Competition of marine psychrophilic bacteria at low temperatures

The occurrence of obligately and facultatively psychrophilic bacteria in the marine environment suggests that environmental conditions exist which can favour each of these groups in competitive processes. Differences were found in the way in which temperature affected the growth rates of obligate and facultative psychrophiles. Maximum specific growth rates of a number of obligately and facultatively psychrophilic bacteria were determined in batch culture and competition experiments were carried out in a chemostat at growth-limiting substrate concentrations. From the results the relation between the specific growth rate and the concentration of the growth-limiting substrate for both types of organisms at different temperatures was deduced. Both at low and high substrate concentrations obligate psychrophiles grew faster than facultative psychrophiles at the lower temperature extreme (? 4 C). These results suggest that obligately psychrophilic chemoorganotrophs are responsible for mineralization processes in cold natural environments such as ocean waters and the arctic and antarctic regions. In these environments they can successfully compete with facultative psychrophiles because they can grow faster.     

Replication of chromosomal DNA in Chinese hamster cells, cultivated at different temperatures

DNA fiber autoradiography was used to measure the rate of replication and the size of replication units in Chinese hamster cells cultured at 34, 37 and 39 degrees C. The average rate of DNA replication per single fork is 0.6 mcm/min at 34 degrees and 0.8 mcm/min at 37 and 39 degrees. In contrast to the change in the rate of DNA replication, no change was found in the size of replication units, which are more than 200 mcm at 31, 37 and 39 degrees. The change of the length of the S phase at various temperatures is determined only by the rate of DNA replication.     

Triacylglyceride composition and fatty acyl saturation profile of a psychrophilic and psychrotolerant fungal species grown at different temperatures

Pseudogymnoascus destructans is a psychrophilic fungus that infects cutaneous tissues in cave dwelling bats, and it is the causal agent for white nose syndrome (WNS) in North American (NA) bat populations. Geomyces pannorum is a related psychrotolerant keratinolytic species that is rarely a pathogen of mammals. In this study, we grew P. destructans and G. pannorum in static liquid cultures at favourable and suboptimal temperatures to: 1) determine if triacylglyceride profiles are species-specific, and 2) determine if there are differences in fatty acyl (FA) saturation levels with respect to temperature. Total lipids isolated from both fungal spp. were separated by thin-layer chromatography and determined to be primarily sterols (∼15 %), free fatty acids (FFAs) (∼45 %), and triacylglycerides (TAGs) (∼50 %), with minor amounts of mono-/diacylglycerides and sterol esters. TAG compositions were profiled by matrix-assisted laser desorption–ionization time-of-flight mass spectrometry (MALDI–TOF). Total fatty acid methyl esters (FAMEs) and acyl lipid unsaturation levels were determined by gas chromatography–mass spectrometry (GC–MS). Pseudogymnoascus destructans produced higher proportions of unsaturated 18C fatty acids and TAGs than G. pannorum. Pseudogymnoascus destructans and G. pannorum produced up to a two-fold increase in 18:3 fatty acids at 5 °C than at higher temperatures. TAG proportion for P. destructans at upper and lower temperature growth limits was greater than 50 % of total dried mycelia mass. These results indicate fungal spp. alter acyl lipid unsaturation as a strategy to adapt to cold temperatures. Differences between their glycerolipid profiles also provide evidence for a different metabolic strategy to support psychrophilic growth, which may influence P. destructans' pathogenicity to bats.     

Long-term, high-rate anaerobic biological treatment of whey wastewaters at psychrophilic temperatures

Two laboratory-scale anaerobic hybrid reactors, R1 and R2, treated low- (1 kg COD m-3) and high-strength (10 kg COD m-3) whey-based wastewaters, respectively, in a 500-day trial. The chemical oxygen demand (COD) removal efficiencies of R1 averaged 70-80%, at organic loading rates of 0.5-1.3 kg COD m-3 day-1, between 20 and 12 degrees C. The COD removal efficiencies of R2 exceeded 90%, at organic loading rates up to 13.3 kg COD m-3 day-1, between 20 and 14 degrees C. Lowering the operating temperature of R2 to 12 degrees C resulted in a decrease in COD removal efficiency, to between 50% and 60%, and a disintegration of granular sludge. The decline in performance, and granule disintegration, was reversed by decreasing the organic loading rate of R2 to 6.6 kg m-3 day-1. Specific methanogenic activity profiles revealed mesophilic (37 degrees C) temperature optima for biomass in both reactors, even after 500 days of psychrophilic operation, although the development of psychrotolerance in the biomass was noted.     

