Identification at the species and symbiovar levels of strains nodulating Phaseolus vulgaris in saline soils of the Marrakech region (Morocco) and analysis of the otsA gene putatively involved in osmotolerance.

Salinity is an increasing problem in Africa affecting rhizobia-legume symbioses. In Morocco, Phaseolus vulgaris is cultivated in saline soils and its symbiosis with rhizobia depends on the presence of osmotolerant strains in these soils. In this study, 32 osmotolerant rhizobial strains nodulating P. vulgaris were identified at the species and symbiovar levels by analysing core and symbiotic genes, respectively. The most abundant strains were closely related to Rhizobium etli and R. phaseoli and belonged to symbiovar phaseoli. A second group of strains was identified as R. gallicum sv gallicum. The remaining strains, identified as R. tropici, belonged to the CIAT 899(T) nodC group, which has not yet been described as a symbiovar. In representative strains, the otsA gene involved in the accumulation of trehalose and putatively in osmotolerance was analysed. The results showed that the phylogeny of this gene was not completely congruent with those of other core genes, since the genus Ensifer was more closely related to some Rhizobium species than others. Although the role of the otsA gene in osmotolerance is not well established, it can be a useful protein-coding gene for phylogenetic studies in the genus Rhizobium, since the phylogenies of otsA and other core genes are coincident at the species level.

Occurrence, characterization and insecticidal activity of Bacillus thuringiensis strains isolated from argan fields in Morocco.

Soils collected from five locations in the argan forest (an endemic plant) in Morocco were used to form the first collection of Bacillus thuringiensis (Bt) strains from this area (58 strains). Here we found that the argan forest is a major source of Bt, as 90.62% of the samples contained Bt strains. These strains produced mainly spherical or irregular crystals that in some cases remained adhered to the spore after cell lysis. There was no strain producing bipyramidal crystals, suggesting the absence of strains bearing crv1 genes. This was confirmed by PCR analysis using eight primer pairs that can potentially detect 13 different groups of cry and cyt genes. Strains containing cry7/8 were the most abundant (25.53%), followed by strains harbouring cry9A (14.89%), cry11 (8.51%) and cry4 (4.25%). The mixtures of spores and crystals as well as culture supernatants were assayed for toxicity towards Ceratitis capitata (Medfly), showing up to 30% mortality. Our findings suggest that the argan region is a suitable target for future and wider screening programmes looking for strains bearing toxins or combinations of them to develop more efficient Bt-based formulates.

[Groundwater quality in an arid area of Morocco: impact of pollution on the biodiversity and relationships between crustaceans and bacteria of health interest]. / Qualité des eaux souterraines dans une région aride du maroc: impact des pollutions sur la biodiversité et relations crustacés--bactéries d'intérêt sanitaire.

In the north of Marrakesh (Morocco), the high anthropogenic activity and the permeable nature of the geological ground makes the water of Jbilet vulnerable to contamination. The results of physico-chemical analyses conducted in 2006 showed that two groups of wells could be distinguished. Groundwater of wells located on the right bank of the Tensift River, which are far from any source of pollution, is of fairly good quality, well oxygenated, at neutral pH and with rather weak levels of organic compounds. In contrast, in the other wells in the area of the landfill of the city of Marrakesh and those in the peri-urban area demonstrate deteriorated water quality. The nutriment and organic matter content is quite high. Results of bacteriological analyses of water showed a fairly high faecal contamination. In this area the soil is highly permeable and promotes infiltration of organic pollutants and minerals as well as of pathogen and opportunistic bacteria into groundwater. After their penetration, these microorganisms form films around grain particles. The movements of the stygofauna in the interstices allow bacteria to settle on their exoskeleton and seep into their gut, thus being a potential source of groundwater contamination. An analysis of bacterial flora showed that the rate of bacteria is high in the digestive tract of two crustacean species of the stygobites Typhlocirolana haouzensis and Metacrangonyx spinicaudatus, and that it depends on the species and the bacteria. Bacteria may be one of the potential nutritional resources for stygobites.

Environmental pollutions impacts on the bacteriological and physicochemical quality of suburban and rural groundwater supplies in Marrakesh area (Morocco).

