Biochemical Function and Ecological Significance of Novel Bacterial Lipids in Deep-Sea Procaryotes

Pressure effects on in vivo microbial processes

Pressures between 10 and 100 MPa can exert powerful effects on the growth and viability of organisms. Here I describe the effects of elevated pressure in this range on mesophilic (atmospheric pressure adapted) and piezophilic (high-pressure adapted) microorganisms. Examination of pressure effects on mesophiles makes use of this unique physical parameter to aid in the characterization of fundamental cellular processes, while in the case of piezophiles it provides information on the essence of the adaptation of life to high-pressure environments, which comprise the bulk of our biosphere. Research is presented on the isolation of pressure-resistant mutants, high-pressure regulation of gene expression, the role of membrane lipids and proteins in determining growth ability at high pressure, pressure effects on DNA replication and topology as well as on cell division, and the role of extrinsic factors in modulating enzyme activity at high pressure.

Biomarker techniques to screen for bacteria that produce polyunsaturated fatty acids

The production of polyunsaturated fatty acids (PUFA) by bacteria has been firmly established for over two decades although it is still commonly ignored. Investigations of Antarctic sea ice have revealed a high diversity of novel bacterial taxa with the ability to produce PUFA. The majority are psychrophilic (requiring low temperatures for growth) and halophilic (requiring the presence of salts for growth), in contrast to the bacterial community present in the underlying water column. Specific fatty acids may be used as indicators of PUFA-producing bacteria in environmental samples. Structural studies of bacterial phospholipids have been particularly revealing in suggesting biomarkers specific for prokaryotic PUFA input. The use of negative ion fast atom bombardment tandem mass spectrometry for the analysis of bacterial phospholipids has identified species specific for certain groups of bacterial PUFA producers. The phylogeny of PUFA production in the gamma-Proteobacteria also suggests the future use of PUFA genes for the assessment of marine bacterial biodiversity.

Production of polyunsaturated fatty acids by polyketide synthases in both prokaryotes and eukaryotes

Polyunsaturated fatty acids (PUFAs) are essential membrane components in higher eukaryotes and are the precursors of many lipid-derived signaling molecules. Here, pathways for PUFA synthesis are described that do not require desaturation and elongation of saturated fatty acids. These pathways are catalyzed by polyketide synthases (PKSs) that are distinct from previously recognized PKSs in both structure and mechanism. Generation of cis double bonds probably involves position-specific isomerases; such enzymes might be useful in the production of new families of antibiotics. It is likely that PUFA synthesis in cold marine ecosystems is accomplished in part by these PKS enzymes.

Correlation between phylogenetic structure and function: examples from deep-sea Shewanella

The genus Shewanella is one of the typical deep-sea bacterial genera. Two isolated deep-sea Shewanella species, Shewanella benthica and Shewanella violacea, were found to be able to grow better under high hydrostatic pressure conditions than at atmospheric pressure. These species are not only piezophilic (barophilic), but also psychrophilic. Many psychrophilic and psychrotolerant Shewanella species have been isolated and characterized from cold environments, such as seawater in Antarctica or the North Sea. Some of these cold-adapted Shewanella were shown to be piezotolerant, meaning that growth occurs in a high-pressure habitat. In this review, we propose that two major sub-genus branches of the genus Shewanella should be recognized taxonomically, one group characterized as high-pressure cold-adapted species that produce substantial amounts of eicosapentaenoic acid, and the other group characterized as mesophilic pressure-sensitive species.

Characterization of the gene encoding the beta-lactamase of the psychrophilic marine bacterium Moritella marina strain MP-1

The beta-lactamase gene (mbla) of the psychrophilic marine bacterium Moritella marina strain MP-1 was identified in a previously isolated genomic DNA fragment and it was expressed in Escherichia coli cells. The mbla gene encoded a protein consisting of 287 amino acid residues. Its predicted amino acid sequence showed approximately 50% identity with that of a number of class A beta-lactamases, especially with that of CARB/PSE type of beta-lactamases (carbenicillinases). E. coli transformed with the plasmid containing mbla grew on an ampicillin-containing plate at 37 degrees C but not at 42 degrees C, suggesting that the beta-lactamase of this bacterium is heat-labile.