Lipid composition of tobacco cells cultivated at various temperatures

Tobacco cell suspensions were grown under controlled conditions to determine whether temperature aftected the fatty acid pattern of the cellular lipids. At any temperature ranging between 17° and 35°, the total fatty acid content and the levels of fatty acids or individual lipids varied during the growth period, The optimum temperature for lipid biosynthesis and polyunsaturated fatty acid accumulation was between 20° and 26°. Increase in the level of polyunsaturated fatty acids was associated with lower temperatures during the active cell division period.     

Evolutionary relationships of cultivated psychrophilic and barophilic deep-sea bacteria

Evolutionary relationships of cultivated barophilic bacteria were determined. All psychrophilic and barophilic isolates were affiliated with one of five genera of the gamma subdivision of the class Proteobacteria ((gamma)-Proteobacteria): Shewanella, Photobacterium, Colwellia, Moritella, and a new group containing strain CNPT3. The data indicate that the barophilic phenotype has evolved independently in different (gamma)-Proteobacteria genera.     

Growth and survival studies of psychrophilic and mesophilic yeasts.

The effect of temperature on the growth of members of five genera of yeasts was studied in one glucose-containing and two glucose-free media. The maximum growth rate was seen in the glucose-containing medium, and the minimum growth was in either of the two glucose-free media depending upon the organism. Data obtained by optical density measurements was supported by total cell counts. The highest survival at the restrictive temperatures was within 5 degrees C of the optimum temperature for a particular organism. Among the temperatures other than the optimum, the highest growth rate and cell yield was obtained at a temperature 5 degrees C below or above the optimum.     

A rapid method for selecting fermentative yeasts at high temperatures

A rapid and efficient method for isolating and selecting thermotolerant and sugar-fermenting yeasts was developed. Several samples from sugar cane by-products could be analyzed at the same time. Yeast cultures could be isolated in about 3 d, in contrast to the conventional methods, and its fermentative ability was qualitatively maintained at the desired temperature. A broad spectrum of temperatures can be tested. Yeasts of generaSaccharomyces andKluyveromyces were easily identified.     

Isolation and characterization of psychrophilic yeasts producing cold-adapted pectinolytic enzymes

AIMS: The present study was conducted to screen for psychrophilic yeasts that are able to degrade pectin compounds at low temperature, and to examine the cold-active pectinolytic enzymes produced by the isolated psychrophilic yeasts. METHODS AND RESULTS: Psychrophilic yeasts, which grow on pectin as a sole carbon source, pectinolytic-psychrophilic yeast (PPY) strains PPY-3, 4, 5 and 6, were isolated from soil from Abashiri (Hokkaido, Japan). The sequences of 28S rDNA D1/D2 of strains PPY-3 and 4 indicated a taxonomic affiliation to Cryptococcus cylindricus and Mrakia frigida, respectively, strains PPY-5 and 6 belonged to Cystofilobasidium capitatum. The isolated strains were able to grow on pectin at below 5 degrees C, and showed the activities of several cold-active pectinolytic enzymes. CONCLUSION: The findings of this study indicate the possibility that the isolated strains produce novel pectinolytic enzymes that are able to degrade pectin compounds at low temperature. Significance and Impact of the Study: It is possible that the cold-active pectinolytic enzymes from the isolated strains can be applied to the food industry, e.g. the clarification of fruit juice below 5 degrees C.     

Effect of temperature on growth parameters of psychrophilic bacteria and yeasts

Three bacterial (Pedobacter heparinus, Pedobacter piscium, Pedobacter cryoconitis) and three yeast strains (Saccharomyces cerevisiae, Leucosporidiella creatinivora, Rhodotorula glacialis) of different thermal classes (mesophiles and psychrophiles) were tested for the effect of temperature on a range of growth parameters, including optical density, viable cell numbers, and cell dry mass, in order to determine the temperature conditions under which maximum biomass formation is obtained. Maximum values of growth parameters obtained at the stationary growth phase of the strains were used for statistical calculation. Temperature had a significant (P ≤ 0.05) effect on all growth parameters for each strain; correlations between the growth parameters were significant (P ≤ 0.05–0.01). The maximum growth temperature or the temperature at which microbial growth was fastest was in no case the temperature at which the investigated strains produced the highest amount of biomass. All tested psychrophilic bacteria and yeast strains produced highest amounts of cells (as calculated per mg cell dry mass or per OD₆₀₀ unit) at 1°C, while cell numbers of mesophiles were highest at 20°C. Thus, cultivation temperatures close to the maximum growth temperature are not appropriate for studying psychrophiles.     

