The effect of temperature on the survival of microorganisms in a deep space vacuum

A Space Molecular Sink Research Facility (Molsink) was used to evaluate the ability of microorganisms to survive the vacuum of outer space. this facility could be programmed to simulate flight spacecraft vacuum environments at pressures in the 10^–10 torr range and thermal gradients (30 to 60°C) closely associated to surface temperatures of inflight spacecraft.Initial populations ofStaphylococcus epidermidis and aMicrococcus sp. were reduced approximately 1 log while exposed to –105 and 34°C, and approximately 2 logs while exposed to 59°C for 14 days in the vacuum environment.Spores ofBacillus subtilis var.niger were less affected by the environment. Initial spore populations were reduced 0.2, 0.3, and 0.8 log during the 14-day vacuum exposure at –124, 34, and 59°C, respectively.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.     

Leishmania donovani: effect of temperature on RNA metabolism

The present study concerns RNA metabolism of Leishmania donovani and its changes during exposure to higher temperatures. The incorporation of labeled precursors into RNA was found to be greatly decreased during incubation at 37 °C in comparison with that at the optimum temperature of growth (22 °C). The decreased incorporation was shown to be mainly due to augmented template RNA degradation. The RNA-polymerase activity remained unaffected at the elevated temperature, but the uptake of labeled uracil was markedly inhibited.     

The effect of temperature on routine metabolism in Tilapia rendalli boulenger

Using a continuous flow respirometer it was shown that young Tilapia rendalli had three distinct phases of oxygen consumption over the temperature range of 17–40° C. In the first phase (17–28° C) the metabolic energy demand followed the normal logarithmic increase with increasing temperature. Between 28 and 37° C the increased oxygen uptake was suppressed and showed a relatively small increase with increasing temperature. This feature was believed to be a significant energy saving function important to the growth of these fish which feed in the warm eulitoral margins of lakes during the day. The final phase shows a return to the original logarithmic increase in oxygen consumption. These results were related to, and compared with, actual changes in biomass at various temperatures and the theoretical and actual biomass changes were found to compare favourably.     

Global abundance of planktonic heterotrophic protists in the deep ocean

The dark ocean is one of the largest biomes on Earth, with critical roles in organic matter remineralization and global carbon sequestration. Despite its recognized importance, little is known about some key microbial players, such as the community of heterotrophic protists (HP), which are likely the main consumers of prokaryotic biomass. To investigate this microbial component at a global scale, we determined their abundance and biomass in deepwater column samples from the Malaspina 2010 circumnavigation using a combination of epifluorescence microscopy and flow cytometry. HP were ubiquitously found at all depths investigated down to 4000 m. HP abundances decreased with depth, from an average of 72±19 cells ml⁻¹ in mesopelagic waters down to 11±1 cells ml⁻¹ in bathypelagic waters, whereas their total biomass decreased from 280±46 to 50±14 pg C ml⁻¹. The parameters that better explained the variance of HP abundance were depth and prokaryote abundance, and to lesser extent oxygen concentration. The generally good correlation with prokaryotic abundance suggested active grazing of HP on prokaryotes. On a finer scale, the prokaryote:HP abundance ratio varied at a regional scale, and sites with the highest ratios exhibited a larger contribution of fungi molecular signal. Our study is a step forward towards determining the relationship between HP and their environment, unveiling their importance as players in the dark ocean''s microbial food web.     

Ecological structuring of bacterial and archaeal taxa in surface ocean waters

The Global Ocean Sampling (GOS) expedition is currently the largest and geographically most comprehensive metagenomic dataset, including samples from the Atlantic, Pacific, and Indian Oceans. This study makes use of the wide range of environmental conditions and habitats encompassed within the GOS sites in order to investigate the ecological structuring of bacterial and archaeal taxon ranks. Community structures based on taxonomically classified 16S ribosomal RNA (rRNA) gene fragments at phylum, class, order, family, and genus rank levels were examined using multivariate statistical analysis, and the results were inspected in the context of oceanographic environmental variables and structured habitat classifications. At all taxon rank levels, community structures of neritic, oceanic, estuarine biomes, as well as other exotic biomes (salt marsh, lake, mangrove), were readily distinguishable from each other. A strong structuring of the communities with chlorophyll a concentration and a weaker yet significant structuring with temperature and salinity were observed. Furthermore, there were significant correlations between community structures and habitat classification. These results were used for further investigation of one-to-one relationships between taxa and environment and provided indications for ecological preferences shaped by primary production for both cultured and uncultured bacterial and archaeal clades.     

