Stimulus Dependence of Gamma Oscillations in Human Visual Cortex.

A striking feature of some field potential recordings in visual cortex is a rhythmic oscillation within the gamma band (30-80 Hz). These oscillations have been proposed to underlie computations in perception, attention, and information transmission. Recent studies of cortical field potentials, including human electrocorticography (ECoG), have emphasized another signal within the gamma band, a nonoscillatory, broadband signal, spanning 80-200 Hz. It remains unclear under what conditions gamma oscillations are elicited in visual cortex, whether they are necessary and ubiquitous in visual encoding, and what relationship they have to nonoscillatory, broadband field potentials. We demonstrate that ECoG responses in human visual cortex (V1/V2/V3) can include robust narrowband gamma oscillations, and that these oscillations are reliably elicited by some spatial contrast patterns (luminance gratings) but not by others (noise patterns and many natural images). The gamma oscillations can be conspicuous and robust, but because they are absent for many stimuli, which observers can see and recognize, the oscillations are not necessary for seeing. In contrast, all visual stimuli induced broadband spectral changes in ECoG responses. Asynchronous neural signals in visual cortex, reflected in the broadband ECoG response, can support transmission of information for perception and recognition in the absence of pronounced gamma oscillations.

Replacing stressful challenges with positive coping strategies: a resilience program for clinical placement learning.

Clinical education is foundational to health professional training. However, it is also a time of increased stress for students. A student's perception of stressors and their capacity to effectively manage them is a legitimate concern for educators, because anxiety and decreased coping strategies can interfere with effective learning, clinical performance and capacity to care for patients. Resilience is emerging as a valuable construct to underpin positive coping strategies for learning and professional practice. We report the development and evaluation of a psycho-education resilience program designed to build practical skills-based resilience capacities in health science (physiotherapy) students. Six final year undergraduate physiotherapy students attended four action research sessions led by a clinical health psychologist. Resilience strategies drawn from cognitive behavioural therapy, and positive and performance psychology were introduced. Students identified personal learning stressors and their beliefs and responses. They chose specific resilience-based strategies to address them, and then reported their impact on learning performance and experiences. Thematic analysis of the audio-recorded and transcribed action research sessions, and students' de identified notes was conducted. Students' initial descriptions of stressors as 'problems' outside their control resulting in poor thinking and communication, low confidence and frustration, changed to a focus on how they managed and recognized learning challenges as normal or at least expected elements of the clinical learning environment. The research suggests that replacing stressful challenges with positive coping strategies offers a potentially powerful tool to build self-efficacy and cognitive control as well as greater self-awareness as a learner and future health practitioner.

Molecular genetics to inform spatial management in benthic invertebrate fisheries: a case study using the Australian greenlip abalone.

Hierarchical sampling and subsequent microsatellite genotyping of >2300 Haliotis laevigata (greenlip abalone) from 19 locations distributed across five biogeographic regions have substantially advanced our knowledge of population structure and connectivity in this commercially important species. The study has found key differences in stock structure of H. laevigata compared with the sympatric and congeneric Haliotis rubra (blacklip abalone) and yielded valuable insights into the management of fisheries targeting species characterized by spatial structure at small scales (i.e. S-fisheries). As with H. rubra, H. laevigata comprise a series of metapopulations with strong self-recruitment. However, the spatial extent of H. laevigata metapopulations (reefal areas around 30 km(2) ; distances of up to 135 km are effective barriers to larval dispersal) was substantially greater than that identified for H. rubra (Miller et al. 2009). Differences in the dynamics and scale of population processes, even between congeneric haliotids as made evident in this study, imply that for S-fisheries, it is difficult to generalize about the potential consequences of life history commonalities. Consequently, species-specific management reflective of the population structure of the target species remains particularly important. This will likely require integration of information about stock structure and connectivity with data on life history and population dynamics to determine the necessary input (e.g. number of fishers, fishing effort) and output (e.g. minimum legal size, total allowable catch) controls to underpin their sustainable management.

