocins, plantaricin 423 and mundticin ST4SA, in escherichia coli using green fluorescent protein as a fusion partner

CITATION: Vermeulen, R. R., Du Preez Van Staden, A. & Dicks, L. 2020. Heterologous expression of the class IIa bacteriocins, plantaricin 423 and mundticin ST4SA, in escherichia coli using green fluorescent protein as a fusion partner. Frontiers in Microbiology, 11:1634, doi:10.3389/fmicb.2020.01634.The original publication is available at https://www.frontiersin.orgPublication of this article was funded by the Stellenbosch University Open Access FundThe antilisterial class IIa bacteriocins, plantaricin 423 and mundticin ST4SA, have previously been purified from the cell-free supernatants of Lactobacillus plantarum 423 and Enterococcus mundtii ST4SA, respectively. Here, we present the fusions of mature plantaricin 423 and mundticin ST4SA to His-tagged green fluorescent protein (GFP) for respective heterologous expression in Escherichia coli. Fusion of plantaricin 423 and mundticin ST4SA to His-tagged GFP produced the fusion proteins GFP-PlaX and GFP-MunX, respectively. Both fusion proteins were autofluorescent, circumvented inclusion body formation and lowered the toxicity of class IIa bacteriocins during heterologous expression. Not only did GFP-class IIa fusion stabilize heterologous expression and boost yields, the fluorescent intensity of GFP-PlaX and GFP-MunX could be monitored quantitatively and qualitatively throughout expression and purification. This robust fluorometric property allowed rapid optimization of conditions for expression and bacteriocin liberation from GFP via the incorporated WELQut protease cleavage sequence. Incubation temperature and IPTG concentration had a significant effect on bacteriocin yield, and was optimal at 18°C and 0.1–0.2 mM, respectively. GFP-MunX was approximately produced at a yield of 153.30 mg/L culture which resulted in 12.4 mg/L active mundticin ST4SA after liberation and HPLC purification. While GFP-PlaX was produced at a yield of 121.29 mg/L culture, evidence suggests heterologous expression resulted in conformation isomers of WELQut liberated plantaricin 423.https://www.frontiersin.org/articles/10.3389/fmicb.2020.01634/fullPublisher's versio

Bacteria of the genus xenorhabdus, a novel source of bioactive compounds

CITATION: Dreyer, J., Malan, A. P. & Dicks, L. M. T. 2018. Bacteria of the genus xenorhabdus, a novel source of bioactive compounds. Frontiers in Microbiology, 9:3177, doi:10.3389/fmicb.2018.03177.The original publication is available at https://www.frontiersin.orgPublication of this article was funded by the Stellenbosch University Open Access Fund.The genus Xenorhabdus of the family Enterobacteriaceae, are mutualistically associated with entomopathogenic nematodes of the genus Steinernema. Although most of the associations are species-specific, a specific Xenorhabdus sp. may infect more than one Steinernema sp. During the Xenorhabdus–Steinernema life cycle, insect larvae are infected and killed, while both mutualists produce bioactive compounds. These compounds act synergistically to ensure reproduction and proliferation of the nematodes and bacteria. A single strain of Xenorhabdus may produce a variety of antibacterial and antifungal compounds, some of which are also active against insects, nematodes, protozoa, and cancer cells. Antimicrobial compounds produced by Xenorhabdus spp. have not been researched to the same extent as other soil bacteria and they may hold the answer to novel antibacterial and antifungal compounds. This review summarizes the bioactive secondary metabolites produced by Xenorhabdus spp. and their application in disease control. Gene regulation and increasing the production of a few of these antimicrobial compounds are discussed. Aspects limiting future development of these novel bioactive compounds are also pointed out.https://www.frontiersin.org/articles/10.3389/fmicb.2018.03177/fullPublisher's versio

Evaluation of a nisin-eluting nanofiber scaffold to treat Staphylococcus aureus-induced skin infections in mice

Heunis, T. D. J., Smith, C. & Dicks, L. M. T. 2013. Evaluation of a nisin-eluting nanofiber scaffold to treat Staphylococcus aureus-induced skin infections in mice. Antimicrobial Agents and Chemotherapy, 57(8):3928-3935, doi:10.1128/AAC.00622-13, http://aac.asm.org/The original publication is available at https://aac.asm.orgStaphylococcus aureus is a virulent pathogen and a major causative agent of superficial and invasive skin and soft tissue infections (SSSTIs). Antibiotic resistance in S. aureus, among other bacterial pathogens, has rapidly increased, and this is placing an enormous burden on the health care sector and has serious implications for infected individuals, especially immunocompromised patients. Alternative treatments thus need to be explored to continue to successfully treat infections caused by S. aureus, including antibiotic-resistant strains of S. aureus. In this study, an antimicrobial nanofiber wound dressing was generated by electrospinning nisin (Nisaplin) into poly(ethylene oxide) and poly(d,l-lactide) (50:50) blend nanofibers. Active nisin diffused from the nanofiber wound dressings for at least 4 days in vitro, as shown by consecutive transfers onto plates seeded with strains of methicillin-resistant S. aureus (MRSA). The nisin-containing nanofiber wound dressings significantly reduced S. aureus Xen 36 bioluminescence in vivo and viable cell numbers in a murine excisional skin infection model. The bacterial burden of wounds treated with nisin-containing nanofiber wound dressings was 4.3 × 102 CFU/wound, whereas wounds treated with control nanofiber wound dressings had 2.2 × 107 CFU/wound on the last day of the trial (day 7). Furthermore, the wound dressings stimulated wound closure of excisional wounds, and no adverse effects were observed by histological analysis. Nisin-containing nanofiber wound dressings have the potential to treat S. aureus skin infections and to potentially accelerate wound healing of excisional wounds.Post-prin

