COVID-19 and Its Impact on Back Pain in the Eastern Province of Saudi Arabia.

Background Low back pain (LBP) is a common musculoskeletal condition that affects individuals worldwide, causing difficulties in daily tasks and social interactions. It can be categorized based on chronicity, with acute, subacute, and chronic forms. The causes of backache vary among patients and can include inflammatory conditions, radiculopathy, pregnancy, trauma, osteoporosis, nerve root compression, cancer, plexopathy, infection, and other spinal diseases. Aim The aim is to investigate the association between COVID-19 infection and LBP between all Saudi adults and foreign adults who had positive COVID-19 tests in the eastern region of Saudi Arabia. Methods A cross-sectional study was conducted in the Eastern Province of Saudi Arabia over the period from March 2023 to August 2023. Participants were selected by using a convenience sampling method, a sample (n=500) of individuals. The structured questionnaire was used to gather information on sociodemographic variables and COVID-related features. All the statistical calculations were performed using the SPSS software (by IBM) version 29.0.0. Results 482 participants completed the questionnaire. Out of 482 participants, the majority were females with a number of 372 (77.2%) aged between 20 and 29 years (38.4%). Out of the remaining participants, 110 (22.8%) were males. Most of the participants with a number of 301 (62.4%) were from the Hasa province. This was followed by Qatif (79, 16.4%), Dammam (56, 11.6%), Jubail (25, 5.2%), and others (21, 4.4%). The study revealed that 10.1% of participants reported experiencing back pain. The duration of backaches varied among respondents, with 122 (25.3%) experiencing them from a day to a week, 28 (5.8%) enduring them for six weeks, and 65 (13.5%) reporting a duration of six to 12 weeks. The majority, comprising 267 (55.4%) respondents, were uncertain about the period of their backaches. The prevalence of COVID-19 infection among the participants was 357 (74.1%), and 477 (99.0%) had been vaccinated against COVID-19. Approximately 44.4% of the participants experienced back pain, and out of those, 28.2% reported having pain during quarantine. Among the individuals with back pain, 24.7% attributed it to COVID-19. Conclusion This study highlights the significant correlation between back pain and COVID-19, even after the resolution of other symptoms. It underscores the importance of further research into the long-term effects and mechanisms of this association. The findings emphasize the need for healthcare professionals to consider back pain as a potential aspect of the post-COVID-19 symptom profile, ensuring comprehensive care for affected individuals.

Active gas aspiration in reducing pain after laparoscopic cholecystectomy: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Postoperative pain is a common issue following laparoscopic cholecystectomy. This meta-analysis aimed to determine if active gas aspiration is more effective than passive gas aspiration in reducing postoperative pain and analgesic requirements. METHODOLOGY: The study conducted a systematic search of various databases, including Embase, Medline, and Cochrane Central Register of Controlled Trials (CENTRAL) via Ovid. It also searched trial registries and reference lists of included studies, with no date restrictions but limited to English language, up to December 21, 2022. The study included all randomized clinical trials that had documented elective laparoscopic cholecystectomy procedure and reported at least one relevant outcome. Articles that included subdiaphragmatic drain, intraperitoneal normal saline infusion, or pulmonary recruitment maneuver were excluded from the analysis. Two reviewers independently and in duplicate assessed the eligibility of studies and extracted data. The study reported findings according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. The risk of bias of the included trials was assessed using the Revised Cochrane Risk of Bias Assessment Tool. The study used a random-effects model to pool data. RESULTS: This meta-analysis included 5 randomized clinical trials with 367 participants and found that active gas aspiration resulted in significantly lower residual gas volume and total analgesia requirements compared to passive gas aspiration. Active gas aspiration also led to significantly lower shoulder pain scores at 24 h postoperatively. However, no significant differences were observed in hospital stay duration or abdominal pain scores. CONCLUSION: The study found that active gas aspiration can be effective in reducing postoperative shoulder pain and analgesic requirements after laparoscopic cholecystectomy, which has important implications for patient care and healthcare costs. Importantly, this intervention does not impose any additional time or financial burden. However, further research is needed to evaluate its impact on other laparoscopic procedures.