Assessment of dementia risk in aging adults using both FDG-PET and FDDNP-PET imaging.

BACKGROUND: In a previous study, positron emission tomography (PET) with 2-(1-{6-[(2-[F-18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP), a molecule that binds to plaques and tangles in vitro, identified three subgroups of non-demented subjects according to FDDNP binding patterns: low global (LG) binding; high frontal, parietal, medial temporal binding (HF/PA); and high medial and lateral temporal and posterior cingulate (HT/PC) binding. In this follow-up investigation, we compared 2-deoxy-2-[F-18]fluoro- d-glucose (FDG)-PET cerebral metabolic patterns in the three FDDNP-PET binding subgroups. METHODS: Fifty-four subjects with normal aging (N = 28) or amnestic forms of mild cognitive impairment (N = 26) underwent FDDNP-PET and FDG-PET scanning. Subjects in the LG, HF/PA, and HT/PC FDDNP subgroups were compared according to visual ratings, statistical parametric mapping, and automated region of interest analyses of their FDG-PET data. RESULTS: The FDDNP-PET subgroups demonstrated different glucose metabolic patterns according to visual ratings, region of interest, and statistical parametric mapping analyses of FDG-PET data. The LG FDDNP subgroup showed no areas of significant hypometabolism relative to the other subgroups and had low Alzheimer's disease risk by FDG-PET standards. The HF/PA FDDNP subgroup demonstrated hypometabolism in bilateral inferior parietal/parietotemporal, bilateral posterior cingulate, perisylvian, mid-temporal gyrus, and dorsolateral prefrontal regions, which is a pattern suggestive of high Alzheimer's disease risk. The HT/PC FDDNP subgroup demonstrated heterogeneous FDG-PET patterns with predominant anterior frontal and anterior temporal hypometabolism, suggestive of mixed etiologies, including fronto-temporal dementia risk. CONCLUSIONS: The FDG-PET data provided independent validation that different patterns of FDDNP-PET binding in non-demented individuals may be associated with differential dementia risk.

Evidence that disease-induced population decline changes genetic structure and alters dispersal patterns in the Tasmanian devil.

Infectious disease has been shown to be a major cause of population declines in wild animals. However, there remains little empirical evidence on the genetic consequences of disease-mediated population declines, or how such perturbations might affect demographic processes such as dispersal. Devil facial tumour disease (DFTD) has resulted in the rapid decline of the Tasmanian devil, Sarcophilus harrisii, and threatens to cause extinction. Using 10 microsatellite DNA markers, we compared genetic diversity and structure before and after DFTD outbreaks in three Tasmanian devil populations to assess the genetic consequences of disease-induced population decline. We also used both genetic and demographic data to investigate dispersal patterns in Tasmanian devils along the east coast of Tasmania. We observed a significant increase in inbreeding (F(IS) pre/post-disease -0.030/0.012, P<0.05; relatedness pre/post-disease 0.011/0.038, P=0.06) in devil populations after just 2-3 generations of disease arrival, but no detectable change in genetic diversity. Furthermore, although there was no subdivision apparent among pre-disease populations (θ=0.005, 95% confidence interval (CI) -0.003 to 0.017), we found significant genetic differentiation among populations post-disease (θ=0.020, 0.010-0.027), apparently driven by a combination of selection and altered dispersal patterns of females in disease-affected populations. We also show that dispersal is male-biased in devils and that dispersal distances follow a typical leptokurtic distribution. Our results show that disease can result in genetic and demographic changes in host populations over few generations and short time scales. Ongoing management of Tasmanian devils must now attempt to maintain genetic variability in this species through actions designed to reverse the detrimental effects of inbreeding and subdivision in disease-affected populations.

Decoupling the cortical power spectrum reveals real-time representation of individual finger movements in humans.

