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941.
A. B. Housh G. Powell S. Scott A. Anstaett A. Gerheart M. Benoit S. Waller A. Powell J. M. Guthrie B. Higgins S. L. Wilder M. J. Schueller R. A. Ferrieri 《The ISME journal》2021,15(5):1505
Iron (Fe), an essential element for plant growth, is abundant in soil but with low bioavailability. Thus, plants developed specialized mechanisms to sequester the element. Beneficial microbes have recently become a favored method to promote plant growth through increased uptake of essential micronutrients, like Fe, yet little is known of their mechanisms of action. Functional mutants of the epiphytic bacterium Azospirillum brasilense, a prolific grass-root colonizer, were used to examine mechanisms for promoting iron uptake in Zea mays. Mutants included HM053, FP10, and ipdC, which have varying capacities for biological nitrogen fixation and production of the plant hormone auxin. Using radioactive iron-59 tracing and inductively coupled plasma mass spectrometry, we documented significant differences in host uptake of Fe2+/3+ correlating with mutant biological function. Radioactive carbon-11, administered to plants as 11CO2, provided insights into shifts in host usage of ‘new’ carbon resources in the presence of these beneficial microbes. Of the mutants examined, HM053 exhibited the greatest influence on host Fe uptake with increased plant allocation of 11C-resources to roots where they were transformed and exuded as 11C-acidic substrates to aid in Fe-chelation, and increased C-11 partitioning into citric acid, nicotianamine and histidine to aid in the in situ translocation of Fe once assimilated.Subject terms: Plant sciences, Applied microbiology 相似文献
942.
943.
LUCIMEIRE A. DA SILVEIRA WEBER L. RIBEIRO KARIN KIRCHGATTER GERHARD WUNDERLICH HIROYUKI MATSUOKA KAZUYUKI TANABE MARCELO U. FERREIRA 《The Journal of eukaryotic microbiology》2001,48(4):433-439
ABSTRACT. The merozoite surface protein‐1 (MSP‐1) is a major vaccine candidate for the asexual blood stage of malaria. We examined both the extent of sequence diversity in block 17, the 3′end of Msp‐1 gene coding for a 19‐kDa polypeptide (MSP‐119) putatively involved in red blood cell binding, and the patterns of linkage disequilibrium between polymorphic sites throughout the Msp‐1 locus. The parasite population sample consisted of Plasmodium falciparum isolates collected between 1985 and 1998 in Rondônia. an area of hypoendemic malaria transmission in the southwestern Brazilian Amazon. Results were summarized as follows. (I) Seven block‐17 sequence variants or haplotypes were found among 130 isolates, including two new haplotypes (novel combinations of previously reported amino acid replacements), here named Brazil‐1 (E‐TSR‐F) and Brazil‐2 (Q‐TSR‐F). (2) As previously shown for other Msp‐1 polymorphisms, frequencies of block‐17 haplotypes displayed significant temporal variation. (3) Extensive linkage disequilibrium was demonstrated between neighboring dimorphic sites within block 17, as well as between polymorphisms at the 5′and 3′ends of Msp‐1 (map distance range: 3.83–4.99 kb). (4) The overall patterns of linkage disequilibrium within Msp‐1 remained stable over a period of nearly one decade, and examples of possible ‘epidemic’ expansion of parasites carrying particular Msp‐1 alleles were found in the 1980s and 1990s. These results are discussed in relation to the population biology of P. falciparum and the development of malaria vaccines based on MSP‐1. 相似文献
944.
MARIA C. BLASSIOLI‐MORAES DIEGO M. MAGALHÃES ANDREJ ČOKL RAÚL A. LAUMANN JOSEANE P. DA SILVA CLEONOR C. A. SILVA MIGUEL BORGES 《Physiological Entomology》2014,39(1):1-11
Vibrational communication is important for successful mating in various stink bugs species. The vibrational signals from males and females of Dichelops melacanthus Dallas (Hemiptera: Pentatomidae) are recorded from a nonresonant substrate (i.e. a loudspeaker membrane) to characterize the temporal and spectral properties of these vibrational signals, as well as on a resonant substrate (i.e. bean plants) to obtain information about how these signals are altered when they are transmitted through the plants. On the loudspeaker membrane, D. melacanthus males and females emit only one male or one female song, respectively. However, when the insects are placed on bean leaves, a more complex repertoire is recorded, with three different songs for each sex. The first female and male songs appear to have calling functions and the third male and female songs are emitted during courtship. The second female and male songs are emitted after the first song, although their functions in mating behaviour are not clear. The identified repertoire is similar to those of other Neotropical stink bugs, starting with songs 1 and 2 and developing into song 3. Frequency modulation is observed in the female songs recorded from the loudspeaker membrane and the plants. The signals recorded from plants present higher harmonic peaks compared with the signals recorded from the loudspeaker membrane. The presence of species and sex‐specific songs during mating confirms the important role of vibrational communication in mate location and recognition. The temporal and spectral characteristic signals are influenced by the substrate used to record the songs emitted by D. melacanthus. 相似文献
945.