This study scrutinized bacteriological and chemical quality of groundwater supplies of Marrakesh (Morocco) within a year. It assessed the influence of some chemical factors on fecal and opportunistic pathogenic bacterial communities. The annual average densities of fecal coliforms, fecal streptococci and Pseudomonas aeruginosa were respectively: 1891 colony forming units (CFU)/100 mL, 1246 CFU/100 mL and 206 CFU/100 mL. The total occurrence of these bacteria during the period of study was 94%. Detectable non-O1 Vibrio cholerae was present in 81% of samples and the mean abundances ranged from 0 to 11100 MPN/100 mL. Significant correlations between fecal coliforms and streptococci and between fecal coliforms and non-O1 V. cholerae (p < 0.01) were found. Fecal coliforms can be used to detect the presence of non-O1 V. cholerae in this groundwater. These well waters were greatly mineralized, hard, salt with high concentrations of nitrogenous ions and major elements (Ca(2+), Na(+), Cl(-), SO(2-)(4) and K(+)). Most of chemical parameters were relatively steady with time except for calcium, ammonium, nitrites and organic matter which were seasonally influenced. The degree of correlation between chemical parameters and the abundances of isolated bacteria is heterogeneous. The concentrations of calcium and nitrites favored (p < 0.01) the abundance of fecal coliforms and streptococci, but reduced P. aeruginosa abundances. Calcium, salinity, chlorides, nitrites and nitrates tests can be used for screening in situ when the laboratory facilities are limited. This work is expected to assist local authorities in developing plans and actions to reduce the pollution to acceptable levels.

Bioactive compounds from Pseudanabaena species (Cyanobacteria).

Bioactive products of the multicellular filamentous benthic cyanobacterium, Pseudanabaena species, isolated from wastewater stabilization ponds at Marrakech, were tested against some pathogenic micro-organisms. Extracellular and intracellular products released by this blue-green alga in the stationary, growth phase, reduced the survival of Escherichia coli, Salmonella sp., Staphylococcus aureus and Candida albicans, and stimulated the growth of non-O1 V. cholerae, whereas no significant effect was noted on the growth of Candida tropicalis. Intracellular substances (methanolic extract) had a stronger inhibitory effect on these micro-organisms than that produced by extracellular substances. These antibacterial and antifungal substances may have a pharmacological value. They may have an important ecological effect on the composition of the bacterial community in Marrakech stabilization ponds when blooms of Pseudanabaena species occurred in this sewage treatment ecosystem during hot periods.

Dynamics of non-O1 Vibrio cholerae and fecal coliforms in experimental stabilization ponds in the arid region of Marrakesh, Morocco, and the effect of pH, temperature, and sunlight on their experimental survival.

We studied the spatial-temporal dynamics of non-O1 Vibrio cholerae numbers at a stabilization pond treatment plant. This bacterium's seasonal dynamics were the inverse of those of fecal coliforms, with high levels in hot periods and low levels in cold periods. Stabilization pond treatment did not significantly reduce non-O1 V. cholerae numbers between the system's inflow and outflow points. In contrast, fecal coliforms were reduced by 98.95% in hot periods and by 94.91% in cold periods. Significant rho coefficient values for the Spearman correlation between numbers of non-O1 V. cholerae and temperature and pH of 0.91 and 0.76 respectively, were found at the system's outflow point. An experimental study of the effects of pH, temperature, and sunlight on the survival of non-O1 V. cholerae and fecal coliforms confirmed the inverse behaviour of the two bacterial groups noted in the stabilization ponds. Alkaline pH values of 8 and 8.8 promoted the survival of non-O1 V. cholerae and inhibited that of Escherichia coli. Low temperatures (8 degrees C) prolonged E. coli survival (k = 0.002/h), while a temperature of 23 degrees C reduced it markedly (k = 0.022/h). Non-O1 V. cholerae did not survive as well as E. coli at 8 degrees C (k = 0.009/h). The effect of temperature on non-O1 V. cholerae appeared to be closely linked to nutrient levels. Non-O1 V. cholerae appeared to be less sensitive to sunlight than E. coli whose survival was markedly reduced particularly during summer periods. Non-O1 V. cholerae and E. coli did not behave in the same way in water subjected to stabilization pond treatment. The use of fecal coliforms as an indicator of the potential health hazard of the effluent may not be adequate for this treatment procedure.