Relatedness of cytotoxins from geographically diverse isolates of Moraxella bovis     

Angelos JA  Ball LM 《Veterinary microbiology》2007,124(3-4):382-386

To determine whether amino acid sequence variation exists in the Moraxella bovis (M. bovis) cytotoxin (MbxA) from geographically diverse M. bovis isolated in the United States, mbxA was amplified and sequenced. The MbxA deduced amino acid sequence from M. bovis originally isolated in California, Washington, North Carolina, and Georgia, as well as reference strains of M. bovis isolated at the National Animal Disease Laboratory, Ames, IA, USA, all encoded a nearly identical 927 amino acid protein. MbxA from two of the four California isolates (SFS 9a and SFS 100a) differed from all other isolates at two sites at which the polar amino acids glutamine (position 666) and asparagine (position 823) were replaced by ionized amino acids glutamic acid and aspartic acid, respectively. Rabbit antiserum to the expressed carboxy terminus (amino acids 590-927) of MbxA from M. bovis (Tifton I) neutralized the hemolytic activity of SFS 9a and SFS 100a. The M. bovis cytotoxin appears to be conserved amongst geographically diverse isolates of M. bovis from the USA. Antiserum against the carboxy terminus of MbxA common to the majority of isolates neutralized the hemolytic activity of two strains with a divergent MbxA deduced amino acid sequence. Vaccines against IBK that incorporate MbxA as antigen may offer protection against geographically diverse strains of M. bovis.  相似文献   

A historical perspective on measurement of soil and plant water status and plant water status     

Walter H. Gardner 《Irrigation Science》1988,9(4):255-264

Summary Surrounded by many sophisticated instruments, data acquisition systems and connecting computers, contemporary soil and plant scientists may not fully appreciate what really was known in earlier times and how the science has developed. A short review and a few examples of the growth of measurements and ideas are presented here.  相似文献   

The Exploitation of Nematode-Responsive Plant Genes in Novel Nematode Control Methods     

Godelieve Gheysen  Walter Van der Eycken  Nathalie Barthels  Mansour Karimi  Marc Van Montagu 《Pest management science》1996,47(1):95-101

The molecular interactions between plants and sedentary nematodes are undergoing intense study, not only for reasons of fundamental research but also for the potential benefits to agriculture. The present technology allows the transformation of an increasing number of crop plants, providing new ways to introduce resistance against plant-parasitic nematodes. The ability of sedentary nematodes to induce specialized feeding sites in plant roots is one of the most fascinating aspects of this host–parasite interaction. Molecular approaches have been initiated to identify and characterize plant genes altered in expression after infection by sedentary nematodes. The results obtained indicate that many genes indeed become up-regulated upon nematode infection. Surprisingly, several so-called constitutive promoters that are normally used to achieve high expression in plant cells are completely ‘silenced’ in the feeding sites within days after nematode infection. Generally, there are two options available for the genetic engineering of nematode resistance: the synthesis of anti-nematode proteins or the localized production of a cytotoxic protein that interferes with the development of feeding cells. Nematode-induced promoters are very useful for the production by plants of sufficiently high levels of anti-nematode proteins at feeding sites. Alternatively, interfering with feeding-cell development is somewhat similar to the hypersensitive response evoked by nematodes in a naturally resistant plant. Here, destruction of specific plant cells can be achieved by the localized expression of a cytotoxin such as barnase, a potent ribonuclease. This approach, however, calls for a highly specific ‘non-leaky’ promoter, which is active only in the feeding cells. Another possibility is to use a two-component system, where the leakiness of the promoter in other tissues is counterbalanced by the constitutive expression of a neutralizing gene.  相似文献   

Enzyme Bioprospection of Marine-Derived Actinobacteria from the Chilean Coast and New Insight in the Mechanism of Keratin Degradation in Streptomyces sp. G11C     