During active movement the electric potentials measured from the surface of the motor cortex exhibit consistent modulation, revealing two distinguishable processes in the power spectrum. At frequencies <40 Hz, narrow-band power decreases occur with movement over widely distributed cortical areas, while at higher frequencies there are spatially more focal power increases. These high-frequency changes have commonly been assumed to reflect synchronous rhythms, analogous to lower-frequency phenomena, but it has recently been proposed that they reflect a broad-band spectral change across the entire spectrum, which could be obscured by synchronous rhythms at low frequencies. In 10 human subjects performing a finger movement task, we demonstrate that a principal component type of decomposition can naively separate low-frequency narrow-band rhythms from an asynchronous, broad-spectral, change at all frequencies between 5 and 200 Hz. This broad-spectral change exhibited spatially discrete representation for individual fingers and reproduced the temporal movement trajectories of different individual fingers.

High gamma mapping using EEG.

High gamma (HG) power changes during motor activity, especially at frequencies above 70 Hz, play an important role in functional cortical mapping and as control signals for BCI (brain-computer interface) applications. Most studies of HG activity have used ECoG (electrocorticography) which provides high-quality spatially localized signals, but is an invasive method. Recent studies have shown that non-invasive modalities such as EEG and MEG can also detect task-related HG power changes. We show here that a 27 channel EEG (electroencephalography) montage provides high-quality spatially localized signals non-invasively for HG frequencies ranging from 83 to 101 Hz. We used a generic head model, a weighted minimum norm least squares (MNLS) inverse method, and a self-paced finger movement paradigm. The use of an inverse method enables us to map the EEG onto a generic cortex model. We find the HG activity during the task to be well localized in the contralateral motor area. We find HG power increases prior to finger movement, with average latencies of 462 ms and 82 ms before EMG (electromyogram) onset. We also find significant phase-locking between contra- and ipsilateral motor areas over a similar HG frequency range; here the synchronization onset precedes the EMG by 400 ms. We also compare our results to ECoG data from a similar paradigm and find EEG mapping and ECoG in good agreement. Our findings demonstrate that mapped EEG provides information on two important parameters for functional mapping and BCI which are usually only found in HG of ECoG signals: spatially localized power increases and bihemispheric phase-locking.

Physiotherapy for freezing of gait in Parkinson's disease: a systematic review and meta-analysis. / Fisioterapia para la congelación de la marcha en la enfermedad de Parkinson: revisión sistemática y metaanálisis.

INTRODUCTION: Freezing of gait (FOG) is one of the most severe symptoms associated with Parkinson's disease (PD). Physiotherapy treatment could be an effective strategy for treating FOG, but no systematic review has been carried out in this regard. AIM: To identify the characteristics, methodological quality, and main outcomes of the studies that have analyzed the effects of physiotherapy interventions in FOG up to date, by performing a systematic review and a meta-analysis. PATIENTS AND METHODS: Four electronic databases were searched in order to find randomized controlled trials that provided information regarding the effects of any kind of physiotherapy treatment on FOG. The methodological quality of the included investigations was assessed by means of the PEDro scale. RESULTS: Twelve studies were identified for inclusion into the qualitative analysis, with four randomized controlled trials included in the final meta-analysis. The quality of the trials was generally good. Those physiotherapy modalities including cues were more effective for treating FOG than traditional physiotherapy approaches. The meta-analysis indicated that physiotherapy interventions had a significantly greater impact on FOG than control comparisons. CONCLUSIONS: Physiotherapy treatment, especially those modalities including visual and auditory cueing, should be prescribed to PD patients with FOG. Future studies including PD patients with cognitive impairment and FOG objective measurement tools are need to complete the existing scientific evidence.

