Orobanche crenata (crenate broomrape) produces serious damage to many legume crops and particularly becomes a limiting factor for pea production in the Mediterranean basin. Nodulation effects on pea-broomrape relationships were studied using the commercial pea cultivar Douce de Provence and different Rhizobium strains using pot and Petri dish experiments. First, the benefit of bacterial inoculation on plant growth and efficiency of N incorporation were demonstrated for two isolates, P.SOM and P.1236. These isolates did not influence parasite germination induced by the artificial stimulant, GR24. In contrast, pea root inoculation with P.SOM and P.1236 isolates led to a reduced root infection by O. crenata, resulting from a lower Orobanche germination rate close to pea roots and a limited capacity of the parasitic seedlings to develop tubercles. Broomrape necrosis was observed both before and after parasite attachment to inoculated pea roots. Concomitantly, reduction in infection was accompanied by enhanced peroxidase activity and constantly high phenylalanine ammonia lyase activity in pea roots. These data suggest the involvement of these enzymes in pea resistance to crenate broomrape induced by the compatible rhizobia. Management of Orobanche via crop selection based on these enzyme systems is a viable option. Keywords: biocontrol, legumes, peroxidase, phenylalanine ammonia lyase. MABROUK Y, ZOURGUI L, SIFI B, DELAVAULT P, SIMIER P, BELHADJ O (2007) Some compatible Rhizobium leguminosarum strains in peas decrease infections when parasitised by Orobanche crenata. Weed Research 47, 44-53.

During the first quarter of 1996, a major outbreak of clinical infection caused by multiresistant Klebsiella pneumoniae (MRKP) occurred in the neonatal ward of the 'Maternité Wassila Bourguiba' in Tunis, Tunisia. In total, 32 isolates of MRKP, comprising 23 clinical isolates and nine surveillance isolates, were recovered during this period and analysed for epidemiological relatedness. The isolates were compared with 17 other isolates of MRKP that were recovered during 1995. Macrorestriction profiles of total genomic DNA following XbaI restriction endonuclease digestion were analysed by PFGE; this typing classified 56 % of the 32 isolates recovered in 1996 into two major clusters. Cluster A included ten isolates from 1996 and three isolates recovered in 1995, whereas cluster B included eight isolates from the outbreak of 1996. The remaining isolates were genetically unrelated to those of clusters A and B; they constituted sporadic strains. The two major clusters were also evident using other molecular typing methods, such as random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC)-PCR , where isolates of clusters A and B could be identified on the basis of their discriminative patterns. This investigation showed the predominance of two epidemic strains, and illustrated the ease with which MRKP strains can disseminate and persist within a single ward.

Strong demand for food requires specific efforts by researchers involved in the agricultural sector to develop means for sufficient production. While, agriculture today faces challenges such as soil fertility loss, climate change and increased attacks of pathogens and pests. The production of sufficient quantities in a sustainable and healthy farming system is based on environmentally friendly approaches such as the use of biofertilizers, biopesticides and the return of crop residues. The multiplicity of beneficial effects of soil microorganisms, particularly plant growth promotion (PGP), highlights the need to further strengthen the research and its use in modern agriculture. Rhizobia are considered as PGP comes in symbiosis with legumes taking advantage of nutrients from plant root exudates. When interacting with legumes, rhizobia help in increased plant growth through enriching nutrients by nitrogen fixation, solubilizing phosphates and producing phytohormones, and rhizobia can increase plants' protection by influencing the production of metabolites, improve plant defense by triggering systemic resistance induced against pests and pathogens. In addition, rhizobia contain useful variations to tolerate abiotic stresses such as extreme temperatures, pH, salinity and drought. The search for rhizobium tolerant strains is expected to improve plant growth and yield, even under a combination of constraints. This chapter summarizes the use of rhizobia in agriculture and its benefits.

Using reversible electropermeabilization of cells and spheroplasts, we show that the cell wall and plasma membrane partly account for bleomycin resistance by acting as two independent barriers. We also report on the presence of a membrane protein that may be responsible for bleomycin internalization and toxicity in Saccharomyces cerevisiae.The antitumor drug bleomycin (BLM) was used to analyze the contributions of the cell wall and the cell membrane in limiting the uptake of hydrophilic cytotoxic molecules during the stationary phase of the yeast Saccharomyces cerevisiae. Two yeast strains with different sensitivities to BLM were tested: YPH-1 (MATa ura3-52 lys2-801am ade2-101oc) (14) and FY67 (MATa trp1-⌬36) (15).Yeast cells were grown to a density of approximately 10 8 cells/ml through shaking and aeration in complete YPD (yeast extract-peptane-dextrose) medium (13) at 30°C. We determined the percentage of reversibly permeabilized cells by the lucifer yellow test (6) and prepared spheroplasts as described previously (2) with lyticase from Sigma. A total of 5 ϫ 10 7 cells were electropermeabilized as described previously (1) in the absence of dithiothreitol by using eight 100-s square-wave pulses at a frequency of 1 Hz. Spheroplasts were electroporated in 1.2 M sorbitol-1 mM MgCl 2 -10 mM Tris-HCl (pH 7.5). No effect on survival was detected when electric fields from 0 to 2,000 V/cm were applied to either the cells or the spheroplasts. Optimal conditions were chosen such that the electric field resulted in 70 to 75% survival and electropermeabilization of approximately 85% of those surviving cells (i.e., 4,640 and 3,920 V/cm for FY67 and YPH-1 cells, respectively, and 4,300 and 3,900 V/cm for FY67 and YPH-1 spheroplasts, respectively) (Fig. 1). Our results show that the optimal permeabilization value is a function of the difference between the mean cell diameter for the two strains, as determined by flow cytometry (50.5 Ϯ 2.12 and 58 Ϯ 2.83, in arbitrary units, for FY67 and YPH-1 cells, respectively, and 49 Ϯ 2.15 and 56.5 Ϯ 1.41 for FY67 and YPH-1 spheroplasts, respectively). Our data also show that the removal of the cell wall does not significantly alter the cell diameter and has almost no influence on the optimal electrical field strength applied to the spheroplasts. Thus, the presence of the cell wall does not affect the electropermeabilization of the plasma membrane.Both yeast strains were exposed to BLM for 5 min at concentrations ranging from 0.3 nM to 100 M, with and without application of the electric pulses. In this study, a BLM-Fe complex in a 1:3 molar ratio was used to induce cytotoxicity in the yeasts (7). The cytotoxicity of BLM was determined by determination of the relative cloning efficiencies of the treated cells. The BLM concentration that induced 50% lethality (the minimal bactericidal concentration for 50% of the cells [MBC 50 ]) for the nonelectropermeabilized YPH-1 yeast cells was 4 M. The FY67 yeast cells were approximately 30 times more resistant to BLM, with an MBC 50 of 120 M ( Fig...