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21.
对贵阳地区碳酸盐岩表生地衣资源进行初步调查,鉴定出4科,4属,共计7个种。其中两个是中国新记录种,即:蓝藻橙衣和石灰瓶口衣。瓶口衣属、黄烛衣属、凹盘衣属以及该文所描述的7个种都是贵州首次报道。对壳状地衣体在碳酸盐岩风化过程中的作用进行了初步分析。 相似文献
22.
Guadalupe Albarrán Kenneth E. Collins Carol H. Collins 《Journal of molecular evolution》1987,25(1):12-14
Summary Calcium carbonate labeled with carbon-14 was self-irradiated by means of the -decay of its carbon-14. A number of products containing one or two carbon atoms were identified by high performance liquid chromatography. Formic and oxalic acids were produced in relatively high yields, while glyoxylic, glycolic, and acetic acids, as well as formaldehyde and methanol, were formed in lower yields. These results support the suggestion that carbonates subjected to ionizing radiation could have been a source of carbon for organic synthesis on the primitive earth. 相似文献
23.
24.
Juliet Y. F. Ramey-Lariviere Jian Gong Matthew J. Baldes Nilanjan Chatterjee Tanja Bosak Sara B. Pruss 《Geobiology》2023,21(5):629-643
Marine ooids have formed in microbially colonized environments for billions of years, but the microbial contributions to mineral formation in ooids continue to be debated. Here we provide evidence of these contributions in ooids from Carbla Beach, Shark Bay, Western Australia. Dark 100–240 μm diameter ooids from Carbla Beach contain two different carbonate minerals. These ooids have 50–100 μm-diameter dark nuclei that contain aragonite, amorphous iron sulfide, detrital aluminosilicate grains and organic matter, and 10–20 μm-thick layers of high-Mg calcite that separate nuclei from aragonitic outer cortices. Raman spectroscopy indicates organic enrichments in the nuclei and high-Mg calcite layers. Synchrotron-based microfocused X-ray fluorescence mapping reveals high-Mg calcite layers and the presence of iron sulfides and detrital grains in the peloidal nuclei. Iron sulfide grains within the nuclei indicate past sulfate reduction in the presence of iron. The preservation of organic signals in and around high-Mg calcite layers and the absence of iron sulfide suggest that organics stabilized high-Mg calcite under less sulfidic conditions. Aragonitic cortices that surround the nuclei and Mg-calcite layers do not preserve microporosity, iron sulfide minerals nor organic enrichments, indicating growth under more oxidizing conditions. These morphological, compositional, and mineralogical signals of microbial processes in dark ooids from Shark Bay, Western Australia, record the formation of ooid nuclei and the accretion of magnesium-rich cortical layers in benthic, reducing, microbially colonized areas. 相似文献
25.
We performed a one-year study to determine the effects of on-site sewage disposal systems (OSDS, septic tanks) on the nutrient
relations of limestone groundwaters and nearshore surface waters of the Florida Keys. Monitor wells were installed on canal
residences with OSDS and a control site in the Key Deer National Wildlife Refuge on Big Pine Key. Groundwater and surface
water samples were collected monthly during 1987 and analyzed for concentrations of dissolved inorganic nitrogen (DIN = NOf3/sup- + NOf2/sup- + NH4/su+), soluble reactive phosphate (SRP), temperature and salinity.
Significant nutrient enrichment (up to 5000-fold) occurred in groundwaters contiguous to OSDS; DIN was enriched an average
of 400-fold and SRP some 70-fold compared to control groundwaters. Ammonium was the dominant nitrogenous species and its concentration
ranged from a low of 0.77 μM in control wells to 2.75 mM in OSDS-enriched groundwaters. Concentrations of nitrate plus nitrite
were also highly enriched and ranged from 0.05 μM in control wells to 2.89 mM in enriched groundwaters. Relative to DIN, concentrations
of SRP were low and ranged from 30 nM in control wells to 107 μM in enriched groundwaters. N : P ratios of enriched groundwaters
were consistently > 100 and increased with increasing distance from the OSDS, suggesting significant, but incomplete, adsorption
of SRP by subsurface flow through carbonate substrata.
Nutrient concentrations of groundwaters also varied seasonally and were approximately two-fold higher during the winter (DIN
= 1035 μM; SRP = 10.3 μM) compared to summer (DIN = 470 μM; SRP = 4.0 μM). In contrast, surface water nutrient concentrations
were two-fold higher during the summer (DIN = 5.0 μM; SRP = 0.50 μM) compared to winter (DIN = 2.5 μM; SRP = 0.15 μM).
Direct measurement of subsurface groundwater flow rate indicated that tides and increased groundwater recharge enhanced flow
some two-fold and six-fold, respectively. Accordingly, the observed seasonal coupling of OSDS-derived nutrients from groundwaters
to surface waters is maximum during summer because of seasonally maximum tides and increased hydraulic head during the summer
wet season. The yearly average benthic flux of anthropogenic DIN into contiguous canal surface waters is 55 mmol m-2 day-1, a value some five-fold greater than the highest rate of benthic N-fixation measured in carbonate-rich tropical marine waters. 相似文献
26.
