Degradation products of clavulanic acid promote clavulanic acid production in cultures of Streptomyces clavuligerus

The role of clavulanic acid, an unstable antibiotic produced by Streptomyces clavuligerus, in biomass accumulation and production of clavulanic acid in batch cultures of the organism was examined. The organism was grown in a medium containing either 20 g/l lysine, 1 g/l lysine or 1 g/l lysine supplemented with degraded clavulanic acid as nitrogen sources. Biomass accumulation was highest in cultures grown with supplemented degraded clavulanic acid and reached a maximum of 2.2 g/l, compared with 1.5 g/l when lysine only was used. The yield coefficient for clavulanic acid production was again highest in cultures grown with supplemented degraded clavulanic acid, with a Y-p/x, value of 2 mg/g compared with Y-p/x value of 1.5 mg/g in 20 g/l lysine. No clavulanic acid was produced in cultures containing non-supplemented 1 g/l lysine. Non-degraded clavulanic, acid was added at 60 h to non-producing cultures of the organism containing 1 g/l lysine only. Clavulanic acid concentration immediately decreased on addition from 0.04 g/l over a period of 20 h, then remained constant at 0.02 g/l for a further 30 h until the end of the cultivation. This suggests that the rate of degradation was equivalent to the rate of production of clavulanic acid following a period of initial additive degradation. These results indicate that clavulanic acid is both produced and degraded in cultures of S. clavuligerus and that the products of degradation are used by the organism, resulting in further production of the antibiotic. (C) 2003 Elsevier Inc. All rights reserved.

Effect of high dose selenium enriched yeast diets on the distribution of total selenium and selenium species within lamb tissues

The objective of this study was to determine the distribution of total selenium (Se) and of the proportion of total Se comprised as the selenized amino acids selenomethionine (SeMet) and selenocysteine (SeCys) within the post mortem tissues of lambs that were fed high dose selenized enriched yeast (SY), derived from a specific strain of Saccharomyces cerevisae CNCM (Collection Nationale de Culture de Micro-organism) I-3060. Thirty two Texel X Suffolk lambs (6.87 ± 0.23 kg BW) were offered both reconstituted milk replacer and a pelleted diet, both of which had been either supplemented with high SY (6.30 ± 0.18 mg Se/kg DM) or unsupplemented (0.13 ± 0.01 mg Se/kg of DM), depending on treatment designation, for a continuous period of 91 d. At enrollment and 28, 56 and 91 d following enrollment lambs were blood sampled. At the completion of the treatment period, five lambs from each treatment group were euthanased and samples of heart, liver, kidney and skeletal muscle (Longissimus Dorsi and Psoas Major) were retained for Se analysis. The inclusion of high SY increased (P < 0.001) whole blood Se concentration, reaching a maximum mean value of 815.2 ± 19.1 ng Se/mL compared with 217.8 ± 9.1 ng Se/mL in control animals. Tissue total Se concentrations were significantly (P < 0.001) higher in SY supplemented animals than in controls irrespective of tissue type; values were 26, 16, 8 and 3 times higher in skeletal muscle, liver, heart and kidney tissue of HSY lambs when compared to controls. however, the distribution of total Se and the proportions of total Se comprised as either SeMet or SeCys differed between tissue types. Selenocysteine was the predominant selenized amino acid in glandular tissues, such the liver and kidney. irrespective of treatment, although absolute values were markedly higher in HSY lambs. Conversely selenomethionine was the predominat selenized amino acid in cardiac and skeletal muscle (Longissimus Dorsi, and Psoas Major) tissues in HSY animals, although the same trend was not apparent for control lambs in which SeCys was the predominant selenized amino acid. It was concluded that there were increases in both whole blood and tissue total Se concentrations as a result of dietary supplementation with high dose of SY. Furthermore, distribution of total Se and Se species differed between both treatment designation and tissue type.

