Clinical Relevance of Sternal Foramina: A Morphometric Study

Objectives

The present study aimed at determining the incidence of sternal foramina in adult dry bones of North Indian descent. We also aimed to determine the number, precise location of the sternal foramina with a standard reference point which might have considerable importance with regard to procedures involving sternal puncture.

Methods

This cross sectional descriptive study was conducted on 72 dry adult human sternums. Various measurements in relation to the sternal foramina were taken with a non-stretchable measuring tape and digital vernier calliper and expressed as: [A]-total sternal length, [B]-distance between the jugular notches to the foramen, [C]-distance between the angle of Louis to the foramen and [D]-distance of the foramen from the mid sternal plane. Statistical analysis was performed with Microsoft Excel version 2019. A p-value of <0.05 was considered significant.

Results

We found 6.94% (5 out of 72 sternums) incidence of sternal foramina which corroborates well with the existing literature. Mean sternal length was 127.7 ± 09 mm. The mean distance of the foramina from suprasternal notch, sternal angle and from the median plane were 118.12 ± 0.3 mm, 116.7 mm and 2.4 mm respectively. Incidence of sternal foramina was almost similar to previously reported studies.

Conclusions

The precise knowledge about the expected location of sternal foramina is imperative to avoid intra-thoracic visceral injury during commonly performed acupuncture needle insertion and while doing bone marrow aspiration for diagnostic evaluation.

Complete Ossification of Transverse Acetabular Ligament - Embryological and Clinical Perspective

Abstract

Transverse acetabular ligament (TAL) is one of the important ligaments, which provide stability to the hip joint. On rare occasions, it can get ossified leading to limited mobility of the hip joint. Ossified TAL also converts acetabular notch to a foramen and neurovascular structures passing through the notch can get compressed leading to ischaemic symptoms. During routine demonstration of hip bone to undergraduate students, complete ossification of TAL was found in a right sided hip bone. Present case report with this rare finding also includes a short review of literature impressing on embryological and clinical perspectives of ossified TAL. Ossification of this ligament can be caused by defective ossification of hip bone as three secondary ossification centres develop around the acetabulum in triradiate carti-lage. Also, this can be caused due to heterotopic ossification of TAL after an inflammatory or traumatic injury. This ligament is extremely important in total hip replacement surgery being utilised in determining the position of the acetabular component. Anatomical knowledge of abnormal ossification of TAL is imperative in diagnosis and treatment of various pathologies of the hip joint.

Bilateral Bifid Tendon of Palmaris Longus - Advantageous in Tendon Transfer?

Background

Variable insertions of Palmaris longus (PL) muscle tendon is described by various authors. Presence of extra PL tendon is also described in literature. As autologus tendon grafting is a blooming arena of clinical research at present time, an additional tendinous slip of PL has promising scope for use as an autograft.

Case Report

We report here bilateral bitendinous distal attachment of PL muscle encountered during routine cadaveric dissection. The additional PL tendon in a multitendinous insertion pattern with optimum length and thickness is indeed an additional advantage from the point of view of autograft harvesting. This has also importance in understanding the unusual, altered symptomatology in compressive conditions.

Conclusion

Although relatively common, surgeons should be well aware of the various possible aversion of distal attachment of PL which might have significant impact in alteration of symptomatology of neurovascular compressions in the forearm and hand and while choosing an appropriate tendon autograft.

Clinical Relevance of Nutrient Foramina of Fibula: A Morphometric Study

Background

The fibula is a long bone located at the lateral aspect of the leg. Diaphysis of fibula is supplied by one or more nutrient arteries through an opening referred to as the nutrient foramen. Mor-phometric studies of the nutrient foramina of fibulae are very sparse in literature.

Materials and Methods

This cross-sectional descriptive study was conducted on 51 dry adult human fibulae housed in the department of anatomy, AIIMS, New Delhi. Total fibular length along with the number and location of all nutrient foramina present were recorded. Foraminal indexes (FI) of the fibulae were calculated as well.

Results

The study revealed that the average length of fibulae was 35.48 ± 1.76 cm. 94% fibulae had a single nutrient foramen and 6 % had two. In fibula with single foramen, the most common location was on the medial crest (50%), followed by between medial crest and posterior border (35%), between the medial crest and interosseous border (8%) and on posterior border (6%). Nutrient foramen was located in middle 1/3rd of shaft in 98 % and in inferior 1/3rd of shaft in 2 % of fibulae. The average foraminal index was 44.85 ± 6.67% with a range of 35.7 to 63.8%.

Conclusion

Most common location of nutrient foramen in fibula is middle 1/3rd of shaft on the medial crest with dual nutrient foramina in 6% of fibulae. These parameters show variability in different geographical location and population groups. These data may be helpful for anthropologists, forensic experts, radiologists and might guide in harvesting vascularised fibular bone graft.