Massimiliano Marvasi Lianne M. Casillas-Santiago Tania Henríquez 《Geomicrobiology journal》2017,34(8):722-728
The eftA gene in Bacillus subtilis has been suggested to be involved in the oxidation/reduction reactions during fatty acid metabolism. Interestingly etfA deletion in B. subtilis results in impairment in CaCO3 precipitation on the biofilm. Comparisons between the wild type B. subtilis 168 and its etfA mutant during in vitro CaCO3 crystal precipitation (calcite) revealed changes in phospholipids membrane composition with accumulation of up to 10% of anteiso-C17:0 and 11% iso-C17:0 long fatty acids. Ca2+ nucleation sites such as dipicolinic acid and teichoic acids seem to contribute to the CaCO3 precipitation. etfA mutant strain showed up to 40% less dipicolinic acid accumulation compared with B. subtilis 168, while a B. subtilis mutant impaired in teichoic acids synthesis was unable to precipitate CaCO3. In addition, B. subtilis etfA mutant exhibited acidity production leading to atypical flagella formation and inducing extensive lateral growth on the biofilm when grown on 1.4% agar. From the ecological point of view, this study shows a number of physiological aspects that are involved in CaCO3 organomineralization on biofilms. 相似文献
27.
Summary. When calcium carbonate crystals are formed in mulberry (Morus abla) idioblasts, they are deposited in newly formed cell wall sacs. The initial cytological events leading to cell wall sac formation
were observed in the distal end of young idioblasts and tentatively categorized into four stages. The first indication of
formation was the separation of the innermost cell wall layer from the cell wall, which is followed by the deposition of egg-shaped
polysaccharide on the inner cell wall surface. The size of the deposit area increased, while the thickness of the cell wall
significantly decreased during the next stage. Finally, the condensed cellulosic lamella was invaginated into the deposition
area, resulting in the formation of an elongated cell wall sac. The internal cell wall sac was composed of numerous fibers
with different morphologies. Application of gelatin-methenamine-silver staining allowed us to observe the spatial distribution
of cellulosic polysaccharides as electron-dense images.
Correspondence and reprints: Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo,
Kyoto 606-8585, Japan. 相似文献
28.
β-Galactosidase (EC: 3.2.1.23), one of the glycosidases detected in Erythrina indica seeds, was purified to 135 fold. Amongst the four major glycosidases detected β-galactosidase was found to be least glycosylated, and was not retained by Con-A CL Seralose affinity matrix. A homogenous preparation of the enzyme was obtained by ion-exchange chromatography, followed by gel filtration. The enzyme was found to be a dimmer with a molecular weight of 74 kDa and 78 kDa, by gel filtration and SDS-PAGE, respectively. The optimum pH and optimum temperature for enzyme activity were 4.4 and 50 °C, respectively. The enzyme showed a Km value of 2.6 mM and Vmax of 3.86 U/mg for p-nitrophenyl-β-D-galactopyranoside as substrate and was inhibited by Zn2+ and Hg2+. The enzyme activity was regulated by feed back inhibition as it was found to be inhibited by β-D-galactose. Chemical modification studies revealed involvement of tryptophan and histidine for enzyme activity. Involvement of tryptophan was also supported by fluorescence studies and one tryptophan was found to be present in the active site of β-galactosidase. Circular dichroism studies revealed 37% α helix, 27% β sheet and 38% random coil in the secondary structure of the purified enzyme. 相似文献
29.
Since the correlation between carbon dioxide (CO2) levels and global temperatures was established in the ice core records, quantifying the components of the global carbon
cycle has become a priority with a view to constraining models of the climate system. The marine carbonate budget is still
not adequately constrained and the quantitative significance of the calcareous green alga Halimeda still remains particularly poorly understood. Previously, it has been suggested that Halimeda bioherms on the shelf of the Great Barrier Reef may contain a volume of carbonate equal to or greater than that contained
within the shelf edge coral reefs. This study uses published datasets to test this hypothesis in the Northern Great Barrier
Reef (NGBR) province. It is estimated that Halimeda bioherms on the outer shelf of the NGBR contain at least as much (and up to four times more) CaCO3 sediment as the adjacent ribbon reef facies. Globally, if these findings are even only partially applicable, the contribution
of shallow water carbonate sediments to the global carbon budget based on coral reefs alone is currently substantially underestimated. 相似文献
30.
Use of carbonate extraction in analyzing moderately hydrophobic transmembrane proteins in the mitochondrial inner membrane 下载免费PDF全文
Hayoung Kim Salomé Calado Botelho Kwangjin Park Hyun Kim 《Protein science : a publication of the Protein Society》2015,24(12):2063-2069
Resistance to sodium carbonate extraction is regarded as a canonical way to distinguish integral membrane proteins (MPs) from other membrane‐associated proteins. However, it has been observed that carbonate extraction releases some mitochondrial integral MPs. Here, by analyzing both artificially designed and native mitochondrial inner MPs containing transmembrane domains (TMDs) of different hydrophobicities, we show that carbonate treatment can release moderately hydrophobic TMDs from the mitochondrial inner membrane. These results suggest that resistance and sensitivity to carbonate extraction may be interpreted with caution when analyzing the nature of mitochondrial inner MPs. 相似文献