rDNA Genotypes Research Articles

Clinical aPDT's effect on Candida albicans: Antifungal susceptibility, virulence gene expression, and correlation with leukocyte and neutrophil counts

BackgroundOur previous clinical trial demonstrated that antimicrobial photodynamic therapy (aPDT) with methylene blue (MB) and potassium iodide (KI) effectively killed Candida albicans (C. albicans) in adult AIDS patients with oral candidiasis, regardless of biofilm formation or 25S rDNA genotype. This study evaluated changes in antifungal susceptibility and virulence gene expression in C. albicans before and after aPDT, and explored factors related to clinical aPDT efficacy. MethodsTwenty-one adult AIDS patients with C. albicans oral candidiasis were divided into Group a (400 μM MB, N = 11) and Group b (600 μM MB, N = 10). Both groups received two aPDT treatments, where MB was applied for 5 min, followed by 300 mM KI, and illuminated for 30 min (37.29 J/cm²). C. albicans isolates were collected before and after treatment to assess antifungal susceptibility (fluconazole, itraconazole, flucytosine, amphotericin B) and gene expression (CAT1, HWP1). Peripheral blood tests were analyzed for correlations with aPDT efficacy. ResultsaPDT reduced minimum inhibitory concentration (MIC) values for amphotericin B, fluconazole, and flucytosine, with significant reductions primarily after the first treatment. MIC reductions differed between groups, with Group a showing greater decreases in flucytosine and fluconazole MICs, and Group b in amphotericin B MICs. No significant changes in CAT1 or HWP1 expression were observed. Clinical efficacy of aPDT negatively correlated with leukocyte and neutrophil levels. ConclusionsaPDT effectively reduces MICs of antifungal drugs against C. albicans isolated from treated patients, particularly after the first treatment. The concentration of MB required to reduce MICs varies among different antifungal drugs. aPDT does not alter CAT1 or HWP1 expression, and its clinical efficacy in eradicating C. albicans is negatively associated with leukocyte and neutrophil levels.

Tracking the impacts of nutrient inputs on estuary ecosystem function

Estuaries are one of the most impacted coastal environments globally, subjected to multiple stressors from urban, industry and coastal development. With increasing anthropogenic activity surrounding estuarine systems, sewage inputs have become a common concern. Stable isotope analysis provides a well-established tool to investigate the incorporation of nitrogen into marine organisms and identify major nutrient sources. Benthic macroinvertebrate communities are often used as bioindicators in ecological studies as they typically display predictable responses to anthropogenic pressures, however have a suite of limitations and costs associated with their use. 16S rDNA amplicon sequencing techniques allow for investigation of the microbial communities inhabiting complex environmental samples, with potential as a tool in the ecological assessment of pollution. These communities have not yet been adequately considered for ecological studies and biomonitoring, with a need to better understand interactions with environmental stressors and implications for ecosystem function. This study used a combination of stable isotope analysis to trace the uptake of anthropogenic nitrogen in biota, traditional assessment of benthic macroinvertebrate communities, and 16S rDNA genotyping of benthic microbial communities. Stable isotope analysis of seagrass and epiphytes identified multiple treated and untreated sewage inputs, ranges of 5.2–7.2‰ and 1.9–4.0‰ for δ15N respectively, as the dominant nitrogen source at specific locations. The benthic macroinvertebrate community reflected these inputs with shifts in dominant taxa and high abundances of polychaetes at some sites. Microbial communities provided a sensitive indication of impact with a breadth of information not available using traditional techniques. Composition and predicted function reflected sewage inputs, particularly within sediments, with the relative abundance of specific taxa and putative pathogens linked to these inputs. This research supports the growing body of evidence that benthic microbial communities respond rapidly to anthropogenic stressors and have potential as a monitoring tool in urban estuarine systems.

