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Whitford, W.G,Mun, H.T 公州大學校 基礎科學硏究所 1998 自然科學硏究 Vol.7 No.-
We studied the spatial and temporal patterns of lecomposrtion of roots of a desert sub-shrub, a herbaceous mnual. and four species of perennial grasses at several loarions on nitrogen fertilized and unfertilized transects on a Chihuahuan Desert watershed for 3.5 years. There were few significant differences between the decomposition stes of roots on the NH4NO3 fertilized and unfertilized ransects. Decomposition of all roots followed a two-phase pattern: early rapid mass loss followed by a long period of blow mass loss. Rates of decomposition were negatively pxmelated with the initial lignin content of the roots (r=0.90). Mass loss rates of the roots of the herbaceous annual, Baileya multiradiata, were significantly higher than those of the grasses and the shrub, probably as a result of subterranean termites feeding on B. multiradiata root material. The only location where mass loss rates were significantly different was the dry lake bed, where mass loss rates were lower than those recorded on the upper watershed. The spatial differences in mass loss rates in the dry lake were attributable to the high clay content of the soils, which reduced water availability, and to the absence of termites. Non-polar substances in decomposing roots decreased rapidly during the first year, then decreased at a low but fairly constant rate. Water-soluble compounds decreased rapidly (50-60% of initial concentration) during the first 3-6 months. Lignin concentrations of roots of perennial grasses were higher than those of herbaceous annual plants and woody shrubs. Lignin concentrations increased in all species during decomposition. The chemical changes in decomposing roots followed the patterns described for decomposing litter in mesic environments.
Highly efficient DSB-free base editing for streptomycetes with CRISPR-BEST
Tong, Yaojun,Whitford, Christopher M.,Robertsen, Helene L.,Blin, Kai,Jørgensen, Tue S.,Klitgaard, Andreas K.,Gren, Tetiana,Jiang, Xinglin,Weber, Tilmann,Lee, Sang Yup National Academy of Sciences 2019 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.116 No.41
<P><B>Significance</B></P><P>Although CRISPR-Cas9 tools dramatically simplified the genetic manipulation of actinomycetes, significant concerns of genome instability caused by the DNA double-strand breaks (DSBs) and common off-target effects remain. To address these concerns, we developed CRISPR-BEST, a DSB-free and high-fidelity single-nucleotide–resolution base editing system for streptomycetes and validated its use by determining editing properties and genome-wide off-target effects. Furthermore, our CRISPR-BEST toolkit supports Csy4-based multiplexing to target multiple genes of interest in parallel. We believe that our CRISPR-BEST approach is a significant improvement over existing genetic manipulation methods to engineer streptomycetes, especially for those strains that cannot be genome-edited using normal DSB-based genome editing systems, such as CRISPR-Cas9.</P><P>Streptomycetes serve as major producers of various pharmacologically and industrially important natural products. Although CRISPR-Cas9 systems have been developed for more robust genetic manipulations, concerns of genome instability caused by the DNA double-strand breaks (DSBs) and the toxicity of Cas9 remain. To overcome these limitations, here we report development of the DSB-free, single-nucleotide–resolution genome editing system CRISPR-BEST (CRISPR-Base Editing SysTem), which comprises a cytidine (CRISPR-cBEST) and an adenosine (CRISPR-aBEST) deaminase-based base editor. Specifically targeted by an sgRNA, CRISPR-cBEST can efficiently convert a C:G base pair to a T:A base pair and CRISPR-aBEST can convert an A:T base pair to a G:C base pair within a window of approximately 7 and 6 nucleotides, respectively. CRISPR-BEST was validated and successfully used in different <I>Streptomyces</I> species. Particularly in nonmodel actinomycete <I>Streptomyces collinus</I> Tu¨365, CRISPR-cBEST efficiently inactivated the 2 copies of <I>kirN</I> gene that are in the duplicated kirromycin biosynthetic pathways simultaneously by STOP codon introduction. Generating such a knockout mutant repeatedly failed using the conventional DSB-based CRISPR-Cas9. An unbiased, genome-wide off-target evaluation indicates the high fidelity and applicability of CRISPR-BEST. Furthermore, the system supports multiplexed editing with a single plasmid by providing a Csy4-based sgRNA processing machinery. To simplify the protospacer identification process, we also updated the CRISPy-web (https://crispy.secondarymetabolites.org), and now it allows designing sgRNAs specifically for CRISPR-BEST applications.</P>