Bacteria in the cold deep-sea benthic boundary layer and sediment-water interface of the NE Atlantic

This is a short review of the current understanding of the role of microorganisms in the biogeochemistry in the deep-sea benthic boundary layer (BBL) and sediment-water interface (SWI) of the NE Atlantic, the gaps in our knowledge and some suggestions of future directions. The BBL is the layer of water, often tens of meters thick, adjacent to the sea bed and with homogenous properties of temperature and salinity, which sometimes contains resuspended detrital particles. The SWI is the bioreactive interface between the water column and the upper 1 cm of sediment and can include a large layer of detrital material composed of aggregates that have sedimented from the upper mixed layer of the ocean. This material is biologically transformed, over a wide range of time scales, eventually forming the sedimentary record. To understand the microbial ecology of deep-sea bacteria, we need to appreciate the food supply in the upper ocean, its packaging, passage and transformation during the delivery to the sea bed, the seasonality of variability of the supply and the environmental conditions under which the deep-sea bacteria grow. We also need to put into a microbial context recent geochemical findings of vast reservoirs of intrinsically labile organic material sorped onto sediments. These may well become desorped, and once again available to microorganisms, during resuspension events caused by deep ocean currents. As biotechnologists apply their tools in the deep oceans in search of unique bacteria, an increasing knowledge and understanding of the natural processes undertaken and environmental conditions experienced by deep-sea bacteria will facilitate this exploitation.

FabF is required for piezoregulation of cis-vaccenic acid levels and piezophilic growth of the deep-Sea bacterium Photobacterium profundum strain SS9

To more fully explore the role of unsaturated fatty acids in high-pressure, low-temperature growth, the fabF gene from the psychrotolerant, piezophilic deep-sea bacterium Photobacterium profundum strain SS9 was characterized and its role and regulation were examined. An SS9 strain harboring a disruption in the fabF gene (strain EA40) displayed growth impairment at elevated hydrostatic pressure concomitant with diminished cis-vaccenic acid (18:1) production. However, growth ability at elevated pressure could be restored to wild-type levels by the addition of exogenous 18:1 to the growth medium. Transcript analysis did not indicate that the SS9 fabF gene is transcriptionally regulated, suggesting that the elevated 18:1 levels produced in response to pressure increase result from posttranscriptional changes. Unlike many pressure-adapted bacterial species such as SS9, the mesophile Escherichia coli did not regulate its fatty acid composition in an adaptive manner in response to changes in hydrostatic pressure. Moreover, an E. coli fabF strain was as susceptible to elevated pressure as wild-type cells. It is proposed that the SS9 fabF product, beta-ketoacyl-acyl carrier protein synthase II has evolved novel pressure-responsive characteristics which facilitate SS9 growth at high pressure.

Monounsaturated but not polyunsaturated fatty acids are required for growth of the deep-sea bacterium Photobacterium profundum SS9 at high pressure and low temperature

There is considerable evidence correlating the production of increased proportions of membrane unsaturated fatty acids (UFAs) with bacterial growth at low temperatures or high pressures. In order to assess the importance of UFAs to microbial growth under these conditions, the effects of conditions altering UFA levels in the psychrotolerant piezophilic deep-sea bacterium Photobacterium profundum SS9 were investigated. The fatty acids produced by P. profundum SS9 grown at various temperatures and pressures were characterized, and differences in fatty acid composition as a function of phase growth, and between inner and outer membranes, were noted. P. profundum SS9 was found to exhibit enhanced proportions of both monounsaturated (MUFAs) and polyunsaturated (PUFAs) fatty acids when grown at a decreased temperature or elevated pressure. Treatment of cells with cerulenin inhibited MUFA but not PUFA synthesis and led to a decreased growth rate and yield at low temperature and high pressure. In addition, oleic acid-auxotrophic mutants were isolated. One of these mutants, strain EA3, was deficient in the production of MUFAs and was both low-temperature sensitive and high-pressure sensitive in the absence of exogenous 18:1 fatty acid. Another mutant, strain EA2, produced little MUFA but elevated levels of the PUFA species eicosapentaenoic acid (EPA; 20:5n-3). This mutant grew slowly but was not low-temperature sensitive or high-pressure sensitive. Finally, reverse genetics was employed to construct a mutant unable to produce EPA. This mutant, strain EA10, was also not low-temperature sensitive or high-pressure sensitive. The significance of these results to the understanding of the role of UFAs in growth under low-temperature or high-pressure conditions is discussed.

