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21.
ABSTRACT. Nosema isolates from five lepidopteran forest defoliators, Nosema fumiferanae from spruce budworm, Choristoneura fumiferana ; a Nosema sp. from jack pine budworm, Choristoneura pinus pinus and western spruce budworm, Choristoneura occidentalis ( Nosema sp. CPP and Nosema sp. CO, respectively); Nosema thomsoni from large aspen tortrix, Choristoneura conflictana ; and Nosema disstriae , from the forest tent caterpillar, Malacosoma disstria were compared based on their small subunit (SSU) ribosomal RNA (rRNA) gene sequences. Four of the species sequenced, N. fumiferanae , Nosema sp. CPP, Nosema sp. CO, and N . disstriae have a high SSU rDNA sequence identity (0.6%–1.5%) and are members of the "true Nosema " clade. They all showed the reverse arrangement of the (large subunit [LSU]–internal transcribed spacer [ITS]–SSU) of the rRNA gene. The fifth species, N. thomsoni has the usual (SSU–ITS–LSU) arrangement and is not a member of this clade showing only an 82% sequence similarity. We speculate, therefore, that a genetic reversal may have occurred in the common ancestor to the "true Nosema " clade. Although, the mechanism for rearrangement of the rRNA gene subunits is not known we provide a possible explanation for the localization. N. fumiferanae , Nosema sp. CPP, and Nosema sp. CO clustered together on the inferred phylogenetic tree. The high sequence similarities, the reverse arrangement in the rRNA gene subunits, and the phylogenetic clustering suggest that these three species are closely related but separate species. 相似文献
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D. Nathan Jackson Bailey Davis Sandra M. Tirado Megha Duggal Jessica K. van Frankenhuyzen Deanna Deaville M. A. K. Wijesinghe Michael Tessaro J. T. Trevors 《Antonie van Leeuwenhoek》2009,96(4):377-394
Culture-based isolation and enumeration of bacterial human pathogens from environmental and human food samples has significant
limitations. Many pathogens enter a viable but non-culturable (VBNC) state in response to stress, and cannot be detected via
culturing methods. Favourable growth conditions with a source of energy and an ideal stoichiometric ratio of carbon to inorganic
elements can reverse this VBNC state. This review will focus on the bacterium Campylobacter jejuni which is a leading cause of food borne illness in the developed world. C. jejuni can enter a VBNC state in response to extremes in: pH, moisture content, temperature, nutrient content and salinity. Once
in a VBNC state, the organism must maintain an energy balance from substrate oxidation through respiration to grow, divide
and remain viable. The goal of this review is a greater understanding of how abiotic stress and thermodynamics influence the
viability of C. jejuni. 相似文献
24.
The evolution of clinal variation has become a topic widely studied for invasive species. Most studies of this kind have found
significant correlations between latitude and various plant traits, usually using univariate analytic methods. However, plants
are composed of multiple, interacting traits, and it is this correlation among traits that can affect how quickly or even
whether the populations of invasive plants adapt to their local climatic conditions. We used data from a common garden experiment
to determine the possible formation of latitudinal clines in invasive North American populations of Lythrum salicaria L. (purple loosestrife) from the central portion of its invasive range. Analyses were conducted using the more common univariate
approach (nested and oneway ANOVAs; linear regression) on individual plant traits (e.g., time to flowering, plant height,
various mass measures, and growth rate) and then a multivariate approach (principle components analysis followed by redundancy
analysis). Significant among-population differences (P < 0.01) were noted when using both the nested and oneway ANOVAs, and multivariate techniques. However, there were no significant
relationships between individual plants traits to latitude when using linear regressions, most likely as a result of the small
number of populations used in the study (n = 4). On the contrary, the multivariate analyses showed a significant effect of latitude (P < 0.001) on the invasive populations, but this explained only 4% of the variance; latitude explained 8% of the variance when
both invasive and native populations were analyzed. Because of the integrated nature of plant phenotypes, a multivariate approach
should provide a clearer and deeper understanding of population responses to changing conditions than univariate techniques. 相似文献
25.
