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1.  Directional hearing by linear summation of binaural inputs at the medial superior olive 
Neuron  2013;78(5):936-948.
SUMMARY
Neurons in the medial superior olive (MSO) enable sound localization by their remarkable sensitivity to submillisecond interaural time differences (ITDs). Each MSO neuron has its own “best ITD” to which it responds optimally. A difference in physical path length of the excitatory inputs from both ears cannot fully account for the ITD tuning of MSO neurons. As a result, it is still debated how these inputs interact and whether the segregation of inputs to opposite dendrites, well-timed synaptic inhibition, or asymmetries in synaptic potentials or cellular morphology further optimize coincidence detection or ITD tuning. Using in vivo whole-cell and juxtacellular recordings, we show here that ITD tuning of MSO neurons is determined by the timing of their excitatory inputs. The inputs from both ears sum linearly, whereas spike probability depends nonlinearly on the size of synaptic inputs. This simple coincidence detection scheme thus makes accurate sound localization possible.
doi:10.1016/j.neuron.2013.04.028
PMCID: PMC3741096  PMID: 23764292
2.  Otoacoustic Estimates of Cochlear Tuning: Testing Predictions in Macaque 
AIP conference proceedings  2011;1403:286-292.
Otoacoustic estimates of cochlear frequency selectivity suggest substantially sharper tuning in humans. However, the logic and methodology underlying these estimates remain untested by direct measurements in primates. We report measurements of frequency tuning in macaque monkeys, Old-World primates phylogenetically closer to humans than the small laboratory animals often taken as models of human hearing (e.g., cats, guinea pigs, and chinchillas). We find that measurements of tuning obtained directly from individual nerve fibers and indirectly using otoacoustic emissions both indicate that peripheral frequency selectivity in macaques is significantly sharper than in small laboratory animals, matching that inferred for humans at high frequencies. Our results validate the use of otoacoustic emissions for noninvasive measurement of cochlear tuning and corroborate the finding of sharper tuning in humans.
doi:10.1063/1.3658099
PMCID: PMC3971997  PMID: 24701000
cochlea; frequency tuning; auditory nerve; otoacoustic emissions
3.  Tracking Fungal Community Responses to Maize Plants by DNA- and RNA-Based Pyrosequencing 
PLoS ONE  2013;8(7):e69973.
We assessed soil fungal diversity and community structure at two sampling times (t1 = 47 days and t2 = 104 days of plant age) in pots associated with four maize cultivars, including two genetically modified (GM) cultivars by high-throughput pyrosequencing of the 18S rRNA gene using DNA and RNA templates. We detected no significant differences in soil fungal diversity and community structure associated with different plant cultivars. However, DNA-based analyses yielded lower fungal OTU richness as compared to RNA-based analyses. Clear differences in fungal community structure were also observed in relation to sampling time and the nucleic acid pool targeted (DNA versus RNA). The most abundant soil fungi, as recovered by DNA-based methods, did not necessary represent the most “active” fungi (as recovered via RNA). Interestingly, RNA-derived community compositions at t1 were highly similar to DNA-derived communities at t2, based on presence/absence measures of OTUs. We recovered large proportions of fungal sequences belonging to arbuscular mycorrhizal fungi and Basidiomycota, especially at the RNA level, suggesting that these important and potentially beneficial fungi are not affected by the plant cultivars nor by GM traits (Bt toxin production). Our results suggest that even though DNA- and RNA-derived soil fungal communities can be very different at a given time, RNA composition may have a predictive power of fungal community development through time.
doi:10.1371/journal.pone.0069973
PMCID: PMC3715498  PMID: 23875012
4.  The Spatial Buildup of Compression and Suppression in the Mammalian Cochlea 
We recorded responses of the gerbil basilar membrane (BM) to wideband tone complexes. The intensity of one component was varied and the effects on the amplitude and phase of the others were assessed. This suppression paradigm enabled us to vary probe frequency and suppressor frequency independently, allowing the use of simple scaling arguments to analyze the spatial buildup of the nonlinear interaction between traveling waves. Most suppressors had the same effects on probe amplitude and phase as did wideband intensity increments. The main exception were suppressors above the characteristic frequency (CF) of the recording location, for which the frequency range of most affected probes was not constant, but shifted upward with suppressor frequency. BM displacement reliably predicted the effectiveness of low-side suppressors, but not high-side suppressors. We found “anti-suppression” of probes well below CF, i.e., suppressor-induced enhancement of probe response amplitude. Large (>1 cycle) phase effects occurred for above-CF probes. Phase shifts varied nonmonotonically, but systematically, with suppressor level, probe frequency, and suppressor frequency, reconciling apparent discrepancies in the literature. The analysis of spatial buildup revealed an accumulation of local effects on the propagation of the traveling wave, with larger BM displacement reducing the local forward gain. The propagation speed of the wave was also affected. With larger BM displacement, the basal portion of the wave slowed down, while the apical part sped up. This framework of spatial buildup of local effects unifies the widely different effects of overall intensity, low-side suppressors, and high-side suppressors on BM responses.