Experimental effect of lysozyme on macrophage metabolism and resistance to infection

The peritoneal macrophages of mice treated with lysozyme were studied by cytochemical assay. In single and repeated doses of 0.5-5 mg/kg lysozyme induced an increase in macrophage metabolism. This was evident from an increased activity of succinate dehydrogenase, NADP X N-DH and the enzymes catalyzing glycolysis typical of these cells (lactate dehydrogenase and alpha-glycerophosphate). The changes in the activity of the enzymatic systems were most pronounced in minute and less mature macrophages after repeated administrations of the drugs. In a dose of 50 mg/kg lysozyme somewhat decreased the activity of a number of the enzymes. In the doses optimal for the macrophage activity lysozyme had a low effect on the infection resistance and slightly increased the cephotaxim efficiency in experimental staphylococcal infection. This may be mainly due to the immunomodulating effect of lysozyme and its low effect on the large macrophages having the bactericidal effect.     

The effect of osmotic pressure on the mobility and metabolism of human spermatozoa]

When human sperm was suspended in a hypertonic medium, their motility is damaged and their oxygen consumption is reduced. Hypotonic conditions are more disastrous because the cells become immotile. These results are discussed with reference to high osmolarity of seminal fluid.     

Experimental effect of bruneomycin on the energy metabolism of liver tissue]

The effect of an antitumor antibiotic bruneomycin on the energy metabolism in the liver tissue was studied. Four hours after the drug administration the consumption of glycogen and glucose in the liver tissue increased because of glycogenolysis activation, which was evident from increased activity of prosphorylase, phosphofructokinase, hexokinase and summation glycolytic activity. 24 and 48 hours after the antibiotic administration the balance of consumption and resynthesis of phosphate macroergs in the liver tissue impaired, which was evident from decreased levels of ATP, impairement of conjugation of the processes of oxidation due to impairement of permeability and structural integrity of the mitochondrial membranes. Further decrease in the glycogen liver levels was mainly due to suppressed resynthesis of glycogen because of destructive-necrotic processes. Simultaneously the processes of glycolytic splitting of glucose decreased which was evident from decreased activity of the enzymes and summation glycolytic activity.     

The ocean is not deep enough: pressure tolerances during early ontogeny of the blue mussel Mytilus edulis

Early ontogenetic adaptations reflect the evolutionary history of a species. To understand the evolution of the deep-sea fauna and its adaptation to high pressure, it is important to know the effects of pressure on their shallow-water relatives. In this study we analyse the temperature and pressure tolerances of early life-history stages of the shallow-water species Mytilus edulis. This species expresses a close phylogenetic relationship with hydrothermal-vent mussels of the subfamily Bathymodiolinae. Tolerances to pressure and temperature are defined in terms of fertilization success and embryo developmental rates in laboratory-based experiments. In M. edulis, successful fertilization under pressure is possible up to 500 atm (50.66 MPa), at 10, 15 and 20 degrees C. A slower embryonic development is observed with decreasing temperature and with increasing pressure; principally, pressure narrows the physiological tolerance window in different ontogenetic stages of M. edulis, and slows down metabolism. This study provides important clues on possible evolutionary pathways of hydrothermal vent and cold-seep bivalve species and their shallow-water relatives. Evolution and speciation patterns of species derive mostly from their ability to adapt to variable environmental conditions, within environmental constraints, which promote morphological and genetic variability, often differently for each life-history stage. The present results support the view that a direct colonization of deep-water hydrothermal vent environments by a cold eurythermal shallow-water ancestor is indeed a possible scenario for the Mytilinae, challenging previous hypothesis of a wood/bone to seep/vent colonization pathway.     

The effect of carbon dioxide level and temperature on the in vitro metabolism of testis tissue

• 1.1. Normal testis tissue from sixty mature rabbits was studied to determine the effect of 0, 2, 5 and 10% CO₂ levels, temperature (33 and 37°C) and length of incubation time, at hourly intervals from 1 to 4, on glucose and O₂ uptake and lactate and CO₂ production.
• 2.2. There was generally a significant effect of the time of incubation due to a high activity during the first hour and no evident effect thereafter. This was possibly due to either tissue damage or substrate depletion during preparation.
• 3.3. Increased temperature caused increased metabolic activity as shown by other workers in vivo.
• 4.4. At 0 and 10% CO₂ there was marked decrease in metabolic activity, indicating a need for some CO₂ by the testis tissue and an inhibitory effect by CO₂ at higher levels. At these two levels there was a shift in metabolism from respiration to glycolysis.
• 5.5. The maximum metabolic activity occurred at 2 and 5% Co₂ which is near the levels previously reported in vivo.

     

The adaptation of biological membranes to temperature and pressure: Fish from the deep and cold

The homoeostatic regulation of bilayer order is a property of functional importance. Arguably, it is best studied in those organisms which experience and must overcome disturbances in bilayer order which may be imposed by variations in temperature of hydrostatic pressure. This article reviews our recent work on the adaptations of order in brain membranes of those fish which acclimate to seasonal changes in temperature or which have evolved in extreme thermal or abyssal habitats. The effects of temperature and pressure upon hydrocarbon order and phase state are reviewed to indicate the magnitude of the disturbances experienced by animals in their environments over the seasonal or evolutionary timescale. Acclimation of fish to altered temperature leads to a partial correction of order, while comparison of fish from extreme cold environments with those from temperate or tropical waters reveals a more complete adaptation. Fish from the deep sea also display adaptations of bilayer order which largely overcome the ordering effects of pressure.     