van Frankenhuyzen K Ryall K Liu Y Meating J Bolan P Scarr T 《Journal of invertebrate pathology》2011,108(3):201-208
Microsporidia are believed to play little or no role in outbreaks of the jack pine budworm, Choristoneura pinuspinus Freeman (Lepidoptrera: Tortricidae), because the short duration (2–4 years) of those outbreaks may not permit significant build-up of the pathogen. We conducted the first survey of Nosema sp. (Microsporidia: Nosematidae) over the course of a recent jack pine budworm outbreak in Ontario. Between 2004 and 2010 the outbreak defoliated a cumulative total of 1.78 million ha. Microscopic examination of ∼15,000 overwintering larvae collected over 6 years in sites with densities of 3 larvae per branch or more revealed widespread occurrence of Nosema at generally high infection intensities. The pathogen was present in 69.5% of the 518 plots that were monitored. Prevalence of infection was generally low (below 40% in 84% of plots with infected larvae) but reached high levels (80–95%) locally and increased rapidly in most infestations within 1–2 years of onset. We hypothesize that the habit of early-instar larvae to feed on developing male flowers (pollen cones) after spring emergence is critical in allowing rapid build-up of Nosema by increasing efficiency of horizontal transmission (higher density of both infected larvae and egested spores). Nosema infection may contribute to the complexity of jack pine budworm outbreak patterns by affecting egg recruitment and early-instar survival at the stand level in concert with known effects of budworm-induced reductions in pollen cone production on those processes. 相似文献
26.
Jan Pokorný Jan Květ Alžběta Rejšková Jakub Brom 《Journal of industrial microbiology & biotechnology》2010,37(12):1299-1305
Since wetlands are ecosystems that have an ample supply of water, they play an important role in the energy budgets of their
respective landscapes due to their capacity to shift energy fluxes in favor of latent heat. Rates of evapotranspiration in
wetlands are commonly as high as 6–15 mm day−1, testifying to the large amount of energy that is dissipated through this process. Emergent or semi-emergent wetland macrophytes
substantially influence the solar energy distribution due to their high capacity for transpiration. Wetland ecosystems in
eutrophic habitats show a high primary production of biomass because of the highly efficient use of solar energy in photosynthesis.
In wetlands associated with the slow decomposition of dead organic matter, such as oligotrophic marshes or fens and bogs,
the accumulation of biomass is also high, in spite of the rather low primary production of biomass. Most of the energy exchange
in water-saturated wetlands is, however, linked with heat balance, whereby the largest proportion of the incoming energy is
dissipated during the process of evapotranspiration. An example is shown of energy fluxes during the course of a day in the
wetland ecosystem of Mokré Louky (Wet Meadows) near Třeboň. The negative consequences of the loss of wetlands for the local
and regional climate are discussed. 相似文献
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Jan Květ 《Folia Geobotanica》2016,51(3):187-190
The late Dagmar Dykyjová (1914–2011), who is being honoured by this issue of Folia Geobotanica, was an excellent scientist as well as university teacher and research coordinator. Her research work stretched from both fundamental and applied plant physiology to the ecology of wetlands and wetland plants in particular, and to the ecology of Central European orchids. Apart from having authored, co-authored or edited numerous scientific publications, also including several books, she had great merits in popularizing a sensitive approach to environmental management, nature conservation and management of natural resources, based on up-to-date scientific knowledge. She played an important role in the Czechoslovak participation in the International Biological Programme (IBP, 1965–74), especially in the fields of plant production ecology and wetlands ecology. The history of her life and work is briefly outlined and evaluated (Fig. 1 ). 相似文献
30.
Maize mosaic and stunt, occurring to a considerable degree under Cuban field conditions, was determined as a virus disease, transmissible by the corn planthopperPeregrinus maidis Ashm. Negative results were obtained in the experiments in which aphidsRhopalosiphum maidis Fitch, served as vectors or when transmission was realized mechanically using the sap of infected plants. The incubation period in the infected plants fluctuated between 15 and 27 days. Besides maize, the virus disease could be transmitted also to sorghum(Sorghum vulgare Pees.) and to weed plants of the grassRottboellia exaltata L. It follows from the results that the disease concerned is identical with virus stripe, described in 1927 in Cuba by Stahl as corn stripe (raya del maiz). Under field conditions the disease spread fluctuated in average from 3.4 to 46 per cent of inflected plants. Plant communities concentrated on larger areas which received good agro technique and chemical protection against pests exhibited lower infection for the most part The most suitable time for the determination of spread and infection intensity under field conditions is that shortly before and during flowering of maize. 相似文献