Search results for "bacteria."
showing 10 items of 4757 documents
Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis
2010
Lactococcus lactis can decrease the redox potential at pH 7 (E(h7)) from 200 to -200 mV in oxygen free Man-Rogosa-Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in E(h7) by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final E(h7) (-200 mV) was reached, only thiol-reactive reagents could restore the initial E(h7) value. Inhibition of the proton motive force showed no effect on maintaining the final E(h7) value. These result…
AlkAniline-Seq: A Highly Sensitive and Specific Method for Simultaneous Mapping of 7-Methyl-guanosine (m7G) and 3-Methyl-cytosine (m3C) in RNAs by Hi…
2021
Epitranscriptomics is an emerging field where the development of high-throughput analytical technologies is essential to profile the dynamics of RNA modifications under different conditions. Despite important advances during the last 10 years, the number of RNA modifications detectable by next-generation sequencing is restricted to a very limited subset. Here, we describe a highly efficient and fast method called AlkAniline-Seq to map simultaneously two different RNA modifications: 7-methyl-guanosine (m7G) and 3-methyl-cytosine (m3C) in RNA. Our protocol is based on three subsequent chemical/enzymatic steps allowing the enrichment of RNA fragments ending at position n + 1 to the modified nu…
Ability of Kocuria varians LTH 1540 To Degrade Putrescine: Identification and Characterization of a Novel Amine Oxidase.
2015
This work describes the identification and characterization of an amine oxidase from Kocuria varians LTH 1540 (syn. Micrococcus varians) primarily acting on putrescine. Data from MALDI-TOF MS/MS and the identification of Δ(1)-pyrroline as degradation product from putrescine indicate that the enzyme is a flavin-dependent putrescine oxidase (PuO). Properties of partially purified enzyme have been determined. The enzyme oxidizes diamines, putrescine and cadaverine, and, to a lesser extent, polyamines, such as spermidine, but not monoamines. The kinetic constants (Km and Vmax) for the two major substrates were 94 ± 10 μM and 2.3 ± 0.1 μmol/min·mg for putrescine and 75 ± 5 μM and 0.15 ± 0.02 μmo…
The NreA Protein Functions as a Nitrate Receptor in the Staphylococcal Nitrate Regulation System
2013
Staphylococci are able to use nitrate as an alternative electron acceptor during anaerobic respiration. The regulation of energy metabolism is dependent on the presence of oxygen and nitrate. Under anaerobic conditions, staphylococci employ the nitrate regulatory element (Nre) for transcriptional activation of genes involved in reduction and transport of nitrate and nitrite. Of the three proteins that constitute the Nre system, NreB has been characterized as an oxygen sensor kinase and NreC has been characterized as its cognate response regulator. Here, we present structural and functional data that establish NreA as a new type of nitrate receptor. The structure of NreA with bound nitrate w…
α-L-rhamnosidases: Old and New Insights
2007
L-Rhamnose is a component of plant cell wall pectic polysaccharides (Mutter et al., 1994; Ridley et al., 2001), glycoproteins (Haruko and Haruko, 1999) and secondary metabolites such as anthocyanins (Renault et al., 1997), flavonoids (Bar-Peled et al., 1991) and triterpenoids (Friedman and McDonald, 1997). It has also been found in bacterial heteropolysaccharides (Hashimoto and Murata, 1998), rhamnolipids (Ochsner et al., 1994) and in the repeating units of the O-antigen structure of the lipopolysaccharide component of bacterial outer membranes (Chua et al., 1999). Some rhamnosides are important bioactive compounds, e.g. cytotoxic saponins (Bader et al., 1998; Yu et al., 2002), antifungal p…
Ligands affecting silver antimicrobial efficacy on Listeria monocytogenes and Salmonella enterica
2013
Although silver is being extensively used in food or other applications as the key component to control microbial proliferation, many factors affecting its real potential are still unknown. In the present work, the presence of specific ligands or the contents in organic matter was correlated with silver speciation and its antibacterial performance. Silver was found to be only active in form of free silver ions (FSI). The presence of chloride ions produced an equilibrium of stable silver chloride complexes which were void of antimicrobial efficacy. However, even at relatively high concentrations of chlorides, a small fraction of FSI may still be present, producing a bactericidal effect with …
The effect of iron on the biodegradation of natural dissolved organic matter
2016
Iron (Fe) may alter the biodegradation of dissolved organic matter (DOM), by interacting with (DOM), phosphorus (P) and microbes. We isolated DOM and a bacterial community from boreal lake water and examined bacterial growth on DOM in laboratory experiments. Fe was introduced either together with DOM (DOM-Fe) or into bacterial suspension, which led to the formation of insoluble Fe-precipitates on bacterial surfaces (Fe coating). In the latter case, the density of planktonic bacteria was an order of magnitude lower than that in the corresponding treatment without introduced Fe. The association of Fe with DOM decreased bacterial growth, respiration, and growth efficiency compared with DOM alo…
Effect of chelatants on gellan gel rheological properties and setting temperature for immobilization of living bifidobacteria.
1993
The effect of various concentrations of sequestrants (sodium citrate, sodium metaphosphate, and EDTA) was studied on gellan gel (1.5-2.5% (w/v)) setting temperature and rheological properties. Addition of EDTA between 0 and 0.8% (w/v) led to a progressive decrease of setting temperature. Citrate and metaphosphate decreased this parameter when added up to 0.4 or 0.6%, depending on gellan gum concentration, eventually resulting in the absence of gel formation at room temperature for the 1.5% gellan solution containing 0.4% citrate. This effect was accompanied by a significant decrease of gel strength and stiffness and might be attributed to the binding of the divalent cations required for cha…
Widespread contribution of methane-cycle bacteria to the diets of lake profundal chironomid larvae.
2008
Reports of unexpectedly 13C-depleted chironomid larvae in lakes have led to an hypothesis that significant transfer of detrital organic matter to chironomid larvae may occur via methane-cycle bacteria. However, to date little is known of how such transfer might vary across species and lakes. We gathered data from 87 lakes to determine how widespread this phenomenon might be and to define boundaries for its likely magnitude. Carbon stable isotope values of chironomid larvae varied greatly between taxa. Very marked 13C-depletion was evident only in certain taxa, especially Chironomus plumosus, C. anthracinus, and C. tenuistylus, all characteristic of eutrophic or dystrophic lakes and known to…
Purification and characterization of an inducible p-coumaric acid decarboxylase from Lactobacillus plantarum
2006
Abstract Lactobacillus plantarum cells displayed substrate-inducible decarboxylase activities on p-coumaric and ferulic acids of 0.6 and 0.01 μmol min−1 mg−1, respectively. Activity in uninduced cells or corresponding cell extracts was undetectable (