Sinorhizobium fredii HH103 RirA Is Required for Oxidative Stress Resistance and Efficient Symbiosis with Soybean

Members of Rhizobiaceae contain a homologue of the iron-responsive regulatory protein RirA. In different bacteria, RirA acts as a repressor of iron uptake systems under iron-replete conditions and contributes to ameliorate cell damage during oxidative stress. In Rhizobium leguminosarum and Sinorhizobium meliloti, mutations in rirA do not impair symbiotic nitrogen fixation. In this study, a rirA mutant of broad host range S. fredii HH103 has been constructed (SVQ780) and its free-living and symbiotic phenotypes evaluated. No production of siderophores could be detected in either the wild-type or SVQ780. The rirA mutant exhibited a growth advantage under iron-deficient conditions and hypersensitivity to hydrogen peroxide in iron-rich medium. Transcription of rirA in HH103 is subject to autoregulation and inactivation of the gene upregulates fbpA, a gene putatively involved in iron transport. The S. fredii rirA mutant was able to nodulate soybean plants, but symbiotic nitrogen fixation was impaired. Nodules induced by the mutant were poorly infected compared to those induced by the wild-type. Genetic complementation reversed the mutant's hypersensitivity to H₂O₂, expression of fbpA, and symbiotic deficiency in soybean plants. This is the first report that demonstrates a role for RirA in the Rhizobium-legume symbiosis.

Plant growth promotion in cereal and leguminous agricultural important plants: from microorganism capacities to crop production

Plant growth-promoting rhizobacteria (PGPR) are free-living bacteria which actively colonize plant roots, exerting beneficial effects on plant development. The PGPR may (i) promote the plant growth either by using their own metabolism (solubilizing phosphates, producing hormones or fixing nitrogen) or directly affecting the plant metabolism (increasing the uptake of water and minerals), enhancing root development, increasing the enzymatic activity of the plant or "helping" other beneficial microorganisms to enhance their action on the plants; (ii) or may promote the plant growth by suppressing plant pathogens. These abilities are of great agriculture importance in terms of improving soil fertility and crop yield, thus reducing the negative impact of chemical fertilizers on the environment. The progress in the last decade in using PGPR in a variety of plants (maize, rice, wheat, soybean and bean) along with their mechanism of action are summarized and discussed here.

Biological behavior due to cell proliferation markers of gastrointestinal stromal tumors

BACKGROUND/AIMS

The mitotic index and tumor size are currently the main prognostic indicators of gastrointestinal stromal tumors (GIST). The purpose of this study is to investigate the expression of different immunohistochemical markers and their relation to mortality and relapse, and especially concerning high-risk tumors.

METHODOLOGY

We did a retrospective study of 68 patients who underwent surgery from 1997 to 2007 with a diagnostic of gastrointestinal stromal tumor.

RESULTS

The median follow-up period was 29 months. Relapse and mortality rates were 35.3% (24 cases) and 41.2% (28 cases), respectively. The mitotic index was related to p53 and the cellular proliferation index -Ki67- (p = 0.006 and p = 0.003, respectively). Considering both high and intermediate-risk neoplasms, a significant relation to Ki67 was obtained (p = 0.008). Relapse was related to the mitotic index (p = 0.032) and Ki67 (p = 0.024). Concerning mortality, statistically significant results were obtained with necrosis variables (p = 0.02), mitotic index (p = 0.013), p53 (p = 0.024) and Ki67 (p = 0.033).

CONCLUSIONS

Ki67 could be considered a prognostic marker for both relapse and mortality. Concerning high risk GIST, the usefulness the p53 protein and Ki67 nuclear antigen markers was also evident concerning relapse and mortality.

[Immunohistochemical expression of epidermal growth factor and its prognostic value for gastrointestinal stromal tumors]

INTRODUCTION

The epidermal growth factor receptor, EGFR (HER-1), is a tyrosine kinase receptor. EGFR activation plays an important role in increased cell proliferation, angiogenesis, and decreased apoptosis. Our objective was to study EGFR immuno-expression in GIST, as well as its prognostic value.

PATIENTS AND METHOD

A retrospective study that included all patients operated on with a histologic diagnosis of GIST at Department of Surgery, Hospital General, Ciudad Real, between 1995 and 2007.