Several studies have indicated that olfactory responses are impeded by
amiloride. Therefore, it was of interest to see whether, and if so which,
olfactory epithelial cellular compartments have amiloride- sensitive
structures. Using ultrastructural methods that involved rapid freezing,
freeze-substitution and low temperature embedding of olfactory epithelia,
this study shows that, in the rat, this tissue is immunoreactive to
antibodies against amiloride sensitive Na(+)- channels. However, microvilli
of olfactory supporting cells, as opposed to receptor cilia, contained most
of the immunoreactive sites. Apices from which the microvilli sprout and
receptor cell dendritic knobs had much less if any of the
amiloride-antibody binding sites. Using a direct ligand-binding
cytochemical method, this study also confirms earlier ones that showed that
olfactory receptor cell cilia have Na+, K(+)-ATPase. It is proposed that
supporting cell microvilli and the receptor cilia themselves have
mechanisms, different but likely complementary, that participate in
regulating the salt concentration around the receptor cell cilia. In this
way, both structures help to provide the ambient mucous environment for
receptor cells to function properly. This regulation of the salt
concentration of an ambient fluid environment is a function that the
olfactory epithelium shares with cells of transporting epithelia, such as
those of kidney.
相似文献
946.
Non-proliferating cells of Lactobacillus plantarum accumulated about 1.3 mug of pantothenic acid (PA) per milligram dry cells when placed in a phosphate-buffered solution containing glucose, NaCl, and PA for 21 h. Under the conditions applied for PA uptake, pH 7.5 and 38 degrees C, the accumulated PA existed almost exclusively in a bound form. Free PA was observed only occasionally and then at questionably significant levels. All bound PA was released quantitatively by enzyme hydrolysis with alkaline (intestinal) phosphatase. Chromatographic analysis coupled with differential microbiological analysis of cell extracts using Saccharomyces cerevisiae, Lactobacillus helveticus, and L. plantarum identified the accumulated PA as phosphopantothenic acid (P-PA). Assay of P-PA loaded cell extracts (devoid of free PA) by L. plantarum before and after alkaline phosphatase hydrolysis showed that the growth of this primary assay organism was stimulated by 8.3%. 相似文献
947.
Aim
Sodium acetate (NaAcetate) has received some attention as an alkalinizing agent and possible alternative energy source for the horse, however the effects of oral administration remain largely unknown. The present study used the physicochemical approach to characterize the changes in acid-base status occurring after oral NaAcetate/acetic acid (NAA) administration in horses. 相似文献948.
Objective To quantify the prevalence and characteristics of hardcore
smokers in England.Design Cross sectional survey.Setting Interview in respondents'' household.Participants 7766 adult cigarette smokers.Main outcome measures Hardcore smoking defined by four criteria
(less than a day without cigarettes in the past five years; no attempt to quit
in the past year; no desire to quit; no intention to quit), all of which had
to be satisfied.Results Some 16% of all smokers were categorised as hardcore.
Hardcore smoking was associated with nicotine dependence, socioeconomic
deprivation, and age, rising from 5% in young adults aged 16-24 to 30% in
those aged ≥ 65 years. Hardcore smokers displayed distinctive attitudes
towards and beliefs about smoking. In particular they were likely to deny that
smoking affected their health or would do so in the future. Prevalence of
hardcore smoking was almost four times higher than in California.Conclusion Hardcore smoking presents a serious challenge to public
health efforts to reduce the prevalence of smoking, but the proportion of
hardcore smokers does not necessarily increase as overall prevalence in a
population declines. More hardcore smokers could be persuaded to quit, but
this will require interventions that are targeted to the particular needs and
perceptions of both socially disadvantaged and older smokers. 相似文献
949.
J. L. Padilla-Gami?o T. M. Weatherby R. G. Waller R. D. Gates 《Coral reefs (Online)》2011,30(2):371-380
The majority of scleractinian corals are hermaphrodites that broadcast spawn their gametes separately or packaged as egg–sperm
bundles during spawning events that are timed to the lunar cycle. The egg–sperm bundle is an efficient way of transporting
gametes to the ocean surface where fertilization takes place, while minimizing sperm dilution and maximizing the opportunity
for gamete encounters during a spawning event. To date, there are few studies that focus on the formation and structure of
egg–sperm bundle. This study explores formation, ultrastructure, and longevity of the egg–sperm bundle in Montipora capitata, a major reef building coral in Hawai‘i. Our results show that the egg–sperm bundle is formed by a mucus layer secreted by
the oocytes. The sperm package is located at the center of each bundle, possibly reflecting the development of male and female
gametes in different mesenteries. Once the egg–sperm bundle has reached the ocean surface, it breaks open within 10–35 min,
depending on the environmental conditions (i.e., wind, water turbulence). Although the bundle has an ephemeral life span,
the formation of an egg–sperm bundle is a fundamental part of the reproductive process that could be strongly influenced by
climate change and deterioration of water quality (due to anthropogenic effects) and thus requires further investigation. 相似文献
950.