Gut bacteria profiles of Mus musculus at the phylum and family levels are influenced by saturation of dietary fatty acids

BackgroundMammalian gut microbiota have been implicated in a variety of functions including the breakdown of ingested nutrients, the regulation of energy intake and storage, the control of immune system development and activity, and the synthesis of novel chemicals. Previous studies have shown that feeding mammalian hosts a high-fat diet shifts gut bacteria at the phylum level to reduce the ratio of Bacteroidetes-to-Firmicutes, while feeding hosts a fat-restricted diet increases this ratio. However, few studies have investigated the differential effects of fatty acid type on gut bacterial profile.MethodsOver a 14-week period, Mus musculus were fed a diet rich in omega-3 polyunsaturated fatty acids (n-3 PUFAs), omega-6 polyunsaturated fatty acids (n-6 PUFAs), or saturated fatty acids (SFAs). Fecal pellets were collected before and after the treatment period from 12 randomly selected mice (4 per treatment group). Bacterial DNA was extracted from the pellets and characterized by analysis of the hypervariable V3 region of the 16S rRNA. Nominal logistic regression models were used to assess shifts in microbial profile at the phylum and family levels in response to diet.ResultsA significant decrease in the proportion of phylum Bacteroidetes species was observed for mice fed any of the three diets over time. However, the SFA-rich diet group showed a significantly greater decrease in Bacteroidetes proportion (?28%) than did either the n-3 PUFA group (?10%) or the n-6 PUFA group (?12%). At the family level, a significant decrease in proportion of Porphyromonadaceae was observed for mice fed the n-6 PUFA-rich diet, and a significant decrease in proportion of Lachnospiraceae was observed for mice fed the SFA-rich diet. There was no significant effect of diet type on body mass change.ConclusionOur results indicate that SFAs have stronger effects than PUFAs in shifting gut microbiota profiles toward those typical of obese individuals, and that dietary fatty acid saturation influences shifts in gut microbiota independently of changes in body mass.     

Lipid Classes and Fatty Acids in Ophryotrocha cyclops,a Dorvilleid from Newfoundland Aquaculture Sites

A new opportunistic annelid (Ophryotrocha cyclops) discovered on benthic substrates underneath finfish aquaculture sites in Newfoundland (NL) may be involved in the remediation of organic wastes. At those aquaculture sites, bacterial mats and O. cyclops often coexist and are used as indicators of organic enrichment. Little is known on the trophic strategies used by these annelids, including whether they might consume bacteria or other aquaculture-derived wastes. We studied the lipid and fatty acid composition of the annelids and their potential food sources (degraded flocculent organic matter, fresh fish pellets and bacterial mats) to investigate feeding relationships in these habitats and compared the lipid and fatty acid composition of annelids before and after starvation. Fish pellets were rich in lipids, mainly terrestrially derived C₁₈ fatty acids (18:1ω9, 18:2ω6, 18:3ω3), while bacterial samples were mainly composed of ω7 fatty acids, and flocculent matter appeared to be a mixture of fresh and degrading fish pellets, feces and bacteria. Ophryotrocha cyclops did not appear to store excessive amounts of lipids (13%) but showed a high concentration of ω3 and ω6 fatty acids, as well as a high proportion of the main fatty acids contained in fresh fish pellets and bacterial mats. The dorvilleids and all potential food sources differed significantly in their lipid and fatty acid composition. Interestingly, while all food sources contained low proportions of 20:5ω3 and 20:2ω6, the annelids showed high concentrations of these two fatty acids, along with 20:4ω6. A starvation period of 13 days did not result in a major decrease in total lipid content; however, microscopic observations revealed that very few visible lipid droplets remained in the gut epithelium after three months of starvation. Ophryotrocha cyclops appears well adapted to extreme environments and may rely on lipid-rich organic matter for survival and dispersal in cold environments.     

