Effects of Long-Chain Fatty Acids on Growth of Rumen Bacteria

The effects of low concentrations of long-chain fatty acids (palmitic, stearic, oleic, and vaccenic) on the growth of seven species (13 strains) of rumen bacteria were investigated. Except for Bacteroides ruminicola and several strains of Butyrivibrio fibrisolvens, bacterial growth was not greatly affected by either palmitic or stearic acids. In contrast, growth of Selenomonas ruminantium, B. ruminicola, and one strain of B. fibrisolvens was stimulated by oleic acid, whereas the cellulolytic species were markedly inhibited by this acid. Vaccenic acid (trans Δ11 18:1) had far less inhibitory effect on the cellulolytic species than oleic acid (cis Δ9 18:1). Inclusion of powdered cellulose in the medium appeared to reverse both inhibitory and stimulatory effects of added fatty acids. However, there was little carry-over effect observed when cells were transferred from a medium with fatty acids to one without. Considerable variation in response to added fatty acids was noted among five strains of B. fibrisolvens. In general, exogenous long-chain fatty acids appear to have little, if any, energy-sparing effect on the growth of rumen bacteria.     

Stable-Isotope-Based Labeling of Styrene-Degrading Microorganisms in Biofilters

Deuterated styrene ([²H₈]styrene) was used as a tracer in combination with phospholipid fatty acid (PLFA) analysis for characterization of styrene-degrading microbial populations of biofilters used for treatment of waste gases. Deuterated fatty acids were detected and quantified by gas chromatography-mass spectrometry. The method was evaluated with pure cultures of styrene-degrading bacteria and defined mixed cultures of styrene degraders and non-styrene-degrading organisms. Incubation of styrene degraders for 3 days with [²H₈]styrene led to fatty acids consisting of up to 90% deuterated molecules. Mixed-culture experiments showed that specific labeling of styrene-degrading strains and only weak labeling of fatty acids of non-styrene-degrading organisms occurred after incubation with [²H₈]styrene for up to 7 days. Analysis of actively degrading filter material from an experimental biofilter and a full-scale biofilter by this method showed that there were differences in the patterns of labeled fatty acids. For the experimental biofilter the fatty acids with largest amounts of labeled molecules were palmitic acid (16:0), 9,10-methylenehexadecanoic acid (17:0 cyclo9-10), and vaccenic acid (18:1 cis11). These lipid markers indicated that styrene was degraded by organisms with a Pseudomonas-like fatty acid profile. In contrast, the most intensively labeled fatty acids of the full-scale biofilter sample were palmitic acid and cis-11-hexadecenoic acid (16:1 cis11), indicating that an unknown styrene-degrading taxon was present. Iso-, anteiso-, and 10-methyl-branched fatty acids showed no or weak labeling. Therefore, we found no indication that styrene was degraded by organisms with methyl-branched fatty fatty acids, such as Xanthomonas, Bacillus, Streptomyces, or Gordonia spp.     

Adaptation of anaerobically grown Thauera aromatica,Geobacter sulfurreducens and Desulfococcus multivorans to organic solvents on the level of membrane fatty acid composition

The effect of different solvents and pollutants on the cellular fatty acid composition of three bacterial strains: Thauera aromatica, Geobacter sulfurreducens and Desulfococcus multivorans, representatives of diverse predominant anaerobic metabolisms was investigated. As the prevailing adaptive mechanism in cells of T. aromatica and G. sulfurreducens whose cellular fatty acids patterns were dominated by palmitic acid (C16:0) and palmitoleic acid (C16:1cis), the cells reacted by an increase in the degree of saturation of their membrane fatty acids when grown in the presence of sublethal concentrations of the chemicals. Next to palmitic acid C16:0, the fatty acid pattern of D. multivorans was dominated by anteiso-branched fatty acids which are characteristic for several sulfate-reducing bacteria. The cells responded to the solvents with an increase in the ratio of straight-chain saturated (C14:0, C16:0, C18:0) to anteiso-branched fatty acids (C15:0anteiso, C17:0anteiso, C17:1anteisoΔ9cis). The results show that anaerobic bacteria react with similar mechanisms like aerobic bacteria in order to adapt their membrane to toxic organic solvents. The observed adaptive modifications on the level of membrane fatty acid composition can only be carried out with de novo synthesis of the fatty acids which is strictly related to cell growth. As the growth rates of anaerobic bacteria are generally much lower than in the so far investigated aerobic bacteria, this adaptive response needs more time in anaerobic bacteria. This might be one explanation for the previously observed higher sensitivity of anaerobic bacteria when compared with aerobic ones.     

