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PubMed2000

Wavelike Distributions of Microbial Populations along an Artificial Root Moving through Soil.

In a previous paper, we described wavelike distributions of bacterial populations along roots of wheat, and hypothesized that one mechanism underlying these distributions might be growth and death cycles of microorganisms in response to a moving nutrient source, the root tip. Similar wavelike distributions in microbial biomass were obtained using a simulation model for growth and death of bacteria in relation to their substrate (BACWAVE). The model was parameterized with data from one experiment on rhizosphere bacterial populations along wheat roots, and compared against a similar but independent experiment. In experiments described in this paper, similar wavelike distributions in bacterial populations were observed in response to a single artificial exudate moving linearly through a soil that had been air-dry for almost 2 years. The period of the spatial waves was longer when the tip of the artificial exudate moved at a speed of 4.2 cm/day compared to a tip moving at 1.1 cm/day, but after transformation into the temporal domain, the periods of the waves were similar for both moving speeds. The observed distributions were simulated using the BACWAVE model with similar parameter values as derived from the experiment with wheat roots mentioned above. The results presented in this paper confirm our hypothesis that wavelike distributions of bacterial population along plant roots can arise from "exudates" released primarily from the root tip, without the need for additional exudation points.

Journal Article↗

PubMed1982

Nitrate Reduction by Roots of Soybean (Glycine max [L.] Merr.) Seedlings.

Studies were conducted with 9 to 12 day-old soybean (Glycine max [L.] Merr. cv. Williams) seedlings to determine the contribution of roots to whole plant NO(3) (-) reduction. Using an in vivo -NO(3) (-) nitrate reductase (NR) assay (no exogenous NO(3) (-) added to incubation medium) developed for roots, the roots accounted for approximately 30% of whole plant nitrate reductase activity (NRA) of plants grown on 15 mm NO(3) (-).Nitrogen analyses of xylem exudate showed that 53 to 66% of the total-N was as reduced-N, depending on the time of day of exudate collection. These observations supported enzyme data that suggested roots were contributing significantly to whole plant NO(3) (-) reduction. In short-term feeding studies using (15)N-NO(3) (-) significant and increasing atom percent (15)N excess was found in the reduced-N fraction of xylem exudate at 1.5 and 3 hours after feeding, respectively, which verified that roots were capable of reducing NO(3) (-).Estimated reduced-N accumulation by plants based on in vivo -NO(3) (-) NR assays of all plant parts substantially over-estimated actual reduced-N accumulation by the plants. Thus, the in vivo NR assay cannot be used to accurately estimate reduced-N accumulation but still serves as a useful assay for relative differences in treatment conditions.

Journal Article↗

PubMed1990

Characterization of Root Surface and Endorhizosphere Pseudomonads in Relation to Their Colonization of Roots.

An extensive colonization of the endorhizosphere by fluorescent pseudomonads was observed in tomato plants grown on artificial substrates. These studies reveal that a significantly higher percentage of pseudomonads obtained from the endorhizosphere (30%) reduced plant growth than those obtained from the root surface (4%). Lipopolysaccharide patterns, cell envelope protein patterns, and other biochemical characteristics indicated that Pseudomonas isolates obtained from the endorhizosphere are distinct from Pseudomonas isolates obtained from the root surface. Isolates from the endorhizosphere especially were able to recolonize the endorhizosphere of both sterile and nonsterile tomato roots. The ability of the endorhizosphere isolates to colonize the endorhizosphere significantly correlated with their agglutination by tomato root agglutinin but did not correlate with chemotaxis to seed exudates of tomato. No correlation between colonization of the endorhizosphere and agglutination by root agglutinin could be demonstrated for the root surface isolates. We propose that agglutination of specific Pseudomonas strains by root agglutinin is of importance in the initial phase of adherence of bacteria to the root surface.

Journal Article↗

PubMed2005

Neutrophil elastase levels in periapical exudates of symptomatic and asymptomatic teeth.

The aim of this study was to determine neutrophil elastase levels (NE) in periapical exudates and to evaluate its relationship with clinical signs and symptoms of endodontically involved teeth. A total of 42 teeth with periapical periodontitis of 37 patients were clinically examined and spontaneous pain, swelling, pain on palpation or percussion, sinus tract formation and pus discharge were recorded. Additionally, periapical lesion size was measured on periapical radiographs. Periapical exudate samples were obtained during routine root canal treatment by using paper points. Enzyme levels were determined by spectrophotometric assays using the NE specific substrate N-methoxysuccinil-Ala-Ala-Pro-Val-p-nitroanilide. The teeth with signs and symptoms showed higher NE levels than the teeth without symptoms (p<0.05). The differences were significant when NE levels were presented as total amounts instead of concentration. This study demonstrated that NE in periapical lesions related with clinical symptoms and total enzyme amount may be more reliable mode of data presentation.

