Microbial activity,community structure and potassium dynamics in rhizosphere soil of soybean plants treated with glyphosate

With the advent of glyphosate [N-(phosphonomethyl)glycine] tolerant crops, soils have now been receiving repeated applications of the herbicide for over 10 years in the Midwestern USA. There is evidence that long-term use of glyphosate can cause micronutrient deficiency but little is known about plant potassium (K) uptake interactions with glyphosate. The repeated use of glyphosate may create a selection pressure in soil microbial communities that could affect soil K dynamics and ultimately K availability for crops. Therefore, the objectives of this study were to characterize the effect of foliar glyphosate applied to GR (glyphosate resistant) soybeans on: (1) rhizosphere microbial community profiles using ester linked fatty acid methyl ester (EL-FAME) biomarkers, (2) exchangeable, non-exchangeable, and microbial K in the rhizosphere soil, and (3) concentrations of soybean leaf K. A greenhouse study was conducted in a 2 × 2 × 3 factorial design with two soil treatments (with or without long-term field applications of glyphosate), two plant treatments (presence and absence of soybean plants), and three rates of glyphosate treatments (0×, 1× at 0.87, and 2× at 1.74 kg ae ha^?1, the recommended field rate). After each glyphosate application, rhizosphere soils were sampled and analyzed for microbial community structure using ester linked fatty acid methyl ester biomarkers (EL-FAME), and exchangeable, plant tissue and microbial biomass K. Glyphosate application caused a significant decrease in the total microbial biomass in soybean rhizosphere soil that had no previous exposure to glyphosate, at 7 days after glyphosate application. However, no significant changes were observed in the overall microbial community structure. In conclusion, the glyphosate application lowered the total microbial biomass in the GR soybean rhizosphere soil that had no previous exposure to glyphosate, at 7 days after glyphosate application; caused no changes in the microbial community structure; and did not reduce the plant available K (soil exchangeable or plant tissue K).     

The effect of glyphosate on soil microbial activity,microbial community structure,and soil potassium

The herbicide, glyphosate [N-(phosphonomethyl) glycine] is extensively used worldwide. Long-term use of glyphosate can cause micronutrient deficiency but little is known about potassium (K) interactions with glyphosate. The repeated use of glyphosate may create a selection pressure in soil microbial communities that could affect the nutrient dynamics such as K. The objective of this study was to determine the effect of single or repeated glyphosate applications on microbial and K properties of soils. A 54 day incubation study (Exp I) had a 3 × 5 factorial design with 3 soils (silt loam: fine, illitic, mesic Aeric Epiaqualf) of similar physical and chemical characteristics, that varied in long-term glyphosate applications (no, low, and high glyphosate field treatments) and five glyphosate rates (0, 0.5×, 1×, 2×, and 3× recommended field rates applied once at time zero). A second 6 month incubation study (Exp II) had a 3 × 3 factorial design with three soils (as described above) and three rates of glyphosate (0, 1×, and 2× recommended field application rates applied monthly). For each study microbial properties [respiration; community structure measured by ester linked fatty acid methyl ester (EL-FAME) analysis and microbial biomass K] and K fractions (exchangeable and non-exchangeable) were measured periodically. For Exp I, glyphosate significantly increased microbial respiration that was closely related to glyphosate application rate, most notably in soils with a history of receiving glyphosate. For Exp II, there was no significant effect of repeated glyphosate application on soil microbial structure (EL-FAME) or biomass K. We conclude that glyphosate: (1) stimulates microbial respiration particularly on soils with a history of glyphosate application; (2) has no significant effect on functional diversity (EL-FAME) or microbial biomass K; and (3) does not reduce the exchangeable K (putatively available to plants) or affect non-exchangeable K. The respiration response in soils with a long-term glyphosate response would suggest there was a shift in the microbial community that could readily degrade glyphosate but this shift was not detected by EL-FAME.     

Active starvation responses mediate antibiotic tolerance in biofilms and nutrient-limited bacteria

Bacteria become highly tolerant to antibiotics when nutrients are limited. The inactivity of antibiotic targets caused by starvation-induced growth arrest is thought to be a key mechanism producing tolerance. Here we show that the antibiotic tolerance of nutrient-limited and biofilm Pseudomonas aeruginosa is mediated by active responses to starvation, rather than by the passive effects of growth arrest. The protective mechanism is controlled by the starvation-signaling stringent response (SR), and our experiments link SR-mediated tolerance to reduced levels of oxidant stress in bacterial cells. Furthermore, inactivating this protective mechanism sensitized biofilms by several orders of magnitude to four different classes of antibiotics and markedly enhanced the efficacy of antibiotic treatment in experimental infections.     

Radioreceptor assay of human chorionic gonadotropin: detection of early pregnancy

A rapid, sensitive, and specific radioreceptor assay for the determination of human chorionic gonadotropin and luteinizing hormone in plasma is described. Plasma membranes of bovine corpora lutea of early pregnancy, which bind biologically active labeled human chorionic gonadotropin, have been used as receptor. Pregnancy could be detected by assaying the gonadotropin in plasma samples obtained from day 6 to 8 after conception.     

