Biological control of Botrytis cinerea on stem wounds with moderately halophilic bacteria

International audienceInfection of tomato stem wounds by Botrytis cinerea is an important problem which can cause severe economic losses in greenhouse tomato crops. Three moderately halophilic bacteria were tested for their ability to protect pruning wounds from attacks by B. cinerea under growth chamber conditions. The severity of the disease estimated by the length of the rotted stem was used to calculate the area under the disease progress curves (AUDPC). Bacterial antagonists (B1, B2 and B3) were very effective in controlling Botrytis-infection on the tomato stems during the first 6 days and later by the end of the experiment. Plants treated with Bacillus subtilis (B1) had the lowest AUDPC (0). It was followed by B. subtilis (B3) and Halomonas sp. (B2) with AUDPC of 9.8 and 17.02, respectively. While the B1 strain best inhibited grey mold development when applied as young culture (24 h), the B3 strain performed better as an older culture (48 h). In contrast to the results obtained with Bacillus species, the efficacy of the bacterial treatment B2 seems to be independent of the growth phase. The co-cultures with fungal spores and either B. subtilis (B1) or Halomonas sp. (B2) applied as a 24 h bacterial culture completely inhibited the germination of B. cinerea after 24 h at 21_

MALDI-TOF typing highlights geographical and fluconazole resistance clusters in Candida glabrata2188

Utilizing matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra for Candida glabrata typing would be a cost-effective and easy-to-use alternative to classical DNA-based typing methods. This study aimed to use MALDI-TOF for the typing of C. glabrata clinical isolates from various geographical origins and test its capacity to differentiate between fluconazole-sensitive and -resistant strains. Both microsatellite length polymorphism (MLP) and MALDI-TOF mass spectra of 58 C. glabrata isolates originating from Marseilles (France) and Tunis (Tunisia) as well as collection strains from diverse geographic origins were analyzed. The same analysis was conducted on a subset of C. glabrata isolates that were either susceptible (MIC &lt;/= 8 mg/l) or resistant (MIC &gt;/= 64 mg/l) to fluconazole. According to the seminal results, both MALDI-TOF and MLP classifications could highlight C. glabrata population structures associated with either geographical dispersal barriers (p &lt; 10-5) or the selection of antifungal drug resistance traits (&lt;10-5). In conclusion, MALDI-TOF geographical clustering was congruent with MPL genotyping and highlighted a significant population genetic structure according to fluconazole susceptibility in C. glabrata. Furthermore, although MALDI-TOF and MLP resulted in distinct classifications, MALDI-TOF also classified the isolates with respect to their fluconazole susceptibility profile. Further prospective studies are required to evaluate the capacity of MALDI-TOF typing to investigate C. glabrata infection outbreaks and predict the antifungal susceptibility profile of clinical laboratory isolates</p

Characterization of a novel chitinase from a moderately halophilic bacterium, Virgibacillus marismortui strain M3-23

A new chitinase produced by the moderately halophilic bacterium Virgibacillus marismortui strain M3- 23 was identified and characterized. Distinguishable characteristics of high activity and stability at different pH, temperatures and salinity of M3-23 chitinase are reported. Analysis of the catalytic domain sequence from the enzyme highlighted its relationship to glycosyl hydrolase family 18. Comparison of the deduced chitinase sequence from strain M3-23 to known chitinases from Bacillus species showed low similarity (82%), suggested its novelty. This is the first report of the characterization of chitinase from the species V. marismortui. The halo- and thermo-tolerant nature of the chitinolytic enzyme allows its potential use in agricultural and industrial applications

A survey on approximation algorithms for scheduling with machine unavailability

Abstract. In this chapter we present recent contributions in the field of sequential job scheduling on network machines which work in parallel; these are subject to temporary unavailability. This unavailability can be either unforeseeable (online models) or known a priori (offline models). For the online models we are mainly interested in preemptive schedules for problem formulations where the machine unavailability is given by a probabilistic model; objectives of interest here are the sum of completion times and the makespan. Here, the non-preemptive case is essentially intractable. For the offline models we are interested in non-preemptive schedules where we consider the makespan objective; we present approximation algorithms which are complemented by suitable inapproximability results. Here, the preemptive model is polynomial-time solvable for large classes of settings.