Concurrence of Adenomyoepithelioma of the Breast and Gastrointestinal Stromal Tumor of the Stomach: A Case Report and Review of the Literature.

Adenomyoepithelioma (AME) of the breast and gastrointestinal stromal tumors (GISTs) are rare benign (primarily) tumors observed in the breast and gastrointestinal tract, respectively. The coexistence of both of these rare tumors is extremely rare; therefore, the author describes the clinical presentation and pathophysiological findings of such a unique case in this study. A 56-year-old female patient with no medical history presented with a substantial right breast lump, severe nausea, and vomiting, and suffered from iron deficiency anemia. Radiological observation and a right breast excisional biopsy diagnosed the patient with AME associated with ductal carcinoma in situ (DCIS). Endoscopy and a CT scan of the stomach revealed the existence of GIST. This is the first reported case of concurrence of a huge mass of AME and GIST in a patient. Histological and immunohistochemistry tests using p63, SMA, calponin, and Ki67 markers for the breast tumor and DOG-1, CD34, and CD117 markers for the gastric tumor revealed the non-invasive benign state. The patient had a right breast mastectomy with a negative resection margin. AME of the breast and GIST pose diagnostic challenges due to their erratic morphological characteristics and can cause misinterpretation drawn solely from radiological tests. Effective and accurate diagnostics require assessing the histological and immunohistochemistry findings of the tumor to identify the invasiveness of the neoplasm and the associated risk levels. This report, thus, creates awareness among clinicians and pathologists for the consideration of such possibilities and, therefore, conducts the necessary diagnostics and prophylactic treatments.

Effect of ergonomics awareness in controlling work-related musculoskeletal-pain among dental students: A cross-sectional study.

BACKGROUND: Dentistry is a profession that demands a high level of physical work and excessive repetitive movements in strained positions, both of which are risk factors for developing musculoskeletal pain (MS-P). OBJECTIVE: This study aims to assess the awareness of ergonomics and physical activities in controlling MS-P among dental students. METHODS: A cross-sectional study conducted at a university dental hospital in Saudi Arabia, through a validated self-administered questionnaire, distributed to undergraduates and postgraduate's dental students. RESULTS: Out of 402 students responded to the questionnaire, 337(83.8%) reported suffering from MS-P with 67.7% of participants did not take any measures to alleviate their symptoms and the majority reported limited physical activity. Females reported significantly higher MS-P than males. Lower back (56.5%), neck (56.2%) and shoulder (50%) were the most frequently reported MS-P. Unexpectedly, undergraduate reporting significantly more pain than interns and postgraduate students (P = 0.009). The dental students' awareness of ergonomics and MSDs were insufficient. CONCLUSION: Physical activity, student's awareness of MSD and ergonomics were the major factors for controlling MS-Ps. Therefore, this study highlights the importance of enhancing students' knowledge of the importance of controlling work-related MS-P, especially during their university educational hours.

Validity and reliability of the behavioral signs of respiratory instability (BSRI) © scale during activity for infants with bronchopulmonary dysplasia.

OBJECTIVE: There is no reliable evidence on how best to evaluate the overall status of infants with severe forms of bronchopulmonary dysplasia (BPD). The Behavioral Signs of Respiratory Instability (BSRI) scale was developed as an objective measure of developmental capacity during occupational and physical therapy sessions. The purpose of this study was to determine the psychometric properties of the BSRI Scale. STUDY DESIGN: The BSRI and Respiratory Severity Score (RSS) were compared for 25 infants with BPD and 15 infants without BPD. A cross-sectional design was used to test inter-rater reliability among 10 NICU occupational and physical therapists. A prospective cohort design was used to evaluate validity. RESULTS: The BSRI demonstrated good to excellent inter-rater reliability (ρ = 0.47-0.91) and was strongly correlated with RSS (ρ = -0.77, p < 0.001; concurrent validity). CONCLUSION: The BSRI Scale has preliminary psychometric support. Standardized measures like the BSRI may provide accurate, objective data that can improve care planning within interdisciplinary teams that supports brain growth and potentially improves neurodevelopment.

