Four novel bacterial strains were isolated from cryogenic tubes used to collect air samples at altitudes of 24, 28 and 41 km. The four strains, 24K T , 28K T , 41KF2a T and 41KF2b T , were identified as members of the genus Bacillus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that three of the strains, 24K T , 28K T and 41KF2a T , are very similar to one another (>98 % sequence similarity) and show a similarity of 98-99 % with Bacillus licheniformis and 98 % with Bacillus sonorensis. DNA-DNA hybridization studies showed that strains 24K T , 28K T and 41KF2a T exhibit <70 % similarity with each other and with B. licheniformis and B. sonorensis. Differences in phenotypic and chemotaxonomic characteristics between the novel strains and B. licheniformis and B. sonorensis further confirmed that these three isolates are representatives of three separate novel species. Strain 41KF2b T showed 100 % 16S rRNA gene sequence similarity to Bacillus pumilus, but differed from its nearest phylogenetic neighbour in a number of phenotypic and chemotaxonomic characteristics and showed only 55 % DNA-DNA relatedness. Therefore, the four isolates represent four novel species for which the names Bacillus aerius sp. nov. (type strain, 24K T =MTCC 7303 T =JCM 13348 T), Bacillus aerophilus sp. nov. (type strain, 28K T =MTCC 7304 T =JCM 13347 T), Bacillus stratosphericus sp. nov. (type strain, 41KF2a T =MTCC 7305 T =JCM 13349 T) and Bacillus altitudinis sp. nov. (type strain, 41KF2b T =MTCC 7306 T =JCM 13350 T) are proposed.

Samples of air removed from the stratosphere, at an altitude of 41 km, were previously found to contain viable, but non-cultureable bacteria (cocci and rods). Here, we describe experiments aimed at growing these, together with any other organisms, present in these samples. Two bacteria (Bacillus simplex and Staphylococcus pasteuri) and a single fungus, Engyodontium album (Limber) de Hoog were isolated from the samples. Although the possibility of contamination can never be ruled out when space-derived samples are studied on earth, we are confident that the organisms originated from the stratosphere. Possible mechanisms by which these organisms could have attained such a height are discussed.

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Green synthesis is an attractive and eco-friendly approach to generate potent antibacterial silver nanoparticles (Ag-NPs). Such particles have long been used to fight bacteria and represent a promising tool to overcome the emergence of antibiotic-resistant bacteria. In this study, green synthesis of Ag-NPs was attempted using plant extracts of Aloe vera, Portulaca oleracea and Cynodon dactylon. The identity and size of Ag-NPs was characterized by ultraviolet-visible spectrophotometer and scanning electron microscopy. Monodispersed Ag-NPs were produced with a range of different sizes based on the plant extract used. The bactericidal activity of Ag-NPs against a number of human pathogenic bacteria was determined using the disc diffusion method. The results showed that Gram positive bacteria were more susceptible than Gram negative ones to these antibacterial agents. The minimum inhibitory concentration was determined using the 96-well plate method. Finally, the mechanism by which Ag-NPs affect bacteria was investigated by SEM analysis. Bacteria treated with Ag-NPs were seen to undergo shrinkage and to lose their viability. This study provides evidence for a cheap and effective method for synthesizing potent bactericidal Ag-NPs and demonstrates their effectiveness against human pathogenic bacteria.

The paper reviews the recently published literature (mainly since 1970) on the effects of pesticides on the major biogeochemical cycles in soils, including transformations of' carbon, nitrogen, phosphorus sulphur, trace elements and soil enzymes.The main conclusion is that pesticides. with the exception of fumigants and some broad spectrum fungicides, have little deleterious influence on soil processes when applied at field rates.Obvious gaps in our knowledge of pesticide-soil interactions are pointed out and suggestions are made where future research is needed.