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Selected AbstractsRegulation of the initiation of chromosomal replication in bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 4 2007Jolanta Zakrzewska-Czerwi Abstract The initiation of chromosomal replication occurs only once during the cell cycle in both prokaryotes and eukaryotes. Initiation of chromosome replication is the first and tightly controlled step of a DNA synthesis. Bacterial chromosome replication is initiated at a single origin, oriC, by the initiator protein DnaA, which specifically interacts with 9-bp nonpalindromic sequences (DnaA boxes) at oriC. In Escherichia coli, a model organism used to study the mechanism of DNA replication and its regulation, the control of initiation relies on a reduction of the availability and/or activity of the two key elements, DnaA and the oriC region. This review summarizes recent research into the regulatory mechanisms of the initiation of chromosomal replication in bacteria, with emphasis on organisms other than E. coli. [source] Acute and chronic toxicity of nitrate to fathead minnows (Pimephales promelas), ceriodaphnia dubia, and Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000George Scott Abstract Increasing concentrations of nitrate in surface water and groundwater are becoming a worldwide concern, yet little information has been published on toxicity of nitrate to common organisms used for toxicity testing. The acute and chronic toxicity of nitrate (NO3 -N) to Ceriodaphnia dubia, Daphnia magna, and Pimephales promelas was investigated in 48-h to 17-d laboratory exposures. The 48-h median lethal concentration (LC50) of nitrate to C. dubia and D. magna neonates was 374 mg/L NO3 -N and 462 mg/L NO3 -N. The no-observed-effect concentration (NOEC) and the lowest-observed-effect concentration (LOEC) for neonate production in C. dubia were 21.3 and 42.6 mg/L NO3 -N, respectively. The NOEC and LOEC values for neonate production in D. magna were 358 and 717 mg/L NO3 -N, respectively. The 96-h LC50 for larval fathead minnows (P. promelas) was 1, 341 mg/L NO3 -N. The NOEC and LOEC for 7-d larval and 11-d embryo-larval growth tests were 358 and 717 mg/L NO3 -N, respectively. Additional exposure of breeding P. promelas and their fertilized eggs to nitrate did not increase susceptibility further. The LC50 values for all species tested were above ambient concentrations of nitrate reported for surface water. However, the LOEC for C. dubia was within the range of concentrations that could be found in streams draining areas under extensive agricultural cultivation. [source] Comparison of three enrichment media for the isolation of Campylobacter spp. from foodsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2000C.L. Baylis Aim: This study compared the performance of three Campylobacter enrichment broths: Bolton broth (BB), Campylobacter Enrichment broth (CEB) and Preston broth (PB). Methods and Results: Pure cultures of target and competitor organisms, and naturally-contaminated food samples, were used to establish the performance of these media. In pure culture the PB supported the growth of the greatest number of strains of Campylobacter spp. but failed to inhibit some competitor organisms. The CEB showed the opposite result, inhibiting all 15 competitor organisms used but failing to support the growth of five Campylobacter strains. By comparison, BB showed the best compromise between inhibition of competitors and growth of Campylobacter. Conclusions: Plates inoculated with BB and CEB food enrichments resulted in more Campylobacter growth than those inoculated with PB, which supported significantly less typical growth (P , 0·001). The most common competitor organism isolated from PB was Escherichia coli, and Pseudomonas spp. were frequently isolated from BB and CEB. Both BB and CEB were better than PB for the isolation of Campylobacter from naturally-contaminated foods, although BB yielded more confirmed Campylobacter growth than CEB. Significance and Impact of the Study: This study highlighted differences in performance of media used to isolate Campylobacter spp. from foods. [source] Monthly assessments of proteins, fatty acids and amino acids in Artemia franciscana cultivated in ,Las Salinas de Hidalgo', state of San Luis Potosí, MexicoAQUACULTURE NUTRITION, Issue 2 2009T. CASTRO Abstract This study presents the biochemical contents of Artemia biomass produced in a pond in ,Las Salinas de Hidalgo', State