Selenium persistency and speciation in the tissues of lambs following the withdrawal of dietary high-dose selenium-enriched yeast

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of lambs in the six weeks period following the withdrawal of a diet containing high dose selenized yeast (SY), derived from a specific strain of Saccharomyces cerevisae CNCM (Collection Nationale de Culture de Micro-organism) I-3060. Thirty Texel x Suffolk lambs used in this study had previously received diets (91 days) containing either high dose SY (HSY; 6.30 mg Se/kg DM) or an unsupplemented control (C; 0.13 mg Se/kg DM). Following the period of supplementation all lambs were then offered a complete pelleted diet, without additional Se (0.15 mg Se/kg DM), for 42 days. At enrollment and 21 and 42 days later, five lambs from each treatment were blood sampled, euthanased and samples of heart, liver, kidney and skeletal muscle (Longissimus Dorsi and Psoas Major) tissue were retained. Total Se concentration in whole blood and tissues was significantly (P < 0.001) higher in HSY lambs at all time points that had previously received long term exposure to high dietary concentrations of SY. The distribution of total Se and the proportions of total Se comprised as SeMet and SeCys differed between tissues, treatment and time points. Total Se was greatest in HSY liver and kidney (22.64 and 18.96 mg Se/kg DM, respectively) and SeCys comprised the greatest proportion of total Se. Conversely, cardiac and skeletal muscle (Longissimus Dorsi and Psoas Major) tissues had lower total Se concentration (10.80, 7.02 and 7.82 mg Se/kg DM, respectively) and SeMet was the predominant selenized amino acid. Rates of Se clearance in HSY liver (307 µg Se/day) and kidney (238 µg Se/day) were higher compared with HSY cardiac tissue (120 µg Se/day) and skeletal muscle (20 µg Se/day). In conclusion differences in Se clearance rates were different between tissue types, reflecting the relative metabolic activity of each tissue, and appear to be dependant upon the proportions of total Se comprised as either SeMet or SeCys.

Tolerance of ruminant animals to high dose in-feed administration of a selenium-enriched yeast

The objective of the study was to determine if there were adverse effects on animal health and performance when a range of ruminant animals species were fed at least 10 times the maximum permitted European Union (EU) selenium (Se) dietary inclusion rate (0.568 mg Se/kg DM) in the form of selenium enriched yeast (SY) derived from a specific strain of Saccharomyces cerevisiae CNCM I-3060. In a series of studies, dairy cows, beef cattle, calves and lambs were offered either a control diet which contained no Se supplement or a treatment diet which contained the same basal feed ingredients plus a SY supplement which increased total dietary Se from 0.15 to 6.25, 0.20 to 6.74, 0.15 to 5.86 and 0.14 to 6.63 mg Se/kg DM, respectively. The inclusion of the SY supplement (P < 0.001) increased whole blood Se concentrations, reaching maximum mean values of 716, 1,505, 1,377, and 724 ng Se/mL for dairy cattle, beef cattle, calves and lambs, respectively. Selenomethionine accounted for 10% of total whole blood Se in control animals whereas the proportion in SY animals ranged between 40 and 75%. Glutathione peroxidase (EC 1.11.1.9) activity was higher (P < 0.05) in SY animals when compared with controls. A range of other biochemical and hematological parameters were assessed, but few differences of biological significance were established between treatments groups. There were no differences between treatment groups within each species with regard to animal physical performance or overall animal health. It was concluded that there were no adverse effects on animal health, performance and voluntary feed intake to the administration of at least ten times the EU maximum, or approximately twenty times the US FDA permitted concentration of dietary Se in the form of SY derived from a specific strain of Saccharomyces cerevisiae CNCM I-3060.

