Muscimol and some aza analogues: molecular orbital calculations relating to their potency as GABA mimetics

Ab initio molecular orbital calculations have been carried out on muscimol (1) and on two aza analogues, 5-aminomethylpyrazol-3-one (2) and 5-aminomethyl-1,2,4-triazol-3-one (3). Fully ionized species were studied in each case including the tautomeric forms of (2) and (3). The calculations reveal that the more stable tautomeric forms of (2) and (3) resemble muscimol in having a low energy barrier to rotation of the aminomethyl group (2–4 kcal mol^?1) but differ substantially from muscimol in the electronic character of the heterocyclic ring. The change in π-electron distribution in the more stable tautomers of (2) and (3) compared with muscimol is summarized by the dipole moment decrease (1) 7·75 au, (2) 6·62 au, (3) 5·81 au. In addition, the frontier molecular orbitals show analogous differences. On the other hand, the less stable tautomers of (2) and (3) are similar to muscimol in π-electron distribution and frontier orbitals, but have a high energy barrier to rotation of the aminomethyl group (11–14 kcal mol^?1). The calculated properties of the molecules are related to the ability of the three compounds to displace [³H]-GABA from the postsynaptic receptors of human cerebellum and it is suggested that the dominant influence on biochemical activity is the π-electron distribution in the heterocyclic ring.     

Ortho-metalation, rotational isomerization, and hydride-hydride coupling at rhenium (V) polyhydride complexes stabilized by aromatic amine ligands

An ortho-metalated rhenium (V) polyhydride complex has been prepared through the reaction of ReH₇(PPh₃)₂ with 2-phenylpyridine. Additionally, a small series of neutral rhenium (V) pentahydride complexes, each of which is stabilized by an aromatic amine ligand, has been prepared. E and Z rotational isomers of the ReH₅(PPh₃)₂(aromatic amine) complexes have been observed at low temperatures by NMR spectroscopy. The E and Z rotational isomers arise from a combination of the lack of a mirror plane symmetry element orthogonal to the aromatic ring in the aromatic amine ligands and the restricted rotation about the Re-N bond in such complexes. Restricted rotation about the Re-N bond in the related complex, ReH₅(PPh₃)₂(Py) has previously been observed by Crabtree et al. The restricted rotation about the Re-N bond seems to result from π-donation of the lone electron pair on the rhenium (V) center to the π∗ system of the aromatic amine ligands. Different populations of the E and Z rotational isomers arise from interactions of substituents on the aromatic ring with the other ligands bound to rhenium. The values of ΔG^‡ for the restricted rotation about the Re-N bonds, for the complexes containing 4-phenylpyrimidine, 2-aminopyrimidine, or 2-aminopyridine, range from 9.9 to 11.3 kcal/mole. One of the new compounds reported herein, ReH₅(PPh₃)₂[1-(2-NH₂Pyr)] is the first rhenium (V) polyhydride complex to display hydride-hydride coupling in its ¹H NMR spectrum.     

Changes in the Heterodera glycines Female Index as Affected by Ten-year Cropping Sequences

The objective of this experiment was to measure the change in female index (FI) of Heterodera glycines from bioassays on Bedford, Peking, PI 89772, and PI 90763 soybean (Glycine max) for 12 cropping sequence treatments over a 10-year period. Cropping sequences included continuous plantings of Forrest, Peking, and D72-8927 soybean (all resistant to race 3); Bedford, Nathan, and D75-10710 soybean (all resistant to races 3 and 14); a Bedford-corn (Zea mays) rotation; a rotation of Bedford, Essex (susceptible), and Forrest; and a 70:30 blend of Bedford and Forrest. The FI from bioassays with PI 89772 and PI 90763 decreased over time from 24.3 to 1.6 with treatments involving continuous Bedford, Nathan, and D75-10710 and the Bedford-corn rotation. The FI increased in bioassays using Bedford with treatments involving Bedford, Nathan, D75-10710, the Bedford-Forrest blend, and the two rotations. Results of this field experiment confirm greenhouse experiments in which reciprocal changes occur in FI on PI 89772 and PI 90673 compared with FI on Bedford.     