doi:10.1007/s10162-013-0393-0
PMCID: PMC3705085  PMID: 23690278
cochlear mechanics; laser interferometry; dynamic range compression; two-tone suppression; basilar membrane; traveling waves
5.  Testing Potential Effects of Maize Expressing the Bacillus thuringiensis Cry1Ab Endotoxin (Bt Maize) on Mycorrhizal Fungal Communities via DNA- and RNA-Based Pyrosequencing and Molecular Fingerprinting 
Applied and Environmental Microbiology  2012;78(20):7384-7392.
The cultivation of genetically modified (GM) crops has increased significantly over the last decades. However, concerns have been raised that some GM traits may negatively affect beneficial soil biota, such as arbuscular mycorrhizal fungi (AMF), potentially leading to alterations in soil functioning. Here, we test two maize varieties expressing the Bacillus thuringiensis Cry1Ab endotoxin (Bt maize) for their effects on soil AM fungal communities. We target both fungal DNA and RNA, which is new for AM fungi, and we use two strategies as an inclusive and robust way of detecting community differences: (i) 454 pyrosequencing using general fungal rRNA gene-directed primers and (ii) terminal restriction fragment length polymorphism (T-RFLP) profiling using AM fungus-specific markers. Potential GM-induced effects were compared to the normal natural variation of AM fungal communities across 15 different agricultural fields. AM fungi were found to be abundant in the experiment, accounting for 8% and 21% of total recovered DNA- and RNA-derived fungal sequences, respectively, after 104 days of plant growth. RNA- and DNA-based sequence analyses yielded most of the same AM fungal lineages. Our research yielded three major conclusions. First, no consistent differences were detected between AM fungal communities associated with GM plants and non-GM plants. Second, temporal variation in AMF community composition (between two measured time points) was bigger than GM trait-induced variation. Third, natural variation of AMF communities across 15 agricultural fields in The Netherlands, as well as within-field temporal variation, was much higher than GM-induced variation. In conclusion, we found no indication that Bt maize cultivation poses a risk for AMF.
doi:10.1128/AEM.01372-12
PMCID: PMC3457118  PMID: 22885748
6.  Basilar Membrane Responses to Tones and Tone Complexes: Nonlinear Effects of Stimulus Intensity 
The mammalian inner ear combines spectral analysis of sound with multiband dynamic compression. Cochlear mechanics has mainly been studied using single-tone and tone-pair stimulation. Most natural sounds, however, have wideband spectra. Because the cochlea is strongly nonlinear, wideband responses cannot be predicted by simply adding single-tone responses. We measured responses of the gerbil basilar membrane to single-tone and wideband stimuli and compared them, while focusing on nonlinear aspects of the response. In agreement with previous work, we found that frequency selectivity and its dependence on stimulus intensity were very similar between single-tone and wideband responses. The main difference was a constant shift in effective sound intensity, which was well predicted by a simple gain control scheme. We found expansive nonlinearities in low-frequency responses, which, with increasing frequency, gradually turned into the more familiar compressive nonlinearities. The overall power of distortion products was at least 13 dB below the overall power of the linear response, but in a limited band above the characteristic frequency, the power of distortion products often exceeded the linear response. Our results explain the partial success of a “quasilinear” description of wideband basilar membrane responses, but also indicate its limitations.
doi:10.1007/s10162-012-0345-0
PMCID: PMC3505585  PMID: 22935903
cochlear mechanics; laser interferometry; quasilinear filtering; automatic gain control
7.  Growth Response of Drought-Stressed Pinus sylvestris Seedlings to Single- and Multi-Species Inoculation with Ectomycorrhizal Fungi 
PLoS ONE  2012;7(4):e35275.
