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Applied and Environmental Microbiology Oct 2019Fructophilic lactic acid bacteria (FLAB), composed of spp., , and , are unique in that they prefer d-fructose over d-glucose as a carbon source. Strain F192-5, isolated...
Fructophilic lactic acid bacteria (FLAB), composed of spp., , and , are unique in that they prefer d-fructose over d-glucose as a carbon source. Strain F192-5, isolated from the peel of a satsuma mandarin and identified as , grows well on d-fructose but poorly on d-glucose and produces mainly lactate and acetate, with trace amounts of ethanol, from the metabolism of d-glucose. These characteristics are identical to those of obligate FLAB. However, strain F192-5 ferments a greater variety of carbohydrates than known FLAB. Comparative analyses of the genomes of strain F192-5 and reference strains of revealed no signs of specific gene reductions, especially genes involved in carbohydrate transport and metabolism, in the genome of F192-5. The bifunctional alcohol/acetaldehyde dehydrogenase gene () is conserved in strain F192-5 but is not transcribed. This is most likely due to a deletion in the promoter region upstream of the gene. Strain F192-5 did, however, ferment d-glucose when transformed with a plasmid containing the allochthonous gene. F192-5 is an example of a pseudo-FLAB strain with a deficiency in d-glucose metabolism. This unique phenotypic characteristic appears to be strain specific within the species This might be one of the strategies lactic acid bacteria use to adapt to diverse environmental conditions. Obligate fructophilic lactic acid bacteria (FLAB) lack the metabolic pathways used in the metabolism of most carbohydrates and differ from other lactic acid bacteria in that they prefer to ferment d-fructose instead of d-glucose. These characteristics are well conserved at the genus or species level. F192-5 shows similar growth characteristics. However, the strain is metabolically and genomically different from obligate FLAB. This is an example of a strain that evolved a pseudo-FLAB phenotype to adapt to a fructose-rich environment.
Topics: Alcohol Dehydrogenase; Aldehyde Oxidoreductases; Bacterial Proteins; Citrus; Fructose; Leuconostoc
PubMed: 31399409
DOI: 10.1128/AEM.01077-19 -
BMC Infectious Diseases Jul 2007Commercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic... (Comparative Study)
Comparative Study
BACKGROUND
Commercial diagnostics are commonly used to identify gram-positive bacteria. Errors have been reported mostly at the species level. We have found certain phenotypic criteria used in API systems which significantly misidentify Leuconostoc, an emerging human pathogen, at the genus level. We also attempt to find practical, conventional phenotypic assays for accurate identification of this group of bacteria.
METHODS
Clinical isolates of catalase-negative, gram-positive coccoid or coccobacillary bacteria with non-beta hemolysis in our institute during 1997-2004 were subject to an identification aid by API 20 STREP, following the instruction manual, as an aid to conventional phenotypic tests. Those identified as Leuconostoc by API 20 STREP were re-examined by the same kit and also by API 50 CHL according to the instruction manuals, by our Leuconostoc conventional phenotypic assays, by Leuconostoc- and Lactobacillus-specific PCR's, and, where possible, by 16S rDNA sequence analysis. In addition, catalase-negative gram-positive isolates during 2005-2006 which were resistant to vancomycin at high levels were also evaluated by the same phenotypic and genotypic assays.
RESULTS
Out of several thousands of clinical gram-positive isolates, 26 catalase negative gram-positive isolates initially identified as Leuconostoc by API 20 STREP and 7 vancomycin-resistant gram-positive catalase-negative bacteria entered the study. 11 out of the 26 isolates and all the 7 isolates were identified as Leuconostoc by API 20 STREP. Only 5 isolates, however, were confirmed by both genotypic and all defined conventional phenotypic criteria. API 50 CHL also failed to reliably provide accurate identification of Leuconostoc. We have identified key problem tests in API 20 STREP leading to misidentification of the bacteria. A simple, conventional set of phenotypic tests for Leuconostoc identification is proposed.