Changes in the microbial community in Japan Trench sediment from a depth of 6292 m during cultivation without decompression

A sample of deep-sea sediment was obtained from the Japan Trench at a depth of 6292 m using a pressure-retaining sediment sampler. Microorganisms in the sediment sample were cultivated in marine broth 2216 at ambient pressure (65 MPa) without decompression, and at atmospheric pressure (0.1 MPa) as a control experiment. 16S ribosomal RNA genes (rDNA) were amplified by PCR from DNA extracted from the original sediment sample and the mixed cultures, and the nucleotide sequences were determined. The results of phylogenetic analysis based on 16S rDNA sequences indicated that microbial diversity in the original sediment samples showed a wide distribution of types in the domain Bacteria. Furthermore, in the mixed cultures incubated at 65 MPa without decompression, bacterial strains belonging to the Shewanella barophiles branch and the genus Moritella existed together at the beginning of cultivation, and Moritella strains became dominant towards the end of the cultivation period. Finally, in the mixed cultures incubated at atmospheric pressure, strains belonging to the genus Pseudomonas were dominant at all times. Analysis of fatty acids extracted from the cultures supported the phylogenetic results.

Extremely barophilic bacteria isolated from the Mariana Trench, Challenger Deep, at a depth of 11,000 meters

Two strains of obligately barophilic bacteria were isolated from a sample of the world's deepest sediment, which was obtained by the unmanned deep-sea submersible Kaiko in the Mariana Trench, Challenger Deep, at a depth of 10,898 m. From the results of phylogenetic analysis based on 16S rRNA gene sequences, DNA-DNA relatedness study, and analysis of fatty acid composition, the first strain (DB21MT-2) appears to be most highly similar to Shewanella benthica and close relatives, and the second strain (DB21MT-5) appears to be closely related to the genus Moritella. The optimal pressure conditions for growth of these isolates were 70 MPa for strain DB21MT-2 and 80 MPa for strain DB21MT-5, and no growth was detected at pressures of less than 50 MPa with either strain. This is the first evidence of the existence of an extreme-barophile bacterium of the genus Moritella isolated from the deep-sea environment.

Identification of a regulatory protein required for pressure-responsive gene expression in the deep-sea bacterium Photobacterium species strain SS9

Here, we report the characterization of a gene necessary for hydrostatic pressure regulation of gene expression in the deep-sea bacterium Photobacterium species strain SS9. The deduced amino acid sequence of the gene product shares extensive similarity to ToxR, a transmembrane DNA-binding protein first discovered as a virulence determinant in the pathogenic bacterium Vibrio cholerae. Changes in hydrostatic pressure induce changes in both the abundance and the activity of the SS9 ToxR protein (or the activity of a ToxR-regulated protein). As with other high-pressure-inducible phenomena observed in higher organisms, anaesthetics antagonize high-pressure signalling mediated by ToxR. It is suggested that SS9 ToxR has evolved the ability to respond to pressure-mediated alterations in membrane structure. V. cholerae and SS9 also share similarity in a ToxR-regulated protein, indicating that part of the ToxR regulon is conserved in diverse members of the family Vibrionaceae. The SS9 ToxR system represents a useful model for studies of signal transduction and environmental adaptation in the largest portion of the biosphere, the deep sea.