Antimicrobial photodynamic therapy for oral Candida infection in adult AIDS patients: A pilot clinical trial

BackgroundAntimicrobial photodynamic therapy (aPDT) using methylene blue (MB) plus potassium iodide (KI) has been shown to be effective in killing Candida albicans in many in vitro and in vivo studies, however, there are limited reports of clinical investigations. This study aimed to explore the clinical application of aPDT with MB plus KI for the treatment of oral infection caused by C. albicans in adult acquired immune deficiency syndrome (AIDS) patients. MethodsA total of 21 adult AIDS patients with C. albicans oral candidiasis were divided into two groups according to MB concentration and received two consecutive aPDT treatments. Immediately before and after the aPDT treatments, C. albicans yeast isolates were recovered to measure the colony-forming units per mL (CFU/mL), biofilm formation, and to analyze the 25S rDNA genotype. Patients were assessed for the clinical recovery of oral lesions and improvement of symptoms. ResultsThe Log10 CFU/mL of C. albicans decreased significantly after the second aPDT but not the first aPDT. There was no significant difference between the two MB concentrations. Both aPDT protocols decreased the oral lesions and clinical symptoms with no significant difference after 2-fraction aPDT. The biofilm formation of C. albicans isolates did not change before and after aPDT. The killing efficiency of 2-fraction-aPDT was not associated with either biofilm formation or 25S rDNA genotype. ConclusionsTwo-fraction-aPDT with MB plus KI could reduce the number of viable C. albicans fungal cells and improve the clinical symptoms of oral candidiasis in adult AIDS patients, regardless of the biofilm formation or 25S rDNA genotype of infected C. albicans isolates.

Corroboration That Highly Resistant Impatiens Cultivars Are Not Immune to Downy Mildew Disease: A Report of Crop Losses from Two California Producers

Two new series of Impatiens walleriana (impatiens) cultivars, Beacon and Imara XDR, were released to commercial growers in the United States in 2019 to 2020. Field trials show these new cultivar series are highly resistant to impatiens downy mildew (IDM). However, neither of these two impatiens series are completely immune to the disease, and preventive fungicide programs are still recommended for use throughout production to maintain plant health. Here we report two destructive outbreaks of IDM from Imara XDR in two commercial production facilities in California, one in 2019 and one in 2020. The disease outbreaks were caused by a known rDNA genotype of Plasmopara destructor (synonym = P. obducens). Modified Koch’s postulates showed that the pathogen could infect and cause disease in both Beacon and Imara XDR plants. Mefenoxam applied by both growers may have been ineffective due to resistance in P. destructor populations, which has been demonstrated on several previous occasions. Given these findings, fungicide programs intended to supplement genetic resistance should not be overly reliant upon application of mefenoxam and should utilize effective materials from different mode of action groups, in rotation. Fungicides to supplement genetic resistance are particularly appropriate in frost-free areas or in any circumstances that provide a potential inoculum source.

Virulence and antifungal susceptibility of microsatellite genotypes of Candida albicans from superficial and deep locations.

A set of 185 strains of Candida albicans from patients with vulvovaginal candidiasis (VVC) and from non‐VVC clinical sources in southwest China was analysed. Strains were subjected to genotyping using CAI microsatellite typing and amplification of an intron‐containing region of the 25S rRNA gene. Microsatellite genotypes of strains from non‐VVC sources showed high polymorphism, whereas those of VVC were dominated by few, closely similar genotypes. However, among non‐VVC strains, two genotypes were particularly prevalent in patients with lung cancer. 25S rDNA genotype A was dominant in VVC sources (86.7%), whereas genotypes A, B, and C were rather evenly distributed among non‐VVC sources; known genotypes D and E were not found. In an experimental mouse model, isolates from lung cancer and AIDS patients proved to have higher virulence than VVC strains. Among 156 mice infected with C. albicans, 19 developed non‐invasive urothelial carcinoma. No correlation could be established between parameters of virulence, source of infection, and incidence of carcinoma. C. albicans strains from VVC were less susceptible to itraconazole than the strains from non‐VVC sources, whereas there was small difference in antifungal susceptibility between different 25S rDNA genotypes of C. albicans tested against amphotericin B, itraconazole, fluconazole, and flucytosine.

