Search results for "Streptococcaceae"
showing 10 items of 18 documents
Comparison of growth, acidification and productivity of pure and mixed cultures of Streptococcus salivarius subsp. thermophilus 404 and Lactobacillus…
1994
International audience; Pure and mixed controlled-pH batch cultures of Streptococcus salivarius subsp. thermophilus 404 and Lactobacillus delbrueckii subsp. bulgaricus 398 have been conducted. The characteristics of growth and acidification and the productivity of the cultures were compared. During the mixed cultures, the growth characteristics revealed a pronounced stimulation of S. thermophilus whereas L. bulgaricus metabolism was not significantly improved. The final total population was 1.4 to 4.9 higher than in pure cultures. The acidification characteristics were not enhanced by the mixed culture conditions. The productivity of mixed cultures was 1.7 to 2.4 times higher as compared to…
A descriptive model for citrate utilization by Lactococcus lactis ssp lactis bv diacetylactis
1993
A model for the use of citrate by Lactococcus lactis ssp lactis bv diacetylactis CNRZ 125 is proposed. Citrate metabolism by this strain leads to the production of acetate, CO2 and C4 compounds (diacetyl, acetoin, 2,3-butylene glycol). The model furnishes correct simulations, consistent with published results on the pathways used and on lactose-citrate co-metabolism. Citric acid is incorporated independently of growth. The production of flavoring compounds is a complex process, depending on the rate of citrate utilization, on the proportion of pyruvate arising from citrate and which condenses to form α-acetolactate and CO2, on the rate of transformation of α-acetolactate to diacetyl and ace…
Modeling of growth and lactate fermentation by Lactococcus lactis subsp. lactis biovar. diacetylactis in batch culture
1993
The kinetic behaviour of Lactococcus lactis subsp. lactis biovar. diacetylactis was studied in batch culture under non-limiting conditions that allow high growth and product formation. A model based on laboratory results is proposed for growth and l-lactate fermentation. It shows the necessity for differentiating biomass into three physiological states, two active, Xg (growth + acidification) and Xng (acidification), and one inactive, Xi. The kinetic theory of the model demonstrates the non-competitive nature of fermentation end-product inhibition on growth and acidification, and describes the passage from one physiological state to another. Satisfying simulations were obtained for batch fe…
Medium for Screening Leuconostoc oenos Strains Defective in Malolactic Fermentation
1989
A new sensitive medium was developed to screen and isolate mutagenic Leuconostoc oenos strains defective in malolactic fermentation. The essential components of the medium included fructose (22 mM), l -malic acid (74.6 mM), bromocresol green (as pH indicator), and cellulose powder. The wild-type colonies turned blue, but defective malolactic colonies gave an acid reaction and remained yellow-green.
Conjugative plasmid pIP501 undergoes specific deletions after transfer from Lactococcus lactis to Oenococcus oeni
2003
Conjugal transfer of plasmids pIP501 and its derivative pVA797 from Lactococcus lactis to Oenococcus oeni was assayed by filter mating. Plasmid pIP501 was transferred to a number of O. oeni strains whereas a single transconjugant of O. oeni M42 was recovered when pVA797 was used. Physical analysis of the transconjugant plasmids revealed that pIP501 and pVA797 underwent extensive deletions in O. oeni that affected the tra region (conjugal transfer) and SegB region (stability). All derivatives showed segregational instability in O. oeni, but were stably maintained in L. lactis. These differences correlated with the different plasmid copy numbers and the extent of deletions within the SegB reg…
Streptococcus lactarius sp. nov., isolated from breast milk of healthy women.
2011
Three strains of a hitherto-unknown, Gram-stain-positive coccus were recovered from the milk of three non-related healthy women. The isolates shared 99% 16S rRNA gene sequence similarity with sequences from uncultured members of the Lactobacillales and Streptococcus. The closest sequence corresponding to a defined species was that of Streptococcus peroris GTC 848T, with a similarity of 98%. A partial sequence (488 bp) of the tuf gene also showed 97% similarity with that of S. peroris CCUG 39814T. The combined 16S rRNA/tuf-based phylogeny revealed that all the isolates grouped in a statistically well-supported cluster separate from S. peroris. Enzyme activity profiles as well as fermentation…
Development of a modified DNA extraction method for pulsed-field gel electrophoresis analysis of Staphylococcus aureus and enterococci without using …
2010
A modified pulsed-field gel electrophoresis (PFGE) protocol was developed and applied to clinical isolates of Staphylococcus aureus and enterococci to reduce the cost of using lysostaphin. This protocol reduces the expenses of PFGE typing of S. aureus and enterococci as it removes the use of lysostaphin during the spheroplast formation from these bacteria.
In vitro activity of LY333328, a new glycopeptide, against extracellular and intracellular vancomycin-resistant enterococci.
2000
The objectives of the study were to observe the activity of LY333328, a new semisynthetic glycopeptide, compared to that of vancomycin against six strains of Enterococcus faecium and Enterococcus faecalis, including four vancomycin-resistant strains. Bacteria ingested by polymorphonuclear leukocytes (PMN) as well as extracellular bacteria were studied using a colony count method. The activity against intracellular bacteria was tested with the drugs present in the extracellular medium, as well as after preincubating the PMN and removal of the drugs. LY333328 is active against the tested enterococci, regardless of their susceptibility to vancomycin, with MICs of 1-2 mg/l. It is bacteriostatic…
A selective medium for the isolation of malolactic mutants of Leuconostoc oenos
1994
We have developed a selective medium for the isolation of Leuconostoc oenos mutants defective in malolactic fermentation. Forty per cent of colonies isolated directly on selective plates after UV mutagenesis had lost their ability to degrade malate. None of the tested mutants showed any detectable malolactic activity and all lacked a protein band corresponding in size to that of the malolactic enzyme. The availability of such mutants provides a valuable tool both for physiological and genetic research on malolactic fermentation.
Antimicrobial and antineoplastic activities of new 4-diazopyrazole derivatives
1998
Abstract Several new 4-diazopyrazole derivatives were prepared by the reaction of 3-methyl-5(substituted-benzamido)pyrazoles with an excess of nitrous acid in acetic acid solution. The compounds were tested for antiretroviral activity in HIV-1 infected MT-4 cells and antiproliferative effects against a panel of human leukemia, lymphoma and solid tumor cell lines. They were also tested for activity against representative gram-negative ( Shigella, Salmonella ) and gram-positive ( S. aureus, D group Streptococcus ) bacteria as well as fungi ( C. albicans, C. paratropicalis, C. neoformans and A. fumigatus ). Compounds were devoid of anti HIV-1 and antimicotic activities, whereas they were activ…