Prevalence of Stress, Anxiety, and Depression Among Pregnant Women in Jeddah.

OBJECTIVES: To estimate the prevalence of depression, anxiety, and stress among pregnant women living in Jeddah, Saudi Arabia, and to assess associated risk factors. METHODS: The study, which was a cross-sectional design, was conducted under the supervision of King Abdulaziz University Hospital, a tertiary care center in Jeddah, Saudi Arabia, in May and June of 2021. The sample consisted of 200 pregnant women who completed an online questionnaire that included sociodemographic variables, obstetric information, pregnancy-related depression, stress, and anxiety symptoms, which were evaluated using the Depression Anxiety Stress Scale (DASS-21) and the Perinatal Anxiety Screening Scale (PASS). RESULTS: DASS-21 scores indicated the prevalence of depression, anxiety, and stress were 37.5%, 54.0%, and 25.0%, respectively. The PASS revealed that 29.5% of participants had minimal anxiety symptoms, 44.5% had mild-to-moderate anxiety symptoms, and 26.0% had severe anxiety symptoms. The three psychological health conditions were significantly associated with family/husband support, history of caesarean section, parity, and abortion. CONCLUSIONS: Pregnant women should be screened routinely for any psychological disturbances, and women who are at high risk for mental illness should receive proper psychological care. Pregnant women, their families, and members of society should receive health-related education in order to prevent prenatal psychological issues as much as possible.

Influence of perioperative opioid-related patient education: A systematic review and meta-analysis.

OBJECTIVE: To determine the role of perioperative protocolized opioid-specific patient education on opioid consumption for individuals undergoing surgical procedures. METHODS: We searched Medline, Embase, and the Cochrane Central Register of Controlled Trials for randomized controlled trials (RCTs) that compared protocolized perioperative opioid-specific patient education to the usual care for adult individuals undergoing surgical interventions. The standardized mean difference (SMD) was used to represent continuous outcomes while the risk ratio (RR) was used to represent dichotomous outcomes. RESULTS: In total, 15 RCTs that enrolled 2546 participants were deemed eligible. Protocolized opioid-specific patient education showed a significant reduction in postoperative opioid consumption and postoperative pain score compared to usual care (SMD= -0.15, 95% confidence interval [CI]: -0.28 to -0.03 and SMD= -0.17, 95% CI: -0.28 to -0.06, respectively). No significant difference was found between the protocolized opioid-specific patient education and the usual care in terms of the number of refill requests (RR=0.82, 95% CI: 0.50-1.34), patients with opioid leftovers (RR=0.92, 95% CI: 0.78-1.08), and patients taking opioids after hospital discharge. CONCLUSIONS: This meta-analysis demonstrated that protocolized opioid-specific patient education significantly reduces postoperative opioid consumption and pain score but has no influence on the number of opioid refill requests, opioid leftovers, and opioid use after hospital discharge. PRACTICE IMPLICATIONS: Healthcare professionals may offer opioid-related educational sessions for the surgical patients during the perioperative period through a video-based material that emphasizes the role of alternative analgesics to opioids, patients' expectations about the post-operative pain, and the potential side effects of opioid consumptions.

Risk Factors, Clinical Manifestations and Treatment Outcomes of Colon Cancer Patients in National Guard Hospital in Jeddah, Saudi Arabia.