Fenotipska i genotipska raznolikost sojeva Sinorhizobium meliloti izoliranih iz tala Zadarske županije

Soil bacteria, Sinorhizobium meliloti is of great agricultural importance because of its ability to fix atmospheric nitrogen in symbiosis with alfalfa very valuable forage crop. The main aim of this study was to evaluate tolerance of indigenous S. meliloti strains to stress environmental conditions. Twenty rhizobial strains, isolated from different regions in Croatia, were genotipically characterized to assess diversity amongst natural population. Stress tolerance assays were performed in order to select indigenous rhizobia with tolerance to unfavorable soil conditions. The growth of the strains was studied at different pH values, temperatures, NaCl and heavy metals concentrations. The results of 16S rDNA genotyping using PCR/RFLP analysis showed that 17 isolates could be assigned to S. meliloti while RAPD and ERIC-PCR fingerprints revealed significant genetic diversity among indigenous rhizobial strains. In comparison to the reference strain, higher resistance to adverse growth conditions of indigenous S. meliloti strains was determined. Most of the strains grew at temperatures higher than optimal and tolerated both acidic and alkaline environment. It was found that indigenous strains tolerate extremely high NaCl concentrations. Better understanding of rhizobial response to adverse environmental conditions is of potential value for improving rhizobial inoculants and efficiency of symbiotic nitrogen fixation.

Genetic Variation of the Pathogen Causing Impatiens Downy Mildew Predating and Including Twenty-first Century Epidemics on Impatiens walleriana.

Impatiens downy mildew (IDM) of cultivated Impatiens walleriana has had a significant economic impact on the ornamental horticulture industry in the United States and globally. Although recent IDM outbreaks started in 2003, downy mildews on noncultivated Impatiens species have been documented since the 1880s. To understand the relationship between the pathogen causing recent epidemics and the pathogen historically present in the United States, this work characterized genetic variation among a collection of 1,000 samples on 18 plant hosts. Samples included collections during recent IDM epidemics and historical herbarium specimens. Ten major genotypes were identified from cloned rDNA amplicon sequencing and endpoint SNP genotyping. Three genotypes accounted for >95% of the samples, with only one of these three genotypes found on samples predating recent IDM outbreaks. Based on phylogenetic analysis integrating data from three markers and the presence of individual genotypes on multiple Impatiens species, there was some evidence of pathogen-specific infection of I. noli-tangere, but the distinction between genotypes infecting I. walleriana and I. balsamina was not upheld. Overall, this work provides evidence that the majority of rDNA genotypes recovered from recent IDM epidemics are different from historical U.S. genotypes, and that these genotypes can infect Impatiens spp. other than I. walleriana.

Biological Degradation of Pyrene and Fluoranthene in Porous Media and Attached Growth Systems by Biosurfactant Producing Bacteria

The dissolution and degradation of higher ring-number polycyclic aromatic compounds were tested in batch and attached growth medium using soil biopile and fixed-film bioreactor systems. Bioavailability of polycyclic aromatic hydrocarbons (PAHs) decreases with increasing ring-number. This means high ring-number compounds will survive longer in the environment and will therefore have a longer-term impact. In the current study, pyrene and fluoranthene were degraded using a biosurfactant producing culture of Pseudomonas aeruginosa grown in fixed-bed and soil biopile experiments. High ring-number PAHs prove to be recalcitrant in nature due to their hydrophobicity and poor partitioning to soil media fixed biomass in biofilm reactors. The use of biosurfactant could facilitate faster dissolution of the PAH and thus would increase bioavailability of the PAH compounds to PAH degrading bacteria. The culture used in this study was obtained from engine oil contaminated soil, that grow on HMW PAHs and are capable of degrading PAHs were enriched, isolated and characterize. The isolated microbial cultures were further characterised 16S rDNA gene sequencing and genotype fingerprinting. During baseline study, over 90 % fluoranthene was degraded as a model compound in biofilm reactor system. Over 88 % pyrene was degraded in soil biopiles. In both cases, increased biosurfactant dose improved degradation rate up to the point where the PAH concentration became inhibitory to biomass growth and PAH degradation.

