			Home About us Contact

L. Lactis Strains (l + lacti_strain)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

The long and winding road from the research laboratory to industrial applications of lactic acid bacteria

FEMS MICROBIOLOGY REVIEWS, Issue 3 2005
Martin Bastian Pedersen
Abstract Research innovations are constantly occurring in universities, research institutions and industrial research laboratories. These are reported in the scientific literature and presented to the scientific community in various congresses and symposia as well as through direct contacts and collaborations. Conversion of these research results to industrially useful innovations is, however, considerably more complex than generally appreciated. The long and winding road from the research laboratory to industrial applications will be illustrated with two recent examples from Chr. Hansen A/S: the implementation in industrial scale of a new production technology based on respiration by Lactococcus lactis and the introduction to the market of L. lactis strains constructed using recombinant DNA technology. [source]

Discrepancies between the phenotypic and genotypic characterization of Lactococcus lactis cheese isolates

LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2006
M. De La Plaza
Abstract Aims:, The use of randomly amplified polymorphic DNA (RAPD)-PCR fingerprinting and plasmid profiles to determine at the strain level, the similarity of Lactococcus lactis isolates obtained during sampling of traditional cheeses and to verify its correspondence to the selected phenotypic characteristics. Methods and Results:, A total of 45 L. lactis isolates were genotypically analysed by RAPD-PCR fingerprinting and plasmid patterns. Phenotypic traits used to compare strains were proteolytic, acidifying, aminotransferase (aromatic and branched chain aminotransferase) and , -ketoisovalerate decarboxylase (Kivd) activities. The results show that 23 isolates could be grouped in clusters that exhibited 100% identity in both their RAPD and plasmid patterns, indicating the probable isolation of dominant strains during the cheese sampling process. However, there were phenotypic differences between isolates within the same cluster that included the loss of relevant technological properties such as proteinase activity and acidifying capacity or high variation in their amino acid converting enzyme activities. Likewise, the analysis of a specific attribute, Kivd activity, indicated that 7 of 15 isolates showed no detectable activity despite the presence of the encoding (kivd) gene. Conclusion:, Phenotypic differences found between genotypically similar strains of L. lactis strains could be linked to differences in enzymatic expression. Significance and Impact of the Study:, Phenotypic analysis of L. lactis isolates should be considered when selecting strains with new cheese flavour forming capabilities. [source]

A novel phenotype based on esterase electrophoretic polymorphism for the differentiation of Lactococcus lactis ssp. lactis and cremoris

LETTERS IN APPLIED MICROBIOLOGY, Issue 4 2006
H. Ouzari
Abstract Aims:, To evaluate the esterase phenotype in Lactococcus lactis strains isolated from traditional Tunisian dairy products. Methods and Results:, A collection of 55 L. lactis strains isolated from traditional fermented milk products and three reference strains were identified at species and subspecies level using molecular methods targeted to the 16S rRNA gene and to the histidine operon. The genotypic data obtained allowed the identification of the strains as L. lactis ssp. lactis and L. lactis ssp. cremoris with the prevalence of the ssp. lactis. The phenotypic identification based on arginine hydrolysis, the growth at 40°C and in presence of 4% NaCl showed several discrepancy with the identification data based on genotypic analysis. Additional experiments carried out evaluating the esterase electrophoretic patterns revealed four classes of esterases identified on the basis of their electrophoretic mobility and specific activity on , - and , -naphthyl ester of acetate and propionate. Esterase profiles discriminated the strains in two main groups corresponding to the subspecies cremoris and lactis according to a DNA-based identification. Conclusions:, The evaluation of esterase activity represents a novel phenotype for the taxonomic discrimination of the L. lactis ssp. lactis and cremoris. Significance and Impact of the Study:, Besides the DNA-based techniques that allow the rapid and accurate species/subspecies identification, the electrophoretic esterase profiles of L. lactis strains represents: (i) a new phenotypic tool to understand the physiology and the ecology of this species; and (ii) a new test for the potential selection of flavour producing strains. [source]

Conjugation mediates transfer of the Ll.LtrB group II intron between different bacterial species

MOLECULAR MICROBIOLOGY, Issue 5 2004
Kamila Belhocine
Summary Some self-splicing group II introns (ribozymes) are mobile retroelements. These retroelements, which can insert themselves into cognate intronless alleles or ectopic sites by reverse splicing, are thought to be the evolutionary progenitors of the widely distributed eukaryotic spliceosomal introns. Lateral or horizontal transmission of introns (i.e. between species), although never experimentally demonstrated, is a well-accepted model for intron dispersal and evolution. Horizontal transfer of the ancestral bacterial group II introns may have contributed to the dispersal and wide distribution of spliceosomal introns present in modern eukaryotic genomes. Here, the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis was used as a model system to address the dissemination of introns in the bacterial kingdom. We report the first experimental demonstration of horizontal transfer of a group II intron. We show that the Ll.LtrB group II intron, originally discovered on an L. lactis conjugative plasmid (pRS01) and within a chromosomally located sex factor in L. lactis 712, invades new sites using both retrohoming and retrotransposition pathways after its transfer by conjugation. Ll.LtrB lateral transfer is shown among different L. lactis strains (intraspecies) (retrohoming and retrotransposition) and between L. lactis and Enterococcus faecalis (interspecies) (retrohoming). These results shed light on long-standing questions about intron evolution and propagation, and demonstrate that conjugation is one of the mechanisms by which group II introns are, and probably were, broadly disseminated between widely diverged organisms. [source]