Effect of dietary supplementation with selenium-enriched yeast or sodium selenite on selenium tissue distribution and meat quality in beef cattle

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of beef cattle offered diets containing graded additions of selenized enriched yeast (SY) [Saccharomyces cerevisae CNCM I-3060]), or sodium selenite (SS). Oxidative stability and tissue glutathione peroxidase (GSH-Px) activity of edible muscle tissue were assessed 10 d post-mortem. Thirty two beef cattle were offered, for a period of 112 d, a total mixed ration which had either been supplemented with SY (0, 0.15 or 0.35 mg Se/kg DM) or SS (0.15 mg Se/kg DM). At enrollment (0 d) and at 28, 56, 84 and 112 d following enrollment, blood samples were taken for Se and Se species determination, as well as whole blood GSH-Px activity. At the end of the study beef cattle were euthanized and samples of heart, liver, kidney, and skeletal muscle (LM and psoas major) were retained for Se and Se species determination. Tissue GSH-Px activity and thiobarbituric acid reactive substances (TBARS) were determined in skeletal muscle tissue (LM only). The incorporation into the diet of ascending concentrations of Se as SY increased whole blood total Se and the proportion of total Se comprised as SeMet, as well as GSH-Px activity. There was also a dose dependant response to the graded addition of SY on total Se and proportion of total Se as SeMet in all tissues and GSH-Px activity in skeletal muscle tissue. Furthermore, total Se concentration of whole blood and tissues was greater in those animals offered SY when compared with those receiving a comparable dose of SS, indicating an improvement in Se availability and tissue Se retention. Likewise, GSH-Px activity in whole blood and LM was greater in those animals offered SY when compared with those receiving a comparable dose of SS. However, these increases in tissue total Se and GSH-Px activity appeared to have little or no effect in meat oxidative stability.

Selenium supplementation of lactating dairy cows: effects on milk production and total selenium content and speciation in blood, milk and cheese

Forty-multiparous Holstein cows were used in a 16-wk continuous design study to determine the effects of either selenium (Se) source, selenized yeast (SY) (derived from a specific strain of Saccharomyces cerevisiae CNCM I-3060 Sel-Plex®) or sodium selenite (SS), or inclusion rate of SY on Se concentration and speciation in blood, milk and cheese. Cows received ad libitum a TMR with 1:1 forage:concentrate ratio on a dry matter (DM) basis. There were four diets (T1-T4) which differed only in either source or dose of Se additive. Estimated total dietary Se for T1 (no supplement), T2 (SS), T3 (SY) and T4 (SY) was 0.16, 0.30, 0.30 and 0.45 mg/kg DM, respectively. Blood and milk samples were taken at 28 day intervals and at each time point there were positive linear effects of SY on Se concentration in blood and milk. At day 112 blood and milk Se values for T1-T4 were 177, 208, 248, 279 ± 6.6 and 24, 38, 57, 72 ± 3.7 ng/g fresh material, respectively and indicate improved uptake and incorporation of Se from SY. While selenocysteine (SeCys) was the main selenised amino acid in blood its concentration was not markedly affected by treatment, but the proportion of total Se as selenomethionine (SeMet) increased with increasing inclusion rate of SY. In milk, there were no marked treatment effects on SeCys content, but Se source had a marked effect on the proportion of total Se as SeMet. At day 112 replacing SS (T2) with SY (T3) increased the SeMet concentration of milk from 36 to 111 ng Se/g and its concentration increased further to 157 ng Se/g as the inclusion rate of SY increased further (T4) to provide 0.45 mg Se/kg TMR. Neither Se source nor inclusion rate effected the keeping quality of milk. At day 112, milk from T1, T2, and T3 was made into a hard cheese and Se source had a marked effect on total Se and the proportion of total Se comprised as either SeMet or SeCys. Replacing SS (T2) with SY (T3) increased total Se, SeMet and SeCys content from 180 to 340 ng Se/g, 57 to 153 ng Se/g and 52 to 92 ng Se/g, respectively. Key words: dairy cow, milk and cheese, selenomethionine, selenocysteine, milk keeping quality

Selenium supplementation of lactating dairy cows: Effect on selenium concentration in blood, milk, urine and feces