Origin of triple right coronary with separate ostium

This report highlights a coronary artery anomaly (CAA) involving three right coronary arteries (RCAs) arising from the anterior aortic sinus and a single left coronary artery (LCA) from the left posterior aortic sinus. Furthermore, each of the three RCAs originated with separate ostia. The 1st RCA was the right conus artery which originated through the anterior ostium. The 2nd RCA from the middle ostium mimicked a typical RCA. The 3rd RCA that originated from the posterior ostium had an initial retro-aortic course and then ran between the ascending aorta and atria. It eventually terminated as the circumflex artery after reaching the left end of the posterior coronary sulcus. The LCA was normal anatomically except that it did not give the circumflex branch. The knowledge of this type of unusual branching pattern of the coronary artery may be useful to clinicians.

Ossification of Superior Transverse Scapular Ligament - Incidence, Embryology and Association with Suprascapular Neuropathy

Introduction

Suprascapular notch is present at superior border of scapula just medial to coracoid process. This is covered by superior transverse scapular ligament (STSL). Suprascapular nerve passes below this ligament while suprascapular vessels pass above it. STSL ossification is a rare finding with variable incidences in different population groups.

Materials and Methods

We observed 60 dry bony scapulae, 30 prosected formalin fixed upper limbs with scapula and 10 embalmed cadavers for the presence of ossified STSL.

Results

There were complete ossification of STSL in two dried bony specimens of sacpula.

Conclusion

Ossified STSL may be the causative factor for suprascapular neuropathy. The mainstay of management in cases of neuropathy or compression of suprascapular nerve is release of suprascapular ligament by either open or arthroscopic surgical approach. So, it is extremely important to know this type of variation to minimize any damage to related structure and plan the management accordingly.

An Atypical Case of Meckel's Diverticulum with Small Bowel Obstruction: Surgical Anatomy, Embryology and Clinical Implications

Abstract

Meckel's diverticulum (MD) is the most frequent congenital anomaly of the gastrointestinal (GI) tract. Atypical presentations with life threatening complications include intestinal obstruction, intussusceptions, peritonitis, foreign body lodgement in the MD, perforated viscera etc. which require prompt diagnosis. Ectopic gastric and pancreatic tissues are found in up to half of the cases which can escalate the complications. However clinical diagnosis is not easy especially when the presentation is atypical. A high index of clinical suspicion is required to diagnose elusive MD with associated complications. Surgical resection is safe and the gold standard treatment for complicated MD. A case of Meckel's diverticulum with concomitant mesodiverticular band (MDB) in a 13 years old male child presented as intestinal obstruction to emergency department is described which was promptly managed surgically with required pre-operative investigations. The aim of this report is to make clinicians aware about a complicated MD with MDB clinically presenting as small bowel obstruction.

Myocardial bridge over coronary arteries and myocardial coat over coronary sinus: a cadaveric study

Funding Acknowledgements

Type of funding sources: None.

Background

Myocardial Bridge (MB) over the coronary artery and myocardial coat (MC) over the cardiac veins are sometimes detected in angiography and cadaveric dissection. Left anterior descending (LAD) branch of left coronary artery is most frequent site of MB. Rarely MB is also seen over right coronary artery (RCA) branch. MB has proven association with ischemic heart disease and other critical cardiac consequences like myocardial infarction (MI)(1)(2). MC on the other hand has not gained enough attention in erstwhile studies. Large MB can be readily identified in angiograms, but minute MB can be picked up by newer imaging studies like multi-detector computed tomography (MDCT) and optical coherence tomography (OCT) scan(3). Cadaveric dissection however holds its unique place in direct visualization and studying the macro and micro-anatomical characteristics.

Purpose

To study the prevalence and anatomical attributes of MB and MC in cadaveric hearts.

Methods

Ten adult cadaveric hearts (6 male and 4 female) were dissected as part of routine undergraduate teaching during academic year 2021-22. MB over the coronary artery and MC over cardiac vein was identified. Data pertaining to the MB and MC dimensions were measured with digital vernier calliper. Histology of the MC was carried out to confirm its presence and observe the cyto-architecture pattern. Relevant gross macroscopic and microscopic images were photographed and photomicrographed.

Results

20% of the dissected cadavers revealed MB involving LAD in first heart while LAD and RCA both in second heart with length 7.5 mm, 11.5 mm and 1.8 mm respectively. MC was noted over coronary sinus and proximal few millimeters of great and middle cardiac veins. Histological examination revealed cardiac striated muscle in MC with typical cyto-architecture. The mean myocardial muscle index (MMI) of MBs was 1.39.