CONCLUSION
The current API systems cannot accurately identify Leuconostoc. Identification of vancomycin-resistant, catalase-negative gram-positive bacteria should be performed by a few practical phenotypic assays, with assistance of genotypic assays where available.
Topics: Bacterial Typing Techniques; Genotype; Gram-Positive Bacteria; Humans; Leuconostoc; Phenotype; Reproducibility of Results; Vancomycin
PubMed: 17605772
DOI: 10.1186/1471-2334-7-69 -
Scientific Reports May 2018Alternansucrase catalyses the sequential transfer of glucose residues from sucrose onto another sucrose molecule to form a long chain polymer, known as "alternan". The...
Alternansucrase catalyses the sequential transfer of glucose residues from sucrose onto another sucrose molecule to form a long chain polymer, known as "alternan". The alternansucrase-encoding gene from Leuconostoc citreum ABK-1 (Lcalt) was successfully cloned and expressed in Escherichia coli. Lcalt encoded LcALT of 2,057 amino acid residues; the enzyme possessed an optimum temperature and pH of 40 °C and 5.0, respectively, and its' activity was stimulated up to 2.4-fold by the presence of Mn. Kinetic studies of LcALT showed a high transglycosylation activity, with K 32.2 ± 3.2 mM and kcat 290 ± 12 s. Alternan generated by LcALT (Lc-alternan) harbours partially alternating α-1,6 and α- 1,3 glycosidic linkages confirmed by NMR spectroscopy, methylation analysis, and partial hydrolysis of Lc-alternan products. In contrast to previously reported alternans, Lc-alternan can undergo self-assembly, forming nanoparticles with an average size of 90 nm in solution. At concentrations above 15% (w/v), Lc-alternan nanoparticles disassemble and form a high viscosity solution, while this polymer forms a transparent film once dried.
Topics: Escherichia coli; Glucans; Glycosyltransferases; Kinetics; Leuconostoc; Magnetic Resonance Spectroscopy; Molecular Weight; Sucrose
PubMed: 29844508
DOI: 10.1038/s41598-018-26721-w -
World Journal of Microbiology &... Feb 2024Six lactic acid bacteria (LAB) isolated from Algerian sheep's milk, traditional butter, date palm sap and barley, which produce dextran, mannitol, oligosaccharides and...
Leuconostoc mesenteroides and Liquorilactobacillus mali strains, isolated from Algerian food products, are producers of the postbiotic compounds dextran, oligosaccharides and mannitol.
Six lactic acid bacteria (LAB) isolated from Algerian sheep's milk, traditional butter, date palm sap and barley, which produce dextran, mannitol, oligosaccharides and vitamin B have been characterized. They were identified as Leuconostoc mesenteroides (A4X, Z36P, B12 and O9) and Liquorilactobacillus mali (BR201 and FR123). Their exopolysaccharides synthesized from sucrose by dextransucrase (Dsr) were characterized as dextrans with (1,6)-D-glucopyranose units in the main backbone and branched at positions O-4, O-2 and/or O-3, with D-glucopyranose units in the side chain. A4X was the best dextran producer (4.5 g/L), while the other strains synthesized 2.1-2.7 g/L. Zymograms revealed that L. mali strains have a single Dsr with a molecular weight (Mw) of ~ 145 kDa, while the Lc. mesenteroides possess one or two enzymes with 170-211 kDa Mw. As far as we know, this is the first detection of L. mali Dsr. Analysis of metabolic fluxes from sucrose revealed that the six LAB produced mannitol (~ 12 g/L). The co-addition of maltose-sucrose resulted in the production of panose (up to 37.53 mM), an oligosaccharide known for its prebiotic effect. A4X, Z36P and B12 showed dextranase hydrolytic enzymatic activity and were able to produce another trisaccharide, maltotriose, which is the first instance of a dextranase activity encoded by Lc. mesenteroides strains. Furthermore, B12 and O9 grew in the absence of riboflavin (vitamin B) and synthesized this vitamin, in a defined medium at the level of ~ 220 μg/L. Therefore, these LAB, especially Lc. mesenteroides B12, are good candidates for the development of new fermented food biofortified with functional compounds.