Introduction Colon cancer is the third most common cancer worldwide and its incidence is increasing day by day. Provision of early management to cancer patients can lead to a good prognosis. Hence, we evaluated the risk factors, clinical manifestations and treatment outcomes for colon cancer patients in National Guard Health Affairs (NGHA), Jeddah, Saudi Arabia from January 2010 to December 2020 by comparing those results according to their age groups. Methods A retrospective cohort study was performed on 251 colon cancer patients who underwent a surgical procedure. The patients were divided into the following age groups: ≤ 50 (young), 51-60 and > 60 (old) years old. The demographic variables such as age and gender were collected. The results were classified into risk factors, clinical features and treatment outcomes. The comparison between different age groups was made using Chi-square or Fisher's exact test. The data was stored in Excel 2016 (Microsoft Corporation, Redmond, USA) and analyzed using SPSS (IBM Corp, Armonk, USA). Results The results revealed that most patients were males and the median age for diagnosis was 58 years old. There were 15.1% of patients with a positive family history. Moreover, the most common anatomical position was the left side of the colon in all age groups. Most patients had moderately differentiated colon cancer in the histopathological diagnosis. Laparotomy was the most common procedure done to patients in all age groups. There was no difference between all age groups and the aggressiveness of colon cancer. Young patients (≤ 50 years) had a higher percentage to have 5-year recurrence rate (42 % vs 19% vs 25%, p-value < 0.05) in comparison to patients between 51-60 years and old patients (> 60 years) respectively. However, there was no association between all age groups and 5-year mortality rate (22% vs 9% vs 19%, p-value = 0.171). Conclusion In comparison to old patients (> 60 years), young patients (≤ 50 years) have a more rate of recurrent colon cancer. In relation to all age groups, there were no differences in terms of the aggressive presentation or 5-year mortality rates. In addition, it appears that there were some differences between our study results and worldwide results. This may be because of occupational, cultural and/or genetic variations. Further studies with a higher number of patients and multicenter data collection are highly recommended.

Rare presentation of infective endocarditis due to Salmonella entrica subspecies salamae (subgroup ll) in a sickle cell anemia girl.

Sickle cell anemia (SCA) is a common inherited kind of hemolytic anemia in Africa and some areas of Asia. In Saudi Arabia, SCA is prevalent as well. The patient of SCA is prone to some bacteria species more than the others, and Salmonella is one of the most prevalent infections in SCA that were known to cause bacteremia, osteomyelitis, septic arthritis, and gastroenteritis. Herein, we report a 7-years old girl who presented with a history of fever for five days and jaundice with abdominal pain and mild respiratory distress. Later, the patient was diagnosed to have infective endocarditis due to Salmonella enterica subspecies salamae (subgroup II). The patient improved completely after receiving proper antibiotics. To the best of our knowledge, there is only one case of adult SCA that has been reported with infective endocarditis due to Salmonella entrica but no reported case in pediatric.

Modulatory effect of Turnera diffusa against testicular toxicity induced by fenitrothion and/or hexavalent chromium in rats.

Oxidative stress and increased production of reactive oxygen species have been implicated in pesticides and heavy metals toxicity. The objective of this study was to investigate the efficacy of Turnera diffusa Willd (damiana) on counteracting fenitrothion (FNT) and/or potassium dichromate (CrVI)-induced testicular toxicity and oxidative injury in rats. FNT and/or CrVI intoxicated animals revealed a significant increase in thiobarbituric acid reactive substances and hydrogen peroxide levels. While, reduced glutathione and protein content, as well as antioxidant enzymes, phosphatases, and aminotransferases activities, were significantly decreased. In addition, significant changes in testosterone and follicle-stimulating hormone levels were detected. Furthermore, histological and immunohistochemical alterations were observed in rat testes and this supported the observed biochemical changes. On the other hand, rats treated with damiana alone decreased lipid peroxidation and increased most of the examined parameters. Moreover, damiana pretreatment to FNT and/or CrVI-intoxicated rats showed significant improvement in lipid peroxidation, enzyme activities, and hormones as compared with their respective treated groups. Conclusively, rats treated with both FNT and/or CrVI showed pronounced hazardous effect especially in their combination group in addition, Turnera diffusa had a potential protective role against FNT and/or CrVI induced testicular toxicity.

Maintenance of meristem activity under stress: is there an interplay of RSS1-like proteins with the RBR pathway?

Plants have acquired rapid responses to a constantly changing environment. These adaptive and protective responses are the result of a complex signalling network regulating different aspects, ranging from ion homeostasis to cell cycle control. It is well established that stress inhibits cell division, which negatively impacts plant growth and development and hence results in biomass decrease and yield loss. Therefore understanding the link between stress perception and cell cycle control would allow development of new crops with increased productivity when subjected to stress. However, studies on cell cycle control under stress have been limited to well-known regulators of the cell cycle such as cyclins and stress-related phytohormone integrators. The recent discovery of RSS1, a novel intrinsically unstructured protein of rice, opened up new insights into how stress perception can be connected with cell cycle control in meristematic zones. Whereas RSS1 is well conserved among other plant lineages, eudicots present proteins sharing little sequence homology with RSS1. Here, we discuss how RSS1-like proteins might also be functional in dicots, and possibly act through the retinoblastoma-related pathway to regulate both S-phase transition and cell fate in meristems.