Valentina Gonzlez  María Jos Vargas-Straube  Walter O. Beys-da-Silva  Luclia Santi  Pedro Valencia  Fabrizio Beltrametti  Beatriz Cmara 《Marine drugs》2020,18(11)

Marine actinobacteria are viewed as a promising source of enzymes with potential technological applications. They contribute to the turnover of complex biopolymers, such as pectin, lignocellulose, chitin, and keratin, being able to secrete a wide variety of extracellular enzymes. Among these, keratinases are a valuable alternative for recycling keratin-rich waste, which is generated in large quantities by the poultry industry. In this work, we explored the biocatalytic potential of 75 marine-derived actinobacterial strains, focusing mainly on the search for keratinases. A major part of the strains secreted industrially important enzymes, such as proteases, lipases, cellulases, amylases, and keratinases. Among these, we identified two streptomycete strains that presented great potential for recycling keratin wastes—Streptomyces sp. CHA1 and Streptomyces sp. G11C. Substrate concentration, incubation temperature, and, to a lesser extent, inoculum size were found to be important parameters that influenced the production of keratinolytic enzymes in both strains. In addition, proteomic analysis of culture broths from Streptomyces sp. G11C on turkey feathers showed a high abundance and diversity of peptidases, belonging mainly to the serine and metallo-superfamilies. Two proteases from families S08 and M06 were highly expressed. These results contributed to elucidate the mechanism of keratin degradation mediated by streptomycetes.  相似文献   

Mosquito repellent thermal stability,permeability and air volatility     

Antnio B Mapossa  Alcides Sitoe  Walter W Focke  Homa Izadi  Elizabeth L du Toit  Ren Androsch  Chanita Sungkapreecha  Elizabet M van der Merwe 《Pest management science》2020,76(3):1112-1120

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Management of yellow dwarf disease in Europe in a post‐neonicotinoid agriculture     

Louise Mc Namara  Kevin Gauthier  Lael Walsh  Gaël Thbaud  Michael Gaffney  Emmanuel Jacquot 《Pest management science》2020,76(7):2276-2285

Barley/cereal yellow dwarf viruses (YDVs) cause yellow dwarf disease (YDD), which is a continuous risk to cereals production worldwide. These viruses cause leaf yellowing and stunting, resulting in yield reductions of up to 80%. YDVs have been a consistent but low‐level problem in European cereal cultivation for the last three decades, mostly due to the availability of several effective insecticides (largely pyrethroids and more recently neonicotinoids) against aphid vectors. However, this has changed recently, with many insecticides being lost, culminating in a recent European Union (EU) regulation prohibiting outdoor use of the neonicotinoid‐insecticide compounds. This change is coupled with the growing challenge of insecticide‐resistant aphids, the lack of genetic resources against YDVs, and a knowledge deficit around the parameters responsible for the emergence and spread of YDD. This means that economic sustainability of cereal cultivation in several European countries including France and United Kingdom is now again threatened by this aphid‐vectored viral disease. In this review, we summarize the current knowledge on the YDV pathosystem, describe management options against YDD, analyse the impacts of the neonicotinoid ban in Europe, and consider future strategies to control YDV. © 2020 Society of Chemical Industry  相似文献   

Gene expression pattern of digestive and antioxidant enzymes during the larval development of reared Atlantic bluefin tuna (ABFT), Thunnus thynnus L.          下载免费PDF全文

David Mazurais  Denis Covès  Nikos Papandroulakis  Aurelio Ortega  Elisabeth Desbruyeres  Christine Huelvan  Marie Madeleine Le Gall  Fernando de la Gándara  Chantal Louise Cahu 《Aquaculture Research》2015,46(10):2323-2331

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Soybean molasses as an organic carbon source in the farming of Litopenaeus vannamei (Boone, 1931) in a biofloc system          下载免费PDF全文

Carlos Manoel do Espírito Santo  Isabela Claudiana Pinheiro  Gabriel Fernandes Alves de Jesus  José Luiz Pedreira Mouriño  Felipe do Nascimento Vieira  Walter Quadros Seiffert 《Aquaculture Research》2017,48(4):1827-1835

