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K H Nealson

Publications and source records attributed to K H Nealson.

At least 73 records · Page 4Linked to original sources
PubMed1984

The phylogeny of purple bacteria: the alpha subdivision.

The technique of oligonucleotide cataloging shows the purple photosynthetic eubacteria to comprise three major subdivisions, temporarily called alpha, beta, and gamma--previously designated groups I-III by Gibson et al. (1979). Each subdivision contains a number of non-photosynthetic genera in addition to the photosynthetic ones. The alpha subdivision, the subject of the present report, contains most but not all of the species that fall into the classically defined genera Rhodospirillum, Rhodopseudomonas and Rhodomicrobium. Intermingled with these are a variety of non-photosynthetic species from genera such as Agrobacterium, Rhizobium, Azospirillum, Nitrobacter, Erythrobacter, Phenylobacterium, Aquaspirillum, and Paracoccus. The phylogenetic substructure of the alpha subdivision is presented and the evolutionary significance of the admixture of biochemical phenotypes is discussed.

Base Sequence↗
PubMed1984

Use of poisons in determination of microbial manganese binding rates in seawater.

A method was developed to determine whether microorganisms mediate the precipitation of manganese(II) in the marine environment. Radioactive Mn(II) was used as a tracer to measure the precipitation (binding and oxidation) of Mn(II) [i.e., the Mn(II) trapped on 0.2-mum membrane filters] in the presence and absence of biological poisons. A variety of antibiotics, fixatives, and metabolic inhibitors were tested in laboratory control experiments to select poisons that did not interfere in the chemistry of manganese. The poisons were deemed suitable if (i) they did not complex Mn(II) more strongly than the ion-exchange resin Chelex 100, (ii) they did not interfere in the adsorption of Mn(II) onto synthetic deltaMnO(2) (manganate), (iii) they did not cause desorption of Mn(II) which had been preadsorbed onto synthetic manganate, and (iv) they did not solubilize synthetic manganate. In addition, several known chelators, reducing agents, and buffers normally added to microbiological growth media or used in biochemical assays were tested. Most additions interfered to some extent with manganese chemistry. However, at least one inhibitor, sodium azide, or a mixture of sodium azide, penicillin, and tetracycline was shown to be appropriate for use in field studies of Mn(II) binding. Formaldehyde could also be used in short incubations (1 to 3 h) but was not suitable for longer time course studies. The method was applied to studies of Mn(II) precipitation in Saanich Inlet, British Columbia, Canada. Bacteria were shown to significantly enhance the rate of Mn(II) removal from solution in the manganese-rich particulate layer which occurs just above the oxygen-hydrogen sulfide interface in the water column.

Journal Article↗
PubMed1983

Cloning of the Vibrio harveyi luciferase genes: use of a synthetic oligonucleotide probe.

A mixed-sequence synthetic oligonucleotide probe was used to isolate a clone containing the gene encoding the alpha subunit of bacterial luciferase from Vibrio harveyi and part of the gene coding for the beta subunit. DNA sequence analysis has allowed us to determine that the genes are closely linked on the bacterial chromosome and transcribed in the same direction. Comparison of the sequences in the regions preceding the two structural genes has revealed considerable homology and has identified sites that may be involved in the expression of the genes. Identification of a clone from a clone bank of total genomic DNA from this organism shows that mixed probes can be successfully used to isolate a gene of interest from any bacterium provided some protein sequence for the gene product is available.

Amino Acid Sequence↗
PubMed1982

Surface enhancement of sporulation and manganese oxidation by a marine bacillus.

In a seawater medium containing 0.005% yeast extract and 0.005% peptone, a marine bacillus, SG-1, sporulated only when associated with solid surfaces. The spores (rather than the vegetative cells) were responsible for the oxidation of manganese, and the degree of sporulation was determined by the surface area available rather than by the chemical nature of the clay or silica surface used.

Aluminum Silicates↗
PubMed1982

Manganese binding and oxidation by spores of a marine bacillus.