문형태,W.G.Whitford 한국생태학회 1994 Journal of Ecology and Environment Vol.17 No.3
치화화 사막에서 몇 가지 식물 뿌리의 분해율과 분해 과정에 따른 질소함량의 변화를 조사하였다 (1986년 10월 ~ 1990년 4월). 뿌리의 분해는 리그닌 함량과 역상관 관계를 보였다(r=-0.84, n=5, p<0.05). 1년생 광엽초본인 Baileya multiradiata의 분해율이 가장 높았고 다년생 협엽 초본인 Panicum obtusum의 분해율이 가장 낮았다. 지역에 따른 분해율은 playa에서 가장 낮았다. Baileya multiradiata를 제외하고 모두 분해 초기에 질소의 무기화가 있은 다음 질소의 부동화가 나타났다. Baileya multirdiata의 뿌리는 분해 초기부터 질소함량이 계속 증가하는 것으로 나타났다. 다년생 협엽초본 뿌리의 리그닌 함량은 광엽초본 뿌리의 리그닌 함량보다 높았다. We examined spatial and temporal patterns of root decomposition for three and half years, from October 1986 to April 1990, in semi-arid Chihuahuan Desert. Decomposition of roots occurred in a two-phased pattern: an early period of rapid mass loss followed by a period of slower loss. The rate of root decomposition had a high negative correlation with the initial lignin concentration in roots (r=-0.84, p<0.05). Annual mass loss rate of Baileya multiradiata, a herbaceous annual, was the highest with the value of 0.60, while that of Panicum obtusum. a perennial grass which was restricted to playa, was the lowest with 0.13. The mass loss rate of roots in the playa was the lowest among the vegetation zones along the transect. After 42 months elapsed, fluffgrass roots in playa lost 40% of the initial mass, while in other sites it lost on average 55% of the initial mass. In all roots except for desert marigold, there was an initial release of nitrogen early in decomposition followed by net nitrogen immobilization. Nitrogen concentration of the desert marigold roots showed linear increase from the beginning. Lignin concentration of perennial grass roots were higher than those of herbaceous annual and woody perennial root.
( Ali Abdulnabi ),( David Whitford ),( Fathia Al Qurashi ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1
Background: Although the co-existence of diabetes mellitus and sickle cell disease has been shown to be rare, this has not been established in a population where both conditions are highly prevalent. Both diseases lead to life threatening cardiovascular complications and their relationship might be important in the prevention of cardiovascular disease. The aim of this study was to determine the prevalence of diabetes mellitus in patients with sickle cell disease in a country with a high prevalence of both disorders. Methods: A cross sectional prevalence study in Bahrain. A random sample of 520 patients aged 18 years and over was taken from all sickle cell disease patients admitted to Salmaniya Medical Complex between 2003 to 2010 (n=2204). Patients` files and laboratory records were examined for the presence of diabetes. Data was analysed using descriptive statistics and chi-squared tests of association. Results: 376 patients were included (mean age 33.5 years). 24/376 (6.4%) patients with sickle cell disease were determined to have diabetes. 32/376 (8.5%) patients had impaired glucose tolerance. The age/sex standardized prevalence of diabetes was 8.25%. There was no association between gender of the patients (χ2=1.5, df=2, p=0.47) or number of admissions (χ2=2.2, df=2, p=0.34) and the prevalence of diabetes. Conclusions: The prevalence of diabetes in patients with sickle cell disease in Bahrain is high at 8.25% but lower than expected in this population (15.3%). Lower life expectancy is excluded as an explanation for the lower prevalence of diabetes in sickle cell disease patients by age-standardization. There may be a protective effect of sickle cell disease towards developing diabetes. However, the impact of these two conditions on vascular disease suggests a need for screening and aggressive treatment of vascular risk factors in this population.