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.

Phylogenetic affiliation of the pseudomonads based on 16S rRNA sequence.

Biological properties and classification of the caulobacter group

Based on the partial nucleotide sequence analysis of 16S ribosomal ribonucleic acid (rRNA), presence of unique sphingoglycolipids in cellular lipid, and the major type of ubiquinone (Q10), we propose Sphingomonas gen. nov. with the type species Sphingomonas paucimobilis (Holmes et al, 1977) comb. nov. From the homology values of deoxyribonucleic acid-deoxyribonucleic acid hybridization and the phenotypic characteristics, three new species, Sphingomonas parapaucimobilis, Sphingomonas yanoikuyae, Sphingomonas adhaesiva, and one new combination, Sphingomonas capsulata, are described. S. parapaucimobilis JCM 7510 (= GIFU 11387), S. yanoikuyae JCM 7371 (= GIFU 9882), and S. adhaesiva JCM 7370 (= GIFU 11458) are designated as the type strains of the three new species. Emended description of the type strain of S. capsulata is presented.

Proposals of Sphingomonas paucimobilis gen. nov. and comb. nov., Sphingomonas parapaucimobilis sp. nov., Sphingomonas yanoikuyae sp. nov., Sphingomonas adhaesiva sp. nov., Sphingomonas capsulata comb, nov., and Two Genospecies of the Genus Sphingomonas

Aminopolycarboxylic acids (APCAs) have the ability to form stable, water-soluble complexes with di- and trivalent metal ions. For that reason, synthetic APCAs are used in a broad range of domestic products and industrial applications to control solubility and precipitation of metal ions. Because most of these applications are water-based, APCAs are disposed of in wastewater and reach thus sewage treatment plants and the environment, where they undergo abiotic and/or biotic degradation processes. Recently, also natural APCAs have been described which are produced by plants or micro-organisms and are involved in the metal uptake by these organisms. For the two most widely used APCAs, nitrilotriacetate (NTA) and ethylenediaminetetraacetate (EDTA), transformation and mineralisation processes have been studied rather well, while for other xenobiotic APCAs and for the naturally occurring APCAs little is known on their fate in the environment. Whereas NTA is mainly degraded by bacteria under both oxic and anoxic conditions, biodegradation is apparently of minor importance for the environmental fate of EDTA. Photodegradation of iron(III)-complexed EDTA is supposed to be mostly responsible for its elimination. Isolation of a number of NTA- and EDTA-utilising bacterial strains has been reported and the spectrum of APCAs utilised by the different isolates indicates that some of them are able to utilise a range of different APCAs whereas others seem to be restricted to one compound. The two best characterised obligately aerobic NTA-utilising genera (Chelatobacter and Chelatococcus) are members of the α-subgroup of Proteobacteria. There is good evidence that they are present in fairly high numbers in surface waters, soils and sewage treatment plants. The key enzymes involved in NTA degradation in Chelatobacter and Chelatococcus have been isolated and characterised. The two first catabolic steps are catalysed by a monooxygenase (NTA MO) and a membrane-bound iminodiacetate dehydrogenase. NTA MO has been cloned and sequenced and its regulation as a function of growth conditions has been studied. Under denitrifying conditions, NTA catabolism is catalysed by a NTA dehydrogenase. EDTA breakdown was found to be initiated by a MO also which shares many characteristics with NTA MO from strictly aerobic NTA-degrading bacteria. In contrast, degradation of [S,S]-ethylenediaminedisuccinate ([S,S]-EDDS), a structural isomer of EDTA, was shown to be catalysed by an EDDS lyase in both an EDTA degrader and in a NTA-utilising Chelatococcus strain. So far, transport of APCAs into cells has only been studied for EDTA and the results obtained give strong evidence for an energy-dependent carrier system and Ca2+ seems to be co-transported with EDTA. Due to their metal-complexing capacities, APCAs occur in the environment mostly in the metal-complexed form. Hence, the influence of metal speciation on various degradation processes is of utmost importance to understand the environmental behaviour of these compounds. In case of biodegradation, the effect of metal speciation is rather difficult to assess at the whole cell level and therefore only limited good data are available. In contrast, the influence of metal speciation on the intracellular enzymatic breakdown of APCAs is rather well documented but no generalising pattern applicable to all enzymes was found.

Environmental fate and microbial degradation of aminopolycarboxylic acids

The caulobacters: ubiquitous unusual bacteria.

SUMMARY Names are proposed and descriptions given for five new species of bacteria isolated from stored distilled water from various laboratories. Corynebacterium aquaticum n. sp. has many of the characteristics of the motile plant pathogenic bacteria that have been placed in genus Corynebacterium. Other species named are Flavobacterium capsulatumn. n. sp., Spirillum delicatum n. s p., Pseudomonas Ianceolata n. sp., and Pseudomonas huttiensis n. sp. Cultures of the type strain of each new species have been deposited in the American Type Culture Collection.

The Bacterial Flora of Distilled and Stored Water. III. new species of the genera Corynebacterium, Flavobacterium, Spirillum and Pseudomonas

SUMMARY A total of 36 samples of distilled water from 10 different sources were plated on salt-free agar, incubated at 20°C, and colonies of different appearance fished. Duplicate plates of selected samples were incubated at 37°C. Samples were also plated on agar with 1% NaCl added for study of incidence of psychrophils and halophobes. A number of plates were prepared from fresh river water, from such water stored in the laboratory for several weeks, and from distilled water to which a small amount of soil had been added. A few plates were also exposed directly to laboratory air. From the various plates were fished all colonies which appeared different; a total of 306 isolates was obtained. These cultures were studied morphologically, culturally and physiologically. The great majority of the distilled water isolates were Gram-negative, polar flagellated, nonfermentative straight rods. Sporeformers, cocci, typical spirilla, and fermentative bacteria were absent and the difference between the flora of distilled water on the one hand and river water and air on the other is striking. In addition to the usual types of bacteria, there were found several types of aggregating bacteria which are described in some detail.

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The Bacterial Flora of Distilled and Stored Water. I. General observations, techniques and ecology

SUMMARY
Caulobacter
vibrioides is commonly found in tanks of distilled water. A detailed description is given of cultural, morphologyical and physiological characteristics. Attachment to other bacteria and to inanimate objects with rosette formation is described.

The Bacterial Flora of Distilled And Stored Water. II. Caulobacter vibrioides Henrici and Johnson 1935 in distilled water

A new species of Pseudomonas is described which in its native river-water habitat characteristically has a curved soma with many straight spine-like structures, but no flagella. In pure culture the organism has a very long polar flagellum, a fairly straight soma with several round inclusions. It is psychrophilic and rather halophobic and shows a slight oxidative metabolism of some carbohydrates.

Einar Leifson

Papers

The Bacterial Flora of Distilled and Stored Water. III. new species of the genera Corynebacterium, Flavobacterium, Spirillum and Pseudomonas

The Bacterial Flora of Distilled and Stored Water. I. General observations, techniques and ecology

The Bacterial Flora of Distilled And Stored Water. II. Caulobacter vibrioides Henrici and Johnson 1935 in distilled water

Pseudomonas spinosa n. sp.