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

The fatty acid composition of the membrane lipids in 11 deep-sea bacterial isolates was determined. The fatty acids observed were typical of marine vibrios except for the presence of large amounts of long-chain polyunsaturated fatty acids (PUFAs). These long-chain PUFAs were previously thought to be absent in procaryotes, with the notable exception of a single marine Flexibacter sp. In three barophilic strains tested at 2°C, there was a general increase in the relative amount of PUFAs as pressure was increased from a low growth pressure towards the optimal growth pressure. In Vibrio marinus MP-1, a psychrophilic strain, PUFAs were found to increase as a function of decreasing temperature at constant atmospheric pressure. These results suggest the involvement of PUFAs in the maintenance of optimal membrane fluidity and function over environmentally relevant temperatures and pressures. Furthermore, since these lipids are essential nutrients for higher taxa and are found in large amounts in the lipids of deep-sea vertebrates and invertebrates, an important, specific role for deep-sea bacteria in abyssal food webs is implicated.     

Effect of dietary fatty acids on the body tissues of larval and juvenile cobia and their prey

Polyunsaturated fatty acids (PUFAs) have been used as biomarkers in pelagic ecosystems although previous studies have failed to quantify the timing of conservation of dietary PUFAs in pelagic fishes and invertebrates. Here we investigated the influence of diet upon the timing of conservation of PUFAs throughout multiple trophic exchanges in larval and juvenile cobia (Rachycentron canadum) and their prey. Cobia, rotifers (Brachionus plicatilis), and Artemia (A. franciscana) were fed laboratory processed or natural diets resembling prey and dietary modification of fatty acid signatures was quantified using two-source mixing models. Specimens were collected throughout the experiment to track dietary influences over time. Cobia larvae underwent significant dietary modification of PUFAs after 24 h and conserved > 90% of dietary PUFAs after an average of 6 days. Similar results were identified in juvenile cobia as significant dietary modification of PUFAs took place after 3 days and > 90% were conserved after an average of 12 days. In addition, no significant ontogenetic changes in PUFA signatures were identified in juvenile cobia throughout the 30-day experiment. PUFA signatures in prey items (rotifers and Artemia) underwent significant dietary modification in 24 h, with over 90% incorporation after 5-7 days. Results from this study support the premise that fatty acids are promising dietary indicators and may be useful for future studies examining trophic relationships in marine ecosystems and habitat use of marine fishes.     

A novel unsaturated fatty acid hydratase toward C16 to C22 fatty acids from Lactobacillus acidophilus

Hydroxy FAs, one of the gut microbial metabolites of PUFAs, have attracted much attention because of their various bioactivities. The purpose of this study was to identify lactic acid bacteria with the ability to convert linoleic acid (LA) to hydroxy FAs. A screening process revealed that a gut bacterium, Lactobacillus acidophilus NTV001, converts LA mainly into 13-hydroxy-cis-9-octadecenoic acid and resulted in the identification of the hydratase responsible, fatty acid hydratase 1 (FA-HY1). Recombinant FA-HY1 was purified, and its enzymatic characteristics were investigated. FA-HY1 could convert not only C18 PUFAs but also C20 and C22 PUFAs. C18 PUFAs with a cis carbon-carbon double bond at the Δ12 position were converted into the corresponding 13-hydroxy FAs. Arachidonic acid and DHA were converted into the corresponding 15-hydroxy FA and 14-hydroxy FA, respectively. To the best of our knowledge, this is the first report of a bacterial FA hydratase that can convert C20 and C22 PUFAs into the corresponding hydroxy FAs. These novel hydroxy FAs produced by using FA-HY1 should contribute to elucidating the bioactivities of hydroxy FAs.     

