Acylhomoserine lactone production by bacteria associated with cultivated mushrooms

The main bacterial pathogens of cultivated mushroom as well as mushroom-associated bacteria, which were isolated from Agaricus bisporus, Pleurotus ostreatus and Pleurotus eryngii mushroom niches, were evaluated for the production of N-acyl-L-homoserine lactones (AHLs) by using four bioreporters. Furthermore, identification of AHLs by LC-ESI-FTICR MS was performed on culture filtrates of selected pathogens and mushroom-associated bacteria strains, which resulted in inducing at least one of the four bioreporters. Strains of Burkolderia gladioli pv. agariciola, Pseudomonas agarici and Pseudomonas gingeri, but not those of Pseudomonas tolaasii and Pseudomonas reactans, produced an array of AHLs depending on the strain. This is the first report of AHL production by mushroom bacterial pathogens. Forty-four of 236 bacterial isolates obtained from different niches of cultivated mushrooms, in part identified by the Biolog identification system, were demonstrated to produce AHLs. Among them, seven mushroom-associated bacterial species were for the first time demonstrated to produce the above signal molecules. In the culture filtrates of a certain number of isolates/strains the AHL-hydrolyzed forms were also present. The minimal signal inducing concentration (MSIC) of selected pure AHLs was also determined for the four bioreporters used in this study.     

Studies on pathogenesis of Rhizoctonia solani in beans: an evaluation of the possible roles of phenylacetic acid and its hydroxy derivatives as phytotoxins

All isolates of Rhizoctonia solani used in this study, when grown in Weinhold medium supplemented with phenylalanine, accumulated phenylacetic acid (PAA) and its ortho-, meta- and para-hydroxy derivatives in culture. Major metabolites which accumulated were PAA and m-hydroxyphenylacetic acid (m-OH-PAA). However, the accumulation in vitro of total phenylacetic acid derivatives by isolates of R. solani was not related to their pathogenicity and/or virulence. On the contrary, the non-pathogenic and weakly virulent isolates of R. solani produced the highest quantities of PAA-derivatives per unit weight of mycelium in comparison to the highly virulent isolates.The phenylacetic acid derivatives used in this investigation, when bioassayed at high concentrations, caused inhibition of growth of tomato and bean seedlings. The most active compounds were PAA and -α-methoxy-phenylacetic acid (MeO-PAA). However, when m-OH-PAA was assayed at low concentrations there was a stimulation of seedling growth. In addition, when m-OH-PAA solutions were injected into bean hypocotyls or into tobacco leaves they never caused necrotic lesions or symptoms resembling those caused by R. solani on beans.These results indicate that PAA-derivatives are not directly involved in pathogenesis of R. solani in beans.     

The effect of social isolation,gender and familiarity with the experimental procedure on tests of porcine nociceptive thresholds

ObjectiveTo investigate the effects of habituation and isolation on mechanical nociceptive thresholds in pigs at the pelvic limbs and at the tail.Study designProspective randomized multifactorial study.AnimalsThirty-two healthy castrated male (experiment 1), and 12 castrated male and 12 female (experiment 2) Danish Landrace × Yorkshire pigs, weighing 63.5 ± 0.8 kg and 55.4 ± 0.6 kg (the mean ± SD, experiment 1 and 2, respectively).MethodsMechanical nociceptive thresholds were quantified with a von Frey anesthesiometer applied to two distinct anatomical regions (tail and pelvic limbs). Pigs receiving the mechanical challenge in the pelvic limbs were tested inside a cage, whereas pigs exposed to stimuli at the tail region were tested in an open arena. For both experiments, the effect of familiarity to the procedure was evaluated by comparing thresholds of nociception in habituated versus naïve pigs. The presence of a companion animal was also evaluated in pigs receiving stimuli at the pelvic limbs.ResultsPigs tested inside the cage were affected by the habituation to the procedure as indicated by the increase in willingness and time spent by the animals in the test cage. This effect was reflected in the lower mechanical nociceptive thresholds (medians with 25–75 percentiles) recorded for familiar pigs compared with naïve animals [495 g (302–675) versus 745 g (479–1000), respectively; p = 0.026]. Mechanical nociceptive thresholds measured at the tail of the pigs in the open arena were not affected by the familiarity of the animals with the experimental procedure.Conclusions and clinical relevanceThe current results reiterate the value of habituation in research involving animal behaviour. Further characterization of the methodology is needed to allow its application in the evaluation of clinical conditions in pigs.     

Using energy balance data for assessing evapotranspiration and crop coefficients in a Mediterranean vineyard

Improving water use efficiency is a key element of water management in irrigated viticulture, especially in arid or semi-arid areas. In this study, the micrometeorological technique “Eddy Covariance” was used to directly quantify the crop evapotranspiration (ET) and to analyze the complex relationships between evapotranspiration, energy fluxes, and meteorological conditions. Both observed Direct measurements (DIR) of latent heat flux (LE) and observed from the residual of the energy balance (REB) equation were used for crop evapotranspiration calculations. Observed crop coefficients (K _cms) were then determined using the standardized reference evapotranspiration (ET_o) equation for short canopies. In addition, linear approximations from observations were used to model the seasonal trend lines for crop coefficients and K _cs values were parameterized by first identifying the beginning and end of each growth stage. The modeled K _cs values were used to predict daily ET from ET_o measurements and compared with values from literature. The daily observed DIR ET values (ET_do) were lower than REB ET (ET_ro) during periods with precipitation, but they were similar during dry periods, which implies that energy balance closure is better when the surface is drier. Comparisons between modeled ET and crop ET estimated using K _c values from best agreement was observed between the modeled REB and FAO 56 and the local K _c values provided by the Regional Agency ARPAS showed good agreement with observed ET (from DIR and REB data) than the FAO 56 ones. The study confirmed that the availability of locally driven K _c could be relevant to quantify the crop water requirement and represents the starting point for a sustainable management of water resources.     

