Five strains of an unusual Gram-negative, catalase-positive, oxidase-positive, coccobacillus-shaped bacterium isolated from the lungs and heart of pigs with pneumonia and pericarditis were characterized by phenotypic and molecular genetic methods. On the basis of cellular morphology and biochemical criteria, the isolates were tentatively assigned to the family Neisseriaceae, although they did not appear to correspond to any recognized genus or species. Comparative 16S rRNA gene sequencing showed that the five unidentified strains were phylogenetically highly related to each other and represent a hitherto unknown subline within the family Neisseriaceae. On the basis of both phenotypic and phylogenetic evidence, it is proposed that the unknown isolates from pigs be classified as a novel genus and species within the family Neisseriaceae, for which the name Uruburuella suis gen. nov., sp. nov. is proposed. The type strain of U. suis is 1258/02 T (=CCUG 47806 T =CECT 5685 T ).The family Neisseriaceae was proposed by Prévot in 1933. As circumscribed by Bøvre (1984), it accommodated a group of Gram-negative, oxidase-and catalase-positive, aerobic or facultatively anaerobic, non-spore-forming, rodor coccoid-shaped organisms and embraced four genera: Neisseria, Kingella, Acinetobacter and Moraxella (Bøvre, 1984). The family Neisseriaceae has undergone various revisions over the years, and numerous other genera have been assigned to it [e.g. Psychrobacter (Juni & Heym, 1986), Mesophilobacter (Nishimura et al., 1989), Alysiella (Rossau et al., 1989) and Eikenella and Simonsiella (Dewhirst et al., 1989)]. On the basis of rRNA cistron similarity studies, Rossau et al. (1986) recommended that the genera Acinetobacter, Moraxella and Branhamella be excluded from the family Neisseriaceae. Subsequent studies by Rossau et al. (1989) showed that the genera Neisseria, Kingella, Eikenella, Simonsiella and Alysiella were closely related and should be classified together in the family Neisseriaceae, which comprises a major branch of the b-Proteobacteria. Comparative 16S rRNA gene sequencing studies by Dewhirst et al. (1989) confirmed the results of Rossau et al. (1989) and led to the recommendation that the genera Eikenella and Simonsiella be transferred to the family Neisseriaceae. In recent years, other genera, e.g. Laribacter (Yuen et al., 2001) and Microvirgula (Patureau et al., 1998), have been described and assigned to the family Neisseriaceae.Organisms within the family Neisseriaceae can be isolated from a range of environmental sources (Moss & Bryant, 1982) as well as from different human and animal mucosal surfaces (Kuhn, 1981;Snell, 1984). Only two species, Neisseria gonorrhoeae and Neisseria meningitidis, are wellestablished human pathogens (Morse & Knapp, 1991). Other species of the Neisseriaceae have been implicated as opportunistic human pathogens in a number of different clinical processes (Wong & Janda, 1992;Dolter et al., 1998). In veterinary medicine, too, neisseriae have been implicated as pathogens in a number of ...