Distribution of the pressure-regulated operons in deep-sea bacteria

DNA regions corresponding to portions of two different pressure-regulated operons previously identified in two deep-sea barophilic bacteria were separately PCR amplified from a variety of deep-sea microorganisms and sequenced. With the two sets of primers employed, amplification was particularly successful from the more barophilic bacteria examined. 16S rRNA sequence analysis revealed that these bacteria are all phylogenetically related and belong in a sub-branch of the genus Shewanella containing only the deep-sea Shewanella barophilic bacteria. We define this sub-branch as the 'Shewanella barophile branch' containing at least two different species. Our results suggest that the DNA sequences of the pressure-regulated operons can be regarded as marker sequences to identify the Shewanella barophilic strains.

Adaptive changes in membrane lipids of barophilic bacteria in response to changes in growth pressure

The lipid compositions of barophilic bacterial strains which contained docosahexaenoic acid (DHA [22:6n-3]) were examined, and the adaptive changes of these compositions were analyzed in response to growth pressure. In the facultatively barophilic strain 16C1, phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) were major components which had the same fatty acid chains. However, in PE, monounsaturated fatty acids such as hexadecenoic acid were major components, and DHA accounted for only 3.7% of the total fatty acids, while in PG, DHA accounted for 29.6% of the total fatty acids. In response to an increase in growth pressure in strain 16C1, the amounts of saturated fatty acids in PE were reduced, and these decreases were mainly balanced by an increase in unsaturated fatty acids, including DHA. In PG, the decrease in saturated fatty acids was mainly balanced by an increase in DHA. Similar adaptive changes in fatty acid composition were observed in response to growth pressure in obligately barophilic strain 2D2. Furthermore, these adaptive changes in response were also observed in response to low temperature in strain 16C1. These results confirm that the general shift from saturated to unsaturated fatty acids including DHA is one of the adaptive changes in response to increases in pressure and suggest that DHA may play a role in maintaining the proper fluidity of membrane lipids under high pressure.

Lipid and fatty acid compositions of a novel docosahexaenoic acid-producing marine bacterium

An unidentified bacterial strain, SCRC-21406, isolated from the intestine of a marine fish, Glossanodon semifasciatus, produced docosahexaenoic acid at 23% (mol/mol) [= 28% (w/w)] of total fatty acids in a medium containing 0.5% (wt/vol) peptone and 0.1% (wt/vol) yeast extract at 12 degrees C under atmospheric pressure. The cell yield was 0.43 g/L. The major lipids of the strain were phosphatidylethanolamine and phophatidylglycerol. Docosahexaenoic acid was localized at the sn-2 positions of both phospholipids. The amounts of polyunsaturated fatty acids other than docosahexaenoic acid were extremely small [< 3% (mol/mol)]. Monounsaturated fatty acids of the cis-7, cis-9 and cis-11 types were detected.

Polyunsaturated fatty acids in the psychrophilic bacterium Shewanella gelidimarina ACAM 456T: molecular species analysis of major phospholipids and biosynthesis of eicosapentaenoic acid

The production of eicosapentaenoic acid [20:5omega3; EPA] from Shewanella gelidimarina (ACAM 456T) was investigated with respect to growth temperature and growth on sole carbon sources. The percentage and quantitative yield of EPA remained relatively constant at all growth temperatures within or below the optimal growth temperature region. At higher growth temperatures, these values decreased greatly. Growth on differing sole carbon sources also influenced the percentage and amount of EPA produced, with the fatty acid composition influenced by provision of potential acyl chain primers as sole carbon sources. The highest amounts of EPA occurred from growth on propionic acid and L-leucine respectively, while the highest percentage of EPA occurred from growth on L-proline. Monounsaturated fatty acid components and EPA were concentrated in phosphatidylglycerol (PG), while the proportion of branched-chain fatty acids was elevated in phosphatidylethanolamine (PE); the two major phospholipid classes. Specific associations of EPA with other acyl chains were identified within cellular phospholipid classes. The association of EPA with 17:1 and 18:0 acyl chains in phospholipid species was specific to PG, whereas the association of EPA with i13:0/13:0 and 14:0/i14:0 was specific to PE. Such acyl chain 'tailoring' is indicative of the important role of EPA in bacterial membrane adaptive responses. EPA was also a large component (22%) of a non-esterified fatty acid (NEFA) fraction within the total lipid extract of the bacterium. This may point toward a particular role of NEFA in polyunsaturated fatty acid (PUFA) metabolism. The formation of EPA was investigated by labelling with L-[U-14C]serine and sodium [1-14C]acetate. The accumulation of radiolabel within unsaturated intermediates (di-, tri- and tetraunsaturated fractions) was low, indicating a rapid formation and derivatisation of these components. Similar results were found for the unsaturated fatty acid fractions of both PE and PG using sodium [1-14C]acetate radiolabel. The regulation of triunsaturated fatty acid components may be a potential control site in PUFA biosynthesis.