A pressure-retaining deep ocean sampler and transfer system for measurement of microbial activity in the deep sea

A deep ocean sampler (DOS) has been developed for microbiological sampling and is capable of aseptically collecting 400-ml water samples from any depth in the world oceans. The instrument maintains samples under in situ pressure and temperature. A hyperbaric transfer system has also been developed, enabling transfer of sample volumes up to 150 ml, without decompression or dilution, to pressurized incubation chambers. Utilization of¹⁴C-glutamate (21 to 96g/l) and¹⁴C-acetate (4.6g/l) by microbial populations in undecompressed water samples from the N.W. Atlantic and the Cape and Angola Basins was recorded over incubation periods of 2 to 18 weeks. Rates of substrate utilization ranged from 1 to 38×10^–2 g/l/day.     

An evaluation of the metabolism of sestonic and epilithic communities in running waters using an improved chamber technique

SUMMARY. 1. A chamber technique is described which allows the uptake of nutrients in a lotic system to be assessed during a brief experimental period. Sensitive radioisotope techniques were used to determine the metabolism of the planktonic and epilithic communities simultaneously in a pristine boreal forest stream in N.E. Quebec, Canada.
2. Abiotic adsorption of bicarbonate, glucose, methylammonium and phosphate was unimportant in the riffle investigated. Among the biological components, the epilithon was responsible for more than 87% of the uptake of bicarbonate, glucose and methylammonium.
3. The uptake of orthophosphate was predominantly (80%) by organisms in the overlying water. Phosphorus, the nutrient most limiting the system, may be conserved by the epilithon through internal cycling. Uptake rates are within the range reported for other oligotrophic systems.     

The effect of temperature on the ability of Tilapia mossambica Peters to enter deep water

The ability of adult Tilapia mossambica Peters to enter deep water was determined at 15, 22 and 30°C. At 30°C adults compensate to about 20m depth but at 15°C to only 7 m. Compensation is more rapid at high than at low temperatures. T. mossambica haemoglobin has a marked Root effect which is the same at 22 and 30°C. The oxygen affinity of the haemoglobin is higher at 15°C than at 30°C. There was no measurable difference in the rate of passive oxygen diffusion across the swimbladder wall in the temperature range 15–30°C. It is concluded that the ability to enter deeper water at higher temperatures is related to decreased oxygen affinity of the haemoglobin and higher rates of oxygen secretion and blood circulation.     

Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin

A second group of proteorhodopsin-encoding genes (blue-absorbing proteorhodopsin, BPR) differing by 20-30% in predicted primary structure from the first-discovered green-absorbing (GPR) group has been detected in picoplankton from Hawaiian deep sea water. Here we compare BPR and GPR absorption spectra, photochemical reactions, and proton transport activity. The photochemical reaction cycle of Hawaiian deep ocean BPR in cells is 10-fold slower than that of GPR with very low accumulation of a deprotonated Schiff base intermediate in cells and exhibits mechanistic differences, some of which are due to its glutamine residue rather than leucine at position 105. In contrast to GPR and other characterized microbial rhodopsins, spectral titrations of BPR indicate that a second titratable group, in addition to the retinylidene Schiff base counterion Asp-97, modulates the absorption spectrum near neutral pH. Mutant analysis confirms that Asp-97 and Glu-108 are proton acceptor and proton donor, respectively, in retinylidene Schiff base proton transfer reactions during the BPR photocycle as previously shown for GPR, but BPR contains an alternative acceptor evident in its D97N mutant, possibly the same as the second titratable group modulating the absorption spectrum. BPR, similar to GPR, carries out outward light-driven proton transport in Escherichia coli vesicles but with a reduced translocation rate attributable to its slower photocycle. In energized E. coli cells at physiological pH, the net effect of BPR photocycling is to generate proton currents dominated by a triggered proton influx, rather than efflux as observed with GPR-containing cells. Reversal of the proton current with the K+-ionophore valinomycin supports that the influx is because of voltage-gated channels in the E. coli cell membrane. These observations demonstrate diversity in photochemistry and mechanism among proteorhodopsins. Calculations of photon fluence rates at different ocean depths show that the difference in photocycle rates between GPR and BPR as well as their different absorption maxima may be explained as an adaptation to the different light intensities available in their respective marine environments. Finally, the results raise the possibility of regulatory (i.e. sensory) rather than energy harvesting functions of some members of the proteorhodopsin family.