Nitrification, the oxidation of ammonia via nitrite to nitrate, has always been considered as a two-step process catalyzed by chemolithoautotrophic microorganisms oxidizing either ammonia or nitrite. No known nitrifier carries out both steps, although complete nitrification should be energetically advantageous. This functional separation has puzzled microbiologists for a century. Here we report on the discovery and cultivation of a completely nitrifying bacterium from the genus Nitrospira, a globally distributed group of nitrite oxidizers. The genome of this chemolithoautotrophic organism encodes both the pathways for ammonia and nitrite oxidation, which are concomitantly expressed during growth by ammonia oxidation to nitrate. Genes affiliated with the phylogenetically distinct ammonia monooxygenase and hydroxylamine dehydrogenase genes of Nitrospira are present in many environments and were retrieved on Nitrospira-contigs in new metagenomes from engineered systems. These findings fundamentally change our picture of nitrification and point to completely nitrifying Nitrospira as key components of nitrogen-cycling microbial communities.

135 years ago Ferdinand Cohn, the founder of bacteriology, microscopically observed a conspicuous filamentous bacterium with a complex life cycle and described it as Crenothrix polyspora. This uncultured bacterium is infamous for mass developments in drinking water systems, but its phylogeny and physiology remained unknown. We show that C. polyspora is a gammaproteobacterium closely related to methanotrophs and capable of oxidizing methane. We discovered that C. polyspora encodes a phylogenetically very unusual particulate methane monooxygenase whose expression is strongly increased in the presence of methane. Our findings demonstrate a previously unrecognized complexity of the evolutionary history and cell biology of methane-oxidizing bacteria.drinking water ͉ methane-oxidizing bacteria

The presence and chain length of mycolic acids of bacteria of the genera Corynebacterium, Rhodococcus, Gordona, Mycobacterium, and A,throbacter and of coryneform bacteria containing a type B peptidoglycan were related to the cell surface hydrophobicity ofthe bacteria, which in turn was related to adhesion of the cells to defined surfaces such as Teflon and glass. The onrgin of the overall negative charge of these bacteria is discussed.

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Coryneform bacteria that were isolated from biofilters which are used for waste gas treatment of animal-rendering plant emissions were differentiated and partially identified by using chemotaxonomic methods. On the basis of the results of a numerical analysis of whole-cell fatty acid profiles, 79 isolates were divided into two major groups; the members of the first group contained saturated and monounsaturated fatty acids, whereas the members of the second group were characterized by iso-and anteiso-branched fatty acids. Division into subclusters was based mainly on quantitative differences in fatty acid composition and was confirmed by the results obtained for additional chemical markers (e.g., respiratory quinones, mycolic acids, polar lipids, cell wall amino acids, and whole-cell sugar patterns). By combining the results obtained for chemotaxonomic analyses that were performed for strains containing saturated and monounsaturated fatty acids, we were able to identifly the genus Corynebacterium (two Corynebactenum species were differentiated on the basis of the occurrence of tuberculostearic acid), the genus Gordonu, and the genus Mycobacterium. Among the strains that produced iso-anteiso fatty acid patterns, one subgroup was affiliated with the "nicotianae" group of the genus Arthrobucter; however, some strains contained a new combination of chemical markers. Peptidoglycan type A 4 q L-LYs-G~Y-L-G~u was combined with menaquinones MK-7 and MK-8, whereas peptidoglycan type A 4 q L-LYs-L-G~u occurred together with MK-8 and MK-9. The second subgroup was characterized by a new type B peptidoglycan and MK-11, as well as small amounts of MK-12. Differentiation that was based first on chemotaxonomy and second on physiology gave reliable results. Thus, coryneform strains with new characteristics were isolated from biofilters.Coryneform bacteria have been isolated from the packing material of biofilters that are used for waste gas treatment of animal-rendering plant emissions. These organisms represented a dominant part of the culturable, aerobic, heterotrophic bacterial flora if the waste gases contained a high organic carbon load of mainly carbonyl compounds (3). Valuable information for improving the efficiency and the long-term stability of the process can be derived from analyses of the naturally developing heterogeneous bacterial populations that are responsible for the degradation capacities of biofilters. Studies of the physiological properties of isolates, such as their degradative capacities or their ability to survive under the physicochemical conditions that exist in a biofilter, can disclose the relationship between waste gas composition and adapted bacterial flora. Further characterization of the isolated coryneform bacteria will extend our knowledge about whether these species exist in other habitats, such as wastewater treatment plants or soil, and whether highly specialized, potentially new species might be encountered in biofiltration plants. Therefore, rapid and reliable differentiation and identifica...