Combined use of a specific probe and PCAT medium to study Burkholderia in soil

Due to its pathogenic traits and agricultural benefits, there is some challenge in detecting Burkholderia in the soil environment. In this perspective, an existing semi-selective medium, (PCAT), was combined with a Burkholderia specific molecular probe. Using the complete 16S rRNA sequences of all available Burkholderia species type strains, we selected the following sequence: 5'-ACCCTCTGTTCCGACCATTGTATGA-3'. The probe was validated against GenBank sequences, with dot blots and colony hybridization tests. A diversity study of all strains growing on a PCAT plate after plating a soil dilution (75 strains) was carried out with ARDRA analysis and colony hybridization tests. All the hybridizing strains belonged to genus Burkholderia. The major type of non-hybridizing isolates belonged to Pseudomonas (16S rRNA sequencing). Both tools were combined to compare the Burkholderia populations in a rhizosphere (maize) and a non-rhizosphere soil. Based on hybridizing PCAT isolates, we were able to show an increase in Burkholderia populations in the maize rhizosphere. This genus represented 2% and 16% of the total cultivable microflora in the non-rhizosphere and rhizosphere soils, respectively. Although PCAT was shown not to be appropriate to routinely enumerate Burkholderia populations in soil, it allowed environmental investigations at the genus level, when combined with a molecular specific probe.

Burkholderia cepacia genomovar III Is a common plant-associated bacterium

A polyphasic taxonomic study involving DNA-DNA hybridization, whole-cell protein electrophoresis, and 16S ribosomal DNA sequence analysis revealed that a group of Burkholderia cepacia-like organisms isolated from the rhizosphere or tissues of maize, wheat, and lupine belong to B. cepacia genomovar III, a genomic species associated with "cepacia syndrome" in cystic fibrosis patients. The present study also revealed considerable protein electrophoretic heterogeneity within this species and demonstrated that the B. cepacia complex consists of two independent phylogenetic lineages.

Polyphasic classification of the genus Photorhabdus and proposal of new taxa: P. luminescens subsp. luminescens subsp. nov., P. luminescens subsp. akhurstii subsp. nov., P. luminescens subsp. laumondii subsp. nov., P. temperata sp. nov., P. temperata subsp. temperata subsp. nov. and P. asymbiotica sp. nov

The taxonomic position of Photorhabdus strains was examined through the results of DNA relatedness (S1 nuclease method) studies associated with the determination of delta Tm, 16S rRNA phylogenetic inferences and phenotypic characterization, including morphological, auxanographic, biochemical and physiological properties. Three genomic species were delineated on a consensus assessment. One of these species corresponded to Photorhabdus luminescens, since strains were at least 50% related to the type strain of this species with delta Tm less than 7 degrees C. The two other species were novel genomic species II and III, which were less than 40% related to each other with delta Tm higher than 9 degrees C. A comparison of the complete 16S rDNA sequences of several representatives of genomic species II and genomic species III revealed that each of them formed a stable lineage independent of the cluster generated by P. luminescens strains. The genomic species differed in their maximum temperatures for growth. A correlation with the ecological origin of the bacterial samples was noticed. The heat-tolerant group I (maximum growth temperature 35-39 degrees C) corresponded to the symbionts of Heterorhabditis bacteriophora groups Brecon and HP88 and Heterorhabditis indica, nematodes living in warm and tropical countries, respectively. Group II (maximum growth temperature 33-35 degrees C) encompassed symbionts from Heterorhabditis megidis, Heterorhabditis zealandica and group NC1 of H. bacteriophora, nematodes isolated in temperate climates. Group III were bacteria isolated from human specimens. Two new species, Photorhabdus temperata sp. nov. (type strain CIP 105563T) and Photorhabdus asymbiotica sp. nov. (type strain ATCC 43950T), are proposed for genomic species II and III, respectively. Species I and II can be separated into sub-groups on the basis of high DNA-DNA relatedness (more than 80% DNA binding with delta Tm < 1.5 degrees C), 16S rDNA branching and phenotypic characters. Therefore, we propose that the two species P. luminescens and P. temperata should be subdivided into subspecies as follows: P. luminescens subsp. luminescens subsp. nov. (type strain ATCC 29999T), P. luminescens subsp. akhurstii subsp. nov. (type strain CIP 105564T), P. luminescens subsp. laumondii subsp. nov. (type strain CIP 105565T) and P. temperata subsp. temperata subsp. nov.

