Direct quantitation of fatty acids present in bacteria and fungi: stability of the cyclopropane ring to chlorotrimethylsilane

The stability of the cyclopropane ring and the fatty acid composition of microbial cells were determined using chlorotrimethylsilane as reagent with three different conditions 80 degrees C for 1 h, 60 degrees C for 1 h, and 60 degrees C for 2 h. Chlorotrimethylsilane permits a simultaneous extraction and derivatization of fatty acids. A basic method was used as reference. The bacteria, Escherichia coli, Burkholderia cepacia, and Lactobacillus brevis, and fungi Aspergillus niger and Gibberella fujikuroi were used. The stability of the cyclopropane ring on acidic conditions was tested using the cyclopropanecarboxylic acid and a commercial mixture of bacteria fatty acid methyl esters (BAME). Fisher's least significant difference test showed significant differences among the methods. The method using chlorotrimethylsilane and 1-pentanol for 1 h at 80 degrees C gave the best results in cyclopropane, hydroxyl, and total fatty acid recoveries. This procedure allows the fast and easy one-step direct extraction derivatization.     

Assessment of heavy metal tolerance in two plant species growing in experimental disturbed polluted urban soil

Purpose

Urban soil, which is strongly influenced by anthropogenic activities, receives a major proportion of trace metal wastes. The aim of this work was to determine heavy metal concentration in (a) soil, to know the degree of the soil pollution; (b) roots and leaves of two plant species, Brassica juncea as an accumulator plant and Solanum lycopersicum as a crop plant; and (c) drainage water, to evaluate the heavy metal mobility.

Materials and methods

The study area is located in Sants, a neighborhood in Barcelona (Catalonia, Spain). Thirty kilograms of two representative soil depths (0–15 and 15–40 cm) was sampled and subsequently mixed. The two studied species were cultivated for 3 weeks in greenhouse conditions, and all pots were irrigated with water weekly to field capacity with a nutrient solution (pH = 6.5). If not otherwise stated, given results are means ± standard deviation of four replicated pots each with a composite sample of 12 individual plants per treatment. X-ray fluorescence (FRX) and diethylenetriaminepentaacetic acid soil extraction (DTPA) were used for total and available metal soil contents, respectively. Weekly cumulative drainage water of each pot was collected in polyethylene bottles and stored at 4 °C until analysis.

Results and discussion

The main pollutants are Cu, Pb, and Zn with topsoil total concentrations of approximately 1355, 2230, and 6239 mg kg^?1, respectively. The same soil elements for available fractions were slightly elevated (9.6, 5.8, and 6.7% of total concentration). The concentrations of Cu, Pb, and Zn in the plants’ leaves are greater in B. juncea than in S. lycopersicum. Furthermore, they are greater in the roots than in leaves. The Pb concentrations in a crop plant exceeded the 0.10 mg kg^?1 limit established for vegetables devoted for food in the European legislation. Unusually elevated concentrations of Pb (over 10 μg L^?1) were detected in the drainage water. These values exceeded the acceptable toxic concentrations in waters, according to the Spanish legislation.

Conclusions

The urban soil studied was highly contaminated by Cu, Pb, and Zn, and this pollution is more evident in the topsoil. A great part of these heavy metals was bioavailable for plants. Thus, the two plants (S. lycopersicum and B. juncea) had an ability to transport heavy metals from the roots to the shoots, especially for Zn. Great contents of heavy metals in the drainage water after the irrigation of plants were observed.

     

Crown bulk density and fuel moisture dynamics in <Emphasis Type="Italic">Pinus pinaster</Emphasis> stands are neither modified by thinning nor captured by the Forest Fire Weather Index

Key message

No temporal change was recorded during summer in fuel availability in Pinus pinaster stands, contrary to predictions from the Forest Fire Weather Index. Also, thinning had no mid-term effect on fuel moisture or canopy structure.

Context

Forest fires are a major problem in Mediterranean countries. Management actions, such as fuel reductions, are one of the main tools to diminish fire risk, but the midterm efficacy of such tools remains largely untested with empirical data.

Aims

Here, we test for midterm effects of thinning on fuel moisture and crown bulk density in P. pinaster stands and whether temporal variations in fuel moisture correlated with predictions from the Fire Weather Index, a commonly used index on fire risk, and its components.

Methods

We compared fuel moisture over a fire season and crown bulk density in nine pairs of thinned/unthinned plots 7 years after treatments were applied.

Results

We observed that fuel moisture remained stable during a fire season, as a likely result of drought-induced physiological adjustments, including stomatal regulation and others, which allow leaves to maintain a large humidity even during drought, and that thinning had no midterm effect on fuel moisture or crown bulk density. Moreover, the Fire Weather Index and its components displayed different temporal dynamics than those observed in fuel moisture.

Conclusion

These results are important as they indicate that thinning may only have a limited, short-term impact towards diminishing the potential for crown fire spread in these stands and that current indices to evaluate fire risk may require a re-evaluation.