CLINICAL FEATURES

age, sex, manifestations, mortality, recurrence. Pathological features: origin, size, tumoral necrosis, mitotic index, cell type. Immunohistochemical features: vimentin, (V9, Dako A/s); smooth muscle actin (HHF-35, Biogenex); CD34 (QBEND/10); S100 (Policlonal Dako A/S), CD117, (c-kit Rabbit, antihuman polyclonal antibody, 1:600); PDGFR-alfa (Rabbit polyclonal antibody, 1:50, Sta. Cruz Biotechnology). Prognostic molecular features: P-53, PAb240 (DakoCytomation) 1:75; Ki-67, clona MIBI (Dako, Denmark). Malignancy criteria: Fletcher's criteria.

RESULTS

From 1995 to 2007, 35 GISTs were resected in our Department. Mean age: 61.11 +/- 11.02, with a female predominance of 62.9%. Initial clinical manifestation included digestive hemorrhage in 40%. Median follow-up was 28 months (3-133). Mortality was 54.3%, and recurrence rate was 40%. The most frequent origin was the stomach, 51.4%, (18). There was tumor necrosis in 57.1% (20). There were spindle-like cells in 57.1%, and epithelioid cells in 14.3%. Mean size was 9.58 +/- 6.29. Mitotic index per 50 high-power fields was 13.44 +/- 16.08; 51.45% (18) were high-risk tumors. Immunohistochemical expression: CD117+, 85.7%. PDGFRA+, 85.7%. CD34+, 77.1%. EGFR+, 62.9%. S100+, 34.3%. Actin+, 20%. Vimentin+, 100%. p53+, 40%. ki67+, 10.71 +/- 10.82. There was no correlation between EGFR expression and recurrence and/ or mortality, p = 0.156 and p = 0.332, respectively. Mitosis index related to mortality, p = 0.02, and recurrence, p = 0.013.

CONCLUSION

In our study there was no relation between EGFR immunohistochemical expression and the prognosis of GIST.

[Quality indicators in bariatric surgery: weight loss valoration]

The medical management of MO may be effective in the short and intermediate terms, although it usually fails then leading to surgical management. Our goal is to assess Capella's surgical technique by means of quality indicators including weight loss. The present work has been performed with surgical MO patients at the 12 de Octubre University Hospital during 2000-2001, and registering the follow-up checkups for the period 2000-2001/2003-2004. We reviewed the clinical charts of 23 patients. The average Body Mass Index (BMI) was 52.24 +/- 10.07 kg/m(2), (range, 41-74.41). When compiling the statistical results, we observed statistically significant post-surgical decreases with no differences whether the PEIMCP outcome was excellent (>or= 65%), fair (= 50-65%) or failure (<or= 50%) in the following parameters: BMI (p <or= 0.001); Comorbidities (p <or= 0.001); Hemoglobinemia (p <or= 0.005); Glycemia (p <or= 0.001); Triglyceridemia (p <or= 0.001); Total cholesterolemia (p <or= 0.001); Sideraemia (p <or= 0.001); and serum cianocobalamine (p <or= 0.001). We could not demonstrate statistically significant changes in the remaining parameters. However, under the presumption that the lack of evidence does not mean the evidence of the absence, that is to say, the results have been obtained from a small sample (N = 23) so that they may not be considered definitely conclusive. Considering the percentage of the loss of Body Mass Index excess as one of the quality indexes in bariatric surgery, we may state that Capella's gastric by-pass is efficient in obese patients with BMI <or= 50 kg/m(2), doubtfully effective in patients with BMI 50-60 kg/m(2), and ineffective in super obese patients with BMI >or= 60 kg/m(2).

[Prognostic significance and clinic utility of serum and immunohistochemical cathepsin B levels in colorectal cancer]

BACKGROUND

Aproximately one third of node-negative colorectal cancer recur suggesting the presence of micrometastasis not detected by conventional histopathologic methods. We think that the role of enzymes like Cathepsin B play in the process of invasion and metastasis in colorectal cancer might identify at earlier stages patients with high risk of shorter survival and who need more aggressive treatment. Our porpuse is to evaluate the prognostic significance of preoperative serum and inmunohistochemical levels of cathepsin B to identify colorectal carcinomas with worse prognostic.

METHODS

Fifty five patients undergoing surgical treatment for colorectal cancer from 1998 to 2000. As a control group sera from 23 patients with acute appendicitis. Serum levels of cathepsin B were obtained preoperatively (KRKA, Novo Slovenia;ng/ml); cathepsin B inmunoreactivity was determinated after surgical treatment, (C-19, Santa Cruz Biotechnology). Serum levels of CEA (Inmulit 2000 CEA), and CA 19,9 (Inmulite Gi-Ma, Diagnostic Products Corporation, Los Angeles, CA), and p53 expression (Dako) were determinated in patients with colorectal cancer. Survival analysis was realized using Cox and Kaplan-Meier methods (SPSS 10.0 for Windows).