Burkholderia graminis sp. nov., a rhizospheric Burkholderia species, and reassessment of [Pseudomonas] phenazinium, [Pseudomonas] pyrrocinia and [Pseudomonas] glathei as Burkholderia

In a survey of soil and wheat or maize rhizoplane bacteria isolated using a medium containing azelaic acid and tryptamine as sole carbon and nitrogen sources, respectively, a large proportion of Burkholderia-like bacteria were found. Among them, a homogeneous group of strains was identifiable based on phenotypic properties, fatty acid composition, DNA-DNA hybridizations and 16S rDNA sequences. According to molecular data, this group belongs to the genus Burkholderia but its weak similarity to previously described species suggests that it belongs to a novel species. Closest 16S rDNA phylogenetic neighbours of this species are Burkholderia caryophylli and two previously named Pseudomonas species which clearly appear to be part of the Burkholderia genus and were thus named Burkholderia glathei comb. nov. and Burkholderia phenazinium comb. nov. Strains of the new species are oxidase- and catalase-positive, produce indole and gelatinase, and use L-xylose, lactose, rhamnose, trehalose, D-lyxose, L-arabitol, xylitol and D-raffinose as sole carbon source. This novel taxon is named Burkholderia graminis. In the course of this study, [Pseudomonas] pyrrocinia also proved to be a member of the Burkholderia genus.

Identification and subcellular distribution of the Gi-proteins in the enterocytic-differentiated adenocarcinoma cell-line, Caco-2

As evidenced by pertussis toxin-catalysed [32P]ADP-ribosylation, immunoblotting and Northern blot, the human adenocarcinoma intestinal cell line Caco-2 expresses Gi2 and Gi3 proteins. The localization of these two Gis within the cell was investigated by using subcellular fractionation and confocal microscopy on intact cell layer. A brush-border rich fraction and a pellet containing the remaining cellular membranes were prepared. [32P]ADP-ribosylation and immunoblotting demonstrated the presence of both alpha i2 and alpha i3 in these two preparations. Immunofluorescence studies performed on intact cells grown on Transwell filters and viewed by confocal microscopy further confirmed the localization of alpha i3-subunit on basolateral as well as on apical membranes. In contrast, alpha i2-subunit was shown to accumulate mainly in the intra-cellular compartment while only faint staining of the plasma membrane was detectable. Based upon double-labelling experiments with antibody against rough endoplasmic reticulum (RER), there is a strong possibility that intra-cellular sites of alpha i2-subunit correspond to association with RER membranes.

Identification of alpha 2-adrenoceptors and of non-adrenergic idazoxan binding sites in pancreatic islets from young and adult hamsters

1. The current study was undertaken to investigate the characteristics of alpha 2-adrenoceptors and to search for the presence of NAIBS in hamster pancreatic islets. 2. Pancreatic islets were isolated from young (6-7 weeks) and adult (14-15 weeks) animals. 3. The identification of alpha 2-adrenoceptors using [3H]RX821002 indicated that adults exhibited higher number of alpha 2-adrenoceptors than the young animals (194 +/- 20 vs 105 +/- 16 fmol/mg protein) while the Kd value was unchanged. 4. Glucose-evoked insulin release was completely inhibited by the alpha 2-agonist clonidine (0.1 microM) whatever the age of the animals. Agonist inhibition curves showed the following rank order of potency: clonidine > UK14304 > adrenaline. 5. Blockade of UK14304-elicited inhibition by various antagonists indicated that yohimbine has a low affinity for the receptor supporting the conclusion that the receptor is of the alpha 2-D subtype. 6. Binding experiments with [3H]idazoxan under conditions allowing to discriminate between alpha 2-adrenoceptors and NAIBS showed that hamster pancreatic islets express a high number of NAIBS. The density of NAIBS was similar in young and adult hamsters (1550 +/- 245 and 1342 +/- 332 fmol/mg protein).

Fate of exogenous and newly synthesized cholesterol in intestinal cell lines

1. The current study was undertaken to test the existence of functionally distinct intracellular pools of cholesterol depending on the origin: neosynthesis or exogenous. 2. This was performed on two subpopulations, either differentiated or undifferentiated, of the HT29 cell line. 3. A parallel study was also carried out on Caco-2 cells. 4. First we checked the ability of differentiated HT29 cells to secrete lipids into the medium and found that lipid production was efficient but less so than in Caco-2 cells. 5. In contrast, undifferentiated HT29 cells were unable to secrete lipids into the medium. 6. Then we studied the fate of [14C]cholesterol incorporated into micellar preparations and of [14C]mevalonate in the different models. 7. The data obtained with labelled exogenous cholesterol show that it enters the membrane cholesterol pool as well as, for the differentiated models, the cholesteryl ester pool. 8. Similarly, labelled newly synthesized cholesterol could be used for membrane formation as well as for incorporation into cholesteryl esters. 9. Thus, in HT29 subpopulations as well as in Caco-2 cells, the results suggest the existence of a common pool of cholesterol whatever its origin.