Adult↗

PubMed2005

[Root activity and nitrogen assimilation of rice (Oryza sativa) under free-air CO2 enrichment].

With Free-Air CO2 Enrichment(FACE) technique, this paper studied the root activity and amino acid(aa) synthesis of rice (Oryza sativa )at low N(LN, 150 kgN x hm(-2)) and normal N(NN, 250 kgN x hm(-2)) under ambient air and elevated atmospheric CO2 (Ambient + 200 micromol x mol(-1)). Under elevated CO2, the xylem exudates per hill changed little, while the xylem exudates per stem declined by 1.4% - 21.7% as the result of greater tiller numbers. At tillering and heading stages, elevated CO2 increased aa N/inorganic N in xylem exudates by 11.1% - 143.1%, but did not affect the aa concentration in xylem exudates and the total amount of aa in roots significantly. However, at 35 days after heading, the aa N/inorganic N ratio decreased by 38.1% (LN) and 29.2% (NN) under elevated CO2. FACE also declined the aa concentration in xylem exudates by 34.0% (LN) and 44.7% (NN), and the total amount of aa by 50.8% (LN) and 40.0% (NN), which meant the retarded capability of aa synthesis in roots. N amendment led to a decrease of aa N/inorganic N in xylem exudates by 19.5% (Ambient) and 36.8% (FACE) at heading stage, as the result of unaffected aa and increased inorganic N concentration. There existed a significantly antagonistical CO2 x N interaction on aa N/inorganic N at heading stage.

Air↗

PubMed1991

[An epidural spinal abscess with caudal symptoms as a complication of Crohn's disease].

Progressive symptoms of caudal compression (flaccid paraparesis, sensory disorders), accompanied by severe pain and fever, developed over a few days in a 26-year-old man with Crohn's disease for 11 years. Spinal computed tomography, performed under the diagnosis of herniated disc, revealed intraspinal soft tissue, as well as gas in the spinal canal (L2-S3) and the paravertebral muscles. This led to the diagnosis of acute epidural abscess and a laminectomy was performed (at L4-S2). Intraspinally there was thickened, bluish fatty tissue; thick pus exuded between dura and the sacral roots. Suction-irrigation of the spinal canal was undertaken via an epidural drain. Postoperative contrast infusion into the colon demonstrated a fistula directed towards the sacrum. The postoperative course was complicated by severe respiratory impairment of which the patient died.--Epidural abscess is a rare complication of Crohn's disease. Because of its poor prognosis early diagnosis with magnetic resonance imaging or computed tomography should be undertaken in every patient with Crohn's disease who has back pain, fever or, particularly, symptoms of spinal compression.

Abscess↗

PubMed1977

Developmental Biochemistry of Cottonseed Embryogenesis and Germination: VIII. Free Amino Acid Pool Composition during Cotyledon Development.

The composition of the free amino acid pool in embryonic cotton (Gossypium hirsutum) cotyledons is quite distinct from that of endosperm, and that of germinated, greened cotyledons is quite distinct from that of leaves. During germination (including the precocious germination of immature seeds), the pool expands considerably showing a pronounced accumulation of asparagine. The high level of asparagine found in seedling roots and in the cotyledon vascular exudate indicates that this is the major transported amino acid in germination. There is no pool expansion in the presence of abscisic acid. In the presence of actinomycin D, the pool expands, but an enormous accumulation of glutamine takes place. The composition of the pool at any stage is not related to the composition of the isoacceptor transfer RNA pool, nor to the composition of the storage protein. Anaerobiosis leads to an accumulation of aspartate, alanine, and glycine at the expense of asparagine; however, desiccation does not result in an accumulation of proline. Conspicuously high levels of arginine are maintained through embryogenesis and germination. The levels of individual amino acids are presented as nanomol per cotyledon pair and as per cent of total pool.

Journal Article↗

PubMed2003

Allelopathy and exotic plant invasion: from molecules and genes to species interactions.

Here we present evidence that Centaurea maculosa (spotted knapweed), an invasive species in the western United States, displaces native plant species by exuding the phytotoxin (-)-catechin from its roots. Our results show inhibition of native species' growth and germination in field soils at natural concentrations of (-)-catechin. In susceptible species such as Arabidopsis thaliana, the allelochemical triggers a wave of reactive oxygen species (ROS) initiated at the root meristem, which leads to a Ca2+ signaling cascade triggering genome-wide changes in gene expression and, ultimately, death of the root system. Our results support a "novel weapons hypothesis" for invasive success.