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.

Physiological Responses to Stress Conditions and Barophilic Behavior of the Hyperthermophilic Vent Archaeon Pyrococcus abyssi

The physiology of the deep-sea hyperthermophilic, anaerobic vent archaeon Pyrococcus abyssi, originating from the Fiji Basin at a depth of 2,000 m, was studied under diverse conditions. The emphasis of these studies lay in the growth and survival of this archaeon under the different conditions present in the natural habitat. Incubation under in situ pressure (20 MPa) and at 40 MPa increased the maximal and minimal growth temperatures by 4(deg)C. In situ pressure enhanced survival at a lethal high temperature (106 to 112(deg)C) relative to that at low pressure (0.3 MPa). The whole-cell protein profile, analyzed by one-dimensional sodium dodecyl sulfate gel electrophoresis, did not change in cultures grown under low or high pressure at optimal and minimal growth temperatures, but several changes were observed at the maximal growth temperature under in situ pressure. The complex lipid pattern of P. abyssi grown under in situ and 0.1- to 0.5-MPa pressures at different temperatures was analyzed by thin-layer chromatography. The phospholipids became more complex at a low growth temperature at both pressures but their profiles were not superimposable; fewer differences were observed in the core lipids. The polar lipids were composed of only one phospholipid in cells grown under in situ pressure at high temperatures. Survival in the presence of oxygen and under starvation conditions was examined. Oxygen was toxic to P. abyssi at growth range temperature, but the strain survived for several weeks at 4(deg)C. The strain was not affected by starvation in a minimal medium for at least 1 month at 4(deg)C and only minimally affected at 95(deg)C for several days. Cells were more resistant to oxygen in starvation medium. A drastic change in protein profile, depending on incubation time, was observed in cells when starved at growth temperature.

Isolation and characterization of the gene encoding single-stranded-DNA-binding protein (SSB) from four marine Shewanella strains that differ in their temperature and pressure optima for growth

The ssb gene, coding for single-stranded-DNA-binding protein (SSB), was cloned from four marine Shewanella strains that differed in their temperature and pressure optima and ranges of growth. All four Shewanella ssb genes complemented Escherichia coli ssb point and deletion mutants, with efficiencies that varied with temperature and ssb gene source. The Shewanella SSBs are the largest bacterial SSBs identified to date (24.9-26.3 kDa) and may be divided into conserved amino- and carboy-terminal regions and a highly variable central region. Greater amino acid sequence homology was observed between the Shewanella SSBs as a group (72-87%) than with other bacterial SSBs (52-69%). Analysis of the amino acid composition of the Shewanella SSBs revealed several features that could correlate with pressure or temperature adaptation. SSBs from the three low-temperature-adapted Shewanella strains were an order of magnitude more hydrophilic than that from the mesophilic strain, and differences in the distribution of eight amino acids were identified which could contribute to either the temperature or pressure adaptation of the proteins. The SSBs from all four Shewanella strains were overproduced and partially purified based upon their ability to bind single-stranded DNA. The differences found among the Shewanella SSBs suggest that these proteins will provide a useful system for exploring the adaptation of protein-protein and protein-DNA interactions at low temperature and high pressure.