Lipidomic analysis of bacterial plasmalogens

Plasmalogens are a group of lipids with potentially important, and not yet fully known, functions in organisms from bacteria to protozoans, invertebrates, and mammals. They can protect cells against the damaging effects of reactive oxygen species, protect other phospholipids or lipoprotein particles against oxidative stress, and have been implicated as signaling molecules and modulators of membrane dynamics. They have been found in many anaerobic bacterial species, and their biosynthetic pathways differ in aerobic and anaerobic organisms. The use of advanced techniques permits the identification of not only plasmalogen classes but also their positional isomers and often also individual molecular species. This paper describes direct analyses of plasmalogens from natural sources, frequently very unusual, using electrospray ionization mass spectrometry in combination with high-performance liquid chromatography and/or shotgun lipidomics.     

New data on the distribution of certain psychrophilic yeasts in Moscow oblast

Several rare species and varieties of psychrophilic yeasts were isolated from the Sphagnum mosses and paludal vascular plants of Moscow oblast. Based on their 26S rDNA D1/D2 nucleotide sequences, they were assigned to the species Sterigmatosporidium polymorphum, Rhodotorula psychrophenolica, and Aureobasidium pullulans var. subglaciale. Thus, a new habitat of S. polymorphum was found and yeasts known previously only for the Alpine environments and the Arctic region have been isolated in the central regions of Russia for the first time.     

Cryoanalgesia: electrophysiology at different temperatures

Somatosensory evoked potentials (SEP) and sensory conduction velocity (SCV) were measured in rabbit sciatic nerves following graded cold lesioning. The SEP disappeared when injury was induced at temperatures below -60 degrees C, but returned on day 41+/-4 (mean+/-SD). SEP returned on day 56+/-11 days when the lesion was induced at 100 to -180 degrees C. The SEP latency was prolonged after creating lesions at -100 to -180 degrees C, compared with both the sham operated and the -20 degrees C groups. These experiments suggest the cryolesions produced at temperatures between -60 and -100 degrees C are most suitable for altering the electrophysiological conduction of the nerve, and may result in suitable post-operative analgesia.     

Physiologo-biochemical characteristics of Candida tropicalis yeasts, cultivated on n-alkanes at supraoptimal temperature]

Cultivation of Candida tropicalis IBEM 303 without thermostatic regulation on n-alkanes results in an increase of the temperature in the fermenter to supraoptimal values and to the linear growth of the culture without distinct differentiation according to the growth phases. The cells grown at supraoptimal temperature differ from the cells cultivated at optimal temperature by the amount of some amino acids and oligopeptides liberated by the yeast into the cultural broth, by the chemical composition of the cells and their morphology.     

Growth, lipid accumulation, and fatty acid composition in obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts

Obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts were cultured in a carbon-rich medium at different temperatures to investigate whether growth parameters, lipid accumulation, and fatty acid (FA) composition were adaptive and/or acclimatory responses. Acclimation of facultative psychrophiles and mesophiles to a lower temperature decreased their specific growth rate, but did not affect their biomass yield (Y_X/S). Obligate and facultative psychrophiles exhibited the highest Y_X/S. Acclimation to lower temperature decreased the lipid yield (Y_L/X) in mesophilic yeasts, but did not affect Y_L/X in facultative psychrophilic ones. Similar Y_L/X were found in both groups of psychrophiles, suggesting that lipid accumulation is not a distinctive characteristic of adaptation to permanently cold environments. The unsaturation of FAs was one major adaptive feature of the yeasts colonizing permanently cold ecosystems. Remarkable amounts of α-linolenic acid were found in obligate psychrophiles at the expense of linoleic acid, whereas it was scarce or absent in all the other strains. Increased unsaturation of FAs was also a general acclimatory response of facultative psychrophiles to a lower temperature. These results improve the knowledge of the responses enabling psychrophilic yeasts to cope with the cold and may be of support for potential biotechnological exploitation of these strains.