Bioprospecting endophytic bacteria for biological control of coffee leaf rust Bioprospecção de bactérias endofíticas como agentes de biocontrole da ferrugem do cafeeiro

Suppression of plant diseases due to the action of endophytic microorganisms has been demonstrated in several pathosystems. Experiments under controlled conditions involving endophytic bacteria isolated from leaves and branches of Coffea arabica L and Coffea robusta L were conducted with the objective of evaluating the inhibition of germination of Hemileia vastatrix Berk. & Br., race II, urediniospores and the control of coffee leaf rust development in tests with leaf discs, detached leaves, and on potted seedling of cv. Mundo Novo. The endophytic bacterial isolates tested proved to be effective in inhibiting urediniospore germination and/or rust development, with values above 50%, although the results obtained in urediniospore germination tests were inferior to the treatment with fungicide propiconazole. Endophytic isolates TG4-Ia, TF2-IIc, TF9-Ia, TG11-IIa, and TF7-IIa, demonstrated better coffee leaf rust control in leaf discs, detached leaves, and coffee plant tests. The endophytic isolates TG4-Ia and TF9-Ia were identified as Bacillus lentimorbus Dutky and Bacillus cereus Frank. & Frank., respectively. Some endophytic bacterial isolates were effective in controlling the coffee leaf rust, although some increased the severity of the disease. Even though a relatively small number of endophytic bacteria were tested, promising results were obtained regarding the efficiency of coffee leaf rust biocontrol. These selected agents appears to be an alternative for future replacement of chemical fungicide.<br>Supressão de doenças de plantas por microrganismos endofíticos tem sido demonstrada em diversos patossistemas. Neste trabalho foram selecionados isolados de bactérias endofíticas de folhas e ramos de cafeeiro com potencial para o controle biológico da ferrugem do cafeeiro, pois é conhecido que esses microrganismos podem possuir essa característica. Bactérias endofíticas isoladas previamente de folhas e ramos de Coffea arabica L e Coffea robusta L foram avaliadas quanto ao seu potencial de biocontrole da ferrugem do café causada pelo fungo Hemileia vastatrix Berk. & Br., raça 2. As bactérias foram testadas para a inibição da germinação de urediniosporos do fungo e em bioensaios para o controle do desenvolvimento da ferrugem alaranjada do cafeeiro em discos de folhas, folhas destacadas e mudas da cv. Mundo Novo. Os isolados de bactérias endofíticas testados demonstraram eficácia na inibição da germinação de urediniosporos e/ou no desenvolvimento da ferrugem, com valores acima de 50%, embora os resultados obtidos nos testes de germinação de urediniosporos tenham sido inferiores ao tratamento com propiconazole (testemunha padrão). Nos testes em discos de folhas, folhas destacadas e em plantas de cafeeiro, os isolados endofíticos TG4-Ia, TF2-IIc, TF9-Ia, TG11-IIa e TF7-IIa demonstraram melhor controle da ferrugem do cafeeiro. Os isolados endofíticos TG4-Ia e TF9-Ia foram identificados como Bacillus lentimorbus Dutky e Bacillus cereus Frank. & Frank., respectivamente. De acordo com os resultados verifica-se que alguns isolados foram eficientes em controlar a ferrugem do cafeeiro, embora alguns tenham aumentado a severidade da doença. Apesar do número relativamente baixo de bactérias endofíticas testadas, resultados promissores foram obtidos em relação ao controle biológico da ferrugem, sendo que esses poderão no futuro apresentar uma alternativa aos fungicidas