TITLE: Fisioterapia para la congelación de la marcha en la enfermedad de Parkinson: revisión sistemática y metaanálisis.Introducción. La congelación de la marcha (CDM) es uno de los síntomas más graves asociados con la enfermedad de Parkinson (EP). El tratamiento fisioterapéutico podría ser una estrategia efectiva para su tratamiento, pero no se ha realizado ninguna revisión sistemática al respecto. Objetivo. Identificar las características, la calidad metodológica y los principales resultados de los estudios que han analizado los efectos de las intervenciones fisioterapéuticas en CDM hasta la fecha, mediante la realización de una revisión sistemática y un metaanálisis. Pacientes y métodos. Se realizaron búsquedas en cuatro bases de datos electrónicas para encontrar ensayos controlados aleatorizados que proporcionaran información con respecto a los efectos de cualquier tipo de tratamiento fisioterapéutico sobre la CDM. La calidad metodológica de las investigaciones se evaluó mediante la escala PEDro. Resultados. Se identificaron 12 estudios para su inclusión en el análisis cualitativo y cuatro ensayos controlados aleatorizados se incluyeron en el metaanálisis final. La calidad de los ensayos fue generalmente buena. Las modalidades de fisioterapia que incluían señales fueron más efectivas para tratar la CDM que los enfoques de fisioterapia tradicionales. El meta­análisis indicó que las intervenciones fisioterapéuticas tuvieron un impacto significativamente mayor sobre la CDM que las comparaciones de control. Conclusiones. El tratamiento fisioterapéutico, especialmente las modalidades que incluyen señales visuales y auditivas, debe prescribirse a los pacientes con EP con CDM. Se necesitan estudios futuros que incluyan pacientes con EP con deterioro cognitivo y herramientas de medición objetiva de la CDM para completar la evidencia científica existente.

Defining Critical Genes During Spherule Remodeling and Endospore Development in the Fungal Pathogen, Coccidioides posadasii.

Coccidioides immitis and C. posadasii are soil dwelling dimorphic fungi found in North and South America. Inhalation of aerosolized asexual conidia can result in asymptomatic, acute, or chronic respiratory infection. In the United States there are approximately 350,000 new infections per year. The Coccidioides genus is the only known fungal pathogen to make specialized parasitic spherules, which contain endospores that are released into the host upon spherule rupture. The molecular determinants involved in this key step of infection remain largely elusive as 49% of genes are hypothetical with unknown function. An attenuated mutant strain C. posadasii Δcts2/Δard1/Δcts3 in which chitinase genes 2 and 3 were deleted was previously created for vaccine development. This strain does not complete endospore development, which prevents completion of the parasitic lifecycle. We sought to identify pathways active in the wild-type strain during spherule remodeling and endospore formation that have been affected by gene deletion in the mutant. We compared the transcriptome and volatile metabolome of the mutant Δcts2/Δard1/Δcts3 to the wild-type C735. First, the global transcriptome was compared for both isolates using RNA sequencing. The raw reads were aligned to the reference genome using TOPHAT2 and analyzed using the Cufflinks package. Genes of interest were screened in an in vivo model using NanoString technology. Using solid phase microextraction (SPME) and comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry (GC × GC-TOFMS) volatile organic compounds (VOCs) were collected and analyzed. Our RNA-Seq analyses reveal approximately 280 significantly differentially regulated transcripts that are either absent or show opposite expression patterns in the mutant compared to the parent strain. This suggests that these genes are tied to networks impacted by deletion and may be critical for endospore development and/or spherule rupture in the wild-type strain. Of these genes, 14 were specific to the Coccidioides genus. We also found that the wild-type and mutant strains differed significantly in their production versus consumption of metabolites, with the mutant displaying increased nutrient scavenging. Overall, our results provide the first targeted list of key genes that are active during endospore formation and demonstrate that this approach can define targets for functional assays in future studies.

Genetic diversity and gene flow in collapsed and healthy abalone fisheries.