Soybean molasses was evaluated as a partial replacement for sugarcane molasses as a carbon source for biofloc development in the superintensive culture of Pacific white shrimp (Litopenaeus vannamei). A 50‐day study was conducted with juvenile (3.2 g) shrimp stocked in 16 800 L tanks at a stocking density of 250 shrimp m^?3. Control of total ammonia concentration was performed by the addition of combined mixtures of soybean and sugarcane molasses to the culture water. Three different molasses treatments were evaluated using different soybean‐to‐sugarcane molasses ratios: 15–85%, 38–62% and 60–40% respectively. The control group was treated only with sugarcane molasses. Water quality, chlorophyll a concentration, heterotrophic bacterial load, Vibrio spp. concentration and zootechnical indexes were all evaluated. Total ammonia concentration was controlled by heterotrophic and chemotrophic pathways. Biofloc formation, as quantified by measuring the total suspended solids, was not altered. The Vibrio spp. concentration showed a significant reduction in treatments with soybean‐to‐sugarcane molasses ratios of 38–62% and 60–40%. All combined mixtures of soybean and sugarcane molasses could maintain water quality and productivity in the superintensive culture of L. vannamei using the biofloc system. Thus, the potential use of a residue from agroindustry as a carbon source in a biofloc culture is demonstrated.  相似文献   

Environmental effects on soil NO concentrations and root N uptake in beech and spruce forests          下载免费PDF全文

Fang Dong  Judy Simon  Michael Rienks  Jürgen Schäffer  Klaus von Wilpert  Heinz Rennenberg 《植物养料与土壤学杂志》2016,179(2):244-256

This study aimed to investigate the shifts in net nitrogen (N) uptake and N compounds of fine roots over the vegetation period (i.e., spring, summer, autumn) and correlate this with NO concentration in the soil. Soil NO concentration was measured using gas lysimeters for collection and a chemiluminescence analyzer for quantification. Net N uptake by the roots was determined using the ¹⁵N enrichment technique. N pools were quantified using spectrophotometric techniques. Soil NO concentrations at beech and spruce forest sites were highest in spring (June), and lowest in winter (December). Total N of the roots was similar during the seasons and between the two years under study despite considerable variation of different N compounds. Net N uptake generally increased with higher N supply. Correlation analysis revealed a positive relationship between soil NO concentration and net N uptake only for spruce trees. This relationship seemed to be modulated by environmental factors and tree species.  相似文献   

Phosphate desorption from the surface of soil mineral particles by a phosphate-solubilizing fungus   总被引：1，自引：0，他引：1  

Nelson Walter Osorio  Mitiku Habte 《Biology and Fertility of Soils》2013,49(4):481-486

High phosphate (Pi) sorption in soils is a serious limiting factor for plant productivity and Pi fertilization efficiency, particularly in highly weathered and volcanic ash soils. In these soils, the sorbed Pi is so strongly held on the surfaces of reactive minerals that it is not available for plant root uptake. The use of phosphate-solubilizing microorganisms (PSM) capable of Pi desorption seems to be a complementary alternative in the management of these soils. The aim of this study was to evaluate the effectiveness of the soil fungus Mortierella sp., a known PSM, to desorb Pi from four soil minerals differing in their Pi sorption capacity. The fungus was effective in desorbing Pi from all tested minerals except from allophane, and its desorption depended on the production of oxalic acid. The effectiveness of the fungus to desorb Pi was ranked as montmorillonite > kaolinite > goethite > allophane. The quantity of desorbed Pi increased by increasing the amount of sorbed Pi. The Pi sorption capacity expressed as P_0.2 value (amount of P required to increase a solution P concentration up to 0.2 mg L^?1) was a good indicator of the effectiveness of Mortierella sp. to desorb Pi from soil minerals.  相似文献