A. Aristides Yayanos

Isolation of a deep-sea barophilic bacterium and some of its growth characteristics.

A bacterium, a spirillum, has been isolated from a deep-sea sample and has been found to grow optimally at about 500 bars and 2� to 4�C. These conditions are similar to those prevailing at the 5700-meter depth from which the sample was collected. The organism grows at these pressures and temperatures with a generation time of between 4 and 13 hours; at atmospheric pressure and 2� to 4�C, the generation time is about 3 to 4 days.

Scavenging amphipods from the floor of the Philippine trench

Abstract Free vehicle, baited camera, and baited trap stations at 9600 and 9800 m on the bottom of the axis of the Philippine Trench demonstrate the presence of only one mobile scavenger, the amphipod Hirondellea gigas. This amphipod congregates in large numbers, consumes the bait in a matter of hours, and then disperses. Similar concentrations of amphipods have been recorded for all bait studies at hadal depths to date. In none of these did fish appear, even though they are characteristic of all samplings at shallower depths. The reason for this is obscure. Specimens of H. gigas can be classified according to developmental stage and sex. Except for stages ♂1 and ♀2, the stages are equivalent to instars, of which there are seven to eight for females and four for males. Brooding females were not trapped. The growth ratio is relatively constant among instars, except in the female where it decreases markedly during the period when there is a strong increase in the accumulation of reproductive products. Evidence favors the view that females breed only once. If this is so, total fecundity averages about 97 oocytes per female. Many H. gigas individuals had material in their guts that was ingested before being trapped. The fraction of such individuals decreased linearly with increasing maturity. A major fraction of the volume of this ingested material often consisted of bacteria. Several hypotheses are consistent with this result.

The distribution of methane in the upper waters of the southern California Bight

Profiles of dissolved methane in the upper 300 m of a 190,000 km2 area of southern Californian waters were determined during November 1989 and March 1990. Methane in near-surface waters ranged from 1 to 1416 nmol L−1. The lowest concentrations were at depths >200 m. The highest levels were found along the coast, especially in the region extending from Point Conception to Santa Barbara. Vertical profiles of methane are characterized by maxima in supersaturation within a narrow density band located within the pycnocline; this layer is continuous over a large geographic area. Offshore stations exhibiting elevated levels of methane are spatially coincident with mesoscale eddies of the California Current system. Interpretation of hydrographic and chemical data suggests that CH4-rich waters are upwelled from relatively shallow areas that are characterized by numerous hydrocarbon seeps. The data are consistent with a nearshore source of methane, presumably submarine seeps. Subsurface maxima in offshore waters are likely maintained by lateral transport of allochthonous CH4 along density surfaces from coastal waters and autochthonous microbial production.

Recovery and maintenance of live amphipods at a pressure of 580 bars from an ocean depth of 5700 meters.

Amphipods were collected from an ocean depth of 5700 meters in a windowed pressure-retaining trap, kept alive in the trap for as long as 9 days aboard ship, and transported to a land laboratory. Observations suggest that the animals can easily tolerate decompressions of 29 percent and briefly of 70 percent of the value of 580 bars, the pressure of their natural habitat. The average pleopod beat frequency was 106 beats per minute. Evidence suggests that food (fish bait) can have at least a 4-day residence time in the gut of these animals.

The pressure-volume-temperature (PVT) properties of a lipid mixture from a marine copepod, Calanus plumchrus: Implications for buoyancy and sound scattering

