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31.
A determination was made of the kinds and numbers of bacteria surviving when two soils were maintained in the laboratory under dry conditions for more than half a year. Certain non-spore-forming bacteria were found to survive in the dry condition for long periods. A higher percentage of drought-tolerant than drought-sensitive bacteria was able to grow at low water activities. When they were grown in media with high salt concentrations, bacteria generally became more tolerant of prolonged drought and they persisted longer. The percent of cells in a bacterial population that remained viable when exposed to drought stress varied with the stage of growth. 相似文献
32.
Tetrahymena pyriformis cultures were maintained when transferred serially in solutions containing 105 to 107Klebsiella pneumoniae cells.ml?1, bacterial numbers that were observed to persist in the presence of protozoa. The number of cells of one strain of K. pneumoniae surviving predation in solution was essentially the same in the absence of an alternative prey as in the presence of a second K. pneumoniae strain. Toxins deleterious to protozoa did not appear as the animal consumed the bacteria. T. pyriformis reduced the abundance of Escherichia coli from about 108 to 106.ml?1. but the latter number persisted for 15 days; however, in solutions containing chloramphenicol, the abundance of E. coli fell to 590 cells. ml?1 in 15 days. In solutions containing the antibiotic, T. pyriformis reduced the Rhizobium sp. population from more than 106 to less than 103 cells in 10 days and K. pneumoniae from more than 108.ml?1 to zero in 18 days. An appreciable decline in abundance of these bacteria did not occur in the antibiotic-amended liquid free of protozoa. T. pyriformis did not greatly reduce Rhizobium sp. numbers when both were added to irradiated soil, but the predator caused the bacterial population to decline from 4 × 108 to fewer than 105.g?1 in 16 days in chloramphenicol-treated soil. Colpoda sp. inoculated with Rhizobium sp. into soil sterilized by autoclaving only reduced the prey abundance from 109 to 108.g?1, but the protozoan caused the bacterial population to fall to about 100.g?1 in 15 days in the presence of the antibiotic. The population of Rhizobium sp. added to nonsterile soil dropped from in excess of 108 to 6 × 106.g?1 in 29 days. but it declined to 550. g?1 in the same period when chloramphenicol was also introduced. It is concluded that the ability of these bacteria to maintain themselves in solution and in soil is governed by their capacity to reproduce and replace the cells consumed by predation. 相似文献
33.
A simple trapping procedure for concentration of volatile organic compounds present in a head space and the subsequent analysis of the retained compounds by combined gas chromatographymass spectrometry is described. The procedure was used to study the organic metabolites evolved from various soils when they were amended with glucose and incubated under argon. A number of organic acids, alcohols, aldehydes and esters were evolved during a 4 week period. Less than 10 per cent of the added carbon was recovered as organic compounds, which was largely due to poor recovery of volatile organic acids from soil. Some implications of the observations to microbial ecology are discussed. 相似文献
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Antonis Vlachavas Nikoleta Karaiskou Lambros Kokokiris Foteini‐Izampela Zampeta Elena Drosopoulou Alexander Triantafyllidis 《Aquaculture Research》2019,50(1):312-322
Large quantities of high protein fish meals are needed to sustain cultured species and thus the impact to marine ecosystem has been highly discussed. The aim of this study was to apply a PCR‐cloning methodology for a robust insight into the composition of commercial fish meals and feeds for farmed species of the Greek mariculture, assessing the risk posed by aquaculture to marine ecosystems but also the risk posed by commercial fish feeds to the increase in trophic level of species farmed in Greece. 89% of the sequences were identified to species level and only 11% to genus/family level. Overall, a total of 49 taxa were identified (44 fish species/taxon, five non‐fish species/taxon). Even though small pelagic fish like Engraulis sp. were the main portion, a wide range of species constituted the fish meals and feeds. Plant and animal species were also detected as an alternative protein source. Feed products employed in Greek mariculture still contain large portions of fish meals which increase the mean trophic level of farmed species causing a farming up trend. The results emphasize that such molecular methodologies are needed to certify aquafeeds allowing fish feed producers to demonstrate their commitment to sustainable aquaculture. 相似文献
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George Eng Stephen P. Coddington Laura L. Stockton Alexander D. W. Acholonu 《Pest management science》1989,26(2):117-121
The effect of organotin compounds on the growth of Ceratocystis ulmi, the causative agent of Dutch elm disease, was studied in shake culture. Triphenyltin, (C6H5)3SnX, tricyclohexyltin, (C6H11)3SnX, and tributyltin, (C4H9)3SnX, compounds were all effective in the inhibition of C. ulmi in vitro. The anionic group, X, did not play a major role in the inhibitory activities of these compounds, suggesting that the species involved in the inhibition is R3Sn+ or the hydrated cation. 相似文献
39.
