Roger Y. Stanier

Generic Assignments, Strain Histories and Properties of Pure Cultures of Cyanobacteria

Summary: On the basis of a comparative study of 178 strains of cyanobacteria, representative of this group of prokaryotes, revised definitions of many genera are proposed. Revisions are designed to permit the generic identification of cultures, often difficult through use of the field-based system of phycological classification. The differential characters proposed are both constant and readily determinable in cultured material. The 22 genera recognized are placed in five sections, each distinguished by a particular pattern of structure and development. Generic descriptions are accompanied by strain histories, brief accounts of strain properties, and illustrations; one or more reference strains are proposed for each genus. The collection on which this analysis was based has been deposited in the American Type Culture Collection, where strains will be listed under the generic designations proposed here.

The Aerobic Pseudomonads a Taxonomic Study

SUMMARY A collection of 267 strains, representing many of the principal biotypes among aerobic pseudomonads, has been subjected to detailed study, with particular emphasis on biochemical, physiological and nutritional characters. A total of 146 different organic compounds were tested for their ability to serve as sources of carbon and energy. Other characters that were studied included : production of extracellular hydrolases; nitrogen sources and growth factor requirements H-chemolithotrophy; denitrifying ability; pigment production; ability to accumulate poly-p-hydroxybutyrate as a cellular reserve material; biochemical mechanisms of aromatic ring cleavage; and nature of the aerobic electron transport system. The resultant data have revealed many hitherto unrecognized characters of taxonomic significance. As a consequence, it has become possible to recognize among the biotypes examined a limited number of species which can be readily and clearly distinguished from one another by multiple, unrelated phenotypic differences.

Proposal to reject the genus Hydrogenomonas: Taxonomic implications

ABSTRACT Fifty-six strains of “hydrogen bacteria” and related nonautotrophic bacteria, including nearly all existing named Hydrogenomonas spp., have been compared. It is proposed that the genus Hydrogenomonas should be rejected, since its type species H. pantotropha, appears to be a nomen dubium; and that the various species of “hydrogen bacteria” should be assigned to other genera, not specifically characterized by the ability to grow autotrophically with H2. The two species of hydrogen bacteria most frequently isolated by enrichment show a peritrichous or degenerate peritrichous flagellar arrangement; one is nonpigmented, the other produces yellow (carotenoid) cellular pigments. Of the various possible generic assignments for these two species, assignment to the genus Alcaligenes is proposed. The nonpigmented species, previously named Hydrogenomonas eutropha, but never legitimately described, is here described as A. eutrophus. The yellow species which includes both facultatively autotrophic and nonautotrophic strains, is described as a new species, A. paradoxus. The Gram-negative, coccoid hydrogen bacterium, formerly known as Micrococcus denitrificans, is placed in a new genus, Paracoccus. The polarly flagellated species of hydrogen bacteria, including the previously named species Hydrogenomonas facilis, H. flava, H. ruhlandii and Pseudomonassa saccharophila, are all assigned to the genus Pseudomonas.

Genome Size of Cyanobacteria

Summary: The genome sizes of 128 strains of cyanobacteria, representative of all major taxonomic groups, lie in the range 1.6 × 109 to 8.6 × 109 daltons. The majority of unicellular cyanobacteria contain genomes of 1.6 × 109 to 2.7 × 109 daltons, comparable in size to those of other bacteria, whereas most pleurocapsalean and filamentous strains possess larger genomes. The genome sizes are discontinuously distributed into four distinct groups which have means of 2.2 × 109, 3.6 × 109, 5.0 × 109 and 7.4 × 109 daltons. The data suggest that genome evolution in cyanobacteria occurred by a series of duplications of a small ancestral genome, and that the complex morphological organization characteristic of many cyanobacteria may have arisen as a result of this process.

Deoxyribonucleic Acid Base Composition of Cyanobacteria

Summary: The DNA base compositions of 176 strains of cyanobacteria were determined by thermal denaturation or by CsCl density gradient centrifugation. A summary of all data now available for this prokaryotic group is presented and the taxonomic and evolutionary implications are discussed.

Taxonomy of the aerobic pseudomonads: the properties of the Pseudomonas stutzeri group.

SUMMARY: Strains of Pseudomonas stutzeri and related denitrifying bacteria were compared in their phenotypic properties and mean deoxyribonucleic acid (DNA) base composition. On the basis of this comparison and of in vitro DNA hybridization experiments, it was concluded that, using practical diagnostic tests, no more than two nomenspecies can be recognized within the group. One, P. stutzeri, was extremely variable in phenotypic characteristics and in DNA base composition; we included in it the strains previously assigned to P. stanieri. The other was a new species, P. mendocina Palleroni, which was more homogeneous in phenotypic characters, and in DNA base composition and homology. The comparative properties of known denitrifying pseudomonads are tabulated.

