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排序方式: 共有277条查询结果,搜索用时 267 毫秒
11.
Christopher P. McKay 《Plant biosystems》2013,147(3):359-368
Abstract There is evidence that at one time Mars had liquid water habitats on its surface. Studies of microbial communities in cold and dry environments on the Earth provide a basis for discussion of the possible nature of any life that may have existed on Mars during that time. Of particular relevance are the cyanobacterial communities found in hypolithic and endolithic habitats in deserts. Microbial mats found under ice-covered lakes provide an additional possible Martian system. Results obtained from these field studies can be used to guide the search for fossil evidence of life on Mars. It is possible that in the future life will be reintroduced on Mars in an effort to restore that planet to habitable conditions. In this case the organisms under study as exemplars of past life may provide the hardy stock of pioneering Martian organisms. These first organisms must be followed by plants. The feasibility of reviving Mars will depend on the ability of plants to grow in an abundance of CO2 but at extremely low pressures, temperatures, O2, and N2 levels. On Mars, biology was, and is, destiny. 相似文献
12.
The dearth of new antibiotics and escalating emergence of multidrug resistant bacteria have created a global healthcare crisis and highlight the drastic need for novel antimicrobial agents. Complementary and alternative strategies including the investigation of ancient medicinals could address this problem. Natural clay minerals with a long history of medicinal and biomedical applications have become an interest due to their broad-spectrum antimicrobial activity. Such untapped natural sources may provide new therapeutic agents in the battle against infectious diseases in the post-antibiotic era. 相似文献
13.
Shaphan Y. Chia Chrysantus M. Tanga Isaac M. Osuga Xavier Cheseto Sunday Ekesi Marcel Dicke Joop J.A. van Loon 《Entomologia Experimentalis et Applicata》2020,168(6-7):472-481
Black soldier fly (BSF) larvae, Hermetia illucens L. (Diptera: Stratiomyidae), bio-convert organic side streams into high-quality biomass, the composition of which largely depends on the side stream used. In the present study, BSF larvae were reared on feed substrates composed of dried brewers’ spent grains, each supplemented with either water, waste brewer’s yeast, or a mixture of waste brewer’s yeast and cane molasses to obtain 12 different substrates: barley/water, barley/yeast, barley/yeast/molasses, malted barley/water, malted barley/yeast, malted barley/yeast/molasses, malted corn/water, malted corn/yeast, malted corn/yeast/molasses, sorghum-barley/water, sorghum-barley/yeast, and sorghum-barley/yeast/molasses. The crude protein, fat, ash, and mineral contents of the BSF larvae fed each feed substrate were quantified by chemical analyses. The effect of substrate, supplementation, and their interaction on crude protein, fat, and ash contents of BSF larval body composition was significant. Calcium, phosphorus, and potassium were the most abundant macrominerals in the larvae and their concentrations differed significantly among substrates. These findings provide important information to support the use of BSF larval meal as potential new source of nutrient-rich and sustainable animal feed ingredients to substitute expensive and scarce protein sources such as fishmeal and soya bean meal. 相似文献
14.
To obtain a fundamental understanding of the population behaviour of Acidithiobacillus ferrooxidans at chalcopyrite and pyrite surfaces, the early stage attachment behaviour and biofilm formation by this bacterium on chalcopyrite (CuFeS2) and pyrite (FeS2) were studied by optical microscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The results indicate there was no significant difference in selectivity of bacterial attachment between chalcopyrite and pyrite. However, the result of ToF-SIMS analysis suggests that the surface of the pyrite was covered more extensively by biofilm than that of the chalcopyrite, which may indicate more extracellular polymeric substances (EPS) formation by bacterial cells growing on pyrite. EBSD and optical image analysis indicated that selectivity of bacterial attachment to chalcopyrite was not significantly affected by crystal orientation. The results also suggest that the bacterial population in defective areas of chalcopyrite was significantly higher than on the polished surfaces. 相似文献
15.