Alexander Valverde DVM DVSc DACVA Cornelia I. Gunkel Dr. med. vet. MRCVS 《Journal of Veterinary Emergency and Critical Care》2005,15(4):295-307
Objective: This review discusses the different analgesic drugs and routes of administration used in large animals for acute pain management. General guidelines and doses are given to assist in choosing techniques that provide effective analgesia. Etiology: Noxious stimuli are perceived, recognized, and localized by specialized sensory systems located at spinal and supraspinal levels. Diagnosis: Localizing the source of the noxious stimulus as well as understanding the behavioral aspects and physiological changes that result from such insult is important to adequately diagnose and treat pain. Pain assessment is far from being definite and objective; not only are there species differences, but also individual variation. In addition, the behavioral and physiological manifestations vary with the acute or chronic nature of pain. Therapy: Pain management should include (1) selecting drugs that better control the type of pain elicited by the insult; (2) selecting techniques of analgesic drug administration that act on pathways or anatomical locations where the nociceptive information is being processed or originating from; (3) combining analgesic drugs that act on different pain pathways; and (4) provide the best possible comfort for the animal. Prognosis: Providing pain relief improves the animal's well being and outcome; however, interpreting and diagnosing pain remains difficult. Continuing research in pain management will contribute to the evaluation of the pathophysiology of pain, pain assessment, and newer analgesic drugs and techniques. 相似文献
40.
Binding of ciprofloxacin labelled with technetium Tc 99m versus 99mTc-pertechnetate to a live and killed equine isolate of Escherichia coli 下载免费PDF全文
Kate Alexander Wm. Tod Drost John S. Mattoon Joseph J. Kowalski Julie A. Funk Amanda C. Crabtree 《Canadian journal of veterinary research》2005,69(4):272-277
This paper describes a simple methodology for evaluating the bacterial binding of ciprofloxacin labelled with technetium Tc 99m. Using this methodology, the binding of 99mTc-ciprofloxacin by live Escherichia coli was compared with the binding of 99mTc-ciprofloxacin by killed E. coli and the binding of 99mTc-pertechnetate (99mTcO4-) by live E. coli. The antimicrobial effect of 99mTc-ciprofloxacin on E. coli was evaluated. Four groups were defined: live E. coli with 99mTc-ciprofloxacin, live E. coli with 99mTcO4 , killed E. coli with 99mTc-ciprofloxacin, and killed E. coli with 99mTcO4-. After 0, 2, and 4 h of incubation of 1 x 10(8) colony-forming units of E. coli suspended in 5 mL of sterile distilled water with 1.85 MBq of 99mTc-ciprofloxacin or 99mTcO4, 1 mL from each sample was centrifuged. The radioactivity of the bacterial pellet and that of the supernatant were measured separately, and the percentage of sample radioactivity attributable to bacterial binding was calculated. Of the 99mTc-ciprofloxacin, 3.6% to 5.9% was bound to live or killed E. coli; only 0.1% to 0.2% of the 99mTcO4- was bound to live E. coli (P < 0.0001). No significant difference in 99mTc-ciprofloxacin binding was found between live and killed E. coli (P = 0.887). An antimicrobial effect on E. coli was seen with 99mTc-ciprofloxacin: colony counts were reduced after 4 h. The small amount of 99mTc-ciprofloxacin binding and the lack of difference in binding between live and killed E. coli may limit the utility of this methodology in evaluating the presence of E. coli infection. 相似文献