Insulin sensitivity affects corticolimbic brain responses to visual food cues in polycystic ovary syndrome patients.

BACKGROUND: This study examined the effect of insulin sensitivity on the responsiveness of appetite regulatory brain regions to visual food cues. MATERIALS AND METHODS: Nineteen participants diagnosed with polycystic ovary syndrome (PCOS) were divided into insulin-sensitive (n=8) and insulin-resistant (n=11) groups based on the homeostatic model assessment of insulin resistance (HOMA2-IR). Subjects underwent functional magnetic resonance imaging (fMRI) while viewing food pictures following water or dextrose consumption. The corticolimbic blood oxygen level dependent (BOLD) responses to high-calorie (HC) or low-calorie (LC) food pictures were compared within and between groups. RESULTS: BOLD responses to food pictures were reduced during a glucose challenge in numerous corticolimbic brain regions in insulin-sensitive but not insulin-resistant subjects. Furthermore, the degree of insulin resistance positively correlated with the corticolimbic BOLD response in the medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), anterior cingulate and ventral tegmental area (VTA) in response to HC pictures, and in the dorsolateral prefrontal cortex (DLPFC), mPFC, anterior cingulate, and insula in response to LC pictures following a glucose challenge. BOLD signal in the OFC, midbrain, hippocampus, and amygdala following a glucose challenge correlated with HOMA2-IR in response to HC-LC pictures. CONCLUSION: We conclude that the normal inhibition of corticolimbic brain responses to food pictures during a glucose challenge is compromised in insulin-resistant subjects. The increase in brain responsiveness to food pictures during postprandial hyperinsulinemia may lead to greater non-homeostatic eating and perpetuate obesity in insulin-resistant subjects.

Flavonoid-inducible modifications to rhamnan O antigens are necessary for Rhizobium sp. strain NGR234-legume symbioses.

Rhizobium sp. strain NGR234 produces a flavonoid-inducible rhamnose-rich lipopolysaccharide (LPS) that is important for the nodulation of legumes. Many of the genes encoding the rhamnan part of the molecule lie between 87 degrees and 110 degrees of pNGR234a, the symbiotic plasmid of NGR234. Computational methods suggest that 5 of the 12 open reading frames (ORFs) within this arc are involved in synthesis (and subsequent polymerization) of L-rhamnose. Two others probably play roles in the transport of carbohydrates. To evaluate the function of these ORFs, we mutated a number of them and tested the ability of the mutants to nodulate a variety of legumes. At the same time, changes in the production of surface polysaccharides (particularly the rhamnan O antigen) were examined. Deletion of rmlB to wbgA and mutation in fixF abolished rhamnan synthesis. Mutation of y4gM (a member of the ATP-binding cassette transporter family) did not abolish production of the rhamnose-rich LPS but, unexpectedly, the mutant displayed a symbiotic phenotype very similar to that of strains unable to produce the rhamnan O antigen (NGRDeltarmlB-wbgA and NGROmegafixF). At least two flavonoid-inducible regulatory pathways are involved in synthesis of the rhamnan O antigen. Mutation of either pathway reduces rhamnan production. Coordination of rhamnan synthesis with rhizobial release from infection threads is thus part of the symbiotic interaction.

Gene targeting in Arabidopsis.