Oocyte-specific deletion of Pten causes premature activation of the primordial follicle pool

In the mammalian ovary, progressive activation of primordial follicles from the dormant pool serves as the source of fertilizable ova. Menopause, or the end of female reproductive life, occurs when the primordial follicle pool is exhausted. However, the molecular mechanisms underlying follicle activation are poorly understood. We provide genetic evidence that in mice lacking PTEN (phosphatase and tensin homolog deleted on chromosome 10) in oocytes, a major negative regulator of phosphatidylinositol 3-kinase (PI3K), the entire primordial follicle pool becomes activated. Subsequently, all primordial follicles become depleted in early adulthood, causing premature ovarian failure (POF). Our results show that the mammalian oocyte serves as the headquarters of programming of follicle activation and that the oocyte PTEN-PI3K pathway governs follicle activation through control of initiation of oocyte growth.     

Genome-wide association analysis identifies loci for type 2 diabetes and triglyceride levels

New strategies for prevention and treatment of type 2 diabetes (T2D) require improved insight into disease etiology. We analyzed 386,731 common single-nucleotide polymorphisms (SNPs) in 1464 patients with T2D and 1467 matched controls, each characterized for measures of glucose metabolism, lipids, obesity, and blood pressure. With collaborators (FUSION and WTCCC/UKT2D), we identified and confirmed three loci associated with T2D-in a noncoding region near CDKN2A and CDKN2B, in an intron of IGF2BP2, and an intron of CDKAL1-and replicated associations near HHEX and in SLC30A8 found by a recent whole-genome association study. We identified and confirmed association of a SNP in an intron of glucokinase regulatory protein (GCKR) with serum triglycerides. The discovery of associated variants in unsuspected genes and outside coding regions illustrates the ability of genome-wide association studies to provide potentially important clues to the pathogenesis of common diseases.     

Rice (Oryza sativa L.) plant protection using dual biological control and plant growth-promoting agents: Current scenarios and future prospects

Various microorganisms live in association with different parts of plants and can be harmful, neutral, or beneficial to plant health. Some microbial inhabitants of plants can control plant diseases by contesting with, predating on, or antagonizing plant pathogens and by inducing systems for plant defense. A range of methods, including plant growth-promoting microorganisms(PGPMs) as biological control agents(BCAs)(BCA-PGPMs) are used for the biological management and control of plant pathogens. S...     

Expression analysis of melatonin receptor subtypes in the ovary of domestic chicken

Melatonin (N-acetyl-5-methoxytryptamine), an indole hormone, regulates various biological functions through three different receptor subtypes (Mel-1a, Mel-1b, and Mel-1c). However, the distribution of different melatonin receptor subtypes in chicken reproductive tissues was not known. In the present investigation, the partial sequences of ovarian melatonin receptor subtypes (Mel-1a, Mel-1b, and Mel-1c) were characterized. Further, the expression profile of melatonin receptor subtypes in the granulosa and theca layers of different preovulatory and postovulatory follicles (POF) were studied by semi-quantitative RT-PCR. The expression of all three subtypes of melatonin receptors were observed in the ovary of domestic chicken. Analysis of partial sequences of ovarian melatonin receptors revealed that the melatonin subtypes were identical to the brain receptors. In small white ovary follicles, we observed only the expression of mel-1b receptors, but not mel-1a or mel-1c receptors. In yellow follicles, all the three subtypes of receptors expression were noticed. Interestingly, we observed the expression of mel-1a receptor only in thecal layer, but not in granulosa layer. In contrast, mel-1b and -1c receptors were expressed in both granulosa and thecal layer. During the regression of POF, we observed significant upregulation of melatonin receptors (mel-1a and 1c) expression, that downregulated in the later stages of regression. We assume that the expression of melatonin receptors might have been influenced by the atresia or apoptosis of different follicular layers in POF. Our findings suggest that the differential distribution of melatonin receptor subtypes might have distinct downstream cellular functions in the ovarian tissues.     

Isolation and pathotyping of H9N2 avian influenza viruses in Indian poultry

A total of 1246 faecal and tissue samples collected/received from 119 farms located in various states of India were processed for isolation of avian influenza viruses (AIV) during 2003-2004 as part of a program to monitor AIV infection in Indian poultry population. Avian influenza virus was isolated for the first time in India from poultry farms with history of drop in egg production, respiratory illness and increased mortality in Haryana state. A total of 29 H9N2 AIV isolates were obtained from the states of Punjab, Haryana, Uttar Pradesh, Gujarat, and Orissa and Union Territory Delhi. Subtyping was done by HI, RT-PCR and neuraminidase inhibition assay. Pathotyping of six representative isolates by intravenous pathogenicity index (0.0/3.0) in 6-8 weeks old chicken, trypsin dependency in cell culture and HA cleavage site analysis (335RSSR*GLF341) confirmed that these isolates are low pathogenic. Nucleotide sequence analysis of the HA gene showed that the Indian isolates are very closely related (95.0-99.6%) and shared a homology of 92-96% with H9N2 isolates from Germany and Asian regions other than that of mainland China. Deduced amino acid sequences showed the presence of L226 (234 in H9 numbering) which indicates a preference to binding of alpha (2-6) sialic acid receptors. Two of the six isolates had 7 glycosylation sites in the HA1 cleaved protein and the remaining four had 5 sites. Phylogenetic analysis showed that they share a common ancestor Qa/HK/G1/97 isolate which had contributed internal genes of H5N1 virus circulating in Vietnam. Further characterization of Indian H9N2 isolates is required to understand their nature and evolution.