RESULTS

The mean age of patients with colorectal cancer was 68 years (range 39-87 years). 29 males and 26 females. Tumor size was 4.6 cms., range 1-12. Rectal localization, 32.2%. Moderately differentiated, 49.1%. The median serum and inmunohistochemical levels of cathepsin B were 5.74 ng/ml and 29.56% in patients with acute appendicitis respectively. Preoperative serum levels in patients with colorectal cancer were: CEA, 46.04 ng/ml (range 0.21-7.32 ); CA 19,9, 110.52 UI/ml, (range 2.5-1920); and Cathepsin B, 6.94 ng/ml, range 3.57-11.6). Inmunohistochemical results were: p53, 44.36%, (range 0-95); Cathepsin B, 66.9% (range 10-90). Serum and inmunhistochemical values were significantly increased in patients with colorectal cancer when compared with control group, p=0,011 and p=0,000. High serum levels of cathepsib B were significantly associated wiyh shorter survival of patients with colorectal cancer in univariate and multivariate methods, p=0.041;HR 1.281 95%CI (1.043-1.716) and p= 0.022; HR 1.338.955 CI (1.043-1.716).

CONCLUSIONS

Cathepsin B can be used like an independent prognostic tumoral marker in colorectal cancer. Preoperative serum levels over 6.94 ng/ml, are associated with worse prognostic and shorter survival.

Sinorhizobium fredii HH103 has a truncated nolO gene due to a -1 frameshift mutation that is conserved among other geographically distant S. fredii strains

Strain SVQ121 is a mutant derivative of Sinorhizobium fredii HH103 carrying a transposon Tn5-lacZ insertion into the nolO-coding region. Sequence analysis of the wild-type gene revealed that it is homologous to that of Rhizobium sp. NGR234, which is involved in the 3 (or 4)-O-carbamoylation of the nonreducing terminus of Nod factors. Downstream of nolO, as in Rhizobium sp. NGR234, the noeI gene responsible for methylation of the fucose moiety of Nod factors was found. SVQ121 Nod factors showed lower levels of methylation into the fucosyl residue than those of HH103-suggesting a polar effect of the transposon insertion into nolO over the noel gene. A noeI HH103 mutant was constructed. This mutant, SVQ503, produced Nod factors devoid of methyl groups, confirming that the S. fredii noeI gene is functional. Neither the nolO nor the noeI mutation affected the ability of HH103 to nodulate several host plants, but both mutations reduced competitiveness to nodulate soybean. The Nod factors produced by strain HH103, like those of other S. fredii isolates, lack carbamoyl residues. By using specific polymerase chain reaction primers, we sequenced the nolO gene of S. fredii strains USDA192, USDA193, USDA257, and 042B(s). All the analyzed strains showed the same -1 frameshift mutation that is present in the HH103 nolO-coding region. From these results, it is concluded that, regardless of their geographical origin, S. fredii strains carry the nolO-coding region but that it is truncated by the same base-pair deletion.

Effect of pH and soybean cultivars on the quantitative analyses of soybean rhizobia populations

Quantitative analyses of fast- and slow-growing soybean rhizobia populations in soils of four different provinces of China (Hubei, Shan Dong, Henan, and Xinjiang) have been carried out using the most probable number technique (MPN). All soils contained fast- (FSR) and slow-growing (SSR) soybean rhizobia. Asiatic and American soybean cultivars grown at acid, neutral and alkaline pH were used as trapping hosts for FSR and SSR strains. The estimated total indigenous soybean-rhizobia populations of the Xinjiang and Shan Dong soil samples greatly varied with the different soybean cultivars used. The soybean cultivar and the pH at which plants were grown also showed clear effects on the FSR/SSR rations isolated from nodules. Results of competition experiments between FSR and SSR strains supported the importance of the soybean cultivar and the pH on the outcome of competition for nodulation between FSR and SSR strains. In general, nodule occupancy by FSRs significantly increased at alkaline pH. Bacterial isolates from soybean cultivar Jing Dou 19 inoculated with Xinjiang soil nodulate cultivars Heinong 33 and Williams very poorly. Plasmid and lipopolysaccharide (LPS) profiles and PCR-RAPD analyses showed that cultivar Jing Dou 19 had trapped a diversity of FSR strains. Most of the isolates from soybean cultivar Heinong 33 inoculated with Xinjiang soil were able to nodulate Heinong 33 and Williams showed very similar, or identical, plasmid, LPS and PCR-RAPD profiles. All the strains isolated from Xinjiang province, regardless of the soybean cultivar used for trapping, showed similar nodulation factor (LCO) profiles as judged by thin layer chromatographic analyses. These results indicate that the existence of soybean rhizobia sub-populations showing marked cultivar specificity, can affect the estimation of total soybean rhizobia populations indigenous to the soil, and can also affect the diversity of soybean rhizobial strains isolated from soybean nodules.