Isolation and Characterization of Enterococci from Yoghurts of Bangladesh

Background: Bacteriocin - producing Enterococci have potential probiotic value. In this study, Enterococci possessing stable antibacterial activities were isolated from yoghurts of Bangladesh. Methods: Bacteria were isolated on MRS medium and genotyped based on partial 16S rDNA sequencing. Cultured supernatants were assessed for antibacterial activity by agar - well diffusion method before and after heat, proteinase K, and β - mercaptoethanol treatments. Results: In this study, 18 Enterococci bacteria were isolated from 10 different yoghurt samples of Bangladesh. Partial 16S rDNA genotyping suggested that these bacteria were either E. faecalis or E. faecium, or E. durans. Phylogenetic analysis suggested that these strains are closely related to other dairy Enterococci and distantly related to non - dairy Enterococci. Four isolates showed potent antibacterial activity against seven food - borne pathogens in vitro. The antibacterial property can withstand temperature as high as 90 oC for an hour, 1 µg/mL proteinase K, and 2.5% (v/v) β - mercaptoethanol treatments as well. Conclusions: These isolated yoghurt Enterococci have some probiotic value because of their stable antibacterial activities and further improvement of these Enterococci is necessary to improve yoghurt quality.

25S rDNA genotype and antifungal susceptibility of clinical Candida albicans in Ouagadougou (Burkina Faso).

The present investigation aimed to assess the prevalence of genotypes of C. albicans in Ouagadougou and to analyze the relationship between the genetic diversity and antifungal susceptibility. Ninety-six clinical strains are included. They were diagnosed as C. albicans using germ tube test, chlamydospore formation, and Api-Candida test. Genotyping was performed using PCR targeting 25S rDNA. Antifungal susceptibilities were tested based on the disk diffusion method. The genotypes A (85.4%) was predominant followed by genotypes B (10.4%) and C (4.2%). The highest resistance rate with genotype A was obtained with fluconazole (74.4%). A resistance to amphotericin B was observed with genotypes A (29.3%) and B (30%).

Persistence, dispersal and genetic evolution of recently formed Spartina homoploid hybrids and allopolyploids in Southern England

In Southampton Water, UK, the recent (c. 150 years ago) interspecific hybridisation between Spartina alterniflora (2n = 6x = 62; A-genome) and S. maritima (2n = 6x = 60; M-genome) gave rise to the homoploid hybrid (S. × townsendii, 2n = 6x = 62), and subsequently to the invasive allododecaploid species S. anglica (2n = 12x = 120–124) that has since spread worldwide. To address the question of dynamics of mixed ploidy populations involving these plants, we analysed several Spartina populations (fifty one individuals) in Southern England, UK, one of which was the presumed place of origin of the homoploid hybrid (Hythe). Using a combination of flow cytometry and ribosomal DNA (rDNA) genotyping we were able to identify the genomic composition and ploidy level of each individual analysed. The data show that the homoploid hybrid still dominates the population at Hythe (82 % of individuals collected in that locality) since its origin in the nineteenth century. We also identified S. × townsendii for the first time on Hayling Island (66 % individuals), indicating dispersal beyond its likely origin. The fertile allododecaploid S. anglica was mainly found in populations outside the initial hybridisation site, on Hayling Island and at Eling Marchwood. Quantification of the rDNA contributions from each parental genome showed that the ratios were mostly balanced in S. × townsendii. However, two (3 %) S. anglica individuals analysed have lost nearly all M-genome homeologs, indicating extensive repeat loss. Such variation indicates that despite the presumed single allopolyploid origin of S. anglica and genetic uniformity at other loci, it has undergone substantial changes at the rDNA loci following genome duplication.