Overexploitation of marine species invariably results in population decline but can also have indirect effects on ecological processes such as larval dispersal and recruitment that ultimately affect genetic diversity and population resilience. We compared microsatellite DNA variation among depleted and healthy populations of the black-lip abalone Haliotis rubra from Tasmania, Australia, to determine if over-fishing had affected genetic diversity. We also used genetic data to assess whether variation in the scale and frequency of larval dispersal was linked to greater population decline in some regions than in others, and if larval dispersal was sufficient to facilitate natural recovery of depleted populations. Surprisingly, allelic diversity was higher in depleted populations than in healthy populations (P < 0.05). Significant subdivision across hundreds of metres among our sampling sites (F(ST) = 0.026, P < 0.01), coupled with assignment tests, indicated that larval dispersal is restricted in all regions studied, and that abalone populations across Tasmania are largely self-recruiting. Low levels of larval exchange appear to occur at the meso-scale (7-20 km), but age estimates based on shell size indicated that successful migration of larvae between any two sites may happen only once every few years. We suggest that genetic diversity may be higher in depleted populations due to the higher relative ratio of migrant to self-recruiting larvae. In addition, we expect that recovery of depleted abalone populations will be reliant on sources of larvae at the meso-scale (tens of km), but that natural recovery is only likely to occur on a timescale unacceptable to fishers and resource managers.

The distribution of anionic sites on the surfaces of mitochondrial membranes. Visual probing with polycationic ferritin.

Polycationic ferritin, a multivalent ligand, was used as a visual probe to determine the distribution and density of anionic sites on the surfaces of rat liver mitochondrial membranes. Both the distribution of bound polycationic ferritin and the topography of the outer surface of the inner mitochondrial membrane were studied in depth by utilizing thin sections and critical-point dried, whole mount preparations for transmission electron microscopy and by scanning electron microscopy. Based on its relative affinity for polycationic ferritin, the surface of the inner membrane contains discrete regions of high density and low density anionic sites. Whereas the surface of the cristal membrane contains a low density of anionic sites, the surface of the inner boundary membrane contains patches of high density anionic sites. The high density anionic sites on the inner boundary membrane were found to persist as stable patches and did not dissociate or randomize freely when the membrane was converted osmotically to a spherical configuration. The observations suggest that the inner mitochondrial membrane is composed of two major regions of anionic macromolecular distinction. It is well-known that an intermembrane space exists between the two membranes of the intact mitochondrion; however, a number of contact sites occur between the two membranes. We determined that the outer membrane, partially disrupted by treatment with digitonin, remains attached to the inner membrane at these contact sites as inverted vesicles. Such attached vesicles show that the inner surface of the outer membrane contains anionic sites, but of decreased density, surrounding the contact sites. Thus, the intermembrane space in the intact mitochondrion may be maintained by electronegative surfaces of the two mitochondrial membranes. The distribution of anionic sites on the outer surface of the outer membrane is random. The nature and function of fixed anionic surface charges and membrane contact sites are discussed with regard to recent reports relating to calcium transport, protein assembly into mitochondrial membranes, and membrane fluidity.

Osmotic adaptation by gram-negative bacteria: possible role for periplasmic oligosaccharides.

The cyclic (1----2)-beta-D-glucans produced by species of Agrobacterium and Rhizobium resemble the membrane-derived oligosaccharides of Escherichia coli in their periplasmic localization, intermediate size, and (1----2)-beta-D-glucan backbones. The regulation of the biosynthesis of cyclic (1----2)-beta-D-glucan by Agrobacterium tumefaciens is now shown to parallel the osmotic regulation of membrane-derived oligosaccharide biosynthesis in Escherichia coli. This result suggests a general role for periplasmic oligosaccharides in the osmotic adaptation of Gram-negative bacteria as ecologically diverse as enteric and soil bacteria.

The AsTex: clinimetric properties of a new tool for evaluating hand sensation following stroke.