Topics: Animals; Sheep; Leuconostoc mesenteroides; Dextrans; Dextranase; Mannitol; Mali; Glucosyltransferases; Oligosaccharides; Sucrose; Vitamins; Leuconostoc
PubMed: 38418710
DOI: 10.1007/s11274-024-03913-3 -
Applied and Environmental Microbiology Feb 1988Transfer of the broad-host-range resistance plasmids pIP501 and pAM beta 1 from Streptococcus faecalis to Leuconostoc dextranicum and Leuconostoc cremoris occurred...
Transfer of the broad-host-range resistance plasmids pIP501 and pAM beta 1 from Streptococcus faecalis to Leuconostoc dextranicum and Leuconostoc cremoris occurred between cells that were immobilized on nitrocellulose filters in the presence of DNase. Transfer of pIP501 to Leuconostoc spp. also occurred when Streptococcus sanguis and Streptococcus lactis were used as donors. In addition, transfer of pIP501 and pAM beta 1 was observed from L. cremoris and L. dextranicum transconjugants to S. sanguis and S. faecalis. Expression of the pAM beta 1 erythromycin and pIP501 erythromycin and chloramphenicol resistance determinants was essentially equivalent in donors and transconjugants. Frequencies of transfer generally ranged from 10(-4) to 10(-7) transconjugants per input donor cell. Intrageneric transfer of pIP501 and pAM beta 1 occurred between L. cremoris and L. dextranicum strains in the same approximate range. These data further extend the host range of pIP501 and pAM beta 1 and demonstrate another example of gene transfer in the genus Leuconostoc.
Topics: Chloramphenicol; Chloramphenicol Resistance; Conjugation, Genetic; DNA Restriction Enzymes; DNA, Bacterial; Deoxyribonucleases; Deoxyribonucleases, Type II Site-Specific; Drug Resistance, Microbial; Electrophoresis, Agar Gel; Enterococcus faecalis; Erythromycin; Genes, Bacterial; Lactococcus lactis; Leuconostoc; R Factors; Streptococcus sanguis; Transfection
PubMed: 2833158
DOI: 10.1128/aem.54.2.281-287.1988 -
Clinical Microbiology Reviews Oct 1995Several new genera and species of gram-positive, catalase-negative cocci that can cause infections in humans have been described. Although these bacteria were isolated... (Review)
Review
Several new genera and species of gram-positive, catalase-negative cocci that can cause infections in humans have been described. Although these bacteria were isolated in the clinical laboratory, they were considered nonpathogenic culture contaminants and were not thought to be the cause of any diseases. Isolation of pure cultures of these bacteria from normally sterile sites has led to the conclusion that these bacteria can be an infrequent cause of infection. This review describes the new bacteria and the procedures useful for clinical laboratories to aid in their identification. The clinical relevance and our experience with the various genera and species are reviewed and discussed.
Topics: Animals; Gram-Positive Bacterial Infections; Gram-Positive Cocci; Humans; Lactococcus; Leuconostoc; Pediococcus
PubMed: 8665466
DOI: 10.1128/CMR.8.4.479 -
Applied and Environmental Microbiology Apr 2012After isolation from different doughs and sourdoughs, 177 strains of lactic acid bacteria were screened at the phenotypic level for exopolysaccharide production on media...
Polyphasic screening, homopolysaccharide composition, and viscoelastic behavior of wheat Sourdough from a Leuconostoc lactis and Lactobacillus curvatus exopolysaccharide-producing starter culture.