Short-term effects of crop rotation,residue management,and soil water on carbon mineralization in a tropical cropping system

The purpose of this study was to investigate the short-term effects of maize (Zea mays)-fallow rotation, residue management, and soil water on carbon mineralization in a tropical cropping system in Ghana. After 15 months of the trial, maize–legume rotation treatments had significantly (P?C ₀ (μg CO₂–C g^?1) than maize–elephant grass (Pennisetum purpureum) rotations. The C ₀ for maize–grass rotation treatments was significantly related to the biomass input (r?=?0.95; P?=?0.05), but that for the maize–legume rotation was not. The soil carbon mineralization rate constant, k (per day), was also significantly related to the rotation treatments (P?k values for maize–grass and maize–legume rotation treatments were 0.025 and 0.036 day^?1 respectively. The initial carbon mineralization rate, m ₀ (μg CO₂–C g^?1 day ^?1), was significantly (P?θ. The m ₀ ranged from 3.88 to 18.67 and from 2.30 to 15.35 μg CO₂–C g^?1 day^?1 for maize–legume and maize–grass rotation treatments, respectively, when the soil water varied from 28% to 95% field capacity (FC). A simple soil water content (θ)-based factor, f _w, formulated as: \(f_{\text{w}} = \left[ {\frac{{\theta - \theta _{\text{d}} }}{{\theta _{{\text{FC}}} - \theta _{\text{d}} }}} \right]\), where θ _d and θ _FC were the air-dry and field capacity soil water content, respectively, adequately described the variation of the m ₀ with respect to soil water (R ²?=?0.91; RMSE?=?1.6). Such a simple relationship could be useful for SOC modeling under variable soil water conditions.     

3,4-Dihydroisocoumarin derivatives from the marine-derived fungus Paraconiothyrium sporulosum YK-03

Two new 3,4-dihydroisocoumarin derivatives, (3S, 4S)-4,5-dihydroxymellein (1) and R-(−)-mellein-8-O-β-d-glucopyranoside (2), together with six known analogs (3–8) were isolated from the marine-derived fungus Paraconiothyrium sporulosum YK-03. Their structures including absolute configurations were elucidated by extensive spectroscopic methods in combination with computational electronic circular dichroism (ECD) method, optical rotation analysis and monosaccharide composition analysis using HPLC with optical rotation detector. All of them were evaluated for their cytotoxic activities against the human cancer cell lines A549 and MCF-7.     

Torque Transmission Mechanism via DELSEED Loop of F1-ATPase

F₁-ATPase (F₁) is an ATP-driven rotary motor in which the three catalytic β subunits in the stator ring sequentially induce the unidirectional rotation of the rotary γ subunit. Many lines of evidence have revealed open-to-closed conformational transitions in the β subunit that swing the C-terminal domain inward. This conformational transition causes a C-terminal protruding loop with conserved sequence DELSEED to push the γ subunit. Previous work, where all residues of DELSEED were substituted with glycine to disrupt the specific interaction with γ and introduce conformational flexibility, showed that F₁ still rotated, but that the torque was halved, indicating a remarkable impact on torque transmission. In this study, we conducted a stall-and-release experiment on F₁ with a glycine-substituted DELSEED loop to investigate the impact of the glycine substitution on torque transmission upon ATP binding and ATP hydrolysis. The mutant F₁ showed a significantly reduced angle-dependent change in ATP affinity, whereas there was no change in the equilibrium for ATP hydrolysis. These findings indicate that the DELSEED loop is predominantly responsible for torque transmission upon ATP binding but not for that upon ATP hydrolysis.     

Resolution of optical isomers by high-pressure liquid chromatography: The separation of benzo[a]pyrene trans-diol derivatives

The optical isomers of (±)r-7,t-8-dihydroxy-7,8-dihydrobenzo[a]pyrene and its synthetic precursor (±)r-7,t-8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene were resolved as their di-(−)menthoxyacetates using high-pressure liquid chromatography. Saponification of the resolved diesters yielded the corresponding enantiomers. The specific rotation, CD spectra, and ORD curves are reported. The resolution of these optical isomers permits detailed studies on the enzymatic intermediates and the mechanism of benzo[a]pyrene activation to its carcinogenic form. The method is of general usefulness for the resolution of optical isomers.     

