A bacterium that can grow by using arsenic instead of phosphorus

Life is mostly composed of the elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. Although these six elements make up nucleic acids, proteins, and lipids and thus the bulk of living matter, it is theoretically possible that some other elements in the periodic table could serve the same functions. Here, we describe a bacterium, strain GFAJ-1 of the Halomonadaceae, isolated from Mono Lake, California, that is able to substitute arsenic for phosphorus to sustain its growth. Our data show evidence for arsenate in macromolecules that normally contain phosphate, most notably nucleic acids and proteins. Exchange of one of the major bio-elements may have profound evolutionary and geochemical importance.     

Identification of an alkaline ceramidase gene from Dermatophilus congolensis

A random amplified polymorphic DNA (RAPD) procedure was used to identify a specific 0.6 kb DNA fragment unique to Dermatophilus congolensis. This 0.6 kb fragment was evaluated as a specific DNA probe and used to design oligonucleotide primers for polymerase chain reaction (PCR) amplification. The nucleotide sequences adjacent to this DNA fragment were determined by inverse PCR allowing the identification of a 4.1 kb sequence. Analysis of this revealed a complete open reading frame (ORF) with a high similarity to an alkaline ceramidase from Pseudomonas aeruginosa. The molecular weight of the enzyme derived from the predicted amino acid sequence is 74,662 Da, its pI is 9.81. The predicted N-terminal sequence of the enzyme contains a signal sequence indicating that the enzyme is exported by the bacterium. Since ceramides have important protective and cell regulatory roles in the epidermis we suggest that this ceramidase may have a role in the pathogenesis of dermatophilosis. It is the first completely sequenced gene described for D. congolensis.     

Progressive transfer to seawater enhances intestinal and branchial Na+-K+-ATPase activity in non-anadromous rainbow trout

Two sizes of rainbow trout [170 (4), 91 (3) g] were progressively transferred to seawater in January 1995 using three steps of 9, 20 and 28. Na+-K+-ATPase activity in gills, intestine and kidney, and plasma sodium and magnesium levels were assessed in response to changed external salinity. Gradual transfer to seawater had a stimulatory effect on gill and intestinal Na+-K+-ATPase activities after the transfer to 28, while its activity remained unchanged in the kidney. Plasma sodium content was not modified, while magnesium levels increased in response to increased external salinity. The size-dependent response to seawater transfer described by other authors was not detected in our experiments. The results are discussed in terms of long-term adaptation to seawater.     

Corticotropin-releasing factor-producing neurons in the rat activated by interleukin-1

Intraperitoneal administration of human recombinant interleukin-1 (IL-1) to rats can increase blood levels of corticosterone and adrenocorticotropic hormone (ACTH). The route by which IL-1 affects pituitary-adrenal activity is unknown. That the IL-1-induced pituitary-adrenal activation involves an increased secretion of corticotropin-releasing factor (CRF) is indicated by three lines of evidence. First, immunoneutralization of CRF markedly attenuated the IL-1-induced increase of ACTH blood levels. Second, after blockade of fast axonal transport in hypothalamic neurons by colchicine, IL-1 administration decreased the CRF immunostaining in the median eminence, indicating an enhanced release of CRF in response to IL-1. Third, IL-1 did not stimulate ACTH release from primary cultures of anterior pituitary cells. These data further support the notion of the existence of an immunoregulatory feedback circuit between the immune system and the brain.     

A preliminary survey of viruses in pasture grasses in South Africa

Little work has been done in South Africa on the incidence of viruses in pasture grasses. The aim of this work was to carry out a survey of virus infections of some of the economically‐important pasture grasses in South Africa. Twelve winter and summer pasture grass species and one cereal forage crop species were collected from six different regions in early, mid‐ and late winter and summer. Plants were tested for virus(es) by means of symptomatology, transmission, dot‐blot immunoassays, Ouchterlony tests and electron microscopy. Serological tests indicate that Avena sativa from Roodeplaat and Bromus unioloides from Potchefstroom, Cedara and Nooitgedacht are positive for maize dwarf mosaic virus (MDMV). Lolium multiflorum from Cedara appears to be infected with two viruses, brome mosaic virus (BMV) and a potyvirus‐like agent, possibly ryegrass mosaic virus (RMV).     

Epidemiology of ryegrass mosaic virus in South Africa

The distribution and seasonal occurrence of ryegrass mosaic virus (RMV) in South Africa was determined. Italian ryegrass plants were collected from eight different research stations twice during the growing season in 1990 and 1991. Samples were tested for the presence of RMV by means of symptomology, electron microscopy, transmission and serology. The virus was found in only three of the tested sites, namely, Nooitgedacht (Ermelo), Cedara (Pietermaritzburg) and Glen (Bloemfontein). At Nooitgedacht and Cedara, the number of infected plants increased from mid‐season to late season, while at Glen, the number of infected plants was low at mid‐season and decreased even further by late season. It is suggested that the distribution and intensity of RMV may depend on regional temperature differences.     