After isolation from different doughs and sourdoughs, 177 strains of lactic acid bacteria were screened at the phenotypic level for exopolysaccharide production on media containing different carbohydrate sources. Two exopolysaccharide-producing lactic acid bacteria (Lactobacillus curvatus 69B2 and Leuconostoc lactis 95A) were selected through quantitative analysis on solid media containing sucrose and yeast extract. The PCR detection of homopolysaccharide (gtf and lev) and heteropolysaccharide (epsA, epsB, epsD and epsE, and epsEFG) genes showed different distributions within species and strains of the lactic acid bacteria studied. Moreover, in some strains both homopolysaccharide and heteropolysaccharide genes were detected. Proton nuclear magnetic resonance spectra suggest that Lactobacillus curvatus 69B2 and Leuconostoc lactis 95A produced the same exopolysaccharide, which was constituted by a single repeating glucopyranosyl unit linked by an α-(1→6) glycosidic bond in a dextran-type carbohydrate. Microbial growth, acidification, and viscoelastic properties of sourdoughs obtained by exopolysaccharide-producing and nonproducing lactic acid bacterial strains were evaluated. Sourdough obtained after 15 h at 30°C with exopolysaccharide-producing lactic acid bacteria reached higher total titratable acidity as well as elastic and dissipative modulus curves with respect to the starter not producing exopolysaccharide, but they showed similar levels of pH and microbial growth. On increasing the fermentation time, no difference in the viscoelastic properties of exopolysaccharide-producing and nonproducing samples was observed. This study suggests that dextran-producing Leuconostoc lactis 95A and Lactobacillus curvatus 69B2 can be employed to prepare sourdough, and this would be particularly useful to improve the quality of baked goods while avoiding the use of commercially available hydrocolloids as texturizing additives.
Topics: Fermentation; Food Analysis; Food Microbiology; Lactobacillus; Leuconostoc; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Polymerase Chain Reaction; Polysaccharides, Bacterial; Sequence Analysis, DNA; Triticum
PubMed: 22307283
DOI: 10.1128/AEM.07302-11 -
Applied and Environmental Microbiology Feb 1993A selective medium (LUSM medium) for the isolation of Leuconostoc spp. was developed. This medium contained 1.0% glucose, 1.0% Bacto Peptone (Difco), 0.5% yeast extract... (Comparative Study)
Comparative Study
A selective medium (LUSM medium) for the isolation of Leuconostoc spp. was developed. This medium contained 1.0% glucose, 1.0% Bacto Peptone (Difco), 0.5% yeast extract (BBL), 0.5% meat extract (Difco), 0.25% gelatin (Difco), 0.5% calcium lactate, 0.05% sorbic acid, 75 ppm of sodium azide (Sigma), 0.25% sodium acetate, 0.1% (vol/vol) Tween 80, 15% tomato juice, 30 micrograms of vancomycin (Sigma) per ml, 0.20 microgram of tetracycline (Serva) per ml, 0.5 mg of cysteine hydrochloride per ml, and 1.5% agar (Difco). LUSM medium was used successfully for isolation and enumeration of Leuconostoc spp. in dairy products and vegetables. Of 116 colony isolates obtained from fresh raw milk, curdled milk, or various vegetables, 115 were identified as members of the genus Leuconostoc. A total of 89 of these isolates were identified to species; 13.5% of the isolates were Leuconostoc cremoris, 7.9% were Leuconostoc mesenteroides subsp. mesenteroides, 11.2% were Leuconostoc mesenteroides subsp. dextranicum, 16.9% were Leuconostoc mesenteroides subsp. paramesenteroides, 10.1% were leuconostoc lactis, and 40.4% were Leuconostoc oenos. When we compared the counts obtained for two Leuconostoc strains, Leuconostoc dextranicum 181 and L. cremoris JLL8, on MRS agar and LUSM medium, we found no significant difference between the values obtained on the two media.