Conclusions

Present study highlights 20% prevalence of MBs in cadavers involving both right and left coronary artery. 10% of the subjects had histologically confirmed MC over cardiac veins. MC over coronary sinus and other cardiac veins needs more elaborate explorative studies to quantify the anatomic properties and to examine the possible association with cardiovascular disease. Nevertheless, anatomic attributes should be kept in mind to better appreciate MI in evolution and MI at evaluation in a case with MB.

Yoga: A Natural Solution to Decrease Disease Burden in Children of MTHFR Deficient Parents

Introduction

MTHFR being a key regulatory enzyme of 1-carbon metabolism pathway serves critical function of generation of SAM, replenishment of glutathione and nucleotide synthesis and finally methylation of the bio molecules. MTHFR gene mutation is a rare au-tosomal recessive inborn error of metabolism and presents with severe hyperhomocysteinemia. MTHFR polymorphisms on the other hand are commonly encountered of which two 677 C>T and 1298 A>C have been most widely studied and reported to increase the vulnerability to neural tube defects, congenital heart disease, various neuropsychiatric disorders like autism spectrum diseases and attention deficit hyperactiv-ity disease, cleft lip/ palate, acute leukaemia, cardiovascular diseases, occlusive vascular disease in children.

Methods

We conducted this prospective clinical trial to examine whether yoga practice can up regulate MTHFR gene expression. Considering the prevalence of MTHFR polymorphism, varied spectrum of its implications in disease causation including male infertility, we conducted the trial involving 30 infertile men who underwent 3 weeks of supervised YBLI. Pre and post intervention assessment of the blood and semen sample was done to see the effects.

Results

We have found more than fivefold up-regulation in the expression of MTHFR gene with significant reduction of seminal free radical levels after 3 weeks of yoga practice. Interestingly we noticed significantly higher MTHFR polymorphic variants in infertile male patients compared to healthy fertile controls.

Conclusion

MTHFR polymorphisms are also independently associated with many paediatric diseases. Diagnosing MTHFR deficiency in children is a challenging job and requires high index of suspicion and continuous vigilance. Yoga based lifestyle may be adopted both by parents planning conception and also by adolescent children who are sufferers of this condition to halt the consequences of mild to moderate MTHFR deficiency.

Assessment of gamma radiation through agro-morphological characters in Camellia Sinensis L. (O.) Kuntze

PURPOSE

To study the effects of gamma radiation on tea seed germination, morphological changes, and genetic variation by using gamma radiation.

MATERIAL AND METHOD

Fresh Tea seed material were irradiated with twenty different doses of gamma radiation such as 0, 2, 4, 6, 8, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80 90, 100, 200, 500 and 1000 Gy from Cobalt ⁶⁰Co source from Regional Nuclear Agriculture Research Center, Bidhan Chandra Krishi Viswavidyalaya (BCKV), West Bengal, in between 2019 and 2020.

RESULT AND CONCLUSION

The growth behavior of tea seedling was recorded under varying levels of gamma radiation and its performance at nursery stages. It was observed seed irradiated with doses from 35 Gy to 100 Gy could germinate but could not survive beyond five (05) months. When treated with higher doses as 200 Gy, 500 Gy and 1000 Gy, no seed germination takes places due to possible damages occur in the DNA structure. Screening of growth characteristics of tea plant generally monitored by the characteristics like plant height, number of leaves, number of primary branches, base diameter, and total leaf area of plants and we found that these characteristics significantly increased with the progress of time and increasing levels of gamma radiation; however, the plant height showed decreasing trend with the increasing levels of gamma radiation, which could be due to the change in chromosomal structure and genetic alteration. After 90 weeks of planting, the plant height, no. of primary branches, the number of leaves, plant base diameter, and total leaf area per plant recorded were 36.42 cm, 1/plant, 7.11/plant, 0.62 c.m, 22.92 cm²/plant respectively under the radiation level 30 Gy, whereas the corresponding figures of the above parameters at the control treatment were 85.32 cm, 1/plant, 18.84/plant, 1.18 c.m and 26.68 cm²/plant, respectively. The total plant height, no. of primary branches, the number of leaves, plant base diameter, and total leaf area per plant were significantly influenced by the rising levels of gamma radiation (up to 100 Gy), finally, after 90 weeks of planting, the maximum no. of branching was observed in the treatment of 8 Gy, 10 Gy and 15 Gy respectively. The study reveals a hitherto open the possibility of using gamma radiation on tea plant for creation of variation in the tea seed planting materials. Further studies on mutation using tea planting materials would give an insight into its mutable gene behavior.

