Comparison of the nucleotide sequences of wheat dwarf virus (WDV) isolates from Hungary and Ukraine

Wheat dwarf virus (WDV) is the most ubiquitous virus in cereals causing huge losses in both Hungary and Ukraine. The presence of barley-and wheat-adapted strains has been confirmed, suggesting that the barley strain is restricted to barley, while the wheat strain is present in both wheat and barley plants. Five WDV isolates from wheat plants sampled in Hungary and Ukraine were sequenced and compared with known WDV isolates from GenBank. Four WDV isolates belonged to the wheat strain. Our results indicate that WDV-Odessa is an isolate of special interest since it has originated from wheat, but belongs to the barley-adapted strain, providing novel data on WDV biology and raising issues of pathogen epidemiology.     

Heavy metal soil contamination delays the appearance of virus-induced symptoms on potato but favours virus accumulation

Abstract

Here we report on the investigation of virus infection development in plants undergoing simultaneous heavy metal stress. We carried out small-scale field experiments using model system Potato virus X (PVX) – Solanum tuberosum cv. Povin' (potato) plants. Heavy metals zinc (Zn), copper (Cu) and lead (Pb) were added to the soil separately (monometal contamination) at a range of concentrations. Our results show that heavy metal stress significantly delays the appearance and potentiates severity of virus-specific symptoms on infected potato plants. We also demonstrate that PVX content in plants may increase tremendously in response to this abiotic stressor. Finally, we provide links to the possible consequences in the context of virus epidemiology.     

The Hydrogenase Chip: a tiling oligonucleotide DNA microarray technique for characterizing hydrogen-producing and -consuming microbes in microbial communities

We developed a broad-ranging method for identifying key hydrogen-producing and consuming microorganisms through analysis of hydrogenase gene content and expression in complex anaerobic microbial communities. The method is based on a tiling hydrogenase gene oligonucleotide DNA microarray (Hydrogenase Chip), which implements a high number of probes per gene by tiling probe sequences across genes of interest at 1.67 × –2 × coverage. This design favors the avoidance of false positive gene identification in samples of DNA or RNA extracted from complex microbial communities. We applied this technique to interrogate interspecies hydrogen transfer in complex communities in (i) lab-scale reductive dehalogenating microcosms enabling us to delineate key H₂-consuming microorganisms, and (ii) hydrogen-generating microbial mats where we found evidence for significant H₂ production by cyanobacteria. Independent quantitative PCR analysis on selected hydrogenase genes showed that this Hydrogenase Chip technique is semiquantitative. We also determined that as microbial community complexity increases, specificity must be traded for sensitivity in analyzing data from tiling DNA microarrays.     

Production of neosolaniol monoacetate by an undescribedFusarium species resemblingF camptoceras

Cultures of 12 South African isolates of an undescribedFusarium species resembling but distinct fromF camptoceras were analysed for the presence of diacetoxyscirpenol (DAS), neosolaniol monoacetate (NMA), and T-2 toxin, by capillary gas chromatography utilizing electron capture detection. No DAS or T-2 toxin could be detected in any of the cultures of the isolates. NMA was, however, detected in 10 of the 12 isolates at levels ranging from 310 to 2060 ng/g. The method used, was primarily developed for the determination of DAS and T-2 toxin in fungal cultures and grain samples but was found to be suitable for the coextraction of NMA at an average recovery of 80.8%, with a detection limit in the order of 100 ng/g. Supportive evidence for the presence of the NMA was obtained by capillary gas chromatography / mass spectrometry. Regarded as a relatively rare trichothecene, NMA has never been reported to occur naturally and has previously been shown to be produced by only a fewFusarium strains.     

The sensitivity of Afromontane tarns in the Maloti-Drakensberg region of South Africa and Lesotho to acidic deposition

Despite their remoteness from sources of atmospheric pollutant emissions, the Afromontane tarns in the Maloti-Drakensberg region are perfect candidates to study the negative effects of acidifying atmospheric pollution, because mountain lakes are widely recognised as sentinel ecosystems, unimpacted by direct human disturbance within their catchments. Thirty-four tarns were sampled in the Maloti-Drakensberg region and most were found to be extremely sensitive to acidic deposition, as indicated by their low acid neutralising capacity. There are very few studies of freshwater critical loads for any region within South Africa. The steady-state water chemistry model (SSWC) was adapted and used to determine critical loads, whereas exceedance was estimated relative to modelled regional deposition data, in order to understand the risk of harmful effects to aquatic ecosystems. Seventy-six percent of sampled sites across the Maloti-Drakensberg would exceed critical loads even at the lowest modelled deposition levels, but there are no current measured deposition data for the region. The sensitivity of the Maloti-Drakensberg tarns needs to be considered in future policy formulation regarding acceptable levels of acidifying atmospheric pollution from South Africa’s energy sector and indicates the need for assessing aquatic ecosystem impacts in other regions of South Africa.     

Telomeres and seed banks

We have found that a progressive loss of telomeric sequences occurs in high molecular weight DNA with an increasing appearance at a low molecular weight as the period of storage in the dry state was extended in time to provide seed germination loss from 98 to 0%. Telomere distribution would appear to follow the general pattern of DNA random fragmentation, which occurs in the embryos of seeds stored in a dry state; however, there are also indications of an overall telomere loss from DNA as a consequence of storage. There is a need for a convenient quality marker for the seeds that can be monitored over time. Having reviewed the implications of our results very carefully, we believe that there is considerable potential for the use of telomere sequences to mark the embryo ageing of seeds held in seed banks. The text was submitted by the authors in English.     

Antimicrobial susceptibility patterns,emm type distribution and genetic diversity of Streptococcus pyogenes recovered in Brazil

Streptococcus pyogenes is responsible for a variety of infectious diseases and immunological complications. In this study, 91 isolates of S. pyogenes recovered from oropharynx secretions were submitted to antimicrobial susceptibility testing, emm typing and pulsed-field gel electrophoresis (PFGE) analysis. All isolates were susceptible to ceftriaxone, levofloxacin, penicillin G and vancomycin. Resistance to erythromycin and clindamycin was 15.4%, which is higher than previous reports from this area, while 20.9% of the isolates were not susceptible to tetracycline. The macrolide resistance phenotypes were cMLSB (10) and iMLSB (4). The ermB gene was predominant, followed by the ermA gene. Thirty-two emm types and subtypes were found, but five (emm1, emm4, emm12, emm22, emm81) were detected in 48% of the isolates. Three new emm subtypes were identified (emm1.74, emm58.14, emm76.7). There was a strong association between emm type and PFGE clustering. A variety of PFGE profiles as well as emm types were found among tetracycline and erythromycin-resistant isolates, demonstrating that antimicrobial resistant strains do not result from the expansion of one or a few clones. This study provides epidemiological data that contribute to the development of suitable strategies for the prevention and treatment of such infections in a poorly studied area.