The biosynthesis of omega 3 fatty acids from 18:2 omega 6 in Artemia spp

To examine the biosynthesis of omega 3 fatty acids from 18:2 omega 6, reference Artemia (RAC III, Artemia Reference Center, Gent, Belgium) were fed rice bran supplemented with [1(-14)C]18:2 omega 6 for 2 days following 48 hours starvation since cyst hydration and 1, 2, or 3 days following 72 hours of starvation, under axenic conditions. Artemia fatty acids were analyzed by gas chromatography, AgNO3 thin layer chromatography and high performance liquid chromatography and fatty acid fractions were collected for radioisotope counts. No significant differences were observed in the omega 3 fatty acid content of Artemia cultured under axenic and xenic conditions. Radioisotope studies showed that radioactivity from [1(-14)C]18:2 omega 6 was incorporated into other fatty acids, including 18:3 omega 3, 18:4 omega 3 and 20:5 omega 3. The conversion rate was less than 5% for the two day feeding period. In the three day feeding experiment, the amount of radioactivity recovered in both 18:3 omega 3 and 20:5 omega 3 increased by 2.2- and 1.8-fold, respectively, over the three day feeding period. These results demonstrated that Artemia synthesized these omega 3 polyunsaturated fatty acids from 18:2 omega 6.

High pressure influences on gene and protein expression

Elevated hydrostatic pressure can influence gene and protein expression in both 1 atmosphere-adapted and high pressure-adapted microorganisms. Here we review experiments documenting these effects and describe their significance towards understanding the molecular bases of life in deep-sea high pressure environments.

Pressure effects on the composition and thermal behavior of lipids from the deep-sea thermophile Methanococcus jannaschii

The deep-sea archaeon Methanococcus jannaschii was grown at 86 degrees C and under 8, 250, and 500 atm (1 atm = 101.29 kPa) of hyperbaric pressure in a high-pressure, high-temperature bioreactor. The core lipid composition of cultures grown at 250 or 500 atm, as analyzed by supercritical fluid chromatography, exhibited an increased proportion of macrocyclic archaeol and corresponding reductions in aracheol and caldarchaeol compared with the 8-atm cultures. Thermal analysis of a model core-lipid system (23% archaeol, 37% macrocyclic archaeol, and 40% caldarchaeol) using differential scanning calorimetry revealed no well-defined phase transition in the temperature range of 20 to 120 degrees C. Complementary studies of spin-labeled samples under 10 and 500 atm in a special high-pressure, high-temperature electron paramagnetic resonance spectroscopy cell supported the differential scanning calorimetry phase transition data and established that pressure has a lipid-ordering effect over the full range of M. jannaschii's growth temperatures. Specifically, pressure shifted the temperature dependence of lipid fluidity by ca. 10 degrees C/500 atm.

Production of docosahexaenoic acid by marine bacteria isolated from deep sea fish

Five bacterial strains isolated from the intestine of deep sea fish were shown to produce docosahexaenoic acid (22:6n-3; DHA) at a level of 6.4 to 11.6% of total fatty acids when incubated in DHA-free medium. In all of the strains examined, other polyunsaturated fatty acids were barely detectable, except for eicosapentaenoic acid (20:5n-3). A typical strain, such as T3615, produced DHA at a concentration of about 0.8 mg/L within six days of aerobic incubation at 5 degrees C and under atmospheric pressure. The T3615 strain, belonging to the genus Vibrio, is rod-shaped, Gram-negative, motile and facultatively anaerobic.

Trans-monoenoic and polyunsaturated fatty acids in phospholipids of a Vibrio species of bacterium in relation to growth conditions