Bioremediation: an alternative approach for detoxification of polymers from the contaminated environment

The industries and metropolitan wastes produced by anthropogenic activities are of great concern for nature as it causes soil contamination and deteriorate the environment. Plastic utilization is rapidly enhancing globally with passing days that last for a more extended period in the environment due to slow decomposition and natural degradation. Excessive use of polymer has risked the life of both marine, freshwater and terrestrial organisms. Lack of proper waste management and inappropriate disposal leads to environmental threats. Bioremediation processes involve microbes such as fungi, bacteria, etc. which contribute a crucial role in the breakdown of plastics. Extremophiles secrete extremozymes that are functionally active in extreme conditions and are highly crucial for polymer disaggregation in those conditions.

Mimosine, a Toxin Present in Leguminous Trees (Leucaena spp.), Induces a Mimosine-Degrading Enzyme Activity in Some Rhizobium Strains

Thirty-seven Rhizobium isolates obtained from the nodules of leguminous trees (Leucaena spp.) were selected on the basis of their ability to catabolize mimosine, a toxin found in large quantities in the seeds, foliage, and roots of plants of the genera Leucaena and Mimosa. A new medium containing mimosine as the sole source of carbon and nitrogen was used for selection. The enzymes of the mimosine catabolic pathway were inducible and were present in the soluble fraction of the cell extract of induced cells. On the basis of a comparison of the growth rates of Rhizobium strains on general carbon and nitrogen sources versus mimosine, the toxin appears to be converted mostly to biomass and carbon dioxide. Most isolates able to grow on mimosine as a source of carbon and nitrogen are also able to utilize 3-hydroxy-4-pyridone, a toxic intermediate of mimosine degradation in other organisms.

The mid genes of Rhizobium sp strain TAL1145 are required for degradation of mimosine into 3-hydroxy-4-pyridone and are inducible by mimosine

Mimosine is a toxin present in the tree-legume leucaena (Leucaena leucocephala), including its root nodules and the root exudates. The leucaena-nodulating Rhizobium sp. strain TAL1145 degrades mimosine (Mid(+)) and utilizes it as a source of carbon and nitrogen. Twelve TAL1145 mutants defective in mimosine degradation (Mid(-)) were made through Tn3Hogus, TnphoA or kanamycin-resistance-cassette insertions. A 5.0 kb PstI fragment of TAL1145, subcloned from a cosmid clone containing mid genes for mimosine degradation, complemented most of the Mid(-) mutants. Sequencing this fragment and the adjacent 0.9 kb PstI fragment identified five genes, midA, midB, midC, midD and midR, of which the first three genes encode ABC transporter proteins involved in mimosine uptake, while midD encodes an aminotransferase required for degrading mimosine into 3-hydroxy-4-pyridone, and midR is a regulatory gene encoding a LysR-type transcriptional activator. The location of MidA in the periplasm was shown by making two midA : : phoA fusions, which made active alkaline phosphatase in the periplasm. The various mid : : gus and midA : : phoA fusions were inducible by mimosine, and a midD : : gus fusion mutant showed beta-glucuronidase activity in the leucaena nodules, indicating that midD is expressed in the nodules. Similarly, a midA : : phoA fusion expressed alkaline phosphatase activity in the leucaena nodules, indicating that mimosine induces midA transcription in the bacteroids. mid genes are specific for the Mid(+) strains of leucaena Rhizobium and are absent in strains of other Rhizobium, Sinorhizobium and Bradyrhizobium spp.

Diversity among Bradyrhizobium isolates nodulating yardlong bean and sunnhemp in Guam

AIMS

To isolate and characterize bradyrhizobia that nodulate yardlong bean and sunnhemp in Guam.

METHODS AND RESULTS

Bradyrhizobia populations that nodulate yardlong bean and sunnhemp in Guam were examined for genetic diversity and their relatedness to Bradyrhizobium japonicum and B. elkanii reference strains. Genomic DNA of 58 isolates of Bradyrhizobium spp. was hybridized with B. japonicum nodY and B. elkanii nodK genes. Based on the hybridization patterns, the isolates were classified into three nodY-nodK hybridizing groups. Group I comprised the majority of the isolates and hybridized with nodY whereas group II isolates hybridized with nodK. The group III isolates, that did not hybridize with either nodY or nodK, formed nitrogen-fixing nodules on cowpea but did not nodulate soybean. DNA sequence analysis of a 280-bp fragment of the variable region of the 16S rRNA gene of a few group III isolates showed that these isolates were more similar to Bradyrhizobium spp. than to B. japonicum or B. elkanii.

CONCLUSIONS

The majority of the isolates nodulating yardlong bean and sunnhemp in Guam are similar to B. japonicum, although some isolates are similar to Bradyrhizobium spp. that nodulate a miscellaneous group of legumes including cowpea.

SIGNIFICANCE AND IMPACT OF THE STUDY

Since both yardlong bean and sunnhemp are nodulated by a range of bradyrhizobia, selection of superior strains may be based on nodulation effectiveness on both legumes.

