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An analysis of the nitrogen fixation genes of the Burkholderia endosymbiont of the mycorrhizal fungus Gigaspora margarita show that this organism is closely related to Azospirillum brasilense. Three genes were identified that code for proteins similar to the nitrogenase from other diazotrophs.

Research was conducted to determine whether bacteria in arbuscular mycorrhizal fungal isolates are of common occurrence or sporadic in nature. Data reveal that out of 11 geographically distinct isolates examined, 10 harbored bacteria. The presence of bacteria is confirmed by polymerase chain reaction amplification of their DNA.

A morphological and molecular study shows that the arbuscular-mycorrhizal fungus, Gigaspora margarita, harbors a large homogeneous population of a bacterial endosymbiont within its cytoplasm. The endosymbiont occurs at all stages of the fungal life-cycle. There are about 250,000 live bacteria in each fungal spore. The bacterial endosymbiont is an rRNA group II pseudomonad of the genus Burkholderia. They are viable, and multiply and travel from the spores to the root of the host fungus through the mycelium.

Antimicrobial resistance is a global issue currently resulting in the deaths of hundreds of thousands of people a year worldwide. Data present in the literature illustrate the emergence of many bacterial species that display resistance to known antibiotics; Acinetobacter spp. are a good example of this. We report here that Acinetobacter radioresistens has a Baeyer-Villiger monooxygenase (Ar-BVMO) with 100% amino acid sequence identity to the ethionamide monooxygenase of multidrug-resistant (MDR) Acinetobacter baumannii. Both enzymes are only distantly phylogenetically related to other canonical bacterial BVMO proteins. Ar-BVMO not only is capable of oxidizing two anticancer drugs metabolized by human FMO3, danusertib and tozasertib, but also can oxidize other synthetic drugs, such as imipenem. The latter is a member of the carbapenems, a clinically important antibiotic family used in the treatment of MDR bacterial infections. Susceptibility tests performed by the Kirby-Bauer disk diffusion method demonstrate that imipenem-sensitive Escherichia coli BL21 cells overexpressing Ar-BVMO become resistant to this antibiotic. An agar disk diffusion assay proved that when imipenem reacts with Ar-BVMO, it loses its antibiotic property. Moreover, an NADPH consumption assay with the purified Ar-BVMO demonstrates that this antibiotic is indeed a substrate, and its product is identified by liquid chromatography-mass spectrometry to be a Baeyer-Villiger (BV) oxidation product of the carbonyl moiety of the β-lactam ring. This is the first report of an antibiotic-inactivating BVMO enzyme that, while mediating its usual BV oxidation, also operates by an unprecedented mechanism of carbapenem resistance., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)