Contribution to the knowledge of the Carabus (Archiplectes) satyrus Kurnakov, 1962, species complex in Abkhazia (Coleoptera,Carabidae, Carabini)

This study is based on a comparative analysis of extensive material of Carabus (Archiplectes) satyrus Kurnakov, 1962, its various forms and related taxa recently collected by the authors and some other collectors in Abkhazia. The status or specific affiliations of several subspecies are changed and a subspecies is described. Carabus (Archiplectes) besleticus Kurnakov, 1972, stat. n. is treated as a separate species housing six hitherto established subspecies in addition to the nominal type: Carabus (Archiplectes) besleticus mtsaranus Kurnakov, 1972, Carabus (Archiplectes) besleticus duripshensis Kurnakov, 1972, Carabus (Archiplectes) besleticus napraensis Belousov & Zamotajlov, 1993, Carabus (Archiplectes) besleticus dsychvensis Kurnakov, 1972, Carabus (Archiplectes) besleticus adzinbai Retezár, 2013, and Carabus (Archiplectes) besleticus resheviensis subsp. n. Carabus (Archiplectes) satyrus is treated as monotypical while the specific status of Carabus (Archiplectes) pseudopshuensis Zamotajlov, 1991, earlier proposed by Fominykh and Zamotajlov (2012), is confirmed based on the morphological and morphometric data.     

Effects of Tropical Rotation Crops on Meloidogyne arenaria Population Densities and Vegetable Yields in Microplots

The effects of 12 summer crop rotation treatments on population densities of Meloidogyne arenaria race 1 and on yields of subsequent spring vegetable crops were determined in microplots. The crop sequence was: (i) rotation crops during summer 1991 ; (ii) cover crop of rye (Secale cereale) during winter 1991-92; (iii) squash (Cucurbita pepo) during spring 1992; (iv) rotation crops during summer 1992; (v) rye during winter 1992-93; (vi) eggplant (Solanum melongena) during spring 1993. The 12 rotation treatments were castor (Ricinus communis), cotton (Gossypium hirsutum), velvetbean (Mucuna deeringiana), crotalaria (Crotalaria spectabilis), fallow, hairy indigo (Indigofera hirsuta), American jointvetch (Aeschynomene americana), sorghum-sudangrass (Sorghum bicolor x S. sudanense), soybean (Glycine max), horsebean (Canavalia ensiformis), sesame (Sesamum indicum), and peanut (Arachis hypogaea). Compared to peanut, the first eight rotation treatments resulted in lower (P ≤ 0.05) numbers of M. arenaria juveniles on most sampling dates. Soybean, horsebean, and sesame rotations were less effective in suppressing nematodes. Yield of squash was greater (P ≤ 0.05) following castor, cotton, velvetbean, and crotalaria than following peanut. Compared to the peanut rotation, yield of eggplant was enhanced (P ≤ 0.10) following castor, crotalaria, hairy indigo, American jointvetch, and sorghum-sudangrass. Several of these rotation crops may provide a means for depressing M. arenaria population densities on a short-term basis to enhance yields in a subsequent susceptible vegetable crop.     

Tropical Rotation Crops Influence Nematode Densities and Vegetable Yields

The effects of eight summer rotation crops on nematode densities and yields of subsequent spring vegetable crops were determined in field studies conducted in north Florida from 1991 to 1993. The crop sequence was as follows: (i) rotation crops during summer 1991; (ii) cover crop of rye (Secale cereale) during winter 1991-92; (iii) ''Lemondrop L'' squash (Cucurbita pepo) during spring 1992; (iv) rotation crops during summer 1992; (v) rye during winter 1992-93; (vi) ''Classic'' eggplant (Solanum melongena) during spring 1993. The eight summer crop rotation treatments were as follows: ''Hale'' castor (Ricinus communis), velvetbean (Mucuna deeringiana), sesame (Sesamum indicum), American jointvetch (Aeschynomene americana), weed fallow, ''SX- 17'' sorghum-sudangrass (Sorghum bicolor x S. sudanense), ''Kirby'' soybean (Glycine max), and ''Clemson Spineless'' okra (Hibiscus esculentus) as a control. Rotations with castor, velvetbean, American jointvetch, and sorghum-sudangrass were most effective in maintaining the lowest population densities of Meloidogyne spp. (a mixture of M. incognita race 1 and M. arenaria race 1), but Paratrichodorus minor built up in the sorghum-sudangrass rotation. Yield of squash was lower (P ≤ 0.05) following sorghum-sudangrass than after any of the other treatments except fallow. Yield of eggplant was greater (P ≤ 0.05) following castor, sesame, or American jointvetch than following okra or fallow. Several of the rotation crops evaluated here may be useful for managing nematodes in the field and for improving yields of subsequent vegetable crops.     

