Pseudomonadales Orla-Jensen 1921, 270AL

The broad and vague phenotypic definition allowed the genus Pseudomonas to become a dumping ground for incompletely characterized polarly flagellated, gram-negative, rod-shaped, aerobic bacteria, and a large number of species have been accommodated in the genus Pseudomonas. The 16S rRNA sequences of 128 valid and invalid Pseudomonas species, which included almost valid species of the genus Pseudomonas listed in the Approved Lists of Bacterial Names, were obtained: sequences of 59 species were determined and those of 69 species were obtained from the GenBank/EMBL/DDBJ databases. These sequences were compared with the sequences of other species of the Proteobacteria. Fifty-seven valid or invalid species including Pseudomonas aeruginosa (type species of the genus Pseudomonas Migula 1894) belonged to the genus Pseudomonas (sensu stricto). Seven subclusters were formed in the cluster of the genus Pseudomonas (sensu stricto), and the resulting clusters conformed well to the rRNA-DNA hybridization study by Palleroni (1984). The other species did not belong to the genus Pseudomonas (sensu stricto) and were related to other genera, which were placed in four subclasses of the Proteobacteria (alpha, beta, gamma and gamma-beta subclasses). Twenty-six examined species, which were not included in the cluster of the Pseudomonas (sensu stricto) and have not been transferred to other genera as yet, are listed alphabetically: 'Pseudomonas abikonensis', Pseudomonas antimicrobica, Pseudomonas beijerinckii, Pseudomonas beteli, Pseudomonas boreopolis, 'Pseudomonas butanovora', Pseudomonas carboxydohydrogena, Pseudomonas cissicola, Pseudomonas doudoroffii, Pseudomonas echinoides, Pseudomonas elongata, Pseudomonas flectens, Pseudomonas geniculata, Pseudomonas halophila, Pseudomonas hibiscicola, Pseudomonas huttiensis, Pseudomonas iners, Pseudomonas lanceolata, Pseudomonas lemoignei, Pseudomonas mephitica, Pseudomonas pictorum, Pseudomonas saccharophila, Pseudomonas spinosa, Pseudomonas stanier, Pseudomonas syzygii and Pseudomonas woodsii. The phylogenetic affiliations of these 26 pseudomonads species are shown.

Facultatively psychrophilic alkaliphilic strains were isolated from seawater obtained off the coast of Rumoi, Hokkaido, Japan. They were Gram-negative, aerobic straight rods with polar flagella. The isolates were catalase- and oxidase-positive and able to grow at 4 degrees C, but not at 40 degrees C. They produced acid from D-glucose under aerobic conditions. The isolates reduced nitrate to nitrite and hydrolysed casein and gelatin, but not starch or DNA. NaCl was required for growth at pH 10 but was not required at neutral pH. The major isoprenoid quinone was ubiquinone-9 (Q-9) and the DNA G+C content was 62.3-63.2 mol%. The whole-cell fatty acids mainly consisted of C16:0, C16:1(9c) and C18:1(9c), with 3-OH C10:0 and 3-OH C12:0 as the hydroxyl fatty acids. A larger amount of trans-unsaturated fatty acid, C16:1(9t) was observed when the cells were grown at pH 7 compared to when cells were grown at pH 10. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that the bacteria are members of the genus Pseudomonas. Analysis of DNA-DNA relatedness data with several close phylogenetic neighbours revealed a low level of hybridization (less than 61%). On the basis of phenotypic characteristics, phylogenetic analysis and DNA-DNA relatedness data, it is concluded that these isolates represent a separate new species. Accordingly, the name Pseudomonas alcaliphila is proposed. The type strain is AL15-21T (= JCM 10630T = IAM 14884T).