Bacteria with the ability to grow on nitrogen-free media and with nitrogenase activity under aerobic or microaerobic conditions were isolated from sugarcane roots collected from four different agricultural locations in Granada (Spain). Isolates were Gram negative rods and were identified as Azotobacter chroococcum and Azospirillum brasilense. Our results suggest that Azotobacter isolates do not have a particular affinity for sugarcane rhizospheres and that, on the contrary, Azospirillum isolates show specific association and perhaps endophytic colonization of sugarcane. However, obligate endophytes (Gluconacetobacter diazotrophicus) were not found in the apoplastic fluid of the stems and macerates extracts of sugarcane tissues with the procedure applied. Population of this microorganism might be in low number in the Spanish sugarcane varieties studied which is also discussed.

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We studied the growth and capacities for pesticides removal of bacterial strains isolated from the Laguna Grande, an oligotrophic lake at the South of Spain (Archidona, Málaga). Strains were isolated from water samples amended with 10 and 50 microg/ml of nine pesticides: organochlorinated insecticides (aldrin and lindane), organophosphorous insecticides (dimetoate, methyl-parathion and methidation), s-triazine herbicides (simazine and atrazine), fungicide (captan) and diflubenzuron (1-(-4-chlorophenyl)-3-(2,6-difluorobenzoyl urea), a chitinase inhibitor. The majority of the strains belonged to the genera Pseudomonas and Aeromonas and only 9% of the total of strains were Gram positive. From all the strains isolated, only 22 showed a wide growth range in all the pesticides tested and 4 of them were chosen for pesticide removal studies. The genetic identification of these strains showed their affiliation to Pseudomonas pseudoalcaligenes, Micrococcus luteus, Bacillus sp. and Exiguobacterium aurantiacum. These last two strains were those that showed the highest pesticide removal capacities and a high bacterial growth.

Azotobacter vinelandii strain ATCC 12837 and A. chroococcum strain H23 (CECT 4435) were able to grow on N‐free or NH4Cl‐amended chemically‐defined (Burk's) media, with protocatechuic acid (1–2 mmol l−1) or sodium p‐hydroxybenzoate (1–10 mmol l−1) as sole carbon (C) sources. At a concentration of 2 mmol l−1, both substrates supported nitrogen fixation (acetylene reduction assay) at similar or higher rates than bacteria grown in control media amended with 2 mmol l−1 sodium succinate as C source. The two strains produced the B‐group vitamins niacin, pantothenic acid, thiamine, riboflavin and biotin after 72 h of growth in chemically‐defined media with 2 mmol l−1 protocatechuic acid, sodium p‐hydroxybenzoate or sodium succinate as sole C source, either in N‐free media or in media amended with 0·1% NH4Cl. Quantitative production of all vitamins was affected by the use of the different C and N substrates.

A novel bacterium, strain BM90, previously isolated from Tyrrhenian Sea, was metabolically characterized testing its ability to use 95 different carbon sources by the Biolog system. The bacterium showed a broad capacity to use fatty-, organic- and amino-acids; on the contrary, its ability to use carbohydrates was extremely scarce. Strain BM90 was identified and affiliated to Delftia tsuruhatensis by molecular techniques based on 16S rRNA gene sequencing. D. tsuruhatensis BM90, cultivated in shaken cultures, was able to grow on various phenolic compounds and to remove them from its cultural broth. The phenols used, chosen for their presence in industrial or agro-industrial effluents, were grouped on the base of their chemical characteristics. These included benzoic acid derivatives, cinnamic acid derivatives, phenolic aldehyde derivatives, acetic acid derivatives and other phenolic compounds such as catechol and p-hydroxyphenylpropionic acid. When all the compounds (24) were gathered in the same medium (total concentration: 500 mg/l), BM90 caused the complete depletion of 18 phenols and the partial removal of two others. Only four phenolic compounds were not removed. Flow cytometry studies were carried out to understand the physiological state of BM90 cells in presence of the above phenols in various conditions. At the concentrations tested, a certain toxic effect was exerted only by the four compounds that were not metabolized by the bacterium.

Mixed inoculation of the grain legume faba bean (Vicia faba L.) with Rhizobium leguminosarum bv. viceae strain Z25 and ®ve different Azotobacter chroococcum or A. vinelandii strains, under gnotobiotic conditions of culture, resulted in signi®cant effects on nodulation, plant growth and nitrogenase activity (acetylene-reduction activity, ARA) of nodulated roots at thē owering stage. A. chroococcum strain H23 and A. vinelandii strains ATCC 12837 and Dv42 promoted plant growth, signi®cantly increasing dry matter accumulation in all plant parts including nodules, as well as total N content. A. chroococcum strain DR26 increased ARA of nodulated roots over 100% when compared with control plants inoculated with Rhizobium alone. Only A. chroococcum strain DR25 decreased plant growth. The effects of each Azotobacter strain are signi®cantly related to viable cell numbers applied as inocula. #