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16s rDNA analysis was performed on 32 strains of 26 species of the genera Rhodococcus and Nocardia in order to investigate the phylogenetic structure of these genera within the radiation of other mycolic-acid-containing genera such as Corynebacterium, Dietzia, Gordona, Mycobacterium and Tsukamurella. The genus Rhodococcus shows a complex structure, consisting of six phylogenetically equidistant lineages. The genus Nocardis does not appear to be a sister taxon of Rhodococcus but branches off from within the radiation of Rhodococcus; thus its species can be considered to be derived from a Rhodococcus ancestor. The main known phenotypic feature that separates Nocardia species from those of Rhodococcus appears to be the presence of a cyclic component in menaquinone of the MK-8(H4) type.

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...

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