Search results for "Microbio"

Citrate Sensing by the C 4 -Dicarboxylate/Citrate Sensor Kinase DcuS of Escherichia coli : Binding Site and Conversion of DcuS to a C 4 -Dicarboxylat…

2007

ABSTRACT The histidine protein kinase DcuS of Escherichia coli senses C 4 -dicarboxylates and citrate by a periplasmic domain. The closely related sensor kinase CitA binds citrate, but no C 4 -dicarboxylates, by a homologous periplasmic domain. CitA is known to bind the three carboxylate and the hydroxyl groups of citrate by sites C1, C2, C3, and H. DcuS requires the same sites for C 4 -dicarboxylate sensing, but only C2 and C3 are highly conserved. It is shown here that sensing of citrate by DcuS required the same sites. Binding of citrate to DcuS, therefore, was similar to binding of C 4 -dicarboxylates but different from that of citrate binding in CitA. DcuS could be converted to a C 4 -…

Proton-dependent kinetics of citrate uptake in growing cells ofLactococcus lactissubsp.lactisbv.diacetylactis

1995

The kinetic analysis of citrate uptake in growing cells of Lactococcus lactis subsp. lactis biovar. diacetylactis identified a proton-dependent transport and suggested the divalent anionic species as the form of citrate transported across cell membranes. The reaction followed Michaelis-Menten kinetics for a two-substrate reaction. The limiting steps were the formation of the ternary complex and the rate of transport. Temperature modified the activity of the permease, increasing the uptake rate.

Hunting the plant surrender signal activating apoplexy in grapevines after Neofusicoccum parvum infection

2021

SummaryApoplectic breakdown from Grapevines Trunk Diseases (GTDs) has become a serious challenge to viticulture in consequence to drought stress. We hypothesise that fungal aggressiveness is controlled by a chemical communication between host and colonising fungus.We introduce the new concept of a “plant surrender signal” accumulating in host plants under stress and triggering aggressive behaviour of the strain Neofusicoccum parvum (Bt-67) causing Botryosphaeriaceae-related dieback in grapevines.Using a cell-based experimental system (Vitis cells) and bioactivity-guided fractionation, we identify trans-ferulic acid, a monolignol precursor, as “surrender signal”. We show that this signal spe…

1998

Reaction centers (RC) from the species Erythrobacter (Eb.) litoralis, Erythromonas (Em.) ursincola and Sandaracinobacter (S.) sibiricus have been purified by LDAO treatment of light-harvesting-reaction center complexes and DEAE chromatography. The content and overall organisation of the RCs' chromophores, determined by linear dichroism (LD) and absorption spectroscopy, are similar to those isolated from anaerobic photosynthetic bacteria. The redox properties of the primary electron donor are pH-independent and very similar to those determined for anaerobic photosynthetic bacteria with midpoint potential values equal to 445 (± 10), 475 and 510 mV for Eb. litoralis, S. sibiricus and Em. ursin…

Plant-growth-regulatingN-(phosphonoacetyl)amines

1994

A series of N‐(phosphonacetyl)amine derivatives were synthesized and screened for plant‐growth regulating activity on Lepidium sativum L. and Cucumis sativus L. Aromatic N‐(phosphonoacetyl)amines. which may be considered as possible analogues of N‐acylaniline herbicides obtained by replacement of their acyl group by the phosphonacetyl moiety, exhibited significant or moderate herbicidal activity. In contrast, N‐(phosphonoacetyl)amino acids and N‐(phosphonoacetyl)aminophosphonic acids promoted the growth of L. sativum and C. sativus roots.

Biological activity of resveratrol, a stilbenic compound from grapevines, against Botrytis cinerea, the causal agent for gray mold

1997

The biological activity of resveratrol, a stilbenic compound synthesized by grapevines in response to various stresses, was reevaluated against Botrytis cinerea using a novel in vitro system that enabled direct observation of the fungus with an inverted microscope. We determined that 90 μg resveratrol/ml reduced germination of B. cinerea conidia by ca. 50%. Moreover, resveratrol was shown to significantly reduce mycelial growth of B. cinerea at concentrations ranging from 60 to 140 μg/ml. Exposure to resveratrol at concentrations ranging from 60 to 140 μg/ml resulted in cytological changes in B. cinerea, such as production of secondary or tertiary germ tubes by conidia, cytoplasmic granulat…

Degradation of stilbene-type phytoalexins in relation to the pathogenicity of Botrytis cinerea to grapevines

1996

The ability of eight isolates of Botrytis cinerea to degrade the stilbene phytoalexins, resveratrol and pterostilbene, was compared with their pathogenicity to grapevines. All strains which degraded resveratrol and pterostilbene were highly or moderately pathogenic to in vitro cultures of grapevines (Vitis rupestris) after inoculation with agar disks containing mycelium, while those which were unable to degrade phytoalexins were non-pathogenic. In all cases, the hydroxystilbene-degrading activity was related to the presence of laccase activity in the culture filtrates, as shown by using syringaldazine as substrate. The role of laccase-mediated degradation of phytoalexins in relation to path…

The Significance of Stilbene-Type Phytoalexin Degradation by Culture Filtrates of Botrytis Cinerea in the Vine-Botrytis Interaction

1993

Phytoalexins, antimicrobial compounds, synthesized by a plant in response to infection or a variety of stresses are known to be the most efficient way by which grapevines withstand an attack by Botrytis cinerea Pers., the causal organism for grey mould. In that plant, such responses include the production of a simple stilbene, resveratrol, and the biosynthetically related compounds, viniferins and pterostilbene. If stilbene-type phytoalexins represent a contributory factor in the resistance of grapevines to B.cinerea, the capacity of the pathogen to metabolize antifungal compounds released by the host could also play a significant role in the outcome of the interaction between grapevines an…

The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics.

2014

Escherichia coli contains a versatile respiratory chain that oxidizes 10 different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors. Salmonella is able to use two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. A large number of respiratory pathways can be established by combining different electron donors and acceptors. The respiratory dehydrogenases use quinones as the electron acceptors that are oxidized by the terminal reductase and oxidases. The enzymes vary largely with respect to their composition, architecture, membrane topolog…

Defoliation and the availability of currently assimilated carbon in the Phleum pratense rhizosphere

2002

Abstract It has been hypothesised that defoliation and aboveground herbivory increase the availability of currently assimilated C to organisms living in plant rhizospheres. We established a growth chamber experiment consisting of Phleum pratense individuals growing in sand culture to examine the short- and long-term effects of defoliation on the availability of current C assimilates in the P. pratense rhizosphere. Using 14CO2 pulse labelling, we followed partitioning of currently assimilated C between shoots, roots and rhizosphere-derived organic matter (RDOM). The experiment constituted of two treatments, defoliation history and recent defoliation, in a fully factorial design. Defoliation …