Pneumomediastinum as a complication of extraperitoneal laparoscopic inguinal hernia repair

A 52-year-old man with left indirect groin hernia was admitted for elective inguinal repair using the totally extraperitoneal (TEP) approach. After an uneventful intubation, TEP repair of the hernia was performed with three midline trocars. Immediately after extubation, the patient noted severe chest pain. There was a decrease in PaO2 saturation, and neck subcutaneous emphysema was detected. There was no emphysema of the abdomen or of the back. A chest film and thoracic computed tomographic (CT) scan confirmed the presence of pneumomediastinum without pneumothorax. The patient was discharged without complications.

Mutation in GDP-fucose synthesis genes of Sinorhizobium fredii alters Nod factors and significantly decreases competitiveness to nodulate soybeans

We mutagenized Sinorhizobium fredii HH103-1 with Tn5-B20 and screened about 2,000 colonies for increased beta-galactosidase activity in the presence of the flavonoid naringenin. One mutant, designated SVQ287, produces lipochitooligosaccharide Nod factors (LCOs) that differ from those of the parental strain. The nonreducing N-acetylglucosamine residues of all of the LCOs of mutant SVQ287 lack fucose and 2-O-methylfucose substituents. In addition, SVQ287 synthesizes an LCO with an unusually long, C20:1 fatty acyl side chain. The transposon insertion of mutant SVQ287 lies within a 1.1-kb HindIII fragment. This and an adjacent 2.4-kb HindIII fragment were sequenced. The sequence contains the 3' end of noeK, nodZ, and noeL (the gene interrupted by Tn5-B20), and the 5' end of nolK, all in the same orientation. Although each of these genes has a similarly oriented counterpart on the symbiosis plasmid of the broad-host-range Rhizobium sp. strain NGR234, there are significant differences in the noeK/nodZ intergenic region. Based on amino acid sequence homology, noeL encodes GDP-D-mannose dehydratase, an enzyme involved in the synthesis of GDP-L-fucose, and nolK encodes a NAD-dependent nucleotide sugar epimerase/dehydrogenase. We show that expression of the noeL gene is under the control of NodD1 in S. fredii and is most probably mediated by the nod box that precedes nodZ. Transposon insertion into neoL has two impacts on symbiosis with Williams soybean: nodulation rate is reduced slightly and competitiveness for nodulation is decreased significantly. Mutant SVQ287 retains its ability to form nitrogen-fixing nodules on other legumes, but final nodule number is attenuated on Cajanus cajan.

The soybean cultivar specificity gene nolX is present, expressed in a nodD-dependent manner, and of symbiotic significance in cultivar-nonspecific strains of Rhizobium (Sinorhizobium) fredii

Rhizobium (now Sinorhizobium) fredii is a symbiotic nitrogen-fixing bacterium that can nodulate soybean in a cultivar-specific manner. This process is governed by a set of negatively acting nodulation genes termed nolXWBTUV. These genes prevent R. fredii strain USDA257 from infecting soybean cultivars such as McCall, but they do not block nodulation of cultivar Peking. R. fredii strain USDA191 contains DNA sequences that hybridize to nolXWBTUV, yet it forms normal nitrogen-fixing nodules on both McCall and Peking soybean. These sequences were isolated and their structure and function examined in comparison to nolXWBTUV of strain USDA257. Restriction maps of the two loci are identical, as is a 2-4 kb DNA sequence that corresponds to nolX and its promoter region. Expression of nolX by strain USDA191 is flavonoid-dependent in culture and readily detectable in nodules. The gene is not inducible in a mutant of strain USDA191 that lacks the regulatory nodD1 gene, and its expression is greatly attenuated in a nodD2 mutant. nolX is also present and flavonoid-inducible in HH103, a second R. fredii strain that nodulates McCall soybean normally. Inactivation of nolX in strain HH103, USDA191 or USDA257 leads to retardation of initial nodulation rates on soybean cultivars such as Peking and to acquisition of the capacity to form nitrogen-fixing nodules on two species of Erythrina. nolX is thus of symbiotic significance in all three strains, even though it regulates soybean cultivar specificity only in strain USDA257.