SUMMARY: Pseudomonas stutzeriis a nonfluorescent denitrifying bacterium widely distributed in the environment, and it has also been isolated as an opportunistic pathogen from humans. Over the past 15 years, much progress has been made in elucidating the taxonomy of this diverse taxonomical group, demonstrating the clonality of its populations. The species has received much attention because of its particular metabolic properties: it has been proposed as a model organism for denitrification studies; many strains have natural transformation properties, making it relevant for study of the transfer of genes in the environment; several strains are able to fix dinitrogen; and others participate in the degradation of pollutants or interact with toxic metals. This review considers the history of the discovery, nomenclatural changes, and early studies, together with the relevant biological and ecological properties, ofP. stutzeri.

The genus Caulobacter is composed of prosthecate bacteria often specialized for oligotrophic environments. The taxonomy of Caulobacter has relied primarily upon morphological criteria: A strain that visually appeared to be a member of the Caulobacter has generally been called one without challenge. A polyphasic approach, comprising 16S rDNA sequencing, profiling restriction fragments of 16S-23S rDNA interspacer regions, lipid analysis, immunological profiling and salt tolerance characterizations, was used to clarify the taxonomy of 76 strains of the genera Caulobacter, Brevundimonas, Hyphomonas and Mycoplana. The described species of the genus Caulobacter formed a paraphyletic group with Caulobacter henricii, Caulobacter fusiformis, Caulobacter vibrioides and Mycoplana segnis (Caulobacter segnis comb, nov.) belonging to Caulobacter sensu stricto. Caulobacter bacteroides (Brevundimonas bacteroides comb, nov.), C. henricii subsp. aurantiacus (Brevundimonas aurantiaca comb, nov.), Caulobacter intermedius (Brevundimonas intermedia comb. nov.), Caulobacter subvibrioides (Brevundimonas subvibrioides comb. nov.), C. subvibrioides subsp. albus (Brevundimonas alba comb. nov.), Caulobacter variabilis (Brevundimonas variabilis comb. nov.) and Mycoplana bullata belong to the genus Brevundimonas. The halophilic species Caulobacter maris and Caulobacter halobacteroides are different from these two genera and form the genus Maricaulis gen. nov. with Maricaulis maris as the type specis Caulobacter leidyia was observed to cluster with species of the genus Sphingomonas. Caulobacter crescentus is synonymous with C.vibrioides and C. halobacteroides is synonymous with Maricaulis maris as determined by these analyses and DNA-DNA hybridization. Biomarkers discerning these different genera were determined. The necessary recombinations have been proposed and a description of Maricaulis is presented.

Seven psychrotolerant, Gram-negative bacterial strains, five dust- and airborne isolates (MA101bT, MA306a, MA405/90, MA-olkiT and NW12T) and two from the Antarctic (Ant 20 and M3C203B-B), were subjected to a polyphasic characterization to determine their taxonomic position. High 16S rDNA sequences similarities (99·3–100·0 %) demonstrated that they were closely related to each other. Phylogenetic evaluation of their 16S rDNA sequences revealed that they are members of the genus Sphingomonas sensu stricto, encompassing a separate branch within this genus. They shared 94·4–96·6 % 16S rDNA sequence similarity with species of this genus. All Sphingomonas-specific signature nucleotides were also detected. The presence of the major ubiquinone Q-10, sym-homospermidine as the predominant polyamine, Sphingomonadaceae-specific sphingoglycolipid in the polar lipid patterns and a fatty acid profile containing C14 : 0 2-OH and lacking 3-OH fatty acids were in agreement with identification of these strains as members of the genus Sphingomonas sensu stricto. Results from DNA–DNA hybridizations and comparison of protein patterns indicated that the seven strains are members of three distinct species. One species is represented by strains MA101bT, MA306a and MA405/90, the second by strains NW12T, Ant 20 and M3C203B-B and the third by one strain, MA-olkiT. Their distinction at the species level was also supported by results of biochemical characterization and partly supported by riboprints and genomic fingerprints. On the basis of these results, three novel species of the genus Sphingomonas are proposed: Sphingomonas aurantiaca sp. nov., consisting of strains MA101bT (=DSM 14748T=LMG 21377T), MA306a and MA405/90 (=DSM 14749=LMG 21378), Sphingomonas faeni sp. nov. MA-olkiT (=DSM 14747T=LMG 21379T) and Sphingomonas aerolata sp. nov., represented by strains NW12T (=DSM 14746T=LMG 21376T), Ant 20 (=ICMP 13599) and M3C203B-B (=SMCC M3C203B-B).

The microbial content of printing paper machines, running at a temperature of 45–50 °C and at pH 4·5–5, was studied. Bacteria were prevalent colonizers of the machine wet end and the raw materials. A...

We compared the 16S rRNA gene sequences of 14 strains of Pseudomonas stutzeri, including type strain CCUG 11256 and strain ZoBell (= ATCC 14405), which represented the seven P. stutzeri genomovars (DNA-DNA similarity groups) that have been described. Our sequence analysis revealed clusters which were highly correlated with genomovar clusters derived from DNA-DNA hybridization data. In addition, we identified signature nucleotide positions for each genomovar. We found that the 16S rRNA gene sequences of genomovar 6 strains SP1402T (T = type strain) and LS401 were different enough from the sequence of the type strain of P. stutzeri that these organisms should be placed in a new species, Pseudomonas balearica. The type strain of P. balearica is strain SP1402 (= DSM 6083).