Arabidopsis↗

PubMedDate not supplied

[Effect of phosphorus on the colonization of barley rhizosphere by microorganisms].

The mineral phosphorus supply produced two outbreaks in the bacterial population of the barley rhizosphere and rhizoplane but inhibited the growth of fungal mycelium. The inhibition of mycelial growth might be due to the exudation of specific inhibitors by barley roots, since the most pronounced inhibition was observed at high doses of supplementary phosphorus.

Bacteria↗

PubMed2003

Rice seedling whole exudates and extracted alkylresorcinols induce stress-response in Escherichia coli biosensors.

A set of Escherichia coli sensor strains was used to evaluate the stress exerted on surrounding bacteria by germinating rice seed exudates. These biosensor strains contain Vibrio fischeri luxCDABE genes fused to the promoters of different genes involved in bacterial responses to environmental stresses. They provided clear evidence for a stress exerted by rice exudates, as shown by the induction of the universal stress protein gene uspA as well as genes of the heat shock regulon, grpE, lon and dnaK. The oxidative stress gene katG, and the post-transcriptional ompF regulator encoded by micF were also activated. The lack of derepression of recA, uvrA and alkA indicated that damage to the DNA was not induced in the E. coli strains tested. Interestingly, resorcinolic lipids extracted from rice root seedlings induced the same promoters as whole exudates, suggesting that these compounds may contribute to the stress exerted by seedling exudates. The results obtained with E. coli biosensors thus indicate that, in vivo, exudates may also exert a selective pressure on root-colonizing bacteria.

Bacterial Proteins↗

PubMed2005

Uptake, transport and accumulation of nicotine by the Golden Potho (Epipremnum aureum): the central role of root pressure.

The roots of Epipremnum aureum, though not synthesizing nicotine themselves, take up exogenously fed nicotine as a xenobiotic. The alkaloid is subsequently translocated to the leaves, via the xylem path, where it accumulates in the mesophyll up to levels comparable with nicotine-rich Nicotiana species. The Epipremnum plants accept nicotine only up to a distinct level; saturation is reached after about 10 days. All mature, non-senescent leaves accumulate the same amount of nicotine. By different experimental approaches, unequivocal evidence could be provided that root pressure is the 'translocative force' for nicotine transport in E. aureum. Xylem sap exudates, collected from shoot stumps that were connected to an intact root system immersed in nicotine solution were analyzed for nicotine content. Nicotine uptake from the medium by the root and its subsequent transfer into the xylem of the shoot persisted for more than 10h without measurable decline of the transport rate, provided the nicotine concentrations applied were < or =0.05%. In intact plants, where both components of water transport in the xylem--root pressure and transpirative water flow--are in operation, no surplus transport of nicotine from the roots into the leaves took place beyond the level observed in amputated plants. Under the influence of inhibitors of root respiration, nicotine uptake was halted slowly in case of oxygen deprivation and in case of cyanide, or it stopped very rapidly when CCCP, an uncoupler of mitochondrial ATP formation, was applied to the roots. This threshold of toxicity against the xenobiotic was established by dose effect curves for nicotine sensitivity of the roots for root respiration and by transpiration measurements. Leaves, bearing a heavy 'nicotine load', showed symptoms of senescence only after 3-6 weeks, as indicated by a decline in the chlorophyll content, the chl a/b ratio, and the maximal quantum yield efficiency (Fv/Fm), and by an increase in catalase activity. Our results provide insight into the mechanisms of uptake, transport and storage of nicotine as a xenobiotic.

Araceae↗

PubMed2004

Resolution of persistent periapical infection by endodontic surgery.

AIM: To examine the surfaces of a root tip removed during surgical endodontic treatment for the presence of microorganisms. SUMMARY: The present clinical case illustrates an endodontic retreatment of a maxillary premolar tooth with a fistula and periapical reaction. The case was under treatment for 1 year, during which an intracanal medicament was replaced several times. As the lesion did not decrease and exudate was persistent through the fistula and root canal, root end resection with root end filling was performed. Microbiological samples were collected from the fistula, where Propionibacterium acnes, a species associated with endodontic failures, was detected by appropriate anaerobic technique. The resected root apex was observed by scanning electron microscopy (SEM), which revealed cocci and fungal forms surrounding one of the foramina. After 12 months, the periapical lesion had reduced.

Adult↗

PubMed1990

Polyamine analysis of infected root canal contents related to clinical symptoms.