Topics: Bacteriological Techniques; Culture Media; Dairy Products; Food Microbiology; Leuconostoc; Vegetables
PubMed: 8434926
DOI: 10.1128/aem.59.2.607-609.1993 -
BMC Biotechnology Feb 2021Levan is a well-known homopolymer of fructose composed predominantly of β-(2, 6) fructofuranosyl linkages in the backbone with occasional β-(2, 1) linkages in the...
BACKGROUND
Levan is a well-known homopolymer of fructose composed predominantly of β-(2, 6) fructofuranosyl linkages in the backbone with occasional β-(2, 1) linkages in the branch chains with varied applications. However, high production cost due to low yield of microbial levan has become a bottleneck for its practical applications. Furthermore, factors affecting the molecular mass of the synthesized levan by Leuconostoc spp. during prolonged cultivation is not fully elucidated.
METHODS
The cultivation condition for Leuconostoc citreum BD1707 to synthesize levan was optimized by single-factor experiments and subsequently with response surface methodology (RSM). The average molecular weight (Mw) of levan synthesized by the strain L.citreum BD1707 under the optimized cultivation conditions was monitored by high-performance size exclusion chromatography (HPSEC). Finally, the enzyme with levan-degrading activity was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).
RESULTS
The levan yield of BD1707 reached 34.86 g/L with a corresponding productivity of 7.47 g/L/d under the optimal cultivation conditions deduced by RSM, i.e., cultivation at 26 °C and 200 rpm for 112 h in tomato juice supplemented with 172 g/L sucrose with an initial pH value of 6.12. The Mw of levan reached a peak value of 2.320 × 10 Da at 6 h of cultivation under the optimized cultivation conditions and then gradually decreased to 8.809 × 10 Da after 120 h of cultivation.
CONCLUSION
The levan yield of the strain L.citreum BD1707 could be sufficiently enhanced via cultivation condition optimization. The decrease in molecular mass of the synthesized levan was attributed predominantly to the hydrolytic activity of levansucrase secreted by L.citreum BD1707 during cultivation, with an estimated Mw of 130 KD by SDS-PAGE, while the effect of acid hydrolysis could be nearly neglected.
Topics: Fructans; Fructose; Glucose; Hexosyltransferases; Hydrogen-Ion Concentration; Leuconostoc; Solanum lycopersicum; Molecular Weight; Sucrose; Temperature
PubMed: 33541325
DOI: 10.1186/s12896-021-00673-y -
Journal of Microbiology and... Dec 2022Storage stability of freeze-dried lactic acid bacteria is a critical factor for their cost-effectiveness. Long-term storage of lactic acid bacteria enables microbial...
Storage stability of freeze-dried lactic acid bacteria is a critical factor for their cost-effectiveness. Long-term storage of lactic acid bacteria enables microbial industry to reduce distribution costs. Herein, we investigated the effect of cold adaptation under supercooling conditions at -5°C on the viability of WiKim32 during the freeze-drying process and subsequent storage. Cold adaptation increased the thickness of exopolysaccharides (EPS) and improved the viability of freeze-dried WiKim32. Compared to non-adapted cells, cold-adapted cells showed a 35.4% increase in EPS thickness under supercooling conditions. The viability of EPS-hydrolyzed cells was lower than that of untreated cells, implying that EPS plays a role in protection during the freeze-drying process. Cold adaptation increased the storage stability of freeze-dried WiKim32. Fifty-six days after storage, the highest viability (71.3%) was achieved with cold adaptation at -5°C. When EPS-containing broth was added prior to the freeze-drying process, the viability further increased to 82.7%. These results imply that cold adaptation by supercooling pretreatment would be a good strategy for the long-term storage of WiKim32.
Topics: Leuconostoc mesenteroides; Freeze Drying; Lactobacillales; Leuconostoc
PubMed: 36330746
DOI: 10.4014/jmb.2209.09022