Comparison of molecular and antibiotic resistance profile methods for the population analysis of Bradyrhizobium spp. (TGx) isolates that nodulate the new TGx soybean cultivars in Africa

AIMS

Comparison of molecular and antibiotic resistance profile methods to identify an easy method that can differentiate between strains of introduced Bradyrhizobium japonicum and the indigenous Bradyrhizobium spp. (TGx) isolates which nodulate the newly developed TGx soybean cultivars in Africa.

METHODS AND RESULTS

Restriction fragment length polymorphism (RFLP) of 16S rDNA generated by five restriction enzymes, banding patterns in Southern hybridization using nod and nif genes as probes, and resistance patterns of the isolates to nine antibiotics, were used to group 26 Bradyrhizobium spp. (TGx) isolates and four other Bradyrhizobium strains. The clusters of isolates obtained from the four grouping methods were all different, although all methods revealed large genetic diversity among the isolates.

CONCLUSIONS

Results indicate that the antibiotic resistance profile method is as good as the three molecular methods used in this study for phylogenetic grouping of the Bradyrhizobium spp. (TGx) isolates, which may serve as a basis for further characterization of selected isolates from each group.

SIGNIFICANCE AND IMPACT OF THE STUDY

The antibiotic resistance profile method can be used as a simple means of assessing genetic variability and grouping of a large number of Bradyrhizobium spp. (TGx) isolates. Representative isolates from each group can then be selected for further characterization.

Selection of several classes of mimosine-degradation-defective Tn3Hogus-insertion mutants of Rhizobium sp. strain TAL1145 on the basis of mimosine-inducible GUS activity

Rhizobium sp. strain TAL1145 that nodulates Leucaena leucocephala degrades mimosine, a toxin produced by this tree legume. A cosmid clone, pUHR263, containing ~25 kb cloned DNA was isolated by plating Escherichia coli cells containing the cosmid clone library of TAL1145 on a minimal medium in which 3-hydroxy-4-pyridone (HP), a degradation product of mimosine, was used as the source of nitrogen. Cosmid pUHR263 was mutagenized by random insertions of Tn3Hogus, a transposon that makes transcriptional gus fusions when it is inserted in a gene in the correct orientation. Various pUHR263::Tn3Hogus derivatives that showed mimosine-inducible or mimosine-repressible GUS activities when transferred to the Rhizobium sp. strain TAL1145 were selected. Mutants of TAL1145 were constructed by transferring these Tn3Hogus insertions into the TAL1145 chromosome through double-homologous recombination. These mutants were classified into five classes on the basis of defects in mimosine degradation. The growth of these mutants was inhibited to different extents by mimosine applied to the growth medium. Mimosine forms a red-colored Fe-mimosine complex when FeCl3 is added to the medium. The inhibitory effect of Fe-mimosine on growth of the mutants was much less than that of mimosine.Key words: mimosine, mid and pyd genes, Leucaena leucocephala, tree legume, Tn3Hogus.

Selection of several classes of mimosine-degradation-defective Tn3Hogus-insertion mutants of Rhizobium sp. strain TAL1145 on the basis of mimosine-inducible GUS activity

Rhizobium sp. strain TAL1145 that nodulates Leucaena leucocephala degrades mimosine, a toxin produced by this tree legume. A cosmid clone, pUHR263, containing approximately 25 kb cloned DNA was isolated by plating Escherichia coli cells containing the cosmid clone library of TAL1145 on a minimal medium in which 3-hydroxy-4-pyridone (HP), a degradation product of mimosine, was used as the source of nitrogen. Cosmid pUHR263 was mutagenized by random insertions of Tn3Hogus, a transposon that makes transcriptional gus fusions when it is inserted in a gene in the correct orientation. Various pUHR263::Tn3Hogus derivatives that showed mimosine-inducible or mimosine-repressible GUS activities when transferred to the Rhizobium sp. strain TAL1145 were selected. Mutants of TAL1145 were constructed by transferring these Tn3Hogus insertions into the TAL1145 chromosome through double-homologous recombination. These mutants were classified into five classes on the basis of defects in mimosine degradation. The growth of these mutants was inhibited to different extents by mimosine applied to the growth medium. Mimosine forms a red-colored Fe-mimosine complex when FeCI3 is added to the medium. The inhibitory effect of Fe-mimosine on growth of the mutants was much less than that of mimosine.