Postnatal stability,tissue, and time specific effects of AHRR methylation change in response to maternal smoking in pregnancy

The intrauterine environment has the potential to “program” the developing fetus in a way that can be potentially deleterious to later health. While in utero environmental/stochastic factors are known to influence DNA methylation profile at birth, it has been difficult to assign specific examples of epigenetic variation to specific environmental exposures. Recently, several studies have linked exposure to smoking with DNA methylation change in the aryl hydrocarbon receptor repressor (AHRR) gene in blood. This includes hypomethylation of AHRR in neonatal blood in response to maternal smoking in pregnancy. The role of AHRR as a negative regulator of pathways involved in pleiotropic responses to environmental contaminants raises the possibility that smoking-induced hypomethylation is an adaptive response to an adverse in utero environmental exposure. However, the tissue specificity of the response to maternal smoking, and the stability of the methylation changes early in life remain to be determined. In this study we analyzed AHRR methylation in three cell types—cord blood mononuclear cells (CBMCs), buccal epithelium, and placenta tissue—from newborn twins of mothers who smoked throughout pregnancy and matched controls. Further, we explored the postnatal stability of this change at 18 months. Our results confirm the previous association between maternal smoking and AHRR methylation in neonatal blood. In addition, this study expands the region of AHRR methylation altered in response to maternal smoking during pregnancy and reveals the tissue-specific nature of epigenetic responses to environmental exposures in utero. Further, the evidence for postnatal stability of smoking-induced epigenetic change supports a role for epigenetics as a mediator of long-term effects of specific in utero exposures in humans. Longitudinal analysis of further specific exposures in larger cohorts is required to examine the extent of this phenomenon in humans.     

Biosynthesis of the bisbenzylisoquinoline alkaloid,tetrandrine

The incorporation of (±)-coclaurine, (±)-norcoclaurine, (±)-N-methylcoclaurine and didehydro-N-methyleoclaurinium iodide into tetrandrine in Cocculus laurifolius has been studied and specific utilization of (±)-N-ethylcoclaurine demonstrated. The evidence indicates that tetrandrine is formed in the plants by oxidative dimerization of N-methylcoclaurine. Double labelling experiment with (±)-N- [¹⁴C]-methyl- [1-³H]-coclaurine demonstrated that the hydrogen atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion into tetrandrine. Parallel feedings of (+)-(S)- and (?)-(R)-N-methylcoclaurines showed that the stereospecificity is maintained in the biosynthesis of tetrandrine from the 1-benzylisoquinoline precursor.     

Differentiation among the Vibrio cholerae serotypes O1, O139, O141 and non-O1, non-O139, non-O141 using specific monoclonal antibodies with dot blotting

Seven different monoclonal antibodies (MAbs) specific to only Vibrio cholerae were produced using a combination of five representative serotypes of V. cholerae for immunization. The first three MAbs (VC-93, VC-82 and VC-223) were specific to the V. cholerae serogroup O1 with different avidity for the serotypes O1 Inaba and O1 Ogawa. The fourth and the fifth MAbs were specific to V. cholerae O139 (VC-812) or O141 (VC-191) serogroups, respectively. The sixth MAb (VC-26) bound to all three serogroups of V. cholerae. The seventh MAb (VC-63) bound to all twenty five isolates of V. cholerae used in this study. None of the seven MAbs showed cross-reactivity with other Vibrio spp. or closely-related V. cholerae species, V. mimicus or other gram-negative bacteria. The eighth MAbs (VC-201) specific to almost all Vibrio spp. was also obtained. In dot blotting, these MAbs can be used to detect a diluted pure culture of V. cholerae in solution with a sensitivity range of from 10⁵ to 10⁷ CFU ml^− 1. However, the detection capability could be improved equivalent to that of PCR technique after preincubation of samples in alkaline peptone water (APW). Thus, these MAbs constitute convenient immunological tools that can be used for simple, rapid and simultaneous direct detection and differentiation of the individual serotypes of V. cholerae in complex samples, such as food and infected animals, without the requirement for bacterial isolation or biochemical characterization.     