《Archives of animal nutrition》2013,67(2):151-156
Abstract Browse tree leaves of six species of Acacia (A. angustissima L., A. drepanolobium L., A. nilotica L., A. polyacantha L., A. senegal L., A. tortilis L.) were screened for chemical composition, including minerals and trace elements. Crude protein (CP) varied among the species from 145 (A. senegal) to 229 g/kg DM (A. angustissima). The species had moderate to high levels of minerals. The concentrations of Ca, P, Mg and S varied among the species from 14.6 – 31.5, 3.5 – 4.9, 1.4 – 3.0 and 1.7 – 2.8 g/kg DM, respectively. The forages showed relatively low concentrations of trace elements. Content of trace elements varied among the species from 4.5 – 23.8, 99.4 – 173.6, 146.2 – 432, 41.0 – 90.1, 10.9 – 22.2 and 0.05 – 0.65 mg/kg DM for Cu, Mo, Fe, Mn, Zn and Co, respectively. All leaves of browse species would meet the normal requirements for Ca, P, Mg and S in ruminants, although some species had higher levels of Ca than tabulated mineral requirements in livestock. Assayed Cu, Mn, Zn and Co would satisfy the lower range of recommended requirements of trace elements depending on their bioavailability. Therefore, browse leaves from Acacias could form good sources of CP and mineral supplements to ruminants. 相似文献
16.
Charles J. Mason Ken Keefover‐Ring Caterina Villari Jennifer G. Klutsch Stephen Cook Pierluigi Bonello Nadir Erbilgin Kenneth F. Raffa Philip A. Townsend 《Plant, cell & environment》2019,42(2):633-646
Conifers possess chemical and anatomical defences against tree‐killing bark beetles that feed in their phloem. Resins accumulating at attack sites can delay and entomb beetles while toxins reach lethal levels. Trees with high concentrations of metabolites active against bark beetle‐microbial complexes, and more extensive resin ducts, achieve greater survival. It is unknown if and how conifers integrate chemical and anatomical components of defence or how these capabilities vary with historical exposure. We compared linkages between phloem chemistry and tree ring anatomy of two mountain pine beetle hosts. Lodgepole pine, a mid‐elevation species, has had extensive, continual contact with this herbivore, whereas high‐elevation whitebark pines have historically had intermittent exposure that is increasing with warming climate. Lodgepole pine had more and larger resin ducts. In both species, anatomical defences were positively related to tree growth and nutrients. Within‐tree constitutive and induced concentrations of compounds bioactive against bark beetles and symbionts were largely unrelated to resin duct abundance and size. Fewer anatomical defences in the semi‐naïve compared with the continually exposed host concurs with directional differences in chemical defences. Partially uncoupling chemical and morphological antiherbivore traits may enable trees to confront beetles with more diverse defence permutations that interact to resist attack. 相似文献
17.
With the goal of developing a defined medium for the production of desiccation-tolerant blastospores of the bioinsecticidal
fungus Paecilomyces fumosoroseus, we evaluated the impact of various media components such as amino acids, carbohydrates, trace metals and vitamins on hyphal
growth and sporulation of P. fumosoroseus cultures and on the freeze-drying tolerance of blastospores produced under these conditions. A comparison of 13 amino acids
as sole nitrogen sources showed that glutamate, aspartate, glycine and arginine supported biomass accumulations (12–16 mg ml−1) and blastospore yields (6–11 × 108 blastospores ml−1) comparable to our standard production medium which contains casamino acids as the nitrogen source. Using glutamate as the
sole nitrogen source, tests with various carbohydrates showed that P. fumosoroseus grew best on glucose (18.8 mg biomass ml−1) but produced similar blastospore concentrations (7.3–11.0 × 108) when grown with glucose, glycerol, fructose or sucrose. P. fumosoroseus cultures grown in media with sodium citrate or galactose as the sole carbohydrate produced lower blastospore concentrations
but more-desiccation-tolerant spores. Zinc was the only trace metal tested that was required for optimal growth and sporulation.
In a defined medium with glutamate as the nitrogen source, vitamins were unnecessary for P. fumosoroseus growth or sporulation. When blastospores were freeze-dried in the absence of a suspension medium, residual glucose (>2.5%
w/v) was required for enhanced spore survival. Thus, a defined medium containing basal salts, glucose, glutamate and zinc
can be used to produce optimal concentrations of desiccation-tolerant blastospores of P. fumosoroseus.
Received 27 October 1998/ Accepted in revised form 06 May 1999 相似文献
18.