Many trees species form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve nutrient and water acquisition of their host. Until now it is unclear whether the species richness of ECM fungi is beneficial for tree seedling performance, be it during moist conditions or drought. We performed a pot experiment using Pinus sylvestris seedlings inoculated with four selected ECM fungi (Cenococcum geophilum, Paxillus involutus, Rhizopogon roseolus and Suillus granulatus) to investigate (i) whether these four ECM fungi, in monoculture or in species mixtures, affect growth of P. sylvestris seedlings, and (ii) whether this effect can be attributed to species number per se or to species identity. Two different watering regimes (moist vs. dry) were applied to examine the context-dependency of the results. Additionally, we assessed the activity of eight extracellular enzymes in the root tips. Shoot growth was enhanced in the presence of S. granulatus, but not by any other ECM fungal species. The positive effect of S. granulatus on shoot growth was more pronounced under moist (threefold increase) than under dry conditions (twofold increase), indicating that the investigated ECM fungi did not provide additional support during drought stress. The activity of secreted extracellular enzymes was higher in S. granulatus than in any other species. In conclusion, our findings suggest that ECM fungal species composition may affect seedling performance in terms of aboveground biomass.
doi:10.1371/journal.pone.0035275
PMCID: PMC3320646  PMID: 22496914
8.  Can Arbuscular Mycorrhizal Fungi Reduce the Growth of Agricultural Weeds? 
PLoS ONE  2011;6(12):e27825.
Background
Arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects on plants. However, there is increasing evidence that some ruderal plants, including several agricultural weeds, respond negatively to AMF colonization. Here, we investigated the effect of AMF on the growth of individual weed species and on weed-crop interactions.
Methodology/Principal Findings
First, under controlled glasshouse conditions, we screened growth responses of nine weed species and three crops to a widespread AMF, Glomus intraradices. None of the weeds screened showed a significant positive mycorrhizal growth response and four weed species were significantly reduced by the AMF (growth responses between −22 and −35%). In a subsequent experiment, we selected three of the negatively responding weed species – Echinochloa crus-galli, Setaria viridis and Solanum nigrum – and analyzed their responses to a combination of three AMF (Glomus intraradices, Glomus mosseae and Glomus claroideum). Finally, we tested whether the presence of a crop (maize) enhanced the suppressive effect of AMF on weeds. We found that the growth of the three selected weed species was also reduced by a combination of AMF and that the presence of maize amplified the negative effect of AMF on the growth of E. crus-galli.
Conclusions/Significance
Our results show that AMF can negatively influence the growth of some weed species indicating that AMF have the potential to act as determinants of weed community structure. Furthermore, mycorrhizal weed growth reductions can be amplified in the presence of a crop. Previous studies have shown that AMF provide a number of beneficial ecosystem services. Taken together with our current results, the maintenance and promotion of AMF activity may thereby contribute to sustainable management of agroecosystems. However, in order to further the practical and ecological relevance of our findings, additional experiments should be performed under field conditions.
doi:10.1371/journal.pone.0027825
PMCID: PMC3229497  PMID: 22164216
9.  Responses of Auditory Nerve and Anteroventral Cochlear Nucleus Fibers to Broadband and Narrowband Noise: Implications for the Sensitivity to Interaural Delays 
The quality of temporal coding of sound waveforms in the monaural afferents that converge on binaural neurons in the brainstem limits the sensitivity to temporal differences at the two ears. The anteroventral cochlear nucleus (AVCN) houses the cells that project to the binaural nuclei, which are known to have enhanced temporal coding of low-frequency sounds relative to auditory nerve (AN) fibers. We applied a coincidence analysis within the framework of detection theory to investigate the extent to which AVCN processing affects interaural time delay (ITD) sensitivity. Using monaural spike trains to a 1-s broadband or narrowband noise token, we emulated the binaural task of ITD discrimination and calculated just noticeable differences (jnds). The ITD jnds derived from AVCN neurons were lower than those derived from AN fibers, showing that the enhanced temporal coding in the AVCN improves binaural sensitivity to ITDs. AVCN processing also increased the dynamic range of ITD sensitivity and changed the shape of the frequency dependence of ITD sensitivity. Bandwidth dependence of ITD jnds from AN as well as AVCN fibers agreed with psychophysical data. These findings demonstrate that monaural preprocessing in the AVCN improves the temporal code in a way that is beneficial for binaural processing and may be crucial in achieving the exquisite sensitivity to ITDs observed in binaural pathways.