Acyl-CoA: cholesterol acyltransferase in HT 29 cell subpopulations. Defect of activity in the undifferentiated cells

The ACAT activity was studied on different subpopulations deriving from HT29 cells, a human colon carcinoma cell line. Grown on standard medium (25 mM glucose), about 95% of these cells are undifferentiated (G + cells). From this heterogeneous population, differentiated cells were selected by glucose deprivation and grown either on medium without glucose (G - cells) or in standard medium containing 25 mM glucose (G-Rev cells). The G- and G-Rev cells have the features of differentiated small intestine cells. The two types of differentiated cells (G- and G-Rev) exhibited similar ACAT activities and the kinetic characteristics of the enzyme were also similar. A time-course study showed increasing activity during the exponential phase and a decrease just after confluency. It was possible to stimulate the enzyme by micellar or lipoprotein cholesterol. In contrast, the ACAT activity was hardly detectable in undifferentiated G + cells. In addition, all the experimental conditions known to stimulate ACAT activity, and confirmed in the differentiated HT29 cells, were inefficient in the undifferentiated G + cells. Therefore, the different models derived from HT29 cells provide the opportunity to study cholesterol esterification as well as the consequences of its aberrances in intestinal cells.

Metabolism of low-density lipoprotein in differentiated and undifferentiated HT29 colon cancer cells

The metabolism of human low-density lipoproteins was studied in 2 subpopulations deriving from cells of HT29, a human colon carcinoma cell line. When grown on standard medium (25 mM glucose), about 95% of these cells are undifferentiated (G+ cells). From this heterogeneous population, a subpopulation with features of differentiated small-intestinal cells was selected by glucose deprivation (G- cells). The characteristics of the LDL receptor were first investigated. The results showed that the binding of 125I-LDL to G+ and G- cells performed at 4 degrees C was saturable and specific. The Kd values were not statistically different in the 2 cell subpopulations. The Bmax of G+ cells was 55 +/- 6 ng 125I-LDL/mg cell protein and showed no changes whatever the phase of culture. In G- cells, the Bmax was higher during the exponential phase of culture and decreased in the post-confluent phase (82 +/- 5 versus 15 +/- 6.8 ng 125I-LDL/mg cell protein). Cellular degradation of 125I-LDL was effective in both cell subpopulations but time-course studies showed that, in post-confluent G- cells, degradation was slowed as compared to G+ cells (4 hr vs. 2 hr to reach maximal degradation). The rate of LDL processing at 37 degrees C was enhanced by pre-incubation with FCS-supplemented medium, suggesting the existence of a serum component which stimulates the total degradation of 125I-LDL. Concerning regulation of the LDL receptor activity, we demonstrated that pre-incubation of G+ cells with LDL induced 80% down-regulation of receptor number in both phases of culture. This was also observed in G- cells during the exponential phase while only a 20% decrease of the receptor number was observed in post-confluent G- cells. The LDL degradation of G+ cells resulted in an inhibition of the cholesterogenic activity by 30% and 60% depending on the phase of culture. In G- cells, LDL pre-incubation inhibited cholesterol synthesis to the same extent (45%) in the exponential phase but did not affect the rate of cholesterol synthesis when cells were confluent. The defective regulatory role of LDL on receptor number and cholesterol synthesis suggests that, in the post-confluent differentiated cells, cholesterol derived from LDL does not reach the regulatory pool. Taken together, our findings indicate the existence of functional LDL receptors in the HT29 cell line, either in the differentiated or in the undifferentiated form.

Sequential histochemical and morphometric studies on preneoplastic and neoplastic lesions induced in rat colon by 1,2-dimethylhydrazine

The sequential histochemical changes during colon carcinogenesis were studied in male Sprague-Dawley rats given 16 weekly subcutaneous injections of 15 mg 1,2-dimethylhydrazine per kg body wt and serially killed at regular intervals. Cryostat sections were used to study the mucus content of the colonic mucosa with the periodic acid Schiff's reaction, and enzyme histochemical methods were applied to investigate the activity of some key enzymes of carbohydrate metabolism at different stages of carcinogenesis. Enlarged mucus-rich crypts with a marked hypercellularity (149% of control as determined morphometrically) appearing very early during carcinogenic treatment revealed almost normal activities of glucose-6-phosphatase (G6Pase), glucose-6-phosphate dehydrogenase (G6PDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Hyperbasophilic crypts lacking mucus production were observed later and showed a loss of G6Pase, but marked increase of G6PDH and GAPDH activity. Mucus-rich signet ring cell carcinomas showed the same enzymatic pattern as the mucus-rich crypts, whereas mucus-free adenocarcinomas and undifferentiated carcinomas revealed a loss of G6Pase and highly increased G6PDH and GAPDH activities. The results showed that focal changes in polysaccharide content and in the activity of some enzymes of carbohydrate metabolism, as observed in various organs, also accompany the carcinogenic process in the colon. This supports the concept that aberrations in carbohydrate metabolism play an important role during the process of carcinogenesis.