OBJECTIVES: To investigate the clinimetric properties and clinical utility of the AsTex((R)), a new clinical tool for evaluation of hand sensation following stroke. DESIGN: The AsTex((R)) was administered on two occasions separated by a week to appraise test-retest reliability, and by three assessors on single occasion to establish inter-rater reliability. Pilot normative values were collected in an age-stratified sample. Clinical utility was evaluated based on ease of administration, ceiling and floor effects, and responsiveness to sensory recovery. PARTICIPANTS: Test-retest (n = 31) and inter-rater (n = 31) reliability and normative values (n = 95) for the AsTex((R)) were established in neurologically normal participants aged 18-85 years. Test-retest reliability was investigated in 22 individuals a mean of 46 months (range 12-125) post stroke and clinical utility was evaluated in an additional 24 subacute stroke participants a mean of 29.4 days (range 12-41) post stroke. MAIN MEASURE: The AsTex((R)). RESULTS: The AsTex((R)) demonstrated excellent test-retest (intraclass correlation coefficient (ICC) = 0.98, 95% confidence interval (95% CI) = 0.97-0.99) and inter-rater reliability (ICC = 0.81, 95% CI = 0.73-0.87) in neurologically normal participants. Test-retest reliability of the AsTex((R)) in individuals following stroke was excellent (ICC = 0.86, 95% CI = 0.68-0.94). The AsTex((R)) was simple to administer, demonstrated small standard error of measurement (0.14 mm), minimal floor and ceiling effects (12.5% and 8.3%) and excellent responsiveness (standardized response mean = 0.57) in subacute stroke participants. CONCLUSION: The AsTex((R)) is a reliable, clinically useful and responsive tool for evaluating hand sensation following stroke.

Testing for nested oscillation.

Nested oscillation occurs when the amplitude of a faster rhythm is coupled to the phase of a slower rhythm. It has been proposed to underlie the discrete nature of perception and the capacity of working memory and is a phenomenon observable in human brain imaging data. This paper compares three published methods for detecting nested oscillation and a fourth method proposed in this paper. These are: (i) the modulation index, (ii) the phase-locking value (PLV), (iii) the envelope-to-signal correlation (ESC) and (iv) a general linear model (GLM) measure derived from ESC. We applied the methods to electrocorticographic (ECoG) data recorded during a working-memory task and to data from a simulated hippocampal interneuron network. Further simulations were then made to address the dependence of each measure on signal to noise level, coupling phase, epoch length, sample rate, signal nonstationarity, and multi-phasic coupling. Our overall conclusion is that the GLM measure is the best all-round approach for detecting nested oscillation.

Two-dimensional movement control using electrocorticographic signals in humans.

We show here that a brain-computer interface (BCI) using electrocorticographic activity (ECoG) and imagined or overt motor tasks enables humans to control a computer cursor in two dimensions. Over a brief training period of 12-36 min, each of five human subjects acquired substantial control of particular ECoG features recorded from several locations over the same hemisphere, and achieved average success rates of 53-73% in a two-dimensional four-target center-out task in which chance accuracy was 25%. Our results support the expectation that ECoG-based BCIs can combine high performance with technical and clinical practicality, and also indicate promising directions for further research.

Decoding two-dimensional movement trajectories using electrocorticographic signals in humans.

Signals from the brain could provide a non-muscular communication and control system, a brain-computer interface (BCI), for people who are severely paralyzed. A common BCI research strategy begins by decoding kinematic parameters from brain signals recorded during actual arm movement. It has been assumed that these parameters can be derived accurately only from signals recorded by intracortical microelectrodes, but the long-term stability of such electrodes is uncertain. The present study disproves this widespread assumption by showing in humans that kinematic parameters can also be decoded from signals recorded by subdural electrodes on the cortical surface (ECoG) with an accuracy comparable to that achieved in monkey studies using intracortical microelectrodes. A new ECoG feature labeled the local motor potential (LMP) provided the most information about movement. Furthermore, features displayed cosine tuning that has previously been described only for signals recorded within the brain. These results suggest that ECoG could be a more stable and less invasive alternative to intracortical electrodes for BCI systems, and could also prove useful in studies of motor function.