doi:10.1007/s10162-011-0268-1
PMCID: PMC3123442  PMID: 21567250
coincidence detection; interaural time difference; discrimination; binaural; sound localization
10.  Responses of Auditory Nerve and Anteroventral Cochlear Nucleus Fibers to Broadband and Narrowband Noise: Implications for the Sensitivity to Interaural Delays 
The quality of temporal coding of sound waveforms in the monaural afferents that converge on binaural neurons in the brainstem limits the sensitivity to temporal differences at the two ears. The anteroventral cochlear nucleus (AVCN) houses the cells that project to the binaural nuclei, which are known to have enhanced temporal coding of low-frequency sounds relative to auditory nerve (AN) fibers. We applied a coincidence analysis within the framework of detection theory to investigate the extent to which AVCN processing affects interaural time delay (ITD) sensitivity. Using monaural spike trains to a 1-s broadband or narrowband noise token, we emulated the binaural task of ITD discrimination and calculated just noticeable differences (jnds). The ITD jnds derived from AVCN neurons were lower than those derived from AN fibers, showing that the enhanced temporal coding in the AVCN improves binaural sensitivity to ITDs. AVCN processing also increased the dynamic range of ITD sensitivity and changed the shape of the frequency dependence of ITD sensitivity. Bandwidth dependence of ITD jnds from AN as well as AVCN fibers agreed with psychophysical data. These findings demonstrate that monaural preprocessing in the AVCN improves the temporal code in a way that is beneficial for binaural processing and may be crucial in achieving the exquisite sensitivity to ITDs observed in binaural pathways.
doi:10.1007/s10162-011-0268-1
PMCID: PMC3123442  PMID: 21567250
coincidence detection; interaural time difference; discrimination; binaural; sound localization
11.  Response Characteristics in the Apex of the Gerbil Cochlea Studied Through Auditory Nerve Recordings 
In this study, we analyze the processing of low-frequency sounds in the cochlear apex through responses of auditory nerve fibers (ANFs) that innervate the apex. Single tones and irregularly spaced tone complexes were used to evoke ANF responses in Mongolian gerbil. The spike arrival times were analyzed in terms of phase locking, peripheral frequency selectivity, group delays, and the nonlinear effects of sound pressure level (SPL). Phase locking to single tones was similar to that in cat. Vector strength was maximal for stimulus frequencies around 500 Hz, decreased above 1 kHz, and became insignificant above 4 to 5 kHz. We used the responses to tone complexes to determine amplitude and phase curves of ANFs having a characteristic frequency (CF) below 5 kHz. With increasing CF, amplitude curves gradually changed from broadly tuned and asymmetric with a steep low-frequency flank to more sharply tuned and asymmetric with a steep high-frequency flank. Over the same CF range, phase curves gradually changed from a concave-upward shape to a concave-downward shape. Phase curves consisted of two or three approximately straight segments. Group delay was analyzed separately for these segments. Generally, the largest group delay was observed near CF. With increasing SPL, most amplitude curves broadened, sometimes accompanied by a downward shift of best frequency, and group delay changed along the entire range of stimulus frequencies. We observed considerable across-ANF variation in the effects of SPL on both amplitude and phase. Overall, our data suggest that mechanical responses in the apex of the cochlea are considerably nonlinear and that these nonlinearities are of a different character than those known from the base of the cochlea.
doi:10.1007/s10162-010-0255-y
PMCID: PMC3085685  PMID: 21213012
cochlear mechanics; cochlear apex; phase locking; Meriones unguiculatus
12.  Response Characteristics in the Apex of the Gerbil Cochlea Studied Through Auditory Nerve Recordings 
In this study, we analyze the processing of low-frequency sounds in the cochlear apex through responses of auditory nerve fibers (ANFs) that innervate the apex. Single tones and irregularly spaced tone complexes were used to evoke ANF responses in Mongolian gerbil. The spike arrival times were analyzed in terms of phase locking, peripheral frequency selectivity, group delays, and the nonlinear effects of sound pressure level (SPL). Phase locking to single tones was similar to that in cat. Vector strength was maximal for stimulus frequencies around 500 Hz, decreased above 1 kHz, and became insignificant above 4 to 5 kHz. We used the responses to tone complexes to determine amplitude and phase curves of ANFs having a characteristic frequency (CF) below 5 kHz. With increasing CF, amplitude curves gradually changed from broadly tuned and asymmetric with a steep low-frequency flank to more sharply tuned and asymmetric with a steep high-frequency flank. Over the same CF range, phase curves gradually changed from a concave-upward shape to a concave-downward shape. Phase curves consisted of two or three approximately straight segments. Group delay was analyzed separately for these segments. Generally, the largest group delay was observed near CF. With increasing SPL, most amplitude curves broadened, sometimes accompanied by a downward shift of best frequency, and group delay changed along the entire range of stimulus frequencies. We observed considerable across-ANF variation in the effects of SPL on both amplitude and phase. Overall, our data suggest that mechanical responses in the apex of the cochlea are considerably nonlinear and that these nonlinearities are of a different character than those known from the base of the cochlea.