A system for manipulating the membrane Fatty Acid composition of soybean cell cultures by adding tween-Fatty Acid esters to their growth medium : basic parameters and effects on cell growth

The development of a system for modifying the membrane fatty acid composition of cultured soybean cells (Glycine max [L.] Merr.) is described. Tween-fatty acid esters carrying specific fatty acids were synthesized and added to the medium of suspension cultures. Cells transferred large quantities of exogenous fatty acids from Tweens to all acylated membrane lipids; up to 50% of membrane fatty acids were exogenously derived. C15 to C20 saturated fatty acids and C16, C18, and C20 unsaturated fatty acids with either cis or trans double bonds were incorporated into lipids. Cells elongated saturated fatty acids of C16 or less, and unsaturated fatty acids with cis double bonds were further desaturated. No other types of modifications were observed. Growth ceased in cells treated with excessive concentrations of Tween-fatty acid esters, but frequently not for several days. Cessation of cell growth was correlated with changes in membrane fatty acid composition resulting from incorporation of large amounts of exogenous fatty acids into membrane lipids, although cells tolerated large variations in fatty acid composition. Maximum tolerable Tween concentrations varied widely according to the fatty acid supplied. Potential uses of this system and implications of the observed modifications on the pathway of incorporation are discussed.     

Identification and characterization of thermophilic bacteria isolated from hot springs in Turkey

The present study was conducted to identify and characterize the thermophilic bacteria isolated from various hot springs in Turkey by using phenotypic and genotypic methods including fatty acid methyl ester and rep-PCR profilings, and 16S rRNA sequencing. The data of fatty acid analysis showed the presence of 17 different fatty acids in 15 bacterial strains examined in this study. Six fatty acids, 15:0 iso, 15:0 anteiso, 16:0, 16:0 iso, 17:0 iso, and 17:0 anteiso, were present in all strains. The bacterial strains were classified into three phenotypic groups based on fatty acid profiles which were confirmed by genotypic methods such as 16S rRNA sequence analysis and rep-PCR genomic fingerprint profiles. After evaluating several primer sets targeting the repetitive DNA elements of REP, ERIC, BOX and (GTG)₅, the (GTG)₅ and BOXA1R primers were found to be the most reliable technique for identification and taxonomic characterization of thermophilic bacteria in the genera of Geobacillus, Anoxybacillus and Bacillus spp. Therefore, rep-PCR fingerprinting using the (GTG)₅ and BOXA1R primers can be considered as a promising genotypic tool for the identification and characterization of thermophilic bacteria from species to strain level.     

Phospholipid and acid composition of Nocardia and nocardoid bacteria as criteria of classification

Phospholipid and acid composition of 5 strains of ‘true’ Nocardia and 4 strains of nocardoid bacteria have been studied. A great homogeneity was found in all the Nocardia species: phospholipids consist of cardiolipin, phosphatidyl ethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. Streptomyces (Nocardia) mediterranei did not contain phosphatidylinositol and Oerskovia (Nocardia) turbata had no phosphatidyl ethanolamine. The fatty acid composition of these phospholipids was determined and was found different in Nocardia and nocardoid species. Nocardia were rich in straight chain fatty acids and tuberculostearic acid while the phospholipids of nocardoid bacteria contained greater amounts of branched fatty acids. The fatty acids from acetone soluble lipids consisted of hydroxy and non-hydroxy compounds. Hydroxy acids were found in Nocardia which contained nocardic acids: high MW β-hydroxy α-branched acids and in S. mediterranei which contained β-hydroxy acids with 15–17 carbon atoms. Non-hydroxy acids were essentially palmitic and tuberculostearic acids in Nocardia species while S. mediterranei and O. turbata contained great amounts of iso acids from C₁₄ to C₁₇. Phospholipid and acid composition are discussed as criteria of taxonomic classification of Nocardia and related Actinomycetes.     