The density of a lipid mixture composed of nearly 85% wax esters and isolated from the copepod Calanus plumchrus was determined at 5.13, 14.49, and 23.65°C and at pressures up to 783 bars. At atmospheric pressure, the density was determined at temperatures between 1.64 and 15.54°C. The experimental isotherms and isobars were fitted to several equations of state and these were used to calculate coefficients of thermal expansion and compressibility. The wax ester mixture visibly melted as a function of temperature at atmospheric pressure. The high pressure isotherms show a volume discontinuity as a function of pressure that suggests a first-order liquid-solid phase transition. The coefficient of thermal expansion at atmospheric pressure is quite large (up to ten times that of water) and is apparently due in part to the phase change and its concomitant volume change. The coefficient of compressibility at atmospheric pressure is larger for the more solid form of the wax ester mixture than for the more liquid form. The contribution of wax esters to the buoyant properties of organisms is discussed. The buoyant force on the wax ester in seawater changes more as a function of temperature than as a function of pressure. The data also have implications to understanding sound scattering by wax ester-containing organisms. At depths defined by the pressure-temperature curve for the phase change, the wax ester mixture is on the verge of either melting or freezing. This results in a large coefficient of compressibility and may result in distinctive sound scattering by organisms containing wax esters and swimming at such depths. Furthermore, sound scattering should be different in organisms with solid wax ester mixtures than in those with liquid mixtures.

Enrichment and characterization of a methanogenic bacterium from the oxic upper layer of the ocean

Enrichment cultures containing marine plankton from oxygenated coastal waters (50–108% saturated) with supersaturated levels of methane (>700% saturated) yielded a strictly anaerobic methanogenic bacterium. Nonmotile, non-spore-forming, regular to slightly irregular cocci (0.5–0.8µm) were evident by phase contrast, epifluorescence, and scanning electron microscopies. The unpurified isolate required NaCl for growth, with maximal methanogenesis at 240 mM NaCl at 22°C. The optimal temperature range for growth was 22–31°C, and the optimal range for methanogenesis was 26–35°C. Mono-, di-, and trimethylated amines or methanol were substrates for methanogenesis; sodium acetate and H2:CO2 were not. The DNA base composition was 42 ±1% guanine plus cytosine. Serology suggested the isolate may be a new strain ofMethanococcoides methylutens. Morphology, growth physiology, DNA base content, and serology are all consistent with the type description ofM. methylutens, a methylotrophic methanogen isolated from submarine sediments.

Death of a Hadal Deep-Sea Bacterium After Decompression

An obligately barophilic bacterium that was recovered from a depth of 10,476 meters in the Pacific Ocean slowly lost colony-forming ability (assayed at 101.3 megapascals and 2�C) during incubation at atmospheric pressure and 0�C.

Coupling device for quick high‐pressure connections to 100 MPa

The joining of a pressure vessel to a pumping system was achieved quickly with a threadless coupling device consisting of a coupler and an adapter. The easily made adapters were attached to standard high‐pressure valves having a 6.35‐mm female fitting. The coupler was attached to a high‐pressure pump by flexible stainless‐steel tubing for use to 100 MPa (1000 bars).

Deep-Sea Bacteria

Hydrostatic pressure emerged as a significant environmental factor in ecology and evolution during the second half of the twentieth century. Pressure is not explicitly considered, for example, in Ekman’s classic 1953 book on the biogeography of marine animals (Ekman 1953). The book, a revision of a much earlier edition, was probably completed just as the Galathea Expedition ended in 1952 and was uninfluenced by the discoveries of its scientists (Bruun 1957). ZoBell and Morita, as participants on the Galathea Expedition, showed that pressure must be considered as a significant environmental parameter affecting the distribution of bacteria (Yayanos 2000, ZoBell 1952; ZoBell and Morita 1959). Other members of the expedition found animals in the greatest ocean depths.

Stimulatory effect of hydrostatic pressure on cell division in cultures of Escherichia coli

[14-C] Thymine incorporation into a trichloracetic acid-insoluble fraction of Escherichia coli HMS83 polA1 polB1 and cell division were observed as a function of time. The data presented show that hydrostatic pressures of about 600 x 10-5 N/m-2 stimulate that part of the division process which leads to the separation of cells. The kinetics of [14-C] thymine incorporation by this mutant suggest that completion of rounds of replication at high pressures is not dependent on DNA polymerases I or II or at least on high levels of these enzymes.