EphA3 as a target for antibody immunotherapy in acute lymphoblastic leukemia.

The human EphA3 gene was discovered in a pre-B acute lymphoblastic leukemia (pre-B-ALL) using the EphA3-specific monoclonal antibody (mAb), IIIA4, which binds and activates both human and mouse EphA3. We use two models of human pre-B-ALL to examine EphA3 function, demonstrating effects on pre-B-cell receptor signaling. In therapeutic targeting studies, we demonstrated antitumor effects of the IIIA4 mAb in EphA3-expressing leukemic xenografts and no antitumor effect in the xenografts with no EphA3 expression providing evidence that EphA3 is a functional therapeutic target in pre-B-ALL. Here we show that the therapeutic effect of the anti-EphA3 antibody was greatly enhanced by adding an α-particle-emitting 213Bismuth payload.

Cyclic glucans produced by Agrobacterium tumefaciens are substituted with sn-1-phosphoglycerol residues.

In a previous study (Miller, K.J., Kennedy, E.P. and Reinhold, V.N. (1986) Science 231, 48-51) it was reported that the biosynthesis of periplasmic cyclic beta-1,2-glucans by Agrobacterium tumefaciens is strictly osmoregulated in a pattern closely similar to that found for the membrane-derived oligosaccharides of Escherichia coli (Kennedy, E.P. (1982) Proc. Natl. Acad. Sci. USA 79, 1092-1095). In addition to the well-characterized neutral cyclic glucan, the periplasmic glucans were found to contain an anionic component not previously reported. Biosynthesis of the anionic component is osmotically regulated in a manner indistinguishable from that of the neutral cyclic beta-1,2-glucan. We now find that the anionic component consists of cyclic beta-1,2-glucans substituted with one or more sn-1-phosphoglycerol residues. The presence of sn-1-phosphoglycerol residues represents an additional, striking similarity to the membrane-derived oligosaccharides of E. coli.

Cyclic [beta]-1,6 -1,3 Glucans Are Synthesized by Bradyrhizobium japonicum Bacteroids within Soybean (Glycine max) Root Nodules.

We have previously reported that free-living cultures of Bradyrhizobium species produce novel oligosaccharides that are cyclic, contain between 10 and 13 glucose residues, and are linked by [beta]-1,6 and [beta]-1,3 glycosidic bonds (K.J. Miller, R.S. Gore, R. Johnson, A.J. Benesi, V.N. Reinhold [1990] J Bacteriol 172: 136-142). In the present study, we show that these glucans are also synthesized by bacteroids of Bradyrhizobium japonicum USDA 110 within Glycine max root nodules.

Cyclic [beta]-1,6-1,3-Glucans of Bradyrhizobium japonicum USDA 110 Elicit Isoflavonoid Production in the Soybean (Glycine max) Host.

High levels of cyclic [beta]-1,6-1,3-glucans (e.g. 0.1 mg mg-1 of total protein) are synthesized by free-living cells as well as by bacteroids of Bradyrhizobium japonicum USDA 110 (K.J. Miller, R.S. Gore, R. Johnson, A.J. Benesi, V.N. Reinhold [1990] J Bacteriol 172: 136-142; R.S. Gore and K.J. Miller [1993] Plant Physiol 102: 191-194). These molecules share structural features with glucan fragments isolated from the mycelial cell wall of the soybean (Glycine max) pathogen Phytophthora megasperma. These latter glucans have been shown to be potent elicitors (at nanogram levels) of the phytoalexin glyceollin in G. max. Using the well-characterized soybean cotyledon bioassay, we now show that the cyclic [beta]-1,6-1,3-glucans of B. japonicum USDA 110 are also biologically active elicitors of glyceollin production (but at microgram levels). We further show that both classes of [beta]-glucans elicit the production of the isoflavone daidzein within soybean cotyledon wound droplets.