Characterization of Bacteria That Suppress Rhizoctonia Damping-Off in Bark Compost Media by Analysis of Fatty Acid Biomarkers

Examination of cucumber roots (Cucumis sativus L.) grown in bark compost media and of the surrounding edaphic substrate showed profiles of polar lipid fatty acids commonly found in bacteria. The composition of fatty acids in these profiles differed significantly between roots grown in a medium naturally suppressive to Rhizoctonia damping-off and roots from a conducive medium. Cucumber roots from the suppressive medium had higher proportions of cis-vaccenic acid (18:1 ω 7c) and the iso-branched monoenoic fatty acid i17:1 ω 8 but lower proportions of several iso- and anteiso-branched fatty acids compared with roots from the conducive medium. The concentrations of the bacterial fatty acids were significantly lower in the surrounding media. However, the suppressive and conducive growth substrates had differences in the composition of the bacterial fatty acids similar to those found between the cucumber roots proper. These results suggest major differences in bacterial community composition between suppressive and conducive systems. Fatty acid analyses were also utilized to examine the effects on bacterial community composition of root colonization by Flavobacterium balustinum 299, a biocontrol agent. The concentration of the most prominent fatty acid in this bacterium, i17:1 ω 8, was increased on roots produced from inoculated seeds in a medium rendered suppressive by the treatment. This change was concomitant with a significant increase in the concentration of 18:1 ω 7c, not present in the lipids of the antagonist, indicating a shift in the microflora from a conducive to a suppressive bacterial community.     

Fatty acid changes during maturation of Momordica charantia and Trichosanthes Anguina Seeds

Changes in fatty acids were studied during maturation of Momordica charantia and Trichosanthes anguina seeds, which contain cis-9, trans-11, trans-13-octadecatrienoic acid (α-eleostearic) and cis-9, trans-11, cis-13-octadecatrienoic acid (punicic), respectively. The two seeds matured 30 and 35 days after flowering, respectively. Total lipids as well as α-eleostearic acid accumulated rapidly from 10 to 20 days in M. charantia. In T. anguina the active period of lipid synthesis was from 15 to 30 days but punicic acid continued to be synthesized until maturity. In both species, the disappearance of linolenic acid and the reduction in concentration of linoleic acid were concomitant with the formation of conjugated fatty acids. The conjugated fatty acids were absent from monoacylglycerols and phospholipids of both species, and also from the diacylglycerols of M. charantia, throughout maturation     

Formation of trans Fatty Acids Is Not Involved in Growth-Linked Membrane Adaptation of Pseudomonas putida

Fatty acid compositions in growing and resting cells of several strains of Pseudomonas putida (P8, NCTC 10936, and KT 2440) were studied, with a focus on alterations of the saturation degree, cis-trans isomerization, and cyclopropane formation. The fatty acid compositions of the strains were very similar under comparable growth conditions, but surprisingly, and contrary to earlier reports, trans fatty acids were not found in either exponentially growing cells or stationary-phase cells. During the transition from growth to the starvation state, cyclopropane fatty acids were preferentially formed, an increase in the saturation degree of fatty acids was observed, and larger amounts of hydroxy fatty acids were detected. A lowered saturation degree and concomitant higher membrane fluidity seemed to be optimal for substrate uptake and growth. The incubation of cells under nongrowth conditions rapidly led to the formation of trans fatty acids. We show that harvesting and sample preparation for analysis could provoke the enzyme-catalyzed formation of trans fatty acids. Freeze-thawing of resting cells and increased temperatures accelerated the formation of trans fatty acids. We demonstrate that cis-trans isomerization only occurred in cells that were subjected to an abrupt disturbance without having the possibility of adapting to the changed conditions by the de novo synthesis of fatty acids. The cis-trans isomerization reaction was in competition with the cis-to-cyclopropane fatty acid conversion. The potential for the formation of trans fatty acids depended on the cyclopropane content that was already present.     

Lipid Composition of Novel Shewanella Species Isolated from Far Eastern Seas

A comparative study of the lipid composition of 26 strains (including type strains) of