Effect of glutamine deprivation and glutamate or ammonium chloride addition on growth rate, metabolism and differentiation of human colon cancer cell-line HT29

Effect of glutamine deprivation (GLN- medium) and of its replacement by 4mM ammonium chloride (GLN-/NH4+ medium) or by 4mM glutamate (GLN-/Gt+ medium) was studied on growth rate, morphology and metabolism of HT29 human colon cancer cells. Growth rates were modified as follows: at the first passage, growth of GLN- cells was strongly decreased (doubling time: 192 hr vs 32 hr in control cells grown in GLN+ medium); GLN-/NH4+ cells and GLN-/Gt+ cells were found to have doubling times of 72 and 70 hr, respectively. At the 8th passage, doubling times were decreased in all cases, being: 144 hr for GLN- cells, 60 hr for GLN-/NH4+ cells and 24 hr for GLN-/Gt+ cells, which indicates a capacity of adaptation of the cell-line to new culture conditions. GLN- cells and GLN-/NH4+ cells were found to exhibit an enterocytic type of differentiation (polarization of the cell layer with apical and cystic brush border and tight junctions); GLN-/Gt+ cells remained undifferentiated and comparable to control GLN+ cells. Glycogen level varied according to the phases of the culture, with a trend to lower level in glutamine deprived cells; glucose uptake and lactate production varied as a function of the medium composition and of the phases of the culture. At the 8th passage, all the glutamine deprived cells produced less lactate than control; GLN-/Gt+ cells were found to utilize less glucose than others.

Activity of enzymes related to carbohydrate metabolism in the HT 29 colon adenocarcinoma cell line and tumor

Activity of several enzymes of the glycogen and carbohydrate metabolism is studied in HT 29 colon adenocarcinoma cell line and in HT 29 tumors developed in nude mice, by reference to the normal human colon mucosa. Activity of glycogen synthase, glycogen phosphorylase, pyruvate kinase, fructose-1,6-diphosphatase, glucose-6-phosphate dehydrogenase and lactate dehydrogenase is found to be increased in both the cultured cells and the tumors. It indicates that the biochemical strategy of malignant cells, due to the neoplastic transformation process, involves specific changes in the carbohydrate metabolism of tumor as well as in vitro growing correspondent cell line.

Endogenous urea as a nitrogen source for microorganisms of the rabbit digestive tract

The total urea release, measured in the different secretions of the digestive tract of the rabbit, is estimated to be 22 mmol/day, which represents half of the urea produced by the nitrogen catabolism of the animal. This quantity represents a significant source of nitrogen for symbiotic bacteria and, due to coprophagy , could be recycled in the bacterial proteins digested by the rabbit.

Activity of glycogen metabolizing enzymes in glucose deprived HT 29 adenocarcinoma cell-line

When deprived of glucose, the cultured HT 29 adenocarcinoma cells are able to mobilize their glycogen within 4 hours. Glycogen phosphorylase is strongly activated during the first hour of glucose starvation. Then, while the a/a + b ratio for phosphorylase is declining, glycogen synthase is partially converted into the a form; this conversion does occur although glycogen phosphorylase is far from being totally inactivated. After 4 hours, activity of both a and total forms of glycogen synthase decrease. Cell UDP-glucose and glucose-6-P levels are declining during the 24 hours period of glucose starvation. Cell ATP content decreases by only 50 percent over the same period of time.

Characterization of alpha 2-adrenergic receptors in the human colon adenocarcinoma cell line HT 29 in culture by [3H]yohimbine binding

The presence of specific binding sites for [3H]yohimbine, a labelled alpha 2-adrenergic agent, on crude membranes of HT 29 cells established in culture from a human colon adenocarcinoma, is reported. The estimated affinity and number of sites (KD = 6.3 +/- 0.9 nM; Bmax = 224 +/- 28 fmol/mg protein) as well as the relative potencies of adrenergic agonists (clonidine greater than phenylephrine greater than amidephrine) and adrenergic antagonists (yohimbine greater than dihydroergotamine much greater than prazosin) to displace [3H]yohimbine binding indicate that the yohimbine sites of these cancer cells have similar characteristics to the alpha 2-adrenergic receptors described in other tissues.