Summary auto-generated
This study reclassifies Flavobacterium okeanokoites, a rod-shaped marine bacterium, into the genus Planococcus using polyphasic taxonomy. Although Planococcus species typically form spherical cells while F. okeanokoites forms rods, 16S rRNA gene sequencing revealed 98.6-99.0% similarity to Planococcus species, indicating close phylogenetic relationship. Chemotaxonomic analysis supported this reclassification, showing F. okeanokoites shares key characteristics with Planococcus: menaquinones MK-7 and MK-8 as major quinones, similar polar lipids (phosphatidylglycerol, bisphosphatidylglycerol, phosphatidylethanolamine), branched fatty acids, and comparable DNA G+C content (46.3 mol%). DNA-DNA hybridization confirmed F. okeanokoites represents a distinct species with only 15-27% relatedness to other Planococcus species. The authors propose transferring F. okeanokoites to Planococcus okeanokoites comb. nov. and emending the Planococcus genus description to include rod-shaped cells. This demonstrates that cell morphology (cocci versus rods) should not be the primary criterion for bacterial genus designation, a principle observed in other genera like Bacillus and Arthrobacter.
Key findings
- 16S rRNA gene sequencing showed F. okeanokoites shares 98.6-99.0% similarity with Planococcus species, supporting reclassification despite morphological differences
- F. okeanokoites and Planococcus species share chemotaxonomic characteristics including MK-7 and MK-8 menaquinones, similar polar lipids, branched fatty acids, and comparable DNA G+C content (39-52 mol%)
- DNA-DNA hybridization demonstrated F. okeanokoites is a distinct species (15-27% relatedness to Planococcus species) warranting separate status as P. okeanokoites
- The genus Planococcus description was emended to include rod-shaped cells, demonstrating that cell morphology is not a reliable generic criterion for bacterial taxonomy
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Abstract
The taxonomic position of Flavobacterium okeanokoites IFO 12536T (T = type strain) was determined by 16S rRNA gene sequencing and chemotaxonomic methods. Phylogenetic evidence derived from a 16S rRNA sequence analysis indicated that F. okeanokoites, which forms rod-shaped cells, belongs to the genus Planococcus, which forms spherical cells. A phylogenetically close relationship was supported by chemotaxonomic characteristics, such as the presence of menaquinone 7 and menaquinone 8 as major isoprenoid quinones, the presence of phosphatidylglycerol, bisphosphatydylglycerol, and phosphatidylethanolamine as cellular polar lipids, and the G+C content of the DNA (46.3 mol%). These data suggest that whether a cell is a rod or a coccus is not a generic criterion. Accordingly, we propose that F. okeanokoites should be transferred to the genus Planococcus and that the description of the genus Planococcus should be emended.