25S rDNA genotype and antifungal susceptibility of vaginal Candida albicans

To investigate 25S rDNA genotype distribution of vaginal Candida albicans and its relationship with antifungal susceptibility. A total of 954 isolates of Candida albicans were subjected to genotype analysis according to the presence and the size of transposable group Ⅰ intron in 25S rDNA with PCR; 156 isolates were enrolled to detect their antifungal susceptibility of 5 antifungal agents with the M27-A3 broth microdilution method. Totally 876 isolates were determined to be intronless genotype A(91.8%, 876/954); 58(6.1%, 58/954)and 20 isolates(2.1%, 20/954)were introncontaining genotype B and genotype C, respectively. The minimal inhibitory concentrations(MIC)of itraconazole and fluconazole against the intron-containing group were significantly higher than those of the intronless group(0.25 versus 0.125 μg/ml, P<0.05; 0.25 versus 0.125 μg/ml, P<0.01), whereas the MIC of nystatin against the intron-containing group was lower than that of the intronless group(4 versus 8 μg/ml, P< 0.01). The resistance rate of Candida albicans to itraconazole of the intron-containing group was significantly higher than that of the intronless group[24%(19/78)versus 3%(2/78), P<0.01]. Cross-resistance analysis revealed 5 of the 21(24%)itraconazole resistant isolates were cross-resistant to fluconazole , and 5 of the 6(5/6)fluconazole-resistant strains were cross-resistant to itraconazole. Besides, all the five strains simultaneously resistant to itraconazole and fluconazole belonged to the intron-containing group. The presence of the transposable group Ⅰ intron in 25S rDNA of vaginal Candida albicans might be important in affecting itraconazole, fluconazole and nystatin susceptibility.

Uneven seasonal distribution of Babesia canis and its two 18S rDNA genotypes in questing Dermacentor reticulatus ticks in urban habitats

It has been reported from cities in Central Europe that clinical cases of canine babesiosis are most frequent in spring time, despite the fact that the peak activity of Dermacentor reticulatus (the vector of Babesia canis) is during autumn. The present study was initiated to evaluate the seasonal distribution of B. canis-infected D. reticulatus ticks in this context.In two habitats of Budapest 852 D. reticulatus adults were collected between August, 2014 and June, 2015. Among the molecularly analysed 413 ticks 8.2% were PCR positive for piroplasms. Both formerly reported 18S rDNA genotypes of B. canis: (“A” and “B”) were identified. In habitat-1 B. canis-infected ticks were detected only in spring. Similarly, in habitat-2 B. canis-infected ticks occurred significantly more frequently during winter and spring than in the autumn (24.6% vs. 1.4%), and their monthly distribution showed significant negative correlation with tick size. The prevalence of infected ticks was the highest (43.5%) in late February. In addition, a month-dependent time-shift was noted in the appearance of the two B. canis 18S rDNA genotypes: the less pathogenic “A” predominating earlier, and the more pathogenic “B” later.It is known from literature that D. reticulatus individuals that moult to adult in the spring are smaller in size. Thus, the above results suggest that in urban habitats the occurrence of B. canis-infected ticks (or their questing activity) is more likely, when there are freshly emerged adults in the population, i.e. early in the questing season. It was also observed that the temporal distribution of D. reticulatus ticks carrying different B. canis genotypes was not random.

Interpopulation hybridization generates meiotically stable rDNA epigenetic variants in allotetraploid Tragopogon mirus.

Uniparental silencing of 35S rRNA genes (rDNA), known as nucleolar dominance (ND), is common in interspecific hybrids. Allotetraploid Tragopogon mirus composed of Tragopogon dubius (d) and Tragopogon porrifolius (p) genomes shows highly variable ND. To examine the molecular basis of such variation, we studied the genetic and epigenetic features of rDNA homeologs in several lines derived from recently and independently formed natural populations. Inbred lines derived from T. mirus with a dominant d-rDNA homeolog transmitted this expression pattern over generations, which may explain why it is prevalent among natural populations. In contrast, lines derived from the p-rDNA dominant progenitor were meiotically unstable, frequently switching to co-dominance. Interpopulation crosses between progenitors displaying reciprocal ND resulted in d-rDNA dominance, indicating immediate suppression of p-homeologs in F1 hybrids. Original p-rDNA dominance was not restored in later generations, even in those segregants that inherited the corresponding parental rDNA genotype, thus indicating the generation of additional p-rDNA and d-rDNA epigenetic variants. Despite preserved intergenic spacer (IGS) structure, they showed altered cytosine methylation and chromatin condensation patterns, and a correlation between expression, hypomethylation of RNA Pol I promoters and chromatin decondensation was apparent. Reversion of such epigenetic variants occurred rarely, resulting in co-dominance maintained in individuals with distinct genotypes. Generally, interpopulation crosses may generate epialleles that are not present in natural populations, underlying epigenetic dynamics in young allopolyploids. We hypothesize that highly expressed variants with distinct IGS features may induce heritable epigenetic reprogramming of the partner rDNA arrays, harmonizing the expression of thousands of genes in allopolyploids.