doi:10.1007/s10162-010-0255-y
PMCID: PMC3085685  PMID: 21213012
cochlear mechanics; cochlear apex; phase locking; Meriones unguiculatus
13.  Distortion Product Otoacoustic Emissions Evoked by Tone Complexes 
Distortion product otoacoustic emissions (DPOAEs) are traditionally evoked by two-tone stimuli. In this study, emission data from Mongolian gerbils are reported that were obtained with stimuli consisting of six to 10 tones. The stimuli were constructed by replacing one of the tones of a tone pair by a narrowband multitone complex. This produced rich spectra of the ear canal sound pressure in which many of the third-order DPOAEs originated from the interaction of triplets of stimulus components. A careful choice of the stimulus frequencies ensured that none of these DPOAE components coincided. Three groups of DPOAEs are reported, two of which are closely related to DPOAEs evoked by tone pairs. The third group has no two-tone equivalent and only arises when using a multitone stimulus. We analyzed the relation between multitone-evoked DPOAEs and DPOAEs evoked by tone pairs, and explored the new degrees of freedom offered by the multitone paradigm.
doi:10.1007/s10162-010-0233-4
PMCID: PMC3015028  PMID: 20838846
DPOAEs; otoacoustic; gerbil; Meriones unguiculatus; tone complex; zwuis
14.  Distortion Product Otoacoustic Emissions Evoked by Tone Complexes 
Distortion product otoacoustic emissions (DPOAEs) are traditionally evoked by two-tone stimuli. In this study, emission data from Mongolian gerbils are reported that were obtained with stimuli consisting of six to 10 tones. The stimuli were constructed by replacing one of the tones of a tone pair by a narrowband multitone complex. This produced rich spectra of the ear canal sound pressure in which many of the third-order DPOAEs originated from the interaction of triplets of stimulus components. A careful choice of the stimulus frequencies ensured that none of these DPOAE components coincided. Three groups of DPOAEs are reported, two of which are closely related to DPOAEs evoked by tone pairs. The third group has no two-tone equivalent and only arises when using a multitone stimulus. We analyzed the relation between multitone-evoked DPOAEs and DPOAEs evoked by tone pairs, and explored the new degrees of freedom offered by the multitone paradigm.
doi:10.1007/s10162-010-0233-4
PMCID: PMC3015028  PMID: 20838846
DPOAEs; otoacoustic; gerbil; Meriones unguiculatus; tone complex; zwuis
15.  Interaural Correlation Fails to Account for Detection in a Classic Binaural Task: Dynamic ITDs Dominate N0Sπ Detection 
Binaural signal detection in an NoSπ task relies on interaural disparities introduced by adding an antiphasic signal to diotic noise. What metric of interaural disparity best predicts performance? Some models use interaural correlation; others differentiate between dynamic interaural time differences (ITDs) and interaural level differences (ILDs) of the effective stimulus. To examine the relative contributions of ITDs and ILDs in binaural detection, we developed a novel signal processing technique that selectively degrades different aspects (potential cues) of binaural stimuli (e.g., only ITDs are scrambled). Degrading a particular cue will affect performance only if that cue is relevant to the binaural processing underlying detection. This selective scrambling technique was applied to the stimuli of a classic N0Sπ task in which the listener had to detect an antiphasic 500-Hz signal in the presence of a diotic wideband noise masker. Data obtained from five listeners showed that (1) selective scrambling of ILDs had little effect on binaural detection, (2) selective scrambling of ITDs significantly degraded detection, and (3) combined scrambling of ILDs and ITDs had the same effect as exclusive scrambling of ITDs. Regarding the question which stimulus properties determine detection, we conclude that for this binaural task (1) dynamic ITDs dominate detection performance, (2) ILDs are largely irrelevant, and (3) interaural correlation of the stimulus is a poor predictor of detection. Two simple stimulus-based models that each reproduce all binaural aspects of the data quite well are described: (1) a single-parameter detection model using ITD variance as detection criterion and (2) a compressive transformation followed by a crosscorrelation analysis. The success of both of these contrasting models shows that our data alone cannot reveal the mechanisms underlying the dominance of ITD cues. The physiological implications of our findings are discussed.
