排序方式： 共有42条查询结果，搜索用时 15 毫秒
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Deirdre B. Gleeson Anke M. Herrmann Stephen J. Livesley Daniel V. Murphy 《Applied soil ecology》2008,40(1):189-194
The objective of this study was to examine the relationship between soil water potential, nitrifier community structure and nitrification activity in semiarid soils. Soils were collected after a 5-month dry period (end of summer) and subsequently rewetted to specific water potentials and incubated for 7 days prior to analysis of nitrification activity and nitrifier community structure. The approach used in this study targeted a 491bp segment of the amoA gene which encodes the active site of the ammonia monooxygenase enzyme, which is the key enzyme for all aerobic ammonia oxidisers. amoA serves as a useful target for environmental studies since it is both specific and universal for all ammonia oxidisers and reflects the phylogeny of the ammonia oxidisers. Our results suggest that in semiarid soils water potential plays a key role in determining the structure of ammonia oxidising bacteria (AOB), and that additionally AOB community structure is correlated to potential nitrification rate in these soils. 相似文献
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Kemner KM Kelly SD Lai B Maser J O'loughlin EJ Sholto-Douglas D Cai Z Schneegurt MA Kulpa CF Nealson KH 《Science (New York, N.Y.)》2004,306(5696):686-687
High-energy x-ray fluorescence measurements were used to make elemental maps and qualitative chemical analyses of individual Pseudomonas fluorescens strain NCIMB 11764 cells. Marked differences between planktonic and adhered cells were seen in the morphology, elemental composition, and sensitivity to Cr(VI) of hydrated cells at spatial scales of 150 nm. This technology can be applied to natural geomicrobiological systems. 相似文献
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Joy DA Feng X Mu J Furuya T Chotivanich K Krettli AU Ho M Wang A White NJ Suh E Beerli P Su XZ 《Science (New York, N.Y.)》2003,300(5617):318-321
The emergence of virulent Plasmodium falciparum in Africa within the past 6000 years as a result of a cascade of changes in human behavior and mosquito transmission has recently been hypothesized. Here, we provide genetic evidence for a sudden increase in the African malaria parasite population about 10,000 years ago, followed by migration to other regions on the basis of variation in 100 worldwide mitochondrial DNA sequences. However, both the world and some regional populations appear to be older (50,000 to 100,000 years old), suggesting an earlier wave of migration out of Africa, perhaps during the Pleistocene migration of human beings. 相似文献
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Jennifer L Doyle Deirdre C Purfield Tom Moore Tara R Carthy Siobhan W Walsh Roel F Veerkamp Ross D Evans Donagh P Berry 《Journal of animal science》2021,99(5)
Sexual dimorphism, the phenomenon whereby males and females of the same species are distinctive in some aspect of appearance or size, has previously been documented in cattle for traits such as growth rate and carcass merit using a quantitative genetics approach. No previous study in cattle has attempted to document sexual dimorphism at a genome level; therefore, the objective of the present study was to determine whether genomic regions associated with size and muscularity in cattle exhibited signs of sexual dimorphism. Analyses were undertaken on 10 linear-type traits that describe the muscular and skeletal characteristics of both males and females of five beef cattle breeds: 1,444 Angus (AA), 6,433 Charolais (CH), 1,129 Hereford, 8,745 Limousin (LM), and 1,698 Simmental. Genome-wide association analyses were undertaken using imputed whole-genome sequence data for each sex separately by breed. For each single-nucleotide polymorphism (SNP) that was segregating in both sexes, the difference between the allele substitution effect sizes for each sex, in each breed separately, was calculated. Suggestively (P ≤ 1 × 10−5) sexually dimorphic SNPs that were segregating in both males and females were detected for all traits in all breeds, although the location of these SNPs differed by both trait and breed. Significantly (P ≤ 1 × 10−8) dimorphic SNPs were detected in just three traits in the AA, seven traits in the CH, and three traits in the LM. The vast majority of all segregating autosomal SNPs (86% in AA to 94% in LM) had the same minor allele in both males and females. Differences (P ≤ 0.05) in allele frequencies between the sexes were observed for between 36% (LM) and 66% (AA) of the total autosomal SNPs that were segregating in both sexes. Dimorphic SNPs were located within a number of genes related to muscularity and/or size including the NAB1, COL5A2, and IWS1 genes on BTA2 that are located close to, and thought to be co-inherited with, the MSTN gene. Overall, sexual dimorphism exists in cattle at the genome level, but it is not consistent by either trait or breed. 相似文献
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Deirdre Cotter Vera O'Donovan Alan Drumm Nicola Roche E Nigel Ling & Noel P Wilkins 《Aquaculture Research》2002,33(1):43-53
The performance of all‐female diploid (AF2N) and triploid (AF3N) Atlantic salmon were compared in fresh water, under commercial production conditions in 1995 and 1996 year classes. The performance of the 1996 year class was also assessed for 14 months in a commercial sea farm. Freshwater mortality was higher in the triploid groups. The majority of losses occurred in the early stages of egg development and during the first feeding period, when the incidence of non‐feeding fry was consistently higher. In growth studies, although diploid fry were significantly heavier during first feeding there were no significant differences in weight between groups some 8 months after fertilization or in presmolt growth periods from February to April in 1996 and 1997. Smolting rates were high (range 93.5–95.3%) and the incidence of deformities was low (< 1%) in both groups. Marine survival was lower in the triploid group, largely as a consequence of higher losses sustained during a period of chronic stress, when triploid losses were 9% higher. Growth patterns were similar for the first 11 months in sea water. Although graded triploid salmon were heavier in January 1998 (AF3N 1.62 ± 0.033 kg, AF2N 1.46 ± 0.36 kg, P < 0.05), when the fish were harvested in May 1998 diploid salmon were significantly heavier than triploid salmon although there was no significant difference in weights after evisceration (AF3N 2.40 kg ± 0.04 AF2N 2.49 kg ±0.03). The increase in weight of the diploids between winter and harvest reflects the growth spurt that occurs in maturing fish in the spring. Overall yields of triploid salmon in salt water were lower as a result of inferior survival. 相似文献
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Plant cell walls within the human diet are compositionally heterogeneous, so defining the basis of nutritive properties is difficult. Using a pig fecal inoculum, in vitro fermentations of soluble forms of arabinoxylan, mixed-linkage glucan, and xyloglucan were compared with the same polymers incorporated into bacterial cellulose composites. Fermentation rates were highest and similar for the soluble polysaccharides. Cellulose composites incorporating those polysaccharides fermented more slowly and at similar rates to wheat bran. Bacterial cellulose and cotton fermented most slowly. Cellulose composite fermentation resulted in a different short-chain fatty acid profile, compared with soluble polysaccharides, with more butyrate and less propionate. The results suggest that physical form is more relevant than the chemistry of plant cell wall polysaccharides in determining both rate and end-products of fermentation using fecal bacteria. This work also establishes bacterial cellulose composites as a useful model system for the fermentation of complex cell wall dietary fiber. 相似文献