The objectives were to determine effects of graded levels of selenized yeast derived from a specific strain of Saccharomyces cerevisiae (CNCM I-3060) on animal performance and in selenium concentrations in the blood, milk, feces, and urine of dairy cows compared with sodium selenite; and to provide preliminary data on the proportion of selenium as selenomethionine in the milk and blood. Twenty Holstein cows were used in a 5 × 5 Latin square design study in which all cows received the same total mixed rations, which varied only in source or concentration of dietary selenium. There were 5 experimental treatments. Total dietary selenium of treatment 1, which received no added selenium, was 0.15 mg/kg of dry matter, whereas values for treatments 2, 3, and 4, derived from selenized yeast, were 0.27, 0.33, and 0.40 mg/kg of dry matter, respectively. Treatment 5 contained 0.25 mg of selenium obtained from sodium selenite/kg of dry matter. There were no significant treatment effects on animal performance, and blood chemistry and hematology showed few treatment effects. Regression analysis noted significant positive linear effects of increasing dietary selenium derived from selenized yeast on selenium concentrations in the milk, blood, urine, and feces. In addition, milk selenium results indicated improved bioavailability of selenium from selenized yeast, compared with sodium selenite. Preliminary analyses showed that compared with sodium selenite, the use of selenized yeast increased the concentration of selenomethionine in the milk and blood. There was no indication of adverse effects on cow health associated with the use of selenized yeast.

Dipole modes on open periodic structures — an experimental study

An experimental study is made of the lower pass-band of waveguides built as necklaces of oblate spheroids. Short lengths of guide are tested in open resonators. The dominant mode is found to be a glow-wave dipole type having no low-frequency cut off. High Q factors indicate low attenuations. Perturbation measurements demonstrate this energy to be concentrated in the vicinity of the guide.

Selenium supplementation of lactating dairy cows: effects on milk production and total selenium content and speciation in blood, milk and cheese

Forty multiparous Holstein cows were used in a 16-week continuous design study to determine the effects of either selenium (Se) source, selenised yeast (SY) (derived from a specific strain of Saccharomyces cerevisiae CNCM 1-3060) or sodium selenite (SS), or Se inclusion rate in the form of SY in the diets of lactating dairy cows on the Se concentration and speciation in blood, milk and cheese. Cows received ad libitum a total mixed ration (TMR) with a 1 : 1 forage: concentrate ratio on a dry matter (DM) basis. There were four diets (T-1 to T-4), which differed only in either source or dose of Se additive. Estimated total dietary Se for T, (no supplement), T-2 (SS), T-3 (SY) and T-4 (SY) was 0.16, 0.30, 0.30 and 0.45 mg/kg DM, respectively. Blood and milk samples were taken at 28-day intervals and at each time point there were positive linear effects of Se in the form of SY on the Se concentration in blood and milk. At day 112 blood and milk Se values for T-1 to T-4 were 177, 208, 248 and 279 +/- 6.6 and 24, 38, 57 and 72 +/- 3.7 ng/g fresh material, respectively, and indicate improved uptake and incorporation of Se from SY. In whole blood, selenocysteine (SeCys) was the main selenised amino acid and the concentration of selenomethionine (SeMet) increased with the increasing inclusion rate of SY In milk, there were no marked treatment effects on the SeCys content, but Se source had a marked effect on the concentration of SeMet. At day 112 replacing SS (T-2) with SY (T-3) increased the SeMet concentration of milk from 36 to 111 ng Se/g and its concentration increased further to 157ng Se/g dried sample as the inclusion rate of SY increased further (T-4) to provide 0.45 mg Se/kg TMR. Neither Se source nor inclusion rate affected the keeping quality of milk. At day 112 milk from T-1, T-2 and T-3 was made into a hard cheese and Se source had a marked effect on total Se and the concentration of total Se comprised as either SeMet or SeCys. Replacing SS (T-2) with SY (T-3) increased total Se, SeMet and SeCys content in cheese from 180 to 340 ng Se/g, 57 to 153 ng Se/g and 52 to 92 ng Se/g dried sample, respectively. The use of SY to produce food products with enhanced Se content as a means of meeting the Se requirements is discussed