Lipid Metabolism of Rumen Ciliates and Bacteria: II. Uptake of Fatty Acids and Lipid Analysis of Isotrichia intestinalis and Rumen Bacteria with Further Information on Entodinium simplex

The total lipid and free fatty acid contents of Isotricha intestinalis, Entodinium simplex, and the rumen bacterial flora of the respective protozoa were determined. Warburg manometric data showed that the sodium salts of tributyrin, oleic, and acetic acids stimulated gas production in I. intestinalis, whereas tributyrin was stimulatory with E. simplex and less active with oleic and acetic acids. Rumen bacteria provided fatty acids produced lower manometric gaseous increases when compared with the protozoa. Volatile fatty acids were produced by I. intestinalis and rumen bacteria with tributyrin, but not with tripalmitin. Sodium oleate gave little volatile fatty acid response with I. intestinalis or rumen bacteria. Washed suspensions of I. intestinalis and rumen bacteria concentrated C¹⁴-labeled oleic, palmitic, stearic, and linoleic acids within the cells during short incubation periods. Autoradiographs demonstrated the conversion of C¹⁴-labeled oleic, palmitic, stearic, linoleic, and acetic acids in the rumen protozoa and bacterial cells.     

The inconstant gut microbiota of Drosophila species revealed by 16S rRNA gene analysis

The gut microorganisms in some animals are reported to include a core microbiota of consistently associated bacteria that is ecologically distinctive and may have coevolved with the host. The core microbiota is promoted by positive interactions among bacteria, favoring shared persistence; its retention over evolutionary timescales is evident as congruence between host phylogeny and bacterial community composition. This study applied multiple analyses to investigate variation in the composition of gut microbiota in drosophilid flies. First, the prevalence of five previously described gut bacteria (Acetobacter and Lactobacillus species) in individual flies of 21 strains (10 Drosophila species) were determined. Most bacteria were not present in all individuals of most strains, and bacterial species pairs co-occurred in individual flies less frequently than predicted by chance, contrary to expectations of a core microbiota. A complementary pyrosequencing analysis of 16S rRNA gene amplicons from the gut microbiota of 11 Drosophila species identified 209 bacterial operational taxonomic units (OTUs), with near-saturating sampling of sequences, but none of the OTUs was common to all host species. Furthermore, in both of two independent sets of Drosophila species, the gut bacterial community composition was not congruent with host phylogeny. The final analysis identified no common OTUs across three wild and four laboratory samples of D. melanogaster. Our results yielded no consistent evidence for a core microbiota in Drosophila. We conclude that the taxonomic composition of gut microbiota varies widely within and among Drosophila populations and species. This is reminiscent of the patterns of bacterial composition in guts of some other animals, including humans.     

The Microbiota of Freshwater Fish and Freshwater Niches Contain Omega-3 Fatty Acid-Producing Shewanella Species

Approximately 30 years ago, it was discovered that free-living bacteria isolated from cold ocean depths could produce polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) (20:5n-3) or docosahexaenoic acid (DHA) (22:6n-3), two PUFA essential for human health. Numerous laboratories have also discovered that EPA- and/or DHA-producing bacteria, many of them members of the Shewanella genus, could be isolated from the intestinal tracts of omega-3 fatty acid-rich marine fish. If bacteria contribute omega-3 fatty acids to the host fish in general or if they assist some bacterial species in adaptation to cold, then cold freshwater fish or habitats should also harbor these producers. Thus, we undertook a study to see if these niches also contained omega-3 fatty acid producers. We were successful in isolating and characterizing unique EPA-producing strains of Shewanella from three strictly freshwater native fish species, i.e., lake whitefish (Coregonus clupeaformis), lean lake trout (Salvelinus namaycush), and walleye (Sander vitreus), and from two other freshwater nonnative fish, i.e., coho salmon (Oncorhynchus kisutch) and seeforellen brown trout (Salmo trutta). We were also able to isolate four unique free-living strains of EPA-producing Shewanella from freshwater habitats. Phylogenetic and phenotypic analyses suggest that one producer is clearly a member of the Shewanella morhuae species and another is sister to members of the marine PUFA-producing Shewanella baltica species. However, the remaining isolates have more ambiguous relationships, sharing a common ancestor with non-PUFA-producing Shewanella putrefaciens isolates rather than marine S. baltica isolates despite having a phenotype more consistent with S. baltica strains.     