Assessing temporal variation of primary and ecosystem production in two Mediterranean forests using a modified 3-PG model

Context

Forest ecosystem carbon uptake is heavily affected by increasing drought in the Mediterranean region.

Aims

The objectives of this study were to assess the capacity of a modified 3-PG model to capture temporal variation in gross primary productivity (GPP), and ecosystem net carbon uptake (NEE) in two Mediterranean forest types.

Methods

The model was upgraded from a monthly (3-PG) to a daily time step (3-PG_day), and a soil water balance routine was included to better represent soil water availability. The model was evaluated against seasonal GPP and NEE dynamics from eddy covariance measurements.

Results

Simulated and measured soil water content values were congruent throughout the study period for both forest types. 3-PG_day effectively described the following: GPP and NEE seasonal patterns; the transition of forest ecosystems from carbon sink to carbon source; however, the model overestimated diurnal ecosystem respiration values and failed to predict ecosystem respiration peaks.

Conclusions

The model served as a rather effective tool to represent seasonal variation in gross primary productivity, and ecosystem net carbon uptake under Mediterranean drought-prone conditions. However, its semi-empirical nature and the simplicity inherent in the original model formulation are obstacles preventing the model working well for short-term daily predictions.     

Paraneoplastic hypoglycemia in a diabetic dog with an insulin growth factor-2-producing mammary carcinoma

A 6-year-old intact female Labrador Retriever had diabetes mellitus, which had been difficult to control with insulin. The dog also had a solid ductal mammary carcinoma with very rapid growth, which was temporally related to onset of hypoglycemia. Eight months after initial diagnosis of diabetes, the dog had a hypoglycemic crisis. Insulin administration was stopped and serum glucose concentration returned to normal. Three months after discontinuing insulin, another hypoglycemic crisis occurred. During subsequent months, serum glucose concentrations remained at life-threatening levels (1.64-2.12 mmol/L, reference interval 4.44-6.66 mmol/L) simultaneously with an increase in the size of the mammary tumor, which reached a diameter of about 16 cm. At the time of surgery for removal of the tumor serum glucose concentration was 2.20 mmol/L and was then monitored every 3 hours after excision of the tumor. The glucose concentration continued to rise and reached 9.99 mmol/L 12 hours after the removal of the mammary tumor. Immunohistochemical staining demonstrated expression of insulin growth factor-2 by tumor cells, which apparently had caused the hypoglycemia during tumor growth even in a diabetic dog. Hyperglycemia associated with diabetes was pronounced after excision of the tumor and had been masked by the paraneoplastic effect of the tumor.     

Characterization of Pseudomonas syringae ssp. savastanoi strains isolated from ash

Isolates of Pseudomonas syringae ssp. savastanoi from ash were examined for their ability to produce phytohormones in culture and for pathogenicity, in comparison with isolates from olive and oleander. Nineteen out of 20 ash isolates produced low levels of indole-3-acetic acid and its methyl ester but no cytokinins. In contrast, the remaining isolate, NCPPB3474, accumulated high levels of auxins and cytokinins in culture, comparable to those of olive and oleander strains. Hybridization of DNA preparations with tryptophan mono-oxygenase ( iaaM ) and isopentenyl transferase ( ipt ) gene-containing probes showed sequences of DNA homologous to both probes only in isolate NCPPB3474, and in which the iaaM and ipt genes were located on the chromosome and on a plasmid of about 80 kb, respectively. When assayed for pathogenicity on ash, olive and oleander, 19 of the 20 ash isolates caused disease only on ash but NCPPB3474 caused knots on both ash and olive. Oleander isolates infected all three hosts whereas those from olive caused symptoms only on olive and ash. All the cultures were able to multiply in host plant tissues, but the growth rates and final population densities were correlated to the plant species inoculated and the host origin of the isolates. In particular, the highest population densities were reached by isolates capable of causing symptoms on the inoculated host. The phytohormone production shown by ash, olive and oleander isolates of P. syringae ssp. savastanoi was in accordance with the type of symptoms: cankers accompanied by wart-like excrescences on ash and knots on olive and oleander. Furthermore, the pathogenic features of these isolates and, in particular, their growth patterns in the different host tissues, support previous evidence on the existence of three distinct pathovars in P. syringae ssp. savastanoi .     

Forest humus forms as potential indicators of soil carbon storage in Mediterranean environments

The aim of this work was to investigate the potential of forest humus forms as indicators of soil C storage. To this purpose, Mediterranean forest soils in Southern and Central Italy were examined. Sites differed for elevation, climate, parent material and vegetation conditions, while summer drought was the common ecological factor. A morpho-functional criterion, based on holorganic layers thickness and A horizon properties, was used to classify humus forms, which ranged from Dysmoder to Eumull. Such variability allowed understanding of factors influencing organic matter storage. The relations between carbon stock and humus form were investigated for the topsoil layer (0–20 cm), which was supposed to contain the soil C pools most sensitive to climate change. We found that humus forms can be grouped in statistically different populations, with respect to topsoil C stocks. The use of A horizon structure was the main diagnostic criterion and represented the most effective approach to humus classification in Mediterranean conditions. It appears that humus forms have a clear potential as indicators of organic carbon status in Mediterranean forest soils.