Taxonomy of the aerobic pseudomonads: Pseudomonas cepacia, P. marginata, P. alliicola and P. caryophylli

SUMMARY: On the basis of phenotypic characterization and DNA-DNA homology studies of strains of phytopathogenic Pseudomonas species, it is concluded that P. cepacia is so similar to P. multivorans that the latter name should be regarded as a synonym. On similar grounds, P. alliicola appears to be a synonym of P. marginata. P. caryophylli is a readily distinguishable species. From the DNA-DNA hybridization studies all of these species seem to be related to each other and to the animal pathogens P. pseudomallei and P. mallei.

Isolation and Purification of Cyanobacteria: Some General Principles

Oxygenic photosynthesis is the dominant mode of nutrition of cyanobacteria. Despite this seeming metabolic uniformity, their ecological diversity is remarkable; they occupy a very wide range of illuminated ecological niches in terrestrial, marine, and freshwater environments.

The Effects of Anaerobiosis on Nitrogenase Synthesis and Heterocyst Development by Nostocacean Cyanobacteria

SUMMARY: Effective nitrogenase synthesis by nostocacean cyanobacteria (including one mutant strain unable to form heterocysts or fix nitrogen aerobically) was induced in the light in the absence of molecular oxygen. Anaerobiosis was maintained during induction by treating the organisms with dichloromethylurea which prevents photosynthetic oxygen production. Under these special conditions both synthesis and activity of nitrogenase were light-dependent, the required ATP being produced by cyclic photophosphorylation. Enzyme synthesis and activity were also dependent on the availability of an organic substrate that could serve both as a general source of carbon and as a source of reductant. The organic requirement could be fulfilled by the intracellular glycogen reserve or, in facultative hetero-trophs, by a utilizable sugar (e.g. glucose). Nitrogenase synthesized anaerobically was highly susceptible to inactivation by molecular oxygen in vivo: exposure of a suspension of anaerobically induced filaments to 20% (v/v) O2 for 1 h caused total and irreversible destruction of the enzyme. Anaerobic nitrogenase synthesis was not accompanied by the differentiation of mature heterocysts, the morphogenetic process being arrested at an early (proheterocyst) stage. After the gratuitous anaerobic synthesis of nitrogenase, introduction of either N2, nitrate or ammonia to the illuminated, anaerobic suspension resulted in a rapid accumulation of cyanophycin granules in both vegetative cells and proheterocysts. Cyanophycin was randomly deposited in vegetative cells, but localized at the cell poles of the proheterocysts. The bearing of these findings on the role played by the heterocyst in nitrogen fixation is discussed.

Glucose-6-phosphate dehydrogenase of Anabaena sp.

The kinetic and molecular properties of cyanobacterial glucose-6-phosphate dehydrogenase, partly purified from Anabaena sp. ATCC 27893, show that it undergoes relatively slow, reversible transitions between different aggregation states which differ in catalytic activity. Sucrose gradient centrifugation and polyacrylamide gel electrophoresis reveal three principal forms, with approximate molecular weights of 120 000 (M1), 240 000 (M2) and 345 000 (M3). The relative catalytic activities are: M1≪M2<M3. In concentrated solutions of the enzyme, the equilibrium favors the more active, oligomeric forms. Dilution in the absence of effectors shifts the equilibrium in favor of the M1 form, with a marked diminution of catalytic activity. This transition is prevented by a substrate, glucose-6-phosphate, and also by glutamine. The other substrate, nicotinamide adenine dinucleotide phosphate (NADP+), and (in crude cell-free extracts) ribulose-1,5-diphosphate are negative effectors, which tend to maintain the enzyme in the M1 form. The equilibrium state between different forms of the enzyme is also strongly dependent on hydrogen ion concentration. Although the optimal pH for catalytic activity is 7.4, dissociation to the hypoactive M1 form is favored at pH values above 7; a pH of 6.5 is optimal for maintenace of the enzyme in the active state. Reduced nicotamide adenine dinucleotide phosphate (NADPH) and adenosine 5′-triphosphate (ATP), inhibit catalytic activity, but do not significantly affect the equilibrium state. The relevance of these findings to the regulation of enzyme activity in vivo is discussed.