Fatty Acid Profiling of Commercially Important Raw and Boiled Seer Fish <Emphasis Type="Italic">Scomberomorus commerson</Emphasis> (Lacepede, 1800) (Scombridae,Teleostei, Pisces)

The present study aims to determine the fatty acid profiling of commercially important fresh and boiled Scomberomorus commerson. Fatty acids in fresh and boiled fish were separated and quantitatively determined by gas chromatography–mass spectrophotometer using standard methods. The findings revealed that the predominant fatty acids in fresh S. commerson were octadecanoic acid methyl ester, octanoic acid, 1,2-benzenedicarboxylic acid and 3-cyclopentylpropionic acid representing respectively 45.91, 5.69, 6.75 and 8.65% of total fatty acids. Boiled S. commerson showed predominant changes in their fatty acid profiles. In the omega-3 and omega-6 families the dominant fatty acids were doconexent, 3-cyclopentylpropionic acid, octadeconoic acid methyl ester and Hexadecane representing respectively 3.87, 12.08, 44.26 and 3.11% of total fatty acids. After boiling, some fatty acids present in fresh fish are damaged and formed new fatty acids which belonged to ω-3 polyunsaturated fatty acids (PUFA). Boiling increased the concentration of PUFAs from 73.25 to 80.37% of total fatty acids and also formed new fatty acids.     

Incorporation of bacterial fatty acids and changes in a wax ester-based omnivory index during a long-term incubation experiment with Calanus glacialis Jaschnov

We traced the incorporation of fatty acid biomarkers into Calanus glacialis Jaschnov (CV) during a long-term incubation experiment using bacterivorous dinoflagellates and diatoms as food. Copepods fed Oxyrrhis marina Dujardin during a 3-week acclimation period developed an omnivorous lipid composition, relative to wild-captured copepods, characterized by significant losses of polyunsaturated fatty acids (PUFA) and diatom fatty acids [16:4(n−1), 20:5(n−3)], and increases in saturated fatty acids (SFA) and 18:1(n−7). Levels of a wax ester-based omnivory index [unsaturation coefficient (UC)], verified by gas chromatography (GC), also decreased in response to the relatively PUFA-poor dinoflagellate. After half of the copepods were switched to a diet comprised of the diatom Thalassiosira hispida Syvertsen (PUFA-rich), the data showed reversal to a more herbivorous lipid composition (increases in UC and relative amounts of PUFA and diatom fatty acids). We assert that UC, derived from routine thin-layer chromatography analysis (Iatroscan) can quickly determine in situ feeding strategies (i.e., degree of omnivory) of wax ester-storing copepods. None of the eight odd and/or branched fatty acids (OBFA) initially detected in C. glacialis increased in response to a diet of O. marina which was rich in these compounds [mainly iso (i)-15:0 and anteiso (ai)-15:0]. Lack of transfer of these and other fatty acids [e.g., 22:6(n−3)] could be related to the physiological state of the copepods (early diapause). We suggest that the bacterial fatty acid 18:1(n−7) may be more useful in inferring connections between Calanus spp. and the microbial food web than the odd and/or branched chains.     

A comparison of lipid components of the fresh and dead leaves and pneumatophores of the mangrove Avicennia marina

The component hydrocarbons, sterols, alcohols, monobasic, α,ω-dibasic and ω-hydroxy acids of the fresh hand decayed leaves and the pneumatophores of the mangrove Avicennia marina are reported in detail. From the quantitative comparisons which can be drawn, relative changes in the lipid classes occurring during leaf decay can be highlighted. These base-line data are important to our understanding of inputs to marine intertidal sediments. During leaf decay the only significant changes were a reduction in the total absolute concentrations of monobasic acids due largely to a decrease in concentration of the C₁₈ polyunsaturated fatty acids, and an enhancement of the concentrations of the long-chain monobasic acids, ω-hydroxy acids and α,ω-dibasic acids. This resistance to degradation shown by the cutin derived acids (α,ω-dibasic, ω-hydroxy and long-chain monobasic acids) relative to the cellular and wax derived lipids may allow these cutin components to be used as quantitative markers of A. marina in mangrove associated sediments.     

