A new method is proposed to measure relatedness amongst bacteria, based on renaturation rate determinations of DNA types and their mixture. The equations, relating the degree of binding with renaturation rates, are calculated for several cases. The optimal conditions for measurements are given. The method was checked in several ways. The advantages are summarized.

Hybridization experiments were carried out between DNAs from more than 70 strains of Campylobacter spp. and related taxa and either 3H-labeled 23s rRNAs from reference strains belonging to Campylobacter fetus, Campylobacter concisus, Campylobacter sputorum, Campylobacter coli, and Campylobacter nitrofigilis, an unnamed Campylobacter sp. strain, and a Wolinella succinogenes strain or 3H-or 14C-labeled 23s rRNAs from 13 gram-negative reference strains. An immunotyping analysis of 130 antigens versus 34 antisera of campylobacters and related taxa was also performed. We found that all of the named campylobacters and related taxa belong to the same phylogenetic group, which we name rRNA superfamily VI and which is far removed from the gram-negative bacteria allocated to the five rRNA superfamilies sensu De Ley. There is a high degree of heterogeneity within this rRNA superfamily. Organisms belonging to rRNA superfamily VI should be reclassified in several genera. We propose that the emended genus Campylobacter should be limited to Campylo bacter fetus, Campylo bacter hy oin testinalis , Campylo bacter concisus, Campylo bacter m ucosalis , Campylobacter sputorum, Campylobacter jejuni, Campylobacter coli, Campylobacter lari, and "Campylobacter upsaliensis. " Wolinella curva and Wolinella recta are transferred to the genus Campylobacter as Campylobacter curvus comb. nov. and Campylobacter rectus comb. nov., respectively. Bacteroides gracilis and Bacteroides ureolyticus are generically misnamed and are closely related to the genus Campylobacter. Campylobacter nitrofigilis, Campylobacter cryaerophila, and an unnamed Campylobacter sp. strain constitute a new genus, for which the name Arcobacter is proposed; this genus contains two species, Arcobacter nitrofigilis comb. nov. (type species) and Arcobacter cryaerophilus comb. nov. Wolinellu succinogenes so far is the only species of the genus Wolinella. The genus Helicobacter is also emended; Campylobacter cinaedi and Campylobacter fennelliae are included in this genus as Helicobacter cinaedi comb. nov. and Helicobacter fennelliae comb. nov., respectively. The genus "Flexispira," with "Flexispira rappini" as the only species, is closely related to the genus Helicobacter. The free-living, sulfur-reducing campylobacters do not belong to any of these genera; they probably constitute a distinct genus within rRNA superfamily VI.At present, the genus Campylobacter consists of 13 welldefined species (40). Recently, two additional species, Campylobacter pylori and Campylobacter mustelae, were included in the new genus Helicobacter as Helicobacter pylori and Helicobacter mustelae, respectively (20). The clinical significance of all of these organisms was reviewed recently by Penner (40). A study of the taxonomic structure of the genus Campylobacter in which partial 16s rRNA sequence analysis was used revealed that the Campylobacter species can be divided into three major rRNA homology groups (58 It was the aim of this study to include all known campylobacters and possible relatives in...

for the reader's convenience. OCCURRENCE OF ZYMOMONAS AND HISTORY OF ISOLATIONS Ciders and Perries At the turn of this century the taste of the cider-consuming public changed; they began to demand a clear, sweet cider, instead of a rough BACTERIOL. REV.

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