Stereoselective synthesis of chaulmoogric acid and related fatty acid from 2-(±)-cyclopentenecarboxylic acid by Bacillus subtilis (ATCC 7059)

2-(±)-Cyclopentenecarboxylic acid added to the culture medium is incorporated into two new fatty acids by the growing cells of Bacillus subtilis (ATCC 7059). The new fatty acids, amounting to 24% of the total cellular fatty acids, are identified as hydrocarpic [11-(2′-cyclopentenyl)-hendecanoic] and chaulmoogric [13-(2′-cyclopentenyl)-tridecanoic] by gas-liquid chromatography and mass spectrometry. These C₁₆ and C₁₈ fatty acids are optically active, levorotatory, with the specific rotation of ?50.4° as mixture, thus the optical purity of approximately 80%. This indicates that the optical rotation of these bacterial fatty acids are opposite with that of the fatty acids from plant oils.     

Depolarization of the intrinsic and extrinsic fluorescence of pepsinogen and pepsin

1. The effects on the intrinsic tryptophan emission anisotropy of pepsin and pepsinogen solutions produced by (a) changes in temperature, (b) increases in viscosity with added glycerol at constant temperature and (c) decreases in lifetime through collisional quenching by potassium iodide were measured at several excitation wavelengths. The rotational-relaxation times calculated from results provided by method (b) approximate to the theoretical values for the two proteins, on taking hydration and shape factors into account, on the basis of random orientation of the tryptophan groups within the macromolecules. Differences between the results provided by methods (b) and (c) are attributable to inter-tryptophan resonance-energy-transfer depolarization, and the anomalous values recorded in method (a) can be attributed to the temperature-dependence of the limiting anisotropies. 2. Two different monomeric conjugates of pepsin, each containing one extrinsic fluorescent group per macromolecule, gave widely different relaxation times. This difference may arise from a specific orientation of the emission dipole in the enzyme. In active-site-labelled pepsin (1-dimethylaminonaphthalene-5-sulphonylphenylalanine–pepsin) this orientation would be approximately parallel to the symmetry axis of the equivalent ellipsoid, whereas in the other conjugate (1-dimethylaminonaphthalene-5-sulphonyl-pepsin) the orientation may be roughly normal to this direction, or some independent rotation of parts of the protein molecule is possible.     

The change in the electro-rotation of yeast cells effected by silver ions

Pre-treatment of brewer's yeast (Saccharomyces cerevisiae) cells with silver acetate or nitrate at concentrations of 20 nmol/l or higher caused a dramatic increase in the number of cells which rotated in the same direction as the field (‘Co-field rotation’). The change in rotation of single cells correlated very well with the chemically observed loss of potassium induced by Ag⁺. The sensitivity to Ag⁺ was lowered by increasing the cell concentration, and the extent of this change can be used to estimate the binding of Ag⁺ per cell and the limiting sensitivity of the method. The Ag⁺ concentration required to induce a response was found to be increased significantly in the presence of alkali ions (especially K⁺) during the Ag⁺ incubation. The Ag⁺ sensitivity was, therefore, observed to be a function of the type and strength of buffer used in the incubation. Under certain conditions, 1 mM Ca²⁺ increased the Ag⁺ sensitivity. These observations show that the presence or absence of ions that are so common that they are often overlooked may have interesting consequences for the bio-assay of heavy metals.     

Peanut-Cotton Rotations for the Management of Meloidogyne arenaria

The efficacy of ''Deltapine 90'' cotton (Gossypium hirsutum) in rotation with ''Florunner'' peanut (Arachis hypogaea) for the management of Meloidogyne arenaria was studied for 2 years in a field in southeastern Alabama. In 1985, M. arenaria juvenile populations in plots with cotton were 98% lower than in plots with peanut. Peanut and cotton yields were increased by treatment with aldicarb (3.3 kg a.i./ha in a 20-cm-band) in 1985 but not in 1986. In 1986, peanut yields were highest and M. arenaria juvenile populations in soil were lowest in plots that had cotton the previous year. In 1986, numbers of M. arenaria juveniles in plots with peanut both years were reduced by treatment with aldicarb to levels found in plots with cotton-peanut rotation. The use of aldicarb in peanut following cotton similarly treated reduced the incidence of southern blight (Sclerotium rolfsii). Cotton-peanut is a good rotation for the management of M. arenaria and to increase peanut yields without the use of nematicides.     