Regiospecificity of a novel bacterial lipoxygenase from Myxococcus xanthus for polyunsaturated fatty acids

Lipoxygenase (LOX) is the key enzyme involved in the synthesis of oxylipins as signaling compounds that are important for cell growth and development, inflammation, and pathogenesis in various organisms. The regiospecificity of LOX from Myxococcus xanthus, a gram-negative bacterium, was investigated. The enzyme catalyzed oxygenation at the n-9 position in C20 and C22 polyunsaturated fatty acids (PUFAs) to form 12S- and 14S-hydroxy fatty acids (HFAs), respectively, and oxygenation at the n-6 position in C18 PUFAs to form 13-HFAs. The 12S-form products of C20 and C22 PUFAs by M. xanthus LOX is the first report of bacterial LOXs. The residues involved in regiospecificity were determined to be Thr397, Ala461, and Ile664 by analyzing amino acid alignment and a homology model based on human arachidonate 15-LOX with a sequence identity of 25%. Among these variants, the regiospecificity of the T397Y variant for C20 and C22 PUFAs was changed. This may be because of the reduced size of the substrate-binding pocket by substitution of the smaller Thr to the larger Tyr residue. The T397Y variant catalyzed oxygenation at the n-6 position in C20 and C22 PUFAs to form 15- and 17-hydroperoxy fatty acids, respectively. However, the oxygenation position of T397Y for C18 PUFAs was not changed. The discovery of bacterial LOX with novel regiospecificity will facilitate the biosynthesis of regiospecific?oxygenated signaling compounds.     

Assessing within habitat variability in plant demography, faunal density, and secondary production in an eelgrass (Zostera marina L.) bed

This investigation addressed faunal relationships with habitat structure within a Zostera marina community targeting differences between seagrass bed edge and interior. Z. marina biomass was significantly higher from the interior portions of the bed compared to the edge, but shoot density did not vary. Additionally, leaf width and length were significantly greater in the interior of the bed, suggesting greater total leaf area. Densities of larger organisms (> 0.85 mm) were significantly greater in vegetated samples (Z. marina edge and interior) compared to unvegetated, but an analysis of similarities demonstrated significant faunal community differences among each of the identified habitats. Densities of small organisms (0.25-0.85 mm), however, were significantly greater at Z. marina edge compared to unvegetated samples and Z. marina interior. Additionally, secondary production (μg AFDW day^− 1) was estimated based on the size distribution of taxa and showed significantly greater production from samples gathered in Z. marina compared to unvegetated samples. The relative size distribution of taxa was assessed using regression analysis and results showed that the size distribution was similar for samples collected at edge and interior Z. marina, but these distributions differed significantly when compared to unvegetated samples. The results of this study suggest that although similarities exist between edge and interior portions of Z. marina beds, especially compared to unvegetated habitats, noteworthy differences in faunal density, species composition, size distribution, and secondary production exist between edge and interior Z. marina.     

Polyunsaturated fatty acids cause apoptosis in C. albicans and C. dubliniensis biofilms

Background

Polyunsaturated fatty acids (PUFAs) have antifungal properties, but the mode by which they induce their action is not always clear. The aim of the study was to investigate apoptosis as a mode of action of antifungal PUFAs (stearidonic acid, eicosapentaenoic acid and docosapentaenoic acid) which are inhibitory towards biofilm formation of C. albicans and C. dubliniensis.

Methods

Candida biofilms were grown in the absence or presence of 1 mM PUFAs (linoleic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid) for 48 h at 37 °C. The effect of these PUFAs on the membrane fatty acid profile and unsaturation index, oxidative stress, mitochondrial transmembrane potential and apoptosis was evaluated.