     

Incorporating rosemary diterpenes in lamb diet to improve microbial quality of meat packed in different environments

The dietary use of phytochemicals may contribute to improving lamb meat preservation under different packing atmospheres. The objective was to test the preservative potential of a dietary rosemary extract (RE) containing carnosic acid and carnosol (at 1:1 w:w) in chilled lamb patties packed in air, vacuum and 70/30 O₂/CO₂ modified atmosphere. Three experimental diets, (C) control, (RE) C plus 600 mg RE/kg feed and (E) C plus 600 mg vitamin E/kg, were given to fattening lambs. Unlike the C‐ and E‐diets, the RE‐diet had a double antimicrobial and antioxidant effect on the lamb patties packed in all the environments studied. The RE‐diet inhibited total viable and lactic acid bacteria and Enterobacteriaceae, but not Brochothrix thermosphacta and Pseudomonas spp. and also improved oxidative stability (measured as CIE Lab color and thiobarbituric reagent substances), appearance and odor. The E‐diet had a better antioxidant effect than the RE‐diet but had no antimicrobial effects. Escherichia coli and Salmonella spp. were not detected. The dietary use of RE was most suitable for preserving vacuum‐packed meat, which is more exposed to spoilage by anaerobic bacteria, while the use of dietary vitamin E allowed better control of oxidation in the meat packed in a bacteriostatic and oxidizing environment.     

An insight on the ethylene biosynthetic pathway of two major fruit postharvest pathogens with different host specificity: <Emphasis Type="Italic">Penicillium digitatum</Emphasis> and <Emphasis Type="Italic">Penicillium expansum</Emphasis>

Although several studies have reported the stress-induced ethylene burst occurring in fruit in response to pathogen attack, relatively little is known about the role of this hormone in the fungal metabolism of many postharvest pathogens. To gain further knowledge, we investigated the ethylene production capacity and which ethylene biosynthetic pathways (including the 1-aminocyclopropane-1-carboxylic acid (ACC), the 2-oxoglutarate (OXO) and the 2-keto-4-methylthiobutyric acid (KMBA) pathways) were used under different in vitro conditions by Penicillium digitatum and Penicillium expansum. Both pathogens were capable of producing ethylene in vitro using different pathways but were dependant on the growing conditions. For instance, both the KMBA and the OXO pathways seemed to be responsible for ethylene biosynthesis in P. digitatum when grown in more stressful conditions (limited surface and nutrient availability as in PDA tubes), while only the KMBA pathway seemed to be activated under other culture conditions (i.e. on PDA plates) or when the fungal mycelium was placed within aqueous solutions containing ethylene precursors. In contrast, the KMBA appeared to be the exclusive pathway responsible for ethylene production by P. expansum yet only when the fungal mycelium was in contact with aqueous solutions containing ethylene precursors. In both pathogens, ethylene production seemed to be synchronized with certain stages of fungal growth rather than conidiation, suggesting a putative role of this hormone in fungal metabolism.     

A Survey of Trunk Disease Pathogens within Rootstocks of Grapevines in Spain

Grapevine trunk disease pathogens, and specifically Petri disease pathogens, can be spread by planting infected plants. Due to the increasing incidence of Petri disease and other young grapevine declines reported lately in Spain, a sampling of plants used before for new vineyards were carried out in 2002 and 2004. A total number of 208 plants (grafted and non grafted) were collected, of which 94 plants (45.2%) were infected with at least one of the following pathogens: Phaeomoniella chlamydospora, and species of Phaeoacremonium, Botryosphaeria, Cylindrocarpon, and Phomopsis. Species of the genera Phaeoacremonium and Botryosphaeria isolated in 2004 were identified using morphological and molecular characters. Species of Phaeoacremonium identified were P. aleophilum and P. parasiticum; and those of Botryosphaeria were B. obtusa, B. dothidea and B. parva. This is the first report of P. parasiticum and B. parva occurring on grapevines in Spain. Distribution of pathogens within the plants was studied in 2004. Phaeomoniella chlamydospora was not detected in the graft union of any plant; however, species of Botryosphaeria and Phomopsis were detected along the plant, but mainly in the graft union; Phaeoacremonium aleophilum was detected along the grafted plants, but not in rooted rootstocks. The results suggest that infected plants used for new plantings in Spain are an important source of primary inoculum of the pathogens associated with grapevine trunk diseases in the field.     

Cattle Grazing Fails to Control Shrub Encroachment in Mediterranean Landscapes

The Common Agricultural Policy supports the use of free-ranging cattle herds to control woody encroachment and fire hazards in Europe. There is, however, little empirical evidence about the effectiveness of extensive grazing to preserve open landscapes in the Mediterranean Basin. In this work, we evaluated the effects of extensive beef cattle grazing on the vegetation structure in a Mediterranean ecosystem using a twofold framework: 1) analyzing temporal changes in the forest, shrub, and grassland cover in areas under different grazing pressures for 16 yr (1993 ? 2009) and 2) studying diet selection to assess the impact of cattle on the local Mediterranean vegetation. Our landscape structure analyses revealed a remarkable change in land cover over the study period. However, woody community dynamics seemed to be more related to natural vegetation succession than to cattle effects. Extensive grazing seemed to preserve grasslands but only at high stocking rates. On the other hand, the diet analyses supported the lack of a role for cattle in encroachment control. Beef cattle diets were based on herbaceous plants (59%) with lower contribution of woody ones (41%). Cattle only showed a significant preference (P < 0.05) for few woody species (Erica multiflora, Olea europaea, Quercus ilex, and Rosmarinus officinalis), mostly at high-density stocking rates. Hence, our results support the idea that extensive cattle grazing alone exerts a negligible effect on shrub encroachment and thus on the risk of fire in the studied Mediterranean area. We urge a redesign of current research to truly integrate extensive cattle grazing as High Nature Value farming in European policies to successfully meet its putative goals, such as shrub encroachment control and wildfire risk prevention.