Phylogenetic analysis of leuconostoc and lactobacillus species isolated from sugarcane processing streams

CITATION: Nel, S., et al. 2020. Phylogenetic analysis of leuconostoc and lactobacillus species isolated from sugarcane processing streams. MicrobiologyOpen, 9(8):e1065, doi:10.1002/mbo3.1065.The original publication is available at https://onlinelibrary.wiley.comPublication of this article was funded by the Stellenbosch University Open Access FundHigh levels of gums such as dextran, produced by Leuconostoc and Lactobacillus spp., have a severe impact on factory throughput and sugar quality. This study aimed to determine the phylogenetic relationships between gum‐producing Leuconostoc and Lactobacillus bacteria which were isolated from various locations in a sugarcane processing factory at times when low‐ and high‐dextran raw sugar, respectively, were produced. Phylogenetic analysis of 16S rRNA gene sequences grouped 81 isolates with the type strains of Leuconostoc mesenteroides (subspp. mesenteroides , dextranicum, and cremoris ), Leuconostoc pseudomesenteroides, Leuconostoc lactis, and Leuconostoc citreum , respectively. Forty‐three isolates clustered with the type strain of Lactobacillus fermentum . The phylogenetic relatedness of the isolates was determined by sequencing and analysis of the housekeeping genes rpoA and dnaA for Leuconostoc spp. and the pheS and tuf genes for the Lactobacillus spp. The rpoA gene proved discriminatory for the phylogenetic resolution of all of the isolated Leuconostoc spp. and the dnaA housekeeping gene was shown to be effective for isolates clustering with the type strains of Leuc. mesenteroides and Leuc. citreum . None of the loci examined permitted differentiation at the subspecies level of Leuc. mesenteroides . Single‐locus analysis, as well as the concatenation of the pheS and tuf housekeeping gene sequences, yielded identical phylogenies for the Lactobacillus isolates corresponding to L. fermentum.https://onlinelibrary.wiley.com/doi/abs/10.1002/mbo3.1065Publisher's versio

In vivo bioluminescence imaging of the spatial and temporal colonization of lactobacillus plantarum 423 and enterococcus mundtii ST4SA in the intestinal tract of mice

CITATION: Van Zyl, W. F., et al. 2018. In vivo bioluminescence imaging of the spatial and temporal colonization of lactobacillus plantarum 423 and enterococcus mundtii ST4SA in the intestinal tract of mice. BMC Microbiology, 18:171, doi:10.1186/s12866-018-1315-4.The original publication is available at https://bmcmicrobiol.biomedcentral.comBackground: Lactic acid bacteria (LAB) are major inhabitants and part of the normal microflora of the gastrointestinal tract (GIT) of humans and animals. Despite substantial evidence supporting the beneficial properties of LAB, only a few studies have addressed the migration and colonization of probiotic bacteria in the GIT. The reason for this is mostly due to the limitations, or lack of, efficient reporter systems. Here we describe the development and application of a non-invasive in vivo bioluminescence reporter system to study, in real-time, the spatial and temporal persistence of Lactobacillus plantarum 423 and Enterococcus mundtii ST4SA in the intestinal tract of mice. Results: This study reports on the application of the firefly luciferase gene (ffluc) fromPhotinus pyralis to develop luciferase-expressing L. plantarum 423 and E. mundtii ST4SA, using a Lactococcus lactis NICE system on a high copy number plasmid (pNZ8048) and strong constitutive lactate dehydrogenase gene promoters (Pldh and STldh). The reporter system was used for in vivo and ex vivo monitoring of both probiotic LAB strains in the GIT of mice after single and multiple oral administrations. Enterococcus mundtii ST4SA reached the large intestine 45 min after gavage, while L. plantarum 423 reached the cecum/colon after 90 min. Both strains predominantly colonized the cecum and colon after five consecutive daily administrations. Enterococcus mundtii ST4SA persisted in faeces at higher numbers and for more days compared to L. plantarum 423. Conclusions: Our findings demonstrate the efficiency of a high-copy number vector, constitutive promoters and bioluminescence imaging to study the colonization and persistence of L. plantarum 423 and E. mundtii ST4SA in the murine GIT. The system allowed us to differentiate between intestinal transit times of the two strains in the digestive tract. This is the first report of bioluminescence imaging of a luciferase-expressing E. mundtii strain to study colonization dynamics in the murine model. The bioluminescence system developed in this study may be used to study the in vivo colonization dynamics of other probiotic LAB.https://bmcmicrobiol.biomedcentral.com/articles/10.1186/s12866-018-1315-4Publisher's versio