Spatially distinct and regionally endemic Symbiodinium assemblages in the threatened Caribbean reef-building coral Orbicella faveolata

Recently, the Caribbean reef-building coral Orbicella faveolata was listed as “threatened” under the U.S. Endangered Species Act. Despite attention to this species’ conservation, the extent of geographic variation within O. faveolata warrants further investigation. O. faveolata is unusual in that it can simultaneously harbor multiple genetically distinct and co-dominant species of endosymbiotic dinoflagellates in the genus Symbiodinium. Here, we investigate the geographic and within-colony complexity of Symbiodinium-O. faveolata associations from Florida Keys, USA; Exuma Cays, Bahamas; Puerto Morelos, Mexico; and Carrie Bow Cay, Belize. We collected coral samples along intracolony axes, and Symbiodinium within O. faveolata samples was analyzed using the nuclear ITS2 region and chloroplast 23S rDNA genotyping. O. faveolata associated with species of Symbiodinium in clades A (type A3), B (B1 and B17), C (C3, C7, and C7a), and D (D1a/Symbiodinium trenchii). Within-colony distributions of Symbiodinium species correlated with light availability, cardinal direction, and depth, resulting in distinct zonation patterns of endosymbionts within a host. Symbiodinium species from clades A and B occurred predominantly in the light-exposed tops, while species of clade C generally occurred in the shaded sides of colonies or in deeper-water habitats. Furthermore, geographic comparisons of host–symbiont associations revealed regional differences in Symbiodinium associations. Symbiodinium A3 was detected in Mesoamerican coral colonies, but not in colonies from the Florida Keys or Bahamas. Likewise, Symbiodinium B17 was unique to Mesoamerican O. faveolata, whereas Symbiodinium B1 was found at all localities sampled. However, using cp23S genotyping paired with ITS2 analysis revealed geographically endemic haplotypes among Symbiodinium clades A, B, and C. Since Symbiodinium spatial heterogeneity among this coral species is greater than most corals, a question arises as to whether all western Atlantic populations of O. faveolata should be considered equally “threatened”? Alternatively, geographically and spatially distinct coral–symbiont associations may benefit from specialized management protocols.

Distribution of Candida albicans in the oral cavity of children aged 3-5 years of Uygur and Han nationality and their genotype in caries-active groups.

We analyzed the distribution of Candida albicans in the oral cavity of 3-5-year-old children of Uygur and Han nationalities as well as their genotypes in caries-active groups in the Urumqi municipality. CHROMagar Candida was separately cultivated, and we identified 359 Uygur and Han children aged 3-5 years. We randomly selected 20 Han children and 20 Uygur children for this study. We chose a bacterial strain for polymerase chain reaction (PCR) 25S rDNA genotyping and random amplified polymorphic DNA (RAPD) genotyping. The rate of caries-active in Han children was higher than that in Uygur children, with values of 39.6 and 24.3%, respectively. The detection rate of C. albicans was closely correlated to the caries filling index classification (X(2) = 31.037, P = 0.000, r = 0.421; X(2) = 80.454, P = 0.000, r = 0.497). PCR of 25S rDNA from 40 strains of Han and Uygur children revealed 3 genotypes, while RAPD analysis revealed 5 genotypes. The distribution of 25S rDNA genotyping of Han children from PCR differed from that of Uygur children (X(2) = 7.697, P = 0.021), both of which were mainly the A type. RAPD genotyping of both Han and Uygur children showed similar results (X(2) = 1.573, P = 0.814). There were differences in the distributions of C. albicans in children of different nationalities. C. albicans is a key factor causing caries. The PCR 25S rDNA genotyping method is simple and sensitive, while the RAPD genotyping method is reliable and comprehensive.