The impact of traffic emissions on atmospheric ozone and OH: results from QUANTIFY

To estimate the impact of emissions by road, aircraft and ship traffic on ozone and OH in the present-day atmosphere six different atmospheric chemistry models have been used. Based on newly developed global emission inventories for road, ship and aircraft emission data sets each model performed sensitivity simulations reducing the emissions of each transport sector by 5%. The model results indicate that on global annual average lower tropospheric ozone responds most sensitive to ship emissions (50.6%±10.9% of the total traffic induced perturbation), followed by road (36.7%±9.3%) and aircraft exhausts (12.7%±2.9%), respectively. In the northern upper troposphere between 200–300 hPa at 30–60° N the maximum impact from road and ship are 93% and 73% of the maximum effect of aircraft, respectively. The latter is 0.185 ppbv for ozone (for the 5% case) or 3.69 ppbv when scaling to 100%. On the global average the impact of road even dominates in the UTLS-region. The sensitivity of ozone formation per NOx molecule emitted is highest for aircraft exhausts. The local maximum effect of the summed traffic emissions on the ozone column predicted by the models is 0.2 DU and occurs over the northern subtropical Atlantic extending to central Europe. Below 800 hPa both ozone and OH respond most sensitively to ship emissions in the marine lower troposphere over the Atlantic. Based on the 5% perturbation the effect on ozone can exceed 0.6% close to the marine surface (global zonal mean) which is 80% of the total traffic induced ozone perturbation. In the southern hemisphere ship emissions contribute relatively strongly to the total ozone perturbation by 60%–80% throughout the year. Methane lifetime changes against OH are affected strongest by ship emissions up to 0.21 (± 0.05)%, followed by road (0.08 (±0.01)%) and air traffic (0.05 (± 0.02)%). Based on the full scale ozone and methane perturbations positive radiative forcings were calculated for road emissions (7.3±6.2 mWm−2) and for aviation (2.9±2.3 mWm−2). Ship induced methane lifetime changes dominate over the ozone forcing and therefore lead to a net negative forcing (−25.5±13.2 mWm−2).

The concept of a new video detector for ghosted IF signals

The effect of terrestrial television multipath signals on the intermediate frequency (IF) vestigial sideband filter and the video detector are discussed. A new detector is proposed which, by processing the detected phase quadrature information, derives the correct phase for synchronous detection in the presence of multipath effects. This minimizes dispersion and produces a detected video signal with the linear addition of any ghosts.

Brucella melitensis 16M: characterisation of the galE gene and mouse immunisation studies with a galE deficient mutant

The galE gene of Streptomyces lividans was used to probe a cosmid library harbouring Brucella melitensis 16M DNA and the nucleotide sequence of a 2.5 kb ClaI fragment which hybridised was determined. An open reading frame encoding a predicted polypeptide with significant homology to UDP-galactose-4-epimerases of Brucella arbortus strain 2308 and other bacterial species was identified. DNA sequences flanking the B. melitensis galE gene shared no identity with other gal genes and, as for B. abortus, were located adjacent to a mazG homologue. A plasmid which encoded the B. melitensis galE open reading frame complemented a galE mutation in Salmonella typhimurium LB5010, as shown by the restoration of smooth lipopolysaccharide (LPS) biosynthesis, sensitivity to phage P22 infection and restoration of UDP-galactose-4-epimerase activity. The galE gene on the B. melitensis 16M chromosome was disrupted by insertional inactivation and these mutants lacked UDP-galactose-4-epimerase activity but no discernible differences in LPS structure between parent and the mutants were observed. One B. melitensis 16M galE mutant, Bm92, was assessed for virulence in CD-1 and BALB/c mice and displayed similar kinetics of invasion and persistence in tissues compared with the parent bacterial strain. CD-1 mice immunised with B. melitensis 16M galE were protected against B. melitensis 16M challenge. Crown Copyright (C) 1999 Published by Elsevier Science B.V.