A Vibrio species of bacterium known to contain the polyunsaturated fatty acid 20:5n-3 was grown in both freshwater and seawater media at 5 and 20 degrees C and examined for adaptive changes in lipid composition. Phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), together with a smaller proportion of nonesterified fatty acids (NEFA), comprised almost all the lipid under all growth conditions examined. Temperature had a more pronounced effect than the salinity of the medium on lipid composition. The proportion of PE in total lipid was always higher at 5 than at 20 degrees C. Conversely, the proportion of NEFA was lower at 5 than 20 degrees C whereas that of PG was not altered. The levels of saturated fatty acids in total lipid, PE and PG were all decreased by growth at 5 degrees C. No differences were observed with respect to growth temperature in the levels of cis 16:1n-7, the principal monoenoic fatty acid in both PE and PG. Trans 16:1n-7 was found to comprise 12.8-15.2% of fatty acids in PE and PG of bacteria grown at 5 degrees C but only 4.4-8.5% of phospholipid fatty acids in bacteria cultured at 20 degrees C. Regardless of medium composition, a reduction in growth temperature from 20 to 5 degrees C also caused the proportions of 20:5n-3 to increase from around 0.8 to 4.4% in PE and from around 4 to 20% in PG. The simultaneous occurrence of trans 16:1n-7 and 20:5n-3 is unique to this Vibrio species of bacterium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Growth Pressure and Temperature on Fatty Acid Composition of a Barotolerant Deep-Sea Bacterium

The effects of pressure and temperature on the fatty acid composition in a barotolerant deep-sea bacterium that had branched-chain fatty acids were examined. The major fatty acids of the strain at atmospheric pressure were iso-C 15:0 , C 16:1 , iso-C 17:0 , and iso-C 17:1 . As the growth pressure increased, the proportion of unsaturated fatty acid increased because of an increase in the proportion of iso-C 17:1 . On the other hand, as the growth temperature decreased, the proportion of unsaturated fatty acid increased because of the increase in the proportion of C 16:1 and C 18:1 .

Production of Eicosapentaenoic Acid (20:5 n-3) by Vibrio pelagius Isolated from Turbot ( Scophthalmus maximus (L.)) Larvae

Fourteen bacterial strains isolated from turbot, Scophthalmus maximus (L.), larvae were screened for eicosapentaenoic acid (20:5 n-3) (EPA) production. Gas chromatography analysis revealed that one bacterial species, Vibrio pelagius, contained a high proportion of EPA in cellular lipid. This finding was confirmed by gas chromatography-mass spectrometry analysis. A higher concentration of EPA was detected when the bacterium was cultured at 4�C.

Biochemical ecology of deep-sea animals

Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.

Isolation of a gene regulated by hydrostatic pressure in a deep-sea bacterium

Barophilic bacteria inhabit the deep oceans, and the specific functional modifications and regulatory mechanisms which govern adaptation to hydrostatic pressure are beginning to be understood. For example, the rate of production of several proteins by some hydrothermal vent archaebacteria and the degree of saturation of membrane lipids in other deep-sea bacteria have been found to change as a result of cultivation at high pressure. We report here the cloning of gene, ompH, which encodes a major pressure-inducible protein of strain SS9, a gram-negative eubacterium isolated from a depth of 2.5 kilometres in the Sulu Sea. Messenger RNA encoded by ompH is expressed when cells are grown at 280 atm but not at 1 atm, indicating that transcription of the ompH gene is controlled by hydrostatic pressure. The function of the OmpH protein in adaptation to high pressure and the use of the ompH gene in studying how bacteria sense and respond to pressure is discussed.

Phospholipid Fatty Acid Composition of the Syntrophic Anaerobic Bacterium Syntrophomonas wolfei

The membrane phospholipid fatty acids (PLFAs) from several cocultures and a pure culture of Syntrophomonas wolfei were determined by capillary column gas chromatography. Cocultures of S. wolfei with a Desulfovibrio sp. contained PLFAs from both organisms, whereas PLFAs from a coculture with Methanospirillum hungatei contained very little biomass to analyze. The pure culture of S. wolfei grown on crotonate provided the best material for analysis of the PLFAs. The predominant PLFAs of S. wolfei were the monounsaturated 16:1ω7c and 16:1ω9c and the saturated 16:0 and 14:0. A low concentration of the diunsaturated 18:2ω6 was detected. The PLFA analysis provides additional information for consideration in the determination of the profile of PLFAs obtained from anaerobic environments. In addition, this information may aid in the understanding of the physiology and phylogeny of S. wolfei and other syntrophic bacteria.