Palate shelf movement in mouse embryo culture: evidence for skeletal and smooth muscle contractility.

Previous biochemical and morphological studies have shown the presence of contractile proteins in mouse palates at the time of shelf movement. In order to determine whether the palatal contractile proteins function in shelf rotation, an embryo culture system in which palate shelves rotate has been developed. $\text{A}\text{J}$ mouse fetuses with tongues removed (day 14.75) have been cultured close to the time that palatal shelves move in vivo and pharmacological agents added. The anterior end of the palate shelf completely rotated after overnight culture in the presence or absence of drugs. However, rotation of the posterior end of the palate was only partial. Agents that stimulate skeletal and smooth muscle contractility, pyridostigmine (2 × 10^?6–9 × 10^?5M) and bethanechol (10^?10–10^?4M), respectively, both enhanced posterior shelf rotation after overnight culture. Pyridostigmine (9 × 10^?5M) increased posterior shelf rotation 74% over control; bethanechol (10^?4M) 53%. Pyridostigmine effected an appreciable increase in anterior shelf movement within 60 min, while bethanechol stimulated posterior shelf rotation by 60% in that time. These results imply a cholinergic involvement in palate shelf rotation. Furthermore, contraction of “smooth muscle-like” structures previously found on the tongue side extending from top mid-palate to the posterior end may be involved in posterior palate shelf rotation; and contraction of skeletal muscle observed on the oral side posteriorly may aid both posterior and anterior shelf movement.     

Annual Cycle of Bacterial Specific Biovolumes in Howe Sound, a Canadian West Coast Fjord Sound

The mean specific biovolumes (biovolume cell⁻¹) of the bacterioplankton within a 250-m-deep water column in Howe Sound, British Columbia, were determined for the period of 4 September 1984 to 23 October 1985. These bacteria had an annual cycle in mean specific biovolume; they were small (ca. 0.058 μm³) in mid-winter, larger in spring (ca. 0.076 μm³), larger again in summer (up to 0.102 μm³), and largest (ca. 0.133 μm³) in early fall (immediately after the decrease in phytoplankton production). The mean specific biovolumes changed coincidently through the water column with time, although the larger bacterioplankton tended to occur in the surface and deepest water. Although the mean specific biovolumes correlated better with in situ temperature (r = 0.65, a = 0.01) than with in situ chlorophyll a concentration (r = 0.34, a = 0.25), modeling experiments with batch cultures of the dinoflagellate Prorocentrum minimum (Pavillard) and the green alga Dunaliella tertiolecta (Butcher) indicated that the biomass and physiological condition of the phytoplankters may be more important than temperature in determining these bacterial specific biovolumes.     

Effects of Switchgrass (Panicum virgatum) Rotations with Peanut (Arachis hypogaea L.) on Nematode Populations and Soil Microflora

A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virgatum) to suppress root-knot nematodes (Meloidogyne arenaria), southern blight (Sclerotium rolfsii), and aflatoxigenic fungi (Aspergillus sp.) in peanut (Arachis hypogaea L.) and to assess shifts in microbial populations following crop rotation. Switchgrass did not support populations of root-knot nematodes but supported high populations of nonparasitic nematodes. Peanut with no nematicide applied and following 2 years of switchgrass had the same nematode populations as continuous peanut plus nematicide. Neither previous crop nor nematicide significantly reduced the incidence of pods infected with Aspergillus. However, pod invasion by A. flavus was highest in plots previously planted with peanut and not treated with nematicide. Peanut with nematicide applied at planting following 2 years of switchgrass had significantly less incidence of southern blight than either continuous peanut without nematicide application or peanut without nematicide following 2 years of cotton. Peanut yield did not differ among rotations in either sample year. Effects of crop rotation on the microbial community structure associated with peanut were examined using indices for diversity, richness, and similarity derived from culture-based analyses. Continuous peanut supported a distinctly different rhizosphere bacterial microflora compared to peanut following 1 year of switchgrass, or continuous switchgrass. Richness and diversity indices for continuous peanut rhizosphere and geocarposphere were not consistently different from peanut following switchgrass, but always differed in the specific genera present. These shifts in community structure were associated with changes in parasitic nematode populations.