Aims:  Cyanobacteria‐deprived lichens of the species Canoparmelia caroliniana, Canoparmelia crozalsiana, Canoparmelia texana, Parmotrema sancti‐angeli and Parmotrema tinctorum were screened for the presence of chemo‐organotrophic nitrogen‐fixing bacteria. Methods and Results:  Fifty‐three lichen samples subjected to enrichment selection using a nitrogen‐free minimal medium were positive for acetylene reduction. Seventeen isolates, able to fix nitrogen, belonged to Gamma‐proteobacteria group and were identified as: Acinetobacter sp., Pantoea sp., Pseudomonas sp., Pseudomonas stutzeri, Serratia marcescens and Stenotrophomonas maltophilia, according to 16S rRNA gene sequences and biochemical tests. The excretion of amino acid and phytohormone and the ability of mineral phosphate solubilization were determined in 14 isolates. All isolates were able to release amino acids and 3‐indoleacetic acid. About 64% of the isolates solubilized phosphates and 30% released ethylene. Conclusions:  These data confirm sparse evidence from the literature on the occurrence of chemo‐organotrophic nitrogen‐fixing bacteria in cyanobacteria‐deprived lichens; the isolates presented physiologic features which might benefit the host if they are expressed when the bacteria are harboured by lichens. Significance and Impact of the Study:  Chemo‐organotrophic nitrogen‐fixing bacteria were isolated from a high percentage (72·6%) of cyanobacteria‐deprived lichens. All isolates presented important physiological characteristics, some of which are being described here for the first time.

A Gram-negative, rod-shaped, non-spore-forming and nitrogen-fixing bacterium, designated ICB 89 T , was isolated from stems of a Brazilian sugar cane variety widely used in organic farming. 16S rRNA gene sequence analysis revealed that strain ICB 89 T belonged to the genus

Aims: To investigate the ability of Azospirillum sp., a facultative endophitic diazotrophic bacterium, to release plant growth regulators (PGR) such as polyamines, ethylene, indoleacetic acid and amino acids in both combined-N and N-free cultures. Methods and Results: The presence of those substances was analysed by HPLC. Azospirillum sp. is capable of releasing PGR and amino acids into the culture medium. Conclusions: The type and quantity of the released substances varied, depending on the presence of combined-N in the medium. Significance and Impact of the Study: A better knowledge of PGR produced by Azospirillum sp. has been gained.

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