Studying the effects of Mahonia aquifolium populations on small‐scale mountain agro‐ecosystems in Hungary with the view to minimise land degradation

After the political changeover in Hungary in 1989, many farm owners faced problems typical of a small sized farm (<1 ha) as well as a lack of various resources. This led to many farms with great horticultural backgrounds being abandoned, especially in mountainous areas where erosion control is essential for soil conservation. Severe changes can occur on soil through property abandonment. The local socio‐economic aspects must be taken into consideration as well as the problem of soil degradation as this will be a motivating factor in preservation initiatives. Under horticultural management, Mahonia aquifolium was tested to determine its efficiency in water erosion control in mountainous conditions in Hungary. Soil loss and water runoff were measured after every rainfall event at six different plots: four cultivated M. aquifolium populations with different ages (4, 12, 20 and 25 years old) and two control plots. A bare soil field and a grass field represented the control plots. The results show that as the age of the M. aquifolium populations increase, the cumulative runoff and sediment values decrease. It also showed that 2 years after setting up a new M. aquifolium plantation, the cumulative runoff decreased by 69 per cent and the cumulative soil loss decreased by 74 per cent. This indicates that a M. aquifolium population could play a significant role in erosion control within a short period of time. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of dietary oils and alpha-tocopheryl acetate supplementation on lipid (TBARS) and cholesterol oxidation in cooked pork

The effect of n-3 fatty acid-enriched diets (in the form of 0.5% linseed oil with either 1.5% sunflower oil or 1.5% olive oil) and alpha-tocopheryl acetate supplementation (200 mg/kg feed) on lipid oxidation (thiobarbituric acid-reactive substances, TBARS) and cholesterol oxide products (COPS) in cooked pork was investigated. Longissimus muscle was studied. Meat from pigs fed 0.5% linseed oil-enriched diets had a higher proportion of n-3 fatty acid than meat from pigs in other dietary groups in neutral (P < 0.0001) and polar lipids (P < 0.0001), and a 20% reduction in the n-6:n-3 ratio was observed. Alpha-tocopheryl acetate supplementation increased (P < 0.05) monounsaturated fatty acids in polar lipids and increased (P = 0.0001) alpha-tocopherol levels in muscle. Alpha-tocopherol concentration in muscle was affected by dietary fat (P < 0.05). Groups receiving diets enriched with sunflower oil had significantly higher alpha-tocopherol levels (P < 0.05) in muscle than those groups receiving olive oil-enriched diets. Numbers of TBARS were significantly (P < 0.05) lower in the group fed supplemental olive oil than in those fed sunflower oil. Dietary linseed oil increased (P < 0.05) lipid oxidation principally at the initial period of storage in cooked pork. Overall, dietary alpha-tocopheryl acetate supplementation significantly increased (P < 0.001) lipid stability and decreased (P < 0.05) total COP production across the dietary groups. Alpha-tocopherol was a more effective antioxidant for decreasing TBARS values in cooked meat when adding sunflower oil to the diets instead of olive oil.     

Production of Indole-3-acetic Acid and Tryptophol by Pythium ultimum and Pythium Group F: Possible Role in Pathogenesis

Pythium group F is a minor pathogen which induces symptomless infections that occur frequently and results in yield losses in tomato soilless cultures. To elucidate the mode of action of this microorganism, the influence of culture filtrates of Pythium group F on tomato growth was investigated and compared to that of the pathogen Pythium ultimum. Depending on metabolite production by the fungus, marked differences were observed in plant response. Pythium group F crude culture filtrates or low molecular weight fractions (< 500) caused swelling behind the root tip and reduced root growth; the cohesion and adherence of cells within the cortical area were also affected. These symptoms were similar to those observed on plants treated with indole-3-acetic acid. By contrast, P. ultimum filtrates caused a marked distortion of cell shape accompanied with folding of host cell walls, particularly in the cortical area. These symptoms were characteristic of the activity of toxic compound(s) on host cells. Chemical analysis of the filtrates demonstrated that indole-3-acetic acid and tryptophol were produced by Pythium group F and P. ultimum. However, Pythium group F took up and metabolized more indole-3-acetic acid precursors, especially tryptophan, a key amino acid in the pathways leading to indole-3-acetic acid synthesis. The fact that Pythium group F and P. ultimum transformed tryptamine and indole-3-acetaldehyde into indole-3-acetic acid and tryptophol confirms the existence of a tryptamine pathway within both fungi. These results support the hypothesis that auxins facilitate Pythium group F infections. On the other hand, toxin(s) and hydrolytic enzymes are likely involved in P. ultimum pathogenesis.