doi:10.1007/s10162-009-0185-8
PMCID: PMC2820206  PMID: 19760461
binaural detection; masking; ITD; ILD; MLD; binaural modulation
16.  Interaural Correlation Fails to Account for Detection in a Classic Binaural Task: Dynamic ITDs Dominate N0Sπ Detection 
Binaural signal detection in an NoSπ task relies on interaural disparities introduced by adding an antiphasic signal to diotic noise. What metric of interaural disparity best predicts performance? Some models use interaural correlation; others differentiate between dynamic interaural time differences (ITDs) and interaural level differences (ILDs) of the effective stimulus. To examine the relative contributions of ITDs and ILDs in binaural detection, we developed a novel signal processing technique that selectively degrades different aspects (potential cues) of binaural stimuli (e.g., only ITDs are scrambled). Degrading a particular cue will affect performance only if that cue is relevant to the binaural processing underlying detection. This selective scrambling technique was applied to the stimuli of a classic N0Sπ task in which the listener had to detect an antiphasic 500-Hz signal in the presence of a diotic wideband noise masker. Data obtained from five listeners showed that (1) selective scrambling of ILDs had little effect on binaural detection, (2) selective scrambling of ITDs significantly degraded detection, and (3) combined scrambling of ILDs and ITDs had the same effect as exclusive scrambling of ITDs. Regarding the question which stimulus properties determine detection, we conclude that for this binaural task (1) dynamic ITDs dominate detection performance, (2) ILDs are largely irrelevant, and (3) interaural correlation of the stimulus is a poor predictor of detection. Two simple stimulus-based models that each reproduce all binaural aspects of the data quite well are described: (1) a single-parameter detection model using ITD variance as detection criterion and (2) a compressive transformation followed by a crosscorrelation analysis. The success of both of these contrasting models shows that our data alone cannot reveal the mechanisms underlying the dominance of ITD cues. The physiological implications of our findings are discussed.
doi:10.1007/s10162-009-0185-8
PMCID: PMC2820206  PMID: 19760461
binaural detection; masking; ITD; ILD; MLD; binaural modulation
17.  Nonlegumes, Legumes, and Root Nodules Harbor Different Arbuscular Mycorrhizal Fungal Communities 
Applied and Environmental Microbiology  2004;70(10):6240-6246.
Legumes are an important plant functional group since they can form a tripartite symbiosis with nitrogen-fixing Rhizobium bacteria and phosphorus-acquiring arbuscular mycorrhizal fungi (AMF). However, not much is known about AMF community composition in legumes and their root nodules. In this study, we analyzed the AMF community composition in the roots of three nonlegumes and in the roots and root nodules of three legumes growing in a natural dune grassland. We amplified a portion of the small-subunit ribosomal DNA and analyzed it by using restriction fragment length polymorphism and direct sequencing. We found differences in AMF communities between legumes and nonlegumes and between legume roots and root nodules. Different plant species also contained different AMF communities, with different AMF diversity. One AMF sequence type was much more abundant in legumes than in nonlegumes (39 and 13%, respectively). Root nodules contained characteristic AMF communities that were different from those in legume roots, even though the communities were similar in nodules from different legume species. One AMF sequence type was found almost exclusively in root nodules. Legumes and root nodules have relatively high nitrogen concentrations and high phosphorus demands. Accordingly, the presence of legume- and nodule-related AMF can be explained by the specific nutritional requirements of legumes or by host-specific interactions among legumes, root nodules, and AMF. In summary, we found that AMF communities vary between plant functional groups (legumes and nonlegumes), between plant species, and between parts of a root system (roots and root nodules).
doi:10.1128/AEM.70.10.6240-6246.2004
PMCID: PMC522056  PMID: 15466571

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