Selection experiments reveal trade-offs between swimming and twitching motilities in pseudomonas aeruginosa

Bacteria possess a range of mechanisms to move in different environments, and these mechanisms have important direct and correlated impacts on the virulence of opportunistic pathogens. Bacteria use two surface organelles to facilitate motility: a single polar flagellum, and type IV pili, enabling swimming in aqueous habitats and twitching along hard surfaces, respectively. Here, we address whether there are trade-offs between these motility mechanisms, and hence whether different environments could select for altered motility. We experimentally evolved initially isogenic Pseudomonas aeruginosa under conditions that favored the different types of motility, and found evidence for a trade-off mediated by antagonistic pleiotropy between swimming and twitching. Moreover, changes in motility resulted in correlated changes in other behaviors, including biofilm formation and growth within an insect host. This suggests environmental origins of a particular motile opportunistic pathogen could predictably influence motility and virulence

Water, irrigation and plant diseases

Irrigation is a major husbandry tool, vital for world food production and security. The purpose of this review is twofold:- firstly drawing attention to the beneficial and deleterious aspects of irrigation resulting from interactions with the microbial world; secondly, forming a basis for encouraging further research and development. Irrigation is for example, a valuable component in the control of some soil borne pathogens such as Streptomyces scabies, the cause of potato common scab and Fusarium cubense, a cause of banana wilt. By contrast, applying irrigation encourages some foliar pathogens and factors such as splash dispersal of propagules and the retention of leaf wetness are important elements in the successful establishment of disease foci. Irrigation applied at low levels in the canopy directly towards the stem bases and root zones of plants also provides means encouraging disease development. Irrigation also offers means for the direct spread of microbes such as water borne moulds, Oomycetes, and plasmodial pathogens coming from populations present in the water supply. The presence of plant disease causing microbes in sources of irrigation has been associated with outbreaks of diseases such as clubroot (Plasmodiophora brassicae). Irrigation can be utilised as a means for applying agrochemicals, fungigation. The developing technologies of water restriction and root zone drying also have an impact on the success of disease causing organisms. This is an emerging technology and its interactions with benign and pathogenic microbes require consideration.

Enzyme assisted extraction of chitin from shrimp shells (Litopenaeus vannamei)

BACKGROUND: Chemical chitin extraction generates large amounts of wastes and increases partial deacetylation of the product. Therefore, the use of biological methods for chitin extraction is an interesting alternative. The effects of process conditions on enzyme assisted extraction of chitin from the shrimp shells in a systematic way were the focal points of this study. RESULTS: Demineralisation conditions of 25C, 20 min, shells-lactic acid ratio of 1:1.1 w/w; and shells-acetic acid ratio of 1:1.2 w/w, the maximum demineralisation values were 98.64 and 97.57% for lactic and acetic acids, respectively. A total protein removal efficiency of 91.10% by protease from Streptomyces griseus with enzyme-substrate ratio 55 U/g, pH 7.0 and incubation time 3 h is obtained when the particle size range is 50-25 μm, which was identified as the most critical factor. The X-ray diffraction and 13C NMR spectroscopy analysis showed that the lower percent crystallinity and higher degree of acetylation of chitin from enzyme assisted extraction may exhibit better solubility properties and less depolymerisation in comparison with chitin from the chemical extraction. CONCLUSION: The present work investigates the effects of individual factors on process yields, and it has shown that, if the particle size is properly controlled a reaction time of 3 h is more than enough for deproteination by protease. Physicochemical analysis indicated that the enzyme assisted production of chitin seems appropriate to extract chitin, possibly retaining its native structure.