Precise modification by gene targeting (GT) provides an important tool for studies of gene function in vivo. Although routine with many organisms, only isolated examples of GT events have been reported for flowering plants. These were at low frequencies precluding reliable estimation of targeting efficiency and evaluation of GT mechanisms. Here we present an unambiguous and straightforward system for detection of GT events in Arabidopsis using an endogenous nuclear gene encoding protoporphyrinogen oxidase (PPO), involved in chlorophyll and heme syntheses. Inhibition of PPO by the herbicide Butafenacil results in rapid plant death. However, the combination of two particular mutations renders PPO highly resistant to Butafenacil. We exploited this feature for selection of GT events by introducing the mutations into the PPO gene by homologous recombination. We have estimated the basal GT frequency to be 2.4 x 10(-3). Approximately one-third of events were true GT (TGT) leading to the anticipated modification of the chromosomal PPO copy. The remaining events could be classified as ectopic GT (EGT) arising by modification of vector DNA by the chromosomal template and its random integration into the Arabidopsis genome. Thus the TGT frequency in our experimental setup is 0.72 x 10(-3). In view of the high efficiency of Arabidopsis transformation, GT experiments of a reasonable size followed by a PCR screen for GT events should also allow for modification of non-selectable targets. Moreover, the system presented here should contribute significantly to future improvement of GT technology in plants.

Elevated levels of intrachromosomal homologous recombination in Arabidopsis overexpressing the MIM gene.

The Arabidopsis MIM gene encodes a protein belonging to the SMC family (structure maintenance of chromosomes) which is required for intrachromosomal homologous recombination (ICR). Both ICR and MIM gene expression are enhanced by DNA-damaging treatments, suggesting that MIM is a factor limiting DNA repair by homologous recombination (HR) under genotoxic stress. We tested this hypothesis by measuring the levels of recombination in the mim mutant under genotoxic stress, using methyl methanesulfonate. Although the mutant clearly showed diminished basal and induced levels of ICR, enhancement of ICR by DNA-damaging treatments was similar to that observed in the wild type. This suggests that the MIM gene product is required for DNA repair by HR, but is not critical for HR induction. To determine whether enhanced availability of MIM would increase basal HR levels in Arabidopsis, we examined ICR frequencies in transgenic Arabidopsis strains overexpressing the MIM gene after ectopic insertion of additional MIM copies. Two independent lines showed a twofold increase in ICR frequency relative to the wild type. Thus MIM is required for efficient ICR in plants, and its manipulation can be used to change homologous recombination frequencies. Since MIM is one of the components responsible for chromatin dynamics, our results suggest that the chromatin environment determines the frequency of homologous recombination.

In vitro sulfotransferase activity of NoeE, a nodulation protein of Rhizobium sp. NGR234.

Soil bacteria of the genera Azorhizobium, Bradyrhizobium, and Rhizobium liberate morphogenetic lipochitin-oligosaccharides (Nod factors) into legume rhizospheres. Nod factors, which are synthesized by the products of rhizobial nodulation (nod) genes, vary in core length as well as in the number and type of substitutions. In Rhizobium sp. NGR234, the N-acylated pentamers of N-acetyl-D-glucosamine carry an O-methylfucose group on the reducing terminus that is substituted, on a mutually exclusive basis, with either an acetyl or a sulfuryl group. A sulfotransferase encoded by noeE is required for adjunction of activated sulfate donated by 3'-phosphoadenosine 5'-phosphosulfate (PAPS). Here we show that when expressed in NGR234 cured of its symbiotic plasmid (= ANU265) or when purified as a fusion protein (MBP-NoeE), NoeE transfers sulfate from PAPS to fucosylated lipochitin-oligosaccharides. Enzyme assays showed that sulfotransferase activity is dependent on the presence of an acyl group (stearic and vaccenic acids were tested) since no activity was detected when fucosylated oligochitins (oligomers of two to six N-acetyl-D-glucosamine units) were used as substrates. Thus, NoeE is unique in that it is the only characterized sulfotransferase that is specific for fucosylated Nod factors. It probably acts after NodA, which acylates the amino-sugar backbone.

nolO and noeI (HsnIII) of Rhizobium sp. NGR234 are involved in 3-O-carbamoylation and 2-O-methylation of Nod factors.

Loci unique to specific rhizobia direct the adjunction of special groups to the core lipo-oligosaccharide Nod factors. Host-specificity of nodulation (Hsn) genes are thus essential for interaction with certain legumes. Rhizobium sp. NGR234, which can nodulate >110 genera of legumes, possesses three hsn loci and secretes a large family of Nod factors carrying specific substituents. Among them are 3-O (or 4-O)- and 6-O-carbamoyl groups, an N-methyl group, and a 2-O-methylfucose residue which may bear either 3-O-sulfate or 4-O (and 3-O)-acetyl substituents. The hsnIII locus comprises a nod box promoter followed by the genes nodABCIJnolOnoeI. Complementation and mutation analyses show that the disruption of any one of nodIJ, nolO, or noeI has no effect on nodulation. Conjugation of nolO into Rhizobium fredii extends the host range of the recipient to the non-hosts Calopogonium caeruleum and Lablab purpureus, however. Chemical analyses of the Nod factors produced by the NodI, NolO, and NoeI mutants show that the nolO and noeI gene products are required for 3 (or 4)-O-carbamoylation of the nonreducing terminus and for 2-O-methylation of the fucosyl group, respectively. Confirmation that NolO is a carbamoyltransferase was obtained from analysis of the Nod factors produced by R. fredii containing nolO; all are carbamoylated at O-3 (or O-4) on the nonreducing terminus. Since mutation of both nolO and nodU fails to completely abolish production of monocarbamoylated NodNGR factors, it is clear that a third carbamoyltransferase must exist. Nevertheless, the specificities of the two known enzymes are clearly different. NodU is only able to transfer carbamate to O-6 while NolO is specific for O-3 (or O-4) of NodNGR factors.

nodD2 of Rhizobium sp. NGR234 is involved in the repression of the nodABC operon.

Transcriptional regulators of the lysR family largely control the expression of bacterial symbiotic genes. Rhizobium sp. NGR234 contains at least four members of this family: two resemble nodD, while two others are more closely related to syrM. Part of the extremely broad host range of NGR234 can be attributed to nodD1, although the second gene shares a high degree of DNA sequence homology with nodD2 of R. fredii USDA191. A nodD2 mutant of NGR234 was constructed by insertional mutagenesis. This mutant (NGR omega nodD2) was deficient in nitrogen fixation on Vigna unguiculata and induced pseudonodules on Tephrosia vogelii. Several other host plants were tested, but no correlation could be drawn between the phenotype and nodule morphology. Moreover, nodD2 has a negative effect on the production of Nod factors: mutation of this gene results in a fivefold increase in Nod factor production. Surprisingly, while the structure of Nod factors from free-living cultures of NGR omega nodD2 remained unchanged, those from V. unguiculata nodules induced by the same strain are non-fucosylated and have a lower degree of oligomerization. In other words, developmental regulation of Nod factor production is also abolished in this mutant. Competitive RNA hybridizations, gene fusions and mobility shift assays confirmed that nodD2 downregulates expression of the nodABC operon.

Sulphation of Rhizobium sp. NGR234 Nod factors is dependent on noeE, a new host-specificity gene.

Rhizobia secrete specific lipo-chitooligosaccharide signals (LCOs) called Nod factors that are required for infection and nodulation of legumes. In Rhizobium sp. NGR234, the reducing N-acetyl-D-glucosamine of LCOs is substituted at C6 with 2-O-methyl-L-fucose which can be acetylated or sulphated. We identified a flavonoid-inducible locus on the symbiotic plasmid pNGR234a that contains a new nodulation gene, noeE, which is required for the sulphation of NGR234 Nod factors (NodNGR). noeE was identified by conjugation into the closely related Rhizobium fredii strain USDA257, which produces fucosylated but non-sulphated Nod factors (NodUSDA). R. fredii transconjugants producing sulphated LCOs acquire the capacity to nodulate Calopogonium caeruleum. Furthermore, mutation of noeE (NGRdelta noeE) abolishes the production of sulphated LCOs and prevents nodulation of Pachyrhizus tuberosus. The sulphotransferase activity linked to NoeE is specific for fucose. In contrast, the sulphotransferase NodH of Rhizobium meliloti seems to be less specific than NoeE, because its introduction into NGRdelta noeE leads to the production of a mixture of LCOs that are sulphated on C6 of the reducing terminus and sulphated on the 2-O-methylfucose residue. Together, these findings show that noeE is a host-specificity gene which probably encodes a fucose-specific sulphotransferase.