Twenty-seven infants with classical phenylketonuria were evaluated longitudinally for 6 mo while ingesting PhenexTM -1 Amino Acid Modified Medical Food With Iron as their primary protein source. Intake of selected nutrients and biochemical
indices of trace and ultratrace mineral status and plasma retinol and α-tocopherol concentrations were evaluated. The means
of iron status indices (complete blood count, plasma ferritin, iron, transferrin saturation, total iron binding capacity)
and the plasma concentrations of trace and ultratrace minerals (copper, manganese, molybdenum, selenium, zinc) and plasma
retinol and α-tocopherol were in the reference ranges. Vitamin A intakes (r = 0.49,p < 0.05) and plasma retinol-binding protein concentrations (r = 0.42,p < 0.05) were positively correlated with plasma retinol concentrations at 3 mo of study. At 6 mo, concentrations of plasma
transthyretin (r = 0.72,p < 0.01) and retinolbinding protein (r = 0.48,p < 0.05) were positively correlated with plasma retinol concentrations. At 6 mo, concentrations of plasma transthyretin (r = 0.52,p < 0.05) were positively correlated with retinol-binding protein concentrations. Phenex-1 supports normal mean iron status
indices and mean concentrations of trace and ultratrace minerals, retinol, and α-tocopherol when fed in adequate amounts. 相似文献
19.
Two experiments were conducted using completely randomized designs to study the bioavailability of Si from three sources to
growing rats and turkeys fed semipurified diets. The basal diets were dextrose-egg albumin for rats and dextrose-casein for
turkeys. The Si sources were tetraethylorthosilicate (TES), sodium silicate (NaSil), and sodium zeolite A (NaZA). Rats and
turkeys were supplemented at 500 and 270 ppm Si, respectively, from each source. A control group of unsupplemented rats and
turkeys was included in each experiment. In general, irrespective of Si source, Si supplementation slowed (p < 0.05 orp < 0.01) growth rates in both rats and turkeys. Although dietary Si supplementation reduced (p < 0.05) plasma Mg levels and liver Zn concentrations in rats, it increased (p < 0.05) plasma P and reduced (p < 0.05) plasma Cu levels in turkeys. Rats on TES had significantly slower (p < 0.05 orp < 0.01) growth rates (5–10%) than those on NaSil or NaZA. In rats, NaZA and TES reduced (p < 0.05) hemoglobin concentrations and plasma Zn, respectively. However, plasma Mg levels were higher (p < 0.05) in TES than
NaSil-or NaZA-fed rats. The source of the dietary Si did not affect (p < 0.05) the organ weights of rats and their mineral concentrations. Turkeys on TES diets grew at a significantly faster (p < 0.05) rate (15%) than those on NaSil or NaZA diets during the first 2 wk of experimentation. However, after 4 wk, there were
no significant (p > 0.05) differences in growth between the Si sources. In turkeys, NaZA increased (p < 0.05) hematocrit levels and plasma Mg levels. Turkeys on NaZA diets had larger (p < 0.05) hearts and livers than those on
NaSil but not TES. Liver Mn content was higher (p < 0.05) in turkeys on NaSil than TES or NaZA. Heart Zn was lower (p < 0.05) in turkeys on NaSil than TES, but not NaZA. 相似文献
20.
Friel JK Andrews WL Jackson SE Longerich HP Mercer C McDonald A Dawson B Sutradhar B 《Biological trace element research》1999,67(3):225-247
To examine longitudinal and gestational effects of mineral content in human milk, we analyzed human milk from lactating mothers
of premature (PRT,n = 24, < 2000g birth weight, < 37 wk gestation) and fullterm (FT,n = 19, > 2500g, 39–41 wk gestation), living in Newfoundland, Canada. Samples were collected once a week for 8 wk with one final sample collected
at 3 mo. Milk samples collected in acid-washed containers were wet ashed with concentrated HNO3, and barium, cadmium, calcium, cesium, cobalt, copper, cerium, lanthanum, magnesium, manganese, molybdenum, nickel, lead,
rubidium, tin, strontium, and zinc were measured using inductively coupled plasma-mass spectrometry. Data were analyzed using
standard multiple-regression procedures with correlated data analyses to take account of the relationship between successive
weeks. Results indicated lower Ca and Pb in PRT milk. Calcium was the only nutritionally significant element to differ between
groups. Molybdenum in both PRT and FT milk showed a definite decrease with time, suggesting that the Mo content in milk is
homeostatically regulated. However, Ce, La, Ba, and Sn did not display any pattern indicative of biological regulation and
potential human requirement. 相似文献