of San Luis Potosí, Mexico. The culture was realized over a period of 1 year in an 80 × 50 × 0.65 m (200 m3) pond. The feed consisted of a mixture of four micro algae. Samples of 1 kg of Artemia biomass (wet basis) were taken monthly and total protein, total lipid, amino acids and fatty acids were assessed. The contents of total protein and lipids showed a similar tendency from July to December (maintained values of about 300 mg g,1 for protein and 90 mg g,1 for lipids). With the exception of methionine and arginine, other seven indispensable amino acids were detected in the monthly samples, having similar values during the period from July to December. The most common fatty acids determined were the C16, C18, C18:1 and C18:3n6. Both, C20:4n6 and C20:5n3, were observed occasionally, but in high quantities. The use of the four micro algae as food for the Artemia cultured extensively, improved the biochemical composition and allows using this crustacean as feed for several species of aquatic organisms used for ornamental or human consumption. [source] Roles of lipid-soluble vitamins during ontogeny of marine fish larvaeAQUACULTURE RESEARCH, Issue 5 2010Kristin Hamre Abstract The roles of lipid-soluble vitamins during ontogeny of marine fish larvae are a subject topic where only fragments of the whole picture are known. Most of the research has been focussed on the larval requirements and the availability of these vitamins in the live feed organisms used for early-stage larvae, while the function of the vitamins in the larvae themselves is largely unknown. Our knowledge is mostly extrapolated from research on other vertebrates and also in part from juvenile and adult fish. Vitamin A is known to be essential for establishing body and organ axes in vertebrate embryos and interacts with other nutrients such as vitamin D and fatty acids through the steroid/thyroid nuclear hormone receptor family. In marine fish larvae, excess vitamin A stimulates pigmentation, but at the same time induces vertebral deformities. Live feed organisms contain very little vitamin A but marine fish larvae appear to convert carotenoids in Artemia and copepods to vitamin A, while rotifers, which contain little carotenoids, should be enriched with vitamin A. Vitamin E acts as an antioxidant and is important for the protection of marine fish larvae against the oxidation pressure probably present in intensive rearing systems. Vitamin E may also have other roles connected to its modulation of cell and tissue red-ox balance. In marine fish larvae and juveniles, vitamin E has been shown to enhance the symptoms of vitamin C deficiency, while protecting against the oxidative effect of n-3 fatty acids. Vitamin D is important for the modulation of calcium and phosphorus homeostasis and for the development of the vertebrate skeleton. Vitamin K influences bone development and coagulation of the blood. There is little information on vitamins D and K connected to the ontogeny of marine fish larvae. [source] Genome Sequencing and Comparative Genomics of Tropical Disease PathogensCELLULAR MICROBIOLOGY, Issue 12 2003Jane M. Carlton Summary The sequencing of eukaryotic genomes has lagged behind sequencing of organisms in the other domains of life, archae and bacteria, primarily due to their greater size and complexity. With recent advances in ,high-throughput ,technologies ,such ,as ,robotics and improved computational resources, the number of eukaryotic genome sequencing projects has in-creased significantly. Among these are a number of sequencing projects of tropical pathogens of medical and veterinary importance, many of which are responsible for causing widespread morbidity and mortality in peoples of developing countries. Uncovering the complete gene complement of these organisms is proving to be of immense value in the develop-ment of novel methods of parasite control, such as antiparasitic drugs and vaccines, as well as the development of new diagnostic tools. Combining pathogen genome sequences with the host and vector genome sequences is promising to be a robust method for the identification of host,pathogen interactions. Finally, comparative sequencing of related species, especially of organisms used as model systems in the study of the disease, is beginning to realize its potential in the identification of genes, and the evolutionary forces that shape the genes, that are involved in evasion of the host immune response. [source] | |||||||||||||