Results

When biofilms of C. albicans and C. dubliniensis were exposed to certain PUFAs there was an increase in unsaturation index of the cellular membranes and accumulation of intracellular reactive oxygen species (ROS). This resulted in apoptosis, evidenced by reduced mitochondrial membrane potential and nuclear condensation and fragmentation. The most effective PUFA was stearidonic acid.

Conclusions

The resultant cell death of both C. albicans and C. dubliniensis is due to apoptosis.

General significance

Due to the increase in drug resistance, alternative antifungal drugs are needed. A group of natural antifungal compounds is PUFAs. However, understanding their mechanisms of action is important for further use and development of these compounds as antifungal drugs. This paper provides insight into a possible mode of action of antifungal PUFAs.     

Fatty acids,sterols and hydrocarbons in the leaves from eleven species of mangrove

The fatty acid, sterol and hydrocarbon compositions of the fresh leaves from eleven species of mangroves, cultivated in a shadehouse, are reported. The fatty acid and sterol analyses, whilst generally typical of higher plants, showed several chemotaxonomically significant differences between the species. The epicuticular wax hydrocarbons and fatty acids were low in abundance compared to previous reports of mangrove leaf lipids, which may reflect the importance of environmental influences on this group of compounds. Cluster analysis of selected subsets of the data showed clear chemotaxonomic divisions amongst the mangroves. The results grouped the mangroves into genera, except for the Rhizophora and Ceriops tagal which were not separated, and grouped the family Rhizophoraceae distinct from all other species except Xylocarpus granatum. Avicennia marina var. resinifera was able to be distinguished from Avicennia marina by cluster analysis, supporting its assignment as a distinct variety. The results show that the lipids of mangroves are chemotaxonomically significant.     

Biosynthesis and dietary uptake of polyunsaturated fatty acids by piezophilic bacteria

The biochemistry of piezophilic bacteria is unique in that piezophiles produce polyunsaturated fatty acids (PUFAs). A pertinent question is if piezophilic bacteria synthesize PUFA de novo, through dietary uptake, or both. This study was undertaken to examine the biosynthesis and cellular uptake of PUFAs by piezophilic bacteria. A moderately piezophilic (Shewanella violacea DSS12) and two hyperpiezophilic bacteria (S. benthica DB21MT-2 and Moritella yayanosii DB21MT-5) were grown under 50 MPa (megapascal) and 100 MPa, respectively, in media containing marine broth 2216 supplemented with arachidonic acid (AA, sodium salt) and/or antibiotic cerulenin. There was active uptake and cellular incorporation of AA in the hyperpiezophilic bacteria DB21MT-2 (14.7% of total fatty acids) and DB21MT-5 (1.4%), but no uptake was observed in DSS12. When cells were treated with cerulenin, all three strains incorporated AA into cell membranes (13–19%). The biosynthesis of monounsaturated fatty acids was significantly inhibited (10–37%) by the addition of cerulenin, whereas the concentrations of PUFAs increased by 2–4 times. These results suggest that piezophilic bacteria biosynthesize and/or incorporate dietary polyunsaturated fatty acids that are important for their growth and piezoadaptation. The significance of these findings is also discussed in the context of phenotypic classification of piezophiles.     

Bacteria in the gut of Japanese honeybee, Apis cerana japonica, and their antagonistic effect against Paenibacillus larvae, the causal agent of American foulbrood

We assessed the complexity of bacterial communities occurring in the digestive tract of the Japanese honeybee, Apis cerana japonica, using histological and 16S rRNA gene sequence analyzes. Both Gram-positive and -negative bacteria were observed, and the number of gut bacteria was higher in old larvae compared with young larvae. A total of 35 clones were obtained by a culture-dependent method, and 16S rRNA gene sequence analysis revealed that the bacterial population in the gut of Japanese honeybee was diverse, including the phyla firmicutes, actinobacteria, and alpha-, beta-, and gammaproteobacteria. Further investigation by in vitro inhibition assays was carried out to determine the ability of an isolate to inhibit Paenibacillus larvae, the causal agent of American foulbrood. Out of 35 isolates, seven showed strong inhibitory activity against P. larvae. Most of the antagonistic bacteria belonged to Bacillus species, suggesting that the bacterial isolates obtained in this study appear to be potential candidates for the biological control of P. larvae.     

