Biomedical subjects

E G Ruby

Publications and source records attributed to E G Ruby.

45 records · Page 3Linked to original sources

PubMed1983

Differentiation after premature release of intraperiplasmically growing Bdellovibrio bacteriovorous.

Bdellovibrio bacteriovorous attacks and penetrates other gram-negative bacteria, creating a growth chamber termed a bdelloplast. We have found that exposing the bdelloplasts to EDTA, followed by treatment with a lytic enzyme concentrate derived from bdellovirio cultures, prematurely released the intraperiplasmically growing bdellovibrios at any time during their growth cycle. Upon release, the growth-form bdellovibrios terminated any initiated rounds of DNA synthesis and differentiated into motile attack-form cells. The ability of growth-form cells to synthesize DNA appears to depend upon an initiation signal that is not received until about 60 min after attack. Each subsequent round of DNA synthesis by the growing bdellovibrio filaments seems to require an additional initiation signal that is provided by their intraperiplasmic environment. Differentiation included fragmentation into multiple progeny cells to a degree proportional to the extent of intraperiplasmic growth. This differentiation could be performed totally at the expense of cellular reserves. The significance of these data to an understanding of the regulation of differentiation in bdellovibrios is discussed.

Bdellovibrio↗

PubMed1982

Physiological characteristics of Thiomicrospira sp. Strain L-12 isolated from deep-sea hydrothermal vents.

Growth of the obligately chemolithotrophic Thiomicrospira sp. strain L-12, isolated from a hydrothermal vent at a depth of 2,550 m in the Galapagos Rift region, was optimal at pH 8 and required 200 mM Na+ and divalent ions (Ca2+ and Mg2+). The organism was microaerophilic and tolerated 300 microM sulfide without a decrease in the rate of CO2 incorporation. Growth and CO2 incorporation occurred within the temperature range of 10 to 35 degrees C, with both optimal at 25 degrees C. At the in situ pressure of 250 atm. the rate of CO2 incorporation was reduced by 25% relative to that measured at 1 atm: it was entirely suppressed at 500 atm. The results of this physiological characterization suggest that Thiomicrospira sp. strain L-12 can be an active autotroph in the hydrothermal environment.

Bacterial Physiological Phenomena↗

PubMed1981

Chemolithotrophic sulfur-oxidizing bacteria from the galapagos rift hydrothermal vents.

Three distinct physiological types of sulfur-oxidizing bacteria were enriched and isolated from samples collected at several deep-sea hydrothermal vents (2,550 m) of the Galapagos Rift ocean floor spreading center. Twelve strains of the obligately chemolithotrophic genus Thiomicrospira were obtained from venting water and from microbial mats covering surfaces in the immediate vicinity of the vents. From these and other sources two types of obligately heterotrophic sulfur oxidizers were repeatedly isolated that presumably oxidized thiosulfate either to sulfate (acid producing; 9 strains) or to polythionates (base producing; 74 strains). The former were thiobacilli-like, exhibiting a thiosulfate-stimulated increase in growth and CO(2) incorporation, whereas the latter were similar to previously encountered pseudomonad-like heterotrophs. The presence of chemolithotrophic sulfur-oxidizing bacteria in the sulfide-containing hydrothermal water supports the hypothesis that chemosynthesis provides a substantial primary food source for the rich populations of invertebrates found in the immediate vicinity of the vents.

Journal Article↗

PubMed1980

Formation of hybrid luciferases from subunits of different species of Photobacterium.

Enzyme divergence within three species of the genus Photobacterium (P. fischeri, P. leiognathi, and P. phosphoreum) was studied by comparing the catalytic characteristics and quaternary interactions of bacterial luciferases isolated from each species. Each luciferase was composed of two subunits of different molecular weights as determined by sodium dodecyl sulfate--polyacrylamide gel electrophoresis. Subunits were isolated in quantity by DEAE-Sephadex gel filtration in 7 M urea. Isolated subunits had no luciferase activity after renaturation in buffer, but active enzyme could be recovered by renaturation of the heavy and light subunits together. Renaturation of hybrid pairs (containing one subunit from each of two different species) yielded active luciferases, but only in cases where a heavy subunit of one species was combined with a light subunit of another. These hybrids exhibited in vitro catalytic characteristics most like those of the parent luciferase from which the heavy subunit was derived. The light subunit of P. leiognathi luciferase conferred an increased thermal stability to all enzymes containing it. The heavy subunit of each of the three Photobacterium species was sensitive to trypsinization. Thus, on the basis of structural and functional analogies with the luciferase from Beneckea harveyi, the heavy and light subunits of Photobacterium species have been designated alpha and beta, respectively.

Chromatography, Ion Exchange↗

PubMed1980

Planktonic marine luminous bacteria: species distribution in the water column.

Luminous bacteria were isolated from oceanic water samples taken throughout the upper 1,000 m and ranged in density from 0.4 to 30 colony-forming units per 100 ml. Generally, two peaks in abundance were detected: one in the upper 100 m of the water column, which consisted primarily of Beneckea spp.; and a second between 250 and 1,000 m, which consisted almost entirely of Photobacterium phosphoreum. The population of P. phosphoreum remained relatively stable in abundance at one station that was visited three times over a period of 6 months. However, the abundance of luminous Beneckea spp. isolated from the upper waters fluctuated considerably; they were, as high as 30 colony-forming units per 100 ml in the spring and were not detected in the winter. Water samples from depths of 4,000 to 7,000 m contained less than 0.1 luminous colony-forming unit per 100 ml. The apparent vertical stratification of two taxa of oceanic luminous bacteria may reflect not only differences in physiology, but also depth-related, species-specific symbiotic associations.

Journal Article↗

PubMed1979

Luminous enteric bacteria of marine fishes: a study of their distribution, densities, and dispersion.

Three taxa of luminous bacteria (Photobacterium fischeri, P. phosphoreum, and Beneckea spp.) were found in the enteric microbial populations of 22 species of surface- and midwater-dwelling fishes. These bacteria often occurred in concentrations ranging between 10 and 10 colony-forming units per ml of enteric contents. By using a genetically marked strain, it was determined that luminous cells entering the fish during ingestion of seawater or contaminated particles traversed the alimentary tract and survived the digestive processes. After excretion, luminous bacteria proliferated extensively on the fecal material and became distributed into the surrounding seawater. Thus, this enteric habitat may serve as an enrichment of viable cells entering the planktonic luminous population.

Journal Article↗

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

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↗