Mature, dormant spores of a marine bacillus, SG-1, bound and oxidized (precipitated) manganese on their surfaces. The binding and oxidation occurred under dormant conditions, with mature spores suspended in natural seawater. These heat-stable spores were formed in the absence of added manganese in the growth medium. The rate and amount of manganese bound by SG-1 spores was a function of spore concentration. Temperatures greater than 45 degrees C, pH values below 6.5, or the addition of EDTA or the metabolic inhibitors sodium azide, potassium cyanide, and mercuric chloride inhibited manganese binding and oxidation. However, SG-1 spores bound and oxidized manganese after treatment with glutaraldehyde, formaldehyde, ethylene oxide gas, or UV light, all of which killed the spores. Manganese oxidation never occurred in the absence of manganese binding to spores. The data suggest that Mn2+ was complexed by a spore component, perhaps an exosporium or a spore coat protein: once bound, the manganese was rapidly oxidized.

Azides↗
PubMed1981

Structural identification of autoinducer of Photobacterium fischeri luciferase.

Synthesis of bacterial luciferase in some strains of luminous bacteria requires a threshold concentration of an autoinducer synthesized by the bacteria and excreted into the medium. Autoinducer excreted by Photobacterium fischeri strain MJ-1 was isolated from the cell-free medium by extraction with ethyl acetate, evaporation of solvent, workup with ethanol-water mixtures, and silica gel chromatography, followed by normal-phase and then reverse-phase high-performance liquid chromatography. The final product was greater than 99% pure. The structure of the autoinducer as determined by high-resolution 1H nuclear magnetic resonance spectroscopy, infrared spectroscopy, and high-resolution mass spectrometry was N-(3-oxohexanoly)-3-aminodihydro-2(3H)-furanone [or N-(beta-ketocaproyl)homoserine lactone]. The formation of homoserine by hydrolysis of the autoinducer was consistent with this structure. Synthetic autoinducer, obtained as a racemate, was prepared by coupling homoserine lactone to the ethylene glycol ketal of sodium 3-oxohexanoate, followed by mildly acidic removal of the protecting group; this synthetic material showed the appropriate biological activity.

4-Butyrolactone↗
PubMed1977

A luminous bacterium that emits yellow light.

A strain of Photobacterium fischeri that emits yellow light has been isolated from seawater. The bimodal spectrum, which is unique among the luminous bacteria, consists of a major band with a maximum at 545 nanometers and a minor band with a maximum at 500 nanometers. The former represents a heretofore unreported range of emission for luminous bacteria, while the latter coincides with the emission spectrum of typical blue-greeen-emitting strains of P. fischeri. The relative contributions of these two bands to the total in vivo luminescence changes as a function of ambient temperature. When luciferase is extracted and luminescence observed in vitro, the emission is entirely blue-green, identical with that of luciferase isolated from other strains of P. fischeri.

Energy Transfer↗
PubMed1977

Low oxygen is optimal for luciferase synthesis in some bacteria. Ecological implications.

The synthesis of the bioluminescent systems in many strains of two species of the genus Photobacterium which were isolated as symbionts is greater at low oxygen concentrations, where aerobic growth is blocked. In strains of two other species, one Photobacterium of symbiotic orgin, and one (genus Beneckea) whose lent response is observed. At low oxygen concentrations, where there is an inhibition of growth, there is also a similar decrease in the synthesis of the luminescent system. These species-specific differences may indicate important ecological differences along with distinctive differences in the molecular control mechanisms involved in the synthesis of luciferase.

Anaerobiosis↗
PubMed1977

Autoinduction of bacterial luciferase. Occurrence, mechanism and significance.

The synthesis of the luminous system of the marine luminous bacterium Photobacterium fischeri is subject to a complex, self-regulated control system called autoinduction. The bacteria produce an autoinducer which accumulates in the medium at a constant rate (as a function of cell growth). When autoinducer reaches a critical concentration it stimulates, at the level of transcription, the synthesis of the luminous system. Autoinduction is thus viewed as an environmental sensing mechanism, which curtails the synthesis of the luminous system under dilute conditions. For several isolates of P. fischeri it was found that variations in luminescence intensity could be accounted for by correlated variations in autoinducer production.

Cell Division↗
PubMed1977

Pyruvate production and excretion by the luminous marine bacteria.