Litter Breakdown and Microbial Succession on Two Submerged Leaf Species in a Small Forested Stream

Microbial succession during leaf breakdown was investigated in a small forested stream in west-central Georgia, USA, using multiple culture-independent techniques. Red maple (Acer rubrum) and water oak (Quercus nigra) leaf litter were incubated in situ for 128 days, and litter breakdown was quantified by ash-free dry mass (AFDM) method and microbial assemblage composition using phospholipid fatty acid analysis (PLFA), ribosomal intergenic spacer analysis (RISA), denaturing gradient gel electrophoresis (DGGE), and bar-coded next-generation sequencing of 16S rRNA gene amplicons. Leaf breakdown was faster for red maple than water oak. PLFA revealed a significant time effect on microbial lipid profiles for both leaf species. Microbial assemblages on maple contained a higher relative abundance of bacterial lipids than oak, and oak microbial assemblages contained higher relative abundance of fungal lipids than maple. RISA showed that incubation time was more important in structuring bacterial assemblages than leaf physicochemistry. DGGE profiles revealed high variability in bacterial assemblages over time, and sequencing of DGGE-resolved amplicons indicated several taxa present on degrading litter. Next-generation sequencing revealed temporal shifts in dominant taxa within the phylum Proteobacteria, whereas γ-Proteobacteria dominated pre-immersion and α- and β-Proteobacteria dominated after 1 month of instream incubation; the latter groups contain taxa that are predicted to be capable of using organic material to fuel further breakdown. Our results suggest that incubation time is more important than leaf species physicochemistry in influencing leaf litter microbial assemblage composition, and indicate the need for investigation into seasonal and temporal dynamics of leaf litter microbial assemblage succession.     

Cultivation of Microorganisms in the Cultural Medium Made from Squid Internal Organs and Accumulation of Polyunsaturated Fatty Acids in the Cells

The disposal and more efficient utilization of marine wastes is becoming increasingly serious. A culture media for microorganisms has been prepared from squid internal organs that are rich in polyunsaturated fatty acids (PUFAs). Both freshwater and marine bacteria grew well in this medium and some bacteria accumulated PUFAs in their lipids, suggesting uptake of exogenous PUFAs. Higher PUFA accumulations were observed in Escherichia coli mutant cells defective either in unsaturated fatty acid biosynthesis or fatty acid degradation, or both, compared to those without these mutations. Therefore, PUFA accumulation in cells can be improved by genetic modification of fatty acid metabolism in the bacteria. Squid internal organs would be a good source of medium, not only for marine bacteria but also for freshwater bacteria, and that this process may be advantageous to make efficient use of the fishery wastes and to produce PUFA-containing microbial cells and lipids.     

The high-level accumulation of n-3 polyunsaturated fatty acids in transgenic pigs harboring the n-3 fatty acid desaturase gene from Caenorhabditis briggsae

Livestock meat is generally low in n-3 polyunsaturated fatty acids (PUFAs), which are beneficial to human health. An alternative approach to increasing the levels of n-3 PUFAs in meat is to generate transgenic livestock animals. In this study, we describe the generation of cloned pigs that express the cbr-fat-1 gene from Caenorhabditis briggsae, encoding an n-3 fatty acid desaturase. Analysis of fatty acids demonstrated that the cbr-fat-1 transgenic pigs produced high levels of n-3 fatty acids from n-6 analogs; consequently, a significantly reduced ratio of n-6/n-3 fatty acids was observed. We demonstrated that the n-3 desaturase gene from C. briggsae was functionally expressed, and had a significant effect on the fatty acid composition of the transgenic pigs, which may allow the production of pork enriched in n-3 PUFAs.