Erwinia is a genus of Enterobacteriacea containing mostly pathogens, which cause soft rot disease in many ornamental plants and crops, including Asparagus officinalis. Chemical treatments to control Erwinia have lost their attractiveness because of the development of resistant strains and the negative impacts on the environment and human health. Therefore, the study of biological controls of soft rot disease has gained great importance. There are several types of microorganisms that show activity against Erwinia spp. such as Pseudomonas fluorescence, Bacillus subtilis, and Streptomyces spp. Among them, Streptomyces spp. are found to be the most effective control agents. In this study, 64 isolates of Streptomyces were screened for their antibacterial activity against Erwinia spp. The results indicated that 18 isolates showed an antagonistic reaction against Erwinia spp. Among them, isolate D5.1 showed the highest inhibition activity. In addition, the morphological and antibacterial activities of isolate D5.1 grown in different conditions were also characterized.
Fish is a healthy, high protein and low fat food that encourages the health and growth of people, especially children. However, in fact fish is very sensitive to many diseases which affects the productivity and quality of fish. Therefore, identifying the cause of the diseases and finding preventive measures become an urgent task today. In the previous study, we isolated Streptomyces antibioticus strain 1083 that has the ability to antagonize Aeromonas hydrophila - a pathogenic bacterium in fish. Based on the obtained results, we continue to perform this study to determine optimal conditions for the culture of S. antibioticus strain 1083 in order to produce antimicrobial compounds against A. hydrophila. The production of antagonists by the strain 1083 was optimized by controlling the condition of different inoculations such as media, pH, temperature and incubation period. The results indicated that International Streptomyces Project 2 (ISP2) was the best medium for S. antibioticus strain 1083 to produce the highest antimicrobial activity against A. hydrophila with 32 mm in diameter of inhibited zone. The actinomycete strain 1083 could express the maximum antimicrobial activity when they were incubated in shaker incubator (200rpm) at 40oC with pH8 in 8 days. The ability of the actinomycete strain in antagonism against A. hydrophila was evaluated by adding different culture medium volume of S. antibioticus strain 1083. With adding 10% cultured solution volume of S. antibioticus strain 1083 into the culture medium of A. hydrophila, after 1 day of inoculation the number of pathogenic bacteria cells were completely eliminated.
To isolate and characterise free nitrogen-fixing bacteria, we collected randomly soil samples from different areas of Ha Noi. Nitrogen-fixing bacteria were isolated using Burk's medium without nitrogen mineral supplement. The ammonia (NH 4 +) synthesis of these bacterial strains after biomass production was determined by means of Nessler reagent. Based on the results of isolation, we observed and evaluated colony and cellular morphology, pigment production, and metabolic activities of twenty-five isolates. Among the isolated bacteria, two bacterial strains (6.2 and 8.2) with high NH 4 + concentration in the cultural medium were selected as the best strains for nitrogenfixing ability. The optimal pH and temperature for their growth and nitrogen fixation are 7.0 and 30°C, respectively. Growth is best favored in the presence of sucrose. We sequenced the 16S rRNA gene of selected strains and compared the homology of them in GenBank using BLAST search. The result of the comparison shows that the 6.2 and 8.2 strains have 99% and 100% 16S rRNA-sequence similarity with Pseudomonas sp. and Bacillus sp., respectively.
The management of coordination activities among families, schools, and society in the care and education of children in preschools is a system of purposeful and planned impacts, in accordance with the laws of the managing entities, towards the managed entities in the coordination activities among families, schools, and society, aiming to achieve comprehensive care, education, and development goals for children. The principal of the preschool is the managing entity responsible for effective coordination among families, schools, and society in the care and education of children in preschools. This study surveyed the current situation of coordination management among families, schools, and society in the care and education of children in preschools in Lap Thach District, Vinh Phuc Province
In this study, with the aim of determining and assessing the influence of several culture conditions on the ligninolytic enzyme (LiP, MnP, and Lac) activity of bacteria, five lignin-degrading bacteria strains were isolated from two different soil samples and cultured on minimum salt medium agar containing alkaline lignin (MSML agar). Among the five isolated strains, DL1 and X3 expressed strong and stable ligninase enzyme activity at various temperature levels (30°C, 37°C, 50°C, and 60°C) and were selected for further study. Notably, at 60°C, the ligninase activity of both strains lasted until the seventh day before decreasing. The effects of the culture medium conditions, namely, carbohydrate sources, nitrogen sources, and pH, on the ligninolytic system illustrated that both X3 and DL1 were able to generate good enzymatic activity at a pH range of 3.0 to 7.0. These strains could use various sources of carbohydrates and nitrogen, derived from glucose, lactose, peptone, meat extract, and yeast extract. In addition, the analyses of biochemical characteristics revealed that X3 was capable of hydrolyzing starch and cellulose, while DL1 was not. Therefore, the results of this study suggested the potential of applying selected lignin-degrading bacterial strains on lignin treatments of agricultural wastes.
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