The contents of infected root canals were collected by mechanical and chemical debridement. Intracanal polyamines were identified and quantified by HPLC in all canals examined, however, no histamine was detected in any canal. The relationship between the amount of each polyamine and clinical signs of the teeth was analyzed statistically. The teeth without clinical signs tended to have limited varieties and smaller amounts of polyamines. Using chi 2, the amounts were significantly greater in teeth with spontaneous pain, swelling and putrescent odor (p less than 0.01), with exudate (p less than 0.025) and with percussion pain (p less than 0.1) than in teeth without. Amounts of putrescine (p less than 0.05) and total polyamines (p less than 0.01) were greater in teeth with spontaneous pain and percussion pain than in teeth without clinical sign, and those with root canal exudate also had greater amounts of total polyamines than those without (p less than 0.01). The amounts of cadaverine, however, from the teeth with gingival fistulae, was greater than from those without (p less than 0.05). No significant relationship was established between the amount of each polyamine and the presence of putrescent odor or gingival swelling. Intracanal polyamines, especially putrescine may leak out through apical foramen and may be implicated in pain production by eliciting acute inflammatory response in the periapical tissues.

Adolescent↗

PubMed1999

Plant-exuded choline is used for rhizobial membrane lipid biosynthesis by phosphatidylcholine synthase.

Phosphatidylcholine is a major lipid of eukaryotic membranes, but found in only few prokaryotes. Enzymatic methylation of phosphatidylethanolamine by phospholipid N-methyltransferase was thought to be the only biosynthetic pathway to yield phosphatidylcholine in bacteria. However, mutants of the microsymbiotic soil bacterium Sinorhizobium (Rhizobium) meliloti, defective in phospholipid N-methyltransferase, form phosphatidylcholine in wild type amounts when choline is provided in the growth medium. Here we describe a second bacterial pathway for phosphatidylcholine biosynthesis involving the novel enzymatic activity, phosphatidylcholine synthase, that forms phosphatidylcholine directly from choline and CDP-diacylglycerol in cell-free extracts of S. meliloti. We further demonstrate that roots of host plants of S. meliloti exude choline and that the amounts of exuded choline are sufficient to allow for maximal phosphatidylcholine biosynthesis in S. meliloti via the novel pathway.

Choline↗

PubMedDate not supplied

[The influence of aconitum preparations on the development of chronic inflammation].

Experiments show that ethanol extracts prepared from the above-ground parts of Aconitum baicalensis and the above-ground parts and roots of Aconitum septentrionale L. suppressed the exudative and proliferative stages of model chronic inflammation. Both phytopreparations normalized some biochemical indices of the blood (total protein, seromucoids, firbinogen) altered by the inflammation.

Aconitum↗

PubMed1995

Treatment of large periapical lesions by inserting a drainage tube into the root canal.

Long-term drainage and depressurization is performed by inserting a stainless steel tube into the root canal of teeth with persisting periapical exudation. This article presents 2 cases of large periapical lesions showing a complete healing of bone after the drainage tube procedure. The tube allows lasting drainage, relieves the pressure and modifies the local apical environment so the host defense mechanism can exert repair process.

Adolescent↗

PubMed1980

Endotoxic activity in teeth with necrotic pulps.

From root canals of 13 teeth with necrotic pulps, samples were taken for analysis of endotoxin content by means of the Limulus by lysate technique. The results were related to the viable bacteria count of root canal samples, phenol/water-extracted lipopolysaccharides (LPS) from different gram-negative anaerobic bacteria, and to different fractions of inflammation exudate. It was found that the endotoxic activity of the root canal samples was correlated with the presence and the number of gram-negative bacteria in the root canal.

Adolescent↗

PubMed2001

Production of clover broomrape seed germination stimulants by red clover root requires nitrate but is inhibited by phosphate and ammonium.

The effect of nutrients (nitrate, ammonium, urea, phosphate and potassium) on the production and/or exudation of germination stimulants for clover broomrape (Orobanche minor Sm.), a root holoparasite, by its host red clover (Trifolium pratense L.) was examined using hydroponically grown material. Potassium (K2SO4) concentrations up to 100 mg l-1 (based on K) did not affect the production of germination stimulants by red clover while, in contrast, phosphate (NaH2PO4) was highly inhibitory even at concentrations as low as 1 mg l-1 (based on P). Nitrate (NaNO3) markedly promoted stimulant production in a dose-dependent manner from 2 to 50 mg l-1 (based on N). Ammonium [(NH4)2SO4] had no effect at 2 mg l-1 (based on N) but was inhibitory at higher concentrations. Ammonium is known to be a seed germination inhibitor of root parasites, indicating that ammonium has a dual inhibitory action. Urea had no effect at 2 mg l-1 (based on N) but was promotive at higher concentrations. These results provide a basis for the inhibitory effects of nitrogen fertilizer on infection by root parasitic weeds, broomrapes and witchweeds, and explain why these parasites prevail in areas where there is lower phosphorus availability in soils.

Journal Article↗