During aerobic growth on glucose, several species of luminous marine bacteria exhibited an imcomplete oxidative catabolism of substrate. Pyruvate, one of the products of glucose metabolism, was excreted into the medium during exponential growth and accounted for up to 50% of the substrate carbon metabolized. When glucose was depleted from the medium, the excreted pyruvate was promptly utilized, demonstrating that the cells are capable of pyruvate catabolism. Pyruvate excretion is not a general phenomenon of carbohydrate metabolism since it does not occur during the utilization of glycerol or maltose. When cells pregrown on glycerol were exposed to glucose, they began to excrete pyruvate, even if protein synthesis was blocked with chloramphenicol. Glucose thus appears to have an effect on the activity of preexisting catabolic enzymes.

Aerobiosis↗
PubMed1976

Symbiotic association of Photobacterium fischeri with the marine luminous fish Monocentris japonica; a model of symbiosis based on bacterial studies.

Isolation of bacteria from the luminous organ of the fish Monocentris japonica has revealed that the organ contains a pure culture of luminous bacteria. For the four fish examined, all contained Photobacterium fischeri as their luminous bacterial symbiont. This is the first time that P. fischeri has been identified in a symbiotic association. A representative isolate (MJl) of the light organ population was selected for in vivo studies of its luminous system. Several physiological features suggest adaptation for symbiotic existence. First, MJl has been shown to produce and respond to an inducer of luciferase that could accumulate in the light organ. Secondly, the specific activity of light production was seen to be maximal under low, growth-limiting concentrations of oxygen. Thirdly, unlike another luminous species (Beneckea harveyi), synthesis of the light production system of these bacteria is not catabolite repressed by glucose--a possible source of nutrition in the light organ. Fourthly, when grown aerobically on glucose these bacteria excrete pyruvic acid into the medium. This production of pyruvate is a major process, accounting for 30-40% of the glucose utilized and may serve as a form of regulatory and nutritional communication with the host.

Animals↗
PubMed1972

Catabolite repression of bacterial bioluminescence: functional implications.

The synthesis of the bioluminescent system of the marine luminous bacterium Photobacterium fischeri (strain MAV) is subject to both transient and catabolite repression by glucose, and this repression can be reversed by adenosine 3':5'-cyclic monophosphate. Catabolite repression is a mechanism that characteristically controls the synthesis of inducible enzymes involved in energy metabolism. The fact that luciferase synthesis is subject to this control suggests that whatever its role(s) may be, it cannot be considered a nonfunctional or vestigial enzyme system as previously hypothesized, and may actually have some more direct role in metabolic processes.

Cyclic AMP↗
PubMed1970

Mutant analysis and enzyme subunit complementation in bacterial bioluminescence in Photobacterium fischeri.

Chemical mutagens were used to obtain mutants deficient in bioluminescence in the marine bacterium Photobacterium fischeri strain MAV. Acridine dyes were effective in the production of dark mutants but not in the production of auxotrophs. These dark mutants were all of one type and appeared to contain lesions blocking the synthesis of luciferase. ICR-191 was especially effective in the production of aldehyde mutants, i.e., dark strains that luminesce when a long-chain aldehyde such as n-decanal is added to them. However, other mutant types were isolated after treatment with ICR-191. N-methyl-N'-nitro-N-nitrosoguanidine induced many bioluminescence-deficient types with respect to both the site of the lesion and the quantitative effect on the luminescent system. We characterized the dark and dim mutants with respect to their response to exogenous decanal, levels of in vivo and in vitro luminescence, and their rates of reversion to wild type. In addition, the luciferases of the mutant strains were examined by subunit complementation. On the basis of these analyses, we identified mutants which synthesize altered luciferase, strains which are deficient in synthesis of luciferase, and aldehyde mutants. The results of analysis of luciferase from the aldehyde mutants and the complementation studies indicate that the lesions in these strains are in the luciferase itself. Results obtained with wild-type cells grown in minimal medium, and aldehyde mutant cells grown either in complete or minimal medium, indicate that a "natural aldehyde factor" is involved in in vivo light emission. These same studies showed that the long-chain aldehyde(s) could only partially substitute for the natural "aldehyde factor." The possibility that the in vivo aldehyde factor is not a long-chain aldehyde is discussed.

Aldehydes↗