Suppressive effects of Bursaphelenchus mucronatus on pine wilt disease development and mortality of B. xylophilus-inoculated pine seedlings

Bursaphelenchus xylophilus causes pine wilt disease in Pinus trees whereas B. mucronatus has no or little virulence to the trees. Interspecific crossing experiments conducted so far suggest reproductive interference between the two nematode species. Theory predicts that one of the two competing species populations quickly displaces the other through reproductive interference in a frequency-dependent manner. Thus, it is anticipated that B. mucronatus suppresses the virulence of B. xylophilus against pine trees when B. mucronatus heavily outnumber B. xylophilus. To determine the suppressive effects of B. mucronatus, the two nematode species were inoculated simultaneously on 30 3-year-old Pinus thunbergii seedlings at three combinations of different numbers, and B. xylophilus alone was inoculated on 30 other seedlings at the corresponding numbers in early August. Seedlings were observed at intervals of 4 or 6 weeks and two stem sections were sampled from each seedling to determine the density and species composition of nematode populations after death or in December. Inoculation of B. mucronatus significantly retarded the speed of foliage discolouration from 0.170 ± 0.024 week−1 to 0.061 ± 0.017 week−1 and significantly prolonged the survival time of seedlings. Bursaphelenchus mucronatus significantly reduced the nematode density from 1799.7 ± 305.0 to 521.0 ± 148.4 (g dried seedling stem)−1. Analysis of rDNA genotype showed 1846 B xylophilus, no B. mucronatus and one hybrid.

Genotypic diversity in native rhizobial population nodulating Vicia faba in arid and semi-arid regions of Haryana state (India)

A Rhizobium–legume interaction stands out from other plant–microbe interactions as one in which a true developmental mutualism occurs. To study the genotypic diversity in native population of rhizobia-nodulating Vicia faba plants, we retrieved 64 rhizobial isolates from root nodules of faba bean grown in pots holding soils collected from arid and semi-arid regions of the state of Haryana, India. The amplification of nodC in all the isolates authenticated these as rhizobia. The nitrogen-fixing potential of the isolates was tested by the amplification of the nifH gene. Only 50 isolates out of 64 showed nifH gene amplification. The characterization of the isolates by amplified 16S rDNA restriction analysis (ARDRA) categorized these into 36 16S rDNA genotypes using a combination of MspI and HaeIII restriction enzymes. Majority of the isolates resolved into separate genotypes, indicating a wide diversity among them, which seemed to arise from their geographical origin and soil characteristics. These findings may be immensely useful in agriculture towards developing rhizobial inoculants specific for faba beans under arid and semi-arid conditions.

18S rDNA genotyping of &lt;I&gt;Acanthamoeba sp&lt;/I&gt;. CJY/S3 isolated from soil of Yanji city

18S rDNA genotyping of &lt;I&gt;Acanthamoeba sp&lt;/I&gt;. CJY/S3 isolated from soil of Yanji city

Hybridisation between the two major African schistosome species of humans

It is generally accepted that Schistosoma mansoni and Schistosoma haematobium, causing intestinal and urinary schistosomiasis, respectively, are not able to hybridise, due to the high phylogenetic distance between them. Cloning of nuclear internal transcribed spacer rDNA and partial mitochondrial cytochrome c oxidase 1 fragments revealed two internal transcribed spacer rDNA genotypes within single eggs and miracidia, one identical to S. mansoni and the other identical to S. haematobium, suggesting hybrid ancestry. The cytochrome c oxidase 1 clones always belonged to only one of the parental species. This demonstrates that offspring of heterologous pairing between these two species is not (always) parthenogenetic.