Ring opening of donor-acceptor cyclopropanes with variousN-nucleophiles provides a simple approach to 1,3-functionalized compounds that are useful building blocks in organic synthesis, especially in assembling various N-heterocycles, including natural products. In this review, ring-opening reactions of donor-acceptor cyclopropanes with amines, amides, hydrazines, N-heterocycles, nitriles, and the azide ion are summarized.

Nitrogen fixation (NF) potential was measured in more than 40 samples of soda solonchak soils with the pH of water extract between 9.5 and 11.0 collected in several locations of Central Asia and in Egypt, using the acetylene reduction method. NF was detected in most of the samples. Maximal rates were observed under microaerophilic-anaerobic conditions with glucose as a substrate. In most cases, the NF negatively correlated with salt content and alkalinity. Five enrichments at pH 10 under micro-oxic conditions with glucose resulted in stable haloalkaliphilic mixed cultures, with diazotrophic component(s) active up to 2.0-3.0 M total Na(+). The cultures were dominated by Gram-positive spore-forming bacteria. Molecular cloning of nifH genes demonstrated the presence of two phylogenetic lineages of diazotrophs in the enrichments affiliated with the low-GC Gram-positive bacteria (in rRNA groups 1 and 6 of bacilli and in Clostridiales). Isolation of pure cultures of haloalkaliphilic diazotrophs from micro-oxic enrichments yielded nine strains, comprising two phylogenetic lineages. Most of the isolates (eight) were affiliated with the aerotolerant fermentative haloalkaliphilic bacterium Amphibacillus tropicus and a single strain clustered with the obligately anaerobic haloalkaliphile Bacillus arseniciselenatis. Diazotrophy has never been recognized previously in these groups of Gram-positive bacteria. Overall, the results demonstrated the existence, in soda solonchak soils, of a novel group of free-living fermentative diazotrophic bacteria active at extremely haloalkaline conditions.

Strain MS 6 T was obtained from a microoxic enrichment with a soda soil sample from northeastern Mongolia in nitrogen-free alkaline medium at pH 10. The isolate had clostridia-like motile cells and formed ellipsoid endospores. It was able to fix dinitrogen gas growing on nitrogen-free alkaline medium. Strain MS 6 T was a strictly fermentative bacterium without a respiratory chain, although it had a high catalase activity and tolerated aerobic conditions. It was an obligate alkaliphile with a pH range for growth between 7.5 and 10.6 (optimum at 9.0-9.5). Growth and nitrogen fixation at pH 10 were possible at a total salt content of up to 1.2 M Na + (optimum at 0.2-0.3 M). The dominant cellular fatty acids included C 16 : 0 , C 16 : 1 v7, anteiso-C 15 : 0 and C 14 : 0 . The dominant isoprenoid quinone was MK-7. The cell-wall peptidoglycan contained mesodiaminopimelic acid as the diagnostic diamino acid. 16S rRNA gene sequencing identified strain MS 6 T as a member of the genus Bacillus. Its closest relative was Bacillus arseniciselenatis E1H T . The key functional nitrogenase gene nifH was detected in both strain MS 6 T and its close relative and these strains formed a novel lineage in the nifH gene family. On the basis of these phenotypic and genetic comparisons, strain MS 6 T is proposed to represent a novel species of the genus Bacillus, Bacillus alkalidiazotrophicus sp. nov. with the type strain MS 6 T (5NCCB 100213 T 5UNIQEM U377 T ).Soils containing substantial concentrations of sodium carbonates among the dominant soluble salts in their upper profile (soda or sodic soils, soda solonchaks) are a unique extreme habitat that is characterized by high salinity and alkalinity. These soils are distributed in dry steppe and semidesert areas such as south-western Siberia, north-eastern Mongolia and north China in Central Asia, Egypt in Africa, India, Hungary in Europe and North American Steppes (Basilevich, 1965;Kondorskaya, 1965). In contrast to well-studied soda lakes (Jones et al., 1998;Zavarzin et al., 1999;Oren, 2002;Sorokin & Kuenen, 2005), very little is known about the microbial diversity and functioning of soda solonchaks. Their major differences when compared with soda lakes, which include higher aeration and long desiccation periods, might result in the domination of different haloalkaliphilic taxa, such as Gram-positive bacteria, for example. So far, a few studies on nitrogen fixation (NF) in soda lakes have identified cyanobacteria as the only active diazotrophic group (Oremland, 1990;Herbst, 1998;Zavarzin et al., 1999). Quite recently, this potential ability was also discovered in a few haloalkaliphilic bacteria isolated from soda lake sediments, such as the aerobic gammaproteobacteria Thialkalispira microaerophila and Alkalilimnicola halodurans (Tourova et al., 2007) and the obligate anaerobes Clostridium alkalicellulosi (Zhilina et al., 2005) and Geoalkalibacter ferrihydriticus (Zavarzina et al., 2006). A survey of functional nitrogenase genes in the alkaline saline Mono Lake has also shown the possi...

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