Bradyrhizobium spp. (TGx) isolates nodulating the new soybean cultivars in Africa are diverse and distinct from bradyrhizobia that nodulate North American soybeans

The newly developed cultivars of soybean in Africa, known as Tropical Glycine cross (TGx), are nodulated by bradyrhizobia indigenous to African soils, here designated Bradyrhizobium spp. (TGx). Isolates of Bradyrhizobium spp. (TGx) obtained from nodules of TGx soybeans that were inoculated with soils from 65 locations in six African countries were characterized and grouped into 11 phylogenetic clusters on the basis of RFLP of the 16S rRNA gene. Five restriction enzymes (RsaI, HinfI, MspI, CfoI and HaeIII) established RFLP groups within these Bradyrhizobium spp. (TGx) isolates, which were used to construct a phylogenetic tree showing their genetic relationship with other Bradyrhizobium species. RFLP analysis indicated that Bradyrhizobium spp. (TGx) is a heterogeneous group with some isolates related to Bradyrhizobium japonicum and Bradyrhizobium elkanii strains and some to Bradyrhizobium spp. (misc.) reference strains isolated from a variety of tropical legumes. The heterogeneity within the large phylogenetic clusters was further examined through analysis of randomly amplified polymorphic DNA (RAPD) using GC-rich PCR primers. The RAPD analysis showed additional heterogeneity in the Bradyrhizobium spp. (TGx) phylogenetic clusters, which was not revealed by separations based on RFLP analysis. The Bradyrhizobium spp. (TGx) isolates were classified into effective and ineffective types based on their symbiotic performance on TGx soybean. The isolates were randomly distributed throughout the phylogenetic clusters regardless of their symbiotic effectiveness on TGx soybean.

A 150-megadalton plasmid in Rhizobium etli strain TAL182 contains genes for nodulation competitiveness on Phaseolus vulgaris L

Rhizobium etli TAL182, a competitive strain for the nodulation of Phaseolus beans, occupied more than 99% of the nodules when co-inoculated in various proportions with Rhizobium TAL1145 or Rhizobium tropici CIAT899. Two overlapping cosmid clones, pUHR68 and pUHR69, containing genes for nodulation competitiveness from TAL182, were isolated by functional complementation of strain TAL1145. Using one of these cosmid clones, we constructed two Tn5-insertion mutants of TAL182 defective in nodulation competitiveness. The Tn5 insertions in both mutants were localized in identical positions within a 4.6-kb HindIII fragment. One mutant, RUH120, was complemented for nodulation competitiveness by this HindIII fragment. The cloned DNA in pUHR68 is a part of a plasmid, 150 MDa in size, in TAL182 and does not show homology with TAL1145 genomic DNA. The 4.6-kb HindIII fragment contains a gene(s) required for nodulation competitiveness on beans, which is present only in some R. etli strains and absent in other Rhizobium spp.

Cross-resistance of the diamondback moth indicates altered interactions with domain II of Bacillus thuringiensis toxins

We compared responses to six insecticidal crystal proteins from Bacillus thuringiensis by a Cry1A-resistant strain (NO-QA) and a susceptible strain (LAB-P) of the diamondback moth, Plutella xylostella. The resistant strain showed > 100-fold cross-resistance to Cry1J and to H04, a hybrid with domains I and II of Cry1Ab and domain III or Cry1C. Cross-resistance was sixfold to Cry1Bb and threefold to Cry1D. The potency of Cry1I did not differ significantly between the resistant and susceptible strains. Cry2B did not kill resistant or susceptible larvae. By combining these new data with previously published results, we classified responses to 14 insecticidal crystal proteins by strains NO-QA and LAB-P. NO-QA showed high levels of resistance to Cry1Aa, Cry1Ab, and Cry1Ac and high levels of cross-resistance to Cry1F, Cry1J, and H04. Cross-resistance was low or nil to Cry1Ba, Cry1Bb, Cry1C, Cry1D, Cry1I, and Cry2A. Cry1E and Cry2B showed little or no toxicity to susceptible or resistant larvae. In dendrograms based on levels of amino acid sequence similarity among proteins, Cry1F and Cry1J clustered together with Cry1A proteins for domain II, but not for domain I or III. High levels of cross-resistance to Cry1Ab-Cry1C hybrid H04 show that although Cry1C is toxic to NO-QA, domain III or Cry1C is not sufficient to restore toxicity when it is combined with domains I and II of Cry1Ab. Thus, diamondback moth strain NO-QA cross-resistance extends beyond the Cry1A family of proteins to at least two other families that exhibit high levels of amino sequence similarity with Cry1A in domain II (Cry1F and Cry1J) and to a protein that is identical to Cry1Ab in domain II (H04). The results of this study imply that resistance to Cry1A alters interactions between the insect and domain II.

Construction of a single-transposon-insertion mutant in Rhizobium sp. strain TAL1145 from a double-insertion mutant

A method for developing a single-transposon-insertion mutant from a double-insertion mutant in Rhizobium is described. An exopolysaccharide (EPS)-defective mutant containing two Tn5-lacZ insertions was complemented with cloned wild-type DNA for EPS synthesis. One of the Tn5-lacZ insertions from the mutant was transferred to the complementing plasmid by homologous recombination. The plasmid containing the Tn5-lacZ insertion in the gene involved in EPS synthesis was transferred into the wild-type strain and the Tn5-lacZ was homogenized to obtain an EPS-defective mutant with a single Tn5-lacZ insertion.

The psi operon of Rhizobium leguminosarum biovar phaseoli: identification of two genes whose products are located at the bacterial cell surface

We have delineated three short open reading frames, psiA, ORF-P and psiB within the psi operon of Rhizobium leguminosarum biovar phaseoli. psiA, in a multi-copy plasmid, causes inhibition of exopolysaccharide synthesis in R. leguminosarum. In addition, the suppression of exopolysaccharide synthesis due to the multi-copy psiA caused R. leguminosarum strains to stain with the dye calcofluor, a response that does not occur with wild-type strains of this species. Insertions of a defective phoA gene (lacking its promoter, ribosomal binding site and leader sequence) into psiA and psiB were isolated and the precise locations of the insertions were established. PsiA-PhoA and PsiB-PhoA protein fusions were found to express alkaline phosphatase activity indicating that PsiA and PsiB span the inner membrane or are translocated across it.

Genetic characterization of Rhizobium sp. strain TAL1145 that nodulates tree legumes

Rhizobium sp. strain TAL1145 nodulates Leucaena leucocephala and Phaseolus vulgaris, in addition to a wide range of tropical tree legumes. Six overlapping clones that complemented nodulation defects in leucaena and bean rhizobia were isolated and a 40-kb map of the symbiosis region was constructed. The common nod and nifA genes were situated approximately 17 kb apart, with the nodIJ genes in between. These clones enabled a derivative of TAL1145 carrying a partially deleted pSym to form ineffective nodules on both leucaena and bean, and a similar derivative of Rhizobium etli TAL182 to form ineffective nodules on bean. When two representative clones, pUHR9 and pUHR114, were each transferred to wild-type rhizobial strains, they allowed ineffective nodulation by Rhizobium meliloti on both leucaena and bean and by Rhizobium leguminosarum bv. vicia on bean. Transconjugants of R. leguminosarum bv. trifolii formed effective nodules on leucaena and ineffective nodules on bean. Tn5 mutagenesis of the symbiosis region resulted in a variety of nodulation and fixation phenotypes on leucaena and bean. On the basis of 16S rRNA sequences, TAL1145 was found to be distinct from both R. tropici and NGR234, the two groups of leucaena symbionts that were previously described.

Genetic Analysis of Rhizobium leguminosarum bv. Phaseoli Mutants Defective in Nodulation and Nodulation Suppression

Nodulation-defective rhizobia and their nodule-forming derivatives containing cloned DNA from the wild type were used to study nodulation suppression in Phaseolus vulgaris L. Non-nitrogen-fixing derivatives which formed rhizobia-containing white nodules induced partial suppression. Comparison of this with the complete suppression by Fix + derivatives and a Fix - mutant which formed rhizobia-containing pink nodules suggests that the extent of suppression may be related to successive stages of nodule development.

The products of Rhizobium genes, psi and pss, which affect exopolysaccharide production, are associated with the bacterial cell surface

Translational fusions between a mutant phoA (lacking its promoter, ribosomal binding site and signal peptide sequence) and Rhizobium 'symbiotic' genes were isolated. Since these fusions expressed alkaline phosphatase (AP), the product of phoA, the genes into which phoA was inserted apparently specify proteins located in the bacterial periplasm or cell membrane, the compartment in which AP has activity. These genes were psiA and genes upstream of psiA (psiA is required for normal nodule development and strains with multicopy psiA fail to make exopolysaccharide (EPS) and to nodulate). Fusions between phoA and pss (exo) genes, which are required for EPS production, also resulted in the expression of AP indicating that products of these pss genes were located at the cell surface. Using gus fusions to psiA and pssA, we found that the former was expressed in N2-fixing bean root nodules but the latter was not.

Expression, nucleotide sequence and mutational analysis of two open reading frames in the nif gene region of Anabaena sp. strain PCC7120

A 1.8 kb transcript corresponding to a region of the Anabaena 7120 chromosome 4 kb downstream of the nifHDK operon appears 12-18 h after heterocyst induction. The DNA corresponding to this transcript was sequenced and found to contain two open reading frames, designated ORF 1 and ORF 2. Two polypeptides, of 30 kDa and 13 kDa, encoded by these ORFs were expressed in Escherichia coli. An apparent start site for the transcript, detected by S1 nuclease protection, was located 42 bp upstream of the ATG start codon of ORF 1. ORF 2 shows strong sequence similarity to ORF 6 in the nif gene region of Azotobacter vinelandii. ORF 1 was interrupted using a 1.4 kb neomycin resistance cassette and the resulting mutant grew very slowly on medium lacking combined nitrogen. The mutant had 45% of wild-type acetylene reduction activity, which could be complemented by a 2.8 kb EcoRI fragment of wild-type Anabaena DNA containing only ORF 1 and ORF 2. Thus, one or both of these ORFs is required for efficient nitrogen fixation in Anabaena.

Tn5 mutagenesis of Anabaena sp. strain PCC 7120: isolation of a new mutant unable to grow without combined nitrogen

Methylation by Ava methylases in Escherichia coli increases the efficiency to transfer of Tn5 in pBR322bla:: Tn5 from E. coli to Anabaena sp. strain PCC 7120 by conjugation. Following conjugation, Tn5 but not pBR322 sequences were found at many different positions in the Anabaena chromosome. This procedure was used to mutagenize, tag, and clone a previously unrecognized gene required for nitrogen fixation in this Anabaena sp.

Analysis of pss genes of Rhizobium leguminosarum required for exopolysaccharide synthesis and nodulation of peas: their primary structure and their interaction with psi and other nodulation genes

Strains of Rhizobium leguminosarum (R.l.) biovar viciae containing pss mutations fail to make the acidic exopolysaccharides (EPS) and are unable to nodulate peas. It was found that they also failed to nodulate Vicia hirsuta, another host of this biovar. When peas were co-inoculated with pss mutant derivatives of a strain of R.l. by viciae containing a sym plasmid plus a cured strain lacking a sym plasmid (and which is thus Nod-, but for different reasons) but which makes the acidic EPS, normal numbers of nodules were formed, the majority of which failed to fix nitrogen (the occasional Fix+ nodules were presumably induced by strains that arose as a result of genetic exchange between cells of the two inoculants in the rhizosphere). Bacteria from the Fix- nodules contained, exclusively, the strain lacking its sym plasmid. When pss mutant strains were co-inoculated with a Nod- strain with a mutation in the regulatory gene nodD (which is on the sym plasmid pRL1JI), normal numbers of Fix+ nodules were formed, all of which were occupied solely by the nodD mutant strain. Since a mutation in nodD abolishes activation of other nod genes required for early stages of infection, these nod genes appear to be dispensable for subsequent stages in nodule development. Recombinant plasmids, containing cloned pss genes, overcame the inhibitory effects of psi, a gene which when cloned in the plasmid vector pKT230, inhibits both EPS production and nodulation ability. Determination of the sequence of the pss DNA showed that one, or perhaps two, genes are required for correcting strains that either carry pss mutations or contain multi-copy psi.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of two classes of Rhizobium phaseoli genes required for melanin synthesis, one of which is required for nitrogen fixation and activates the transcription of the other

The symbiotic plasmid pRP2JI of Rhizobium phaseoli strain 8002 was shown to contain two separate regions of DNA which are required and sufficient for the synthesis of the pigment melanin. One of these regions containing the class II mel gene(s) was located to other genes involved in nodulation and in nitrogen fixation. Mutations in this region abolished both the ability to synthesize melanin and to fix nitrogen in Phaseolus bean root nodules. Mutations in the other, unlinked region, containing class I mel gene(s), also abolished melanin synthesis but did not affect symbiotic nitrogen fixation. Transcriptional fusions between the class I mel gene and the Escherichia coli lacZ gene were constructed and it was demonstrated that the class II mel gene(s) activated their transcription in free-living culture. Further, strains containing the cloned regulatory class II gene(s) synthesized melanin when growing in minimal medium, in contrast to wild-type strains which became pigmented only in complete medium containing yeast extract and tryptone. It was shown by hybridization experiments that the regulatory mel gene was closely linked to or may correspond to the regulatory nifA gene; a fragment of R. phaseoli DNA which included the class II gene(s) of R. phaseoli hybridized to a previously identified nifA-like gene of R. leguminosarum, the species that nodulates peas.

Sequence of psi, a gene on the symbiotic plasmid of Rhizobium phaseoli which inhibits exopolysaccharide synthesis and nodulation and demonstration that its transcription is inhibited by psr, another gene on the symbiotic plasmid

A gene termed psi (polysaccharide inhibition), located close to the nodulation genes of the Rhizobium phaseoli symbiotic plasmid pRP2JI inhibited exopolysaccharide synthesis (EPS) and nodulation ability (Nod) in Rhizobium when it was cloned in a multicopy plasmid. The sequence of psi showed that it specified a polypeptide of mol. wt. 10,000 that may be associated with the membrane of Rhizobium. A second gene, psr (polysaccharide restoration), was located on pRP2JI. When cloned in multicopy plasmids, psr overcame the EPS and Nod defects in strains carrying multicopy psi. Strains with multicopy psr induced non-fixing nodules on Phaseolus beans. Using gene fusions between psi and lacZ, it was found that psr [corrected] inhibited transcription of psi [corrected].