A comprehensive DNA-DNA hybridization study was performed by using 183 strains of the genus Xanthomonus. This genus was shown to comprise 20 DNA homology groups which are considered genomic species. Four groups corresponded to the previously described species Xanthomonas albilineans, Xanthomonas fiagariae, Xanthomonas oryzae, and Xanthomonas populi. The previously described species Xanthomonas campestris was heterogeneous and was divided into 16 DNA homology groups. One of these groups exhibited a high level of DNA homology with Xanthomonas axonopodis. The 62 pathovars represented in this study were. allocated to appropriate species. Our results, together with previous taxonomic data, supported a comprehensive revision of the classification of the genus Xanthomonas. The species X. albilineans, X. jiagarke, X. oryme, and X. populi are not affected. The type species of the genus,X. campestris (Pammell895) Dowson 1939, is emended to include only the pathovars obtained from crucifers (i.e., X. campestris pv. aberrans, X. campestris pv. armoraciae, X. campestris pv. barbareae, X. campestris pv. campestris, X. campestris pv. incanae, and X. campestris pv. raphani). vesicatoria. Differentiating characteristics were determined for the new species on the basis of metabolic activity on a range of carbon substrates by using the Biolog GN microplate system. X. axonopodisIn the past, the taxonomy of bacteria has been dominated by a phenetic approach, and many classification systems have been and still are based on what were thought to be important phenotypic properties. The taxonomy of the genus Xanthomonas has followed this tendency in that a single phenotypic feature, host specificity, has determined the classification of the genus. Since the first report of a xanthomonad (55) until 1974, it was common practice to define a plant-pathogenic xanthomonad isolated from a new host plant as a new Xanthomonas species. The unreasonable number of nomenspecies resulting from this practice was drastically reduced by Dye and Lelliott (19), who justified their reclassification by referring to the impossibility of differentiating nomenspecies by any feature other than host specificity (10,17). Later, names of former nomenspecies were preserved in a special-purpose classification (18) as Xanthomonas campestris pathovar names.The original classification of the genus Xanthomonas, in which all of the phytopathological variants of X campestris were recognized as separate species, was not sound taxonomically. With the exception of the ambiguous feature of host specificity, few biochemical and phenotypic characteristics were used to differentiate the species. In the last few years, * Corresponding author. Mailing address: Laboratorium voor Microbiologie, Universiteit Gent, Ledeganckstraat 35, B-9000 Ghent, Belgium.workers have provided evidence that the current classification, in whichX. campestris contains more than 140 pathovars, is not a reflection of genomic relationships. The first DNA hybridization experiments performed with Xanthomonas...

The phylogenetic positions and G+C contents of most species belonging to the genera Flavobacterium, Cytophaga, and Flexibacter and several related taxa were determined. Most of the strains included in this study belong to rRNA superfamily V, as shown by DNA-rRNA hybridization data, but the three main genera are highly polyphyletic. Several so-called Cytophaga and Flexibacter species isolated from soil and freshwater cluster with the type species of the genus Flavobacterium, Flavobacterium aquatile, and with Flavobacterium branchiophilum. The fatty acid and protein profiles of members of this group of organisms were determined. We provide an emended description of the genus Flavobacterium and propose new combinations for the following 7 of the 10 validly described species included in this genus: Flavobacterium columnare, Flavobacterium JEevense, Flavobacterium johnsoniae (we also correct the specific epithet of this taxon), Flavobacterium pectinovorum, Flavobacteriurn psychrophilum, Flavobacterium saccharophilum, and Flavobacterium succinicans. A new name, Flavobacterium hy&tis, is proposed for [Cytophaga] aquatilis Strohl and Tait 1978. The emended genus FZavobucterium contains bacteria that have the following main characteristics: gram-negative rods that are motile by gliding, produce yellow colonies on agar, are chemoorganotrophs and aerobes, decompose several polysaccharides but not cellulose, and are widely distributed in soil and freshwater habitats. Three Flavobacterium species are pathogenic for fish. The G+C contents of Flavobacterium DNAs range from 32 to 37 mol%. An emended description of the family Flavobacteriaceae is also provided.The long and complex history of the genera Flavobacterium, Cytophaga, and Flexibacter and the heterogeneity of these genera have been well documented. The most recent reviews of the taxonomy of these organisms were published in Bergey's Manual of Systematic Bacteriology (40, 68), in The Prokaryotes 2nd ed. (37,69), and in Advances in the Taxonomy and Significance of Flavobacterium, Cytophaga and Related Bacteria (38,70). Because of the numerous phenotypic similarities of Flavobacterium, Cytophaga, and Flexibacter strains, for a long time differentiation of these genera has been based on the presence (in the genera Cytophaga and Flexibacter) or absence (in the genus Flavobacterium) of gliding motility. This characteristic, whose relevance for genus delineation has been questioned, is probably an ancestral property of this bacterial group that was lost by some organisms in the course of evolution (68, 101).The genus Flavobacterium was created in 1923 (7) to accommodate gram-negative, non-spore-forming, yellow-pigmented rods that produce acid from carbohydrates weakly (40). Because of this limited definition, the genus rapidly acquired many poorly defined species and consequently became very heterogeneous. However, through successive emendations, the genus Flavobacterium was restricted to nonmotile and nongliding species and thus achieved what could be considered reasonable h...

No abstract

No abstract

NOTESOur present knowledge concerning the genotypic, chemotaxonomic, and phenotypic characteristics of members of the genus Flavobacterium and some related genera, including the genus Weekella, was used to revise the classification of these organisms. The generically misclassified organisms Flavobacterium balustinum, Flavobacterium gleum, Flavobacterium indologenes, Flavobacterium indoltheticum, Flavobacterium meningosepticum, and Flavobacterium scophthalmurn are included in a new genus, Chryseobacterium, with Chryseobacterium gleum as the type species. The generically misclassified organism Flavobacterium breve is included in the revived genus Empedobacter as Empedobacter brevis, whereas the generically misclassified organism W e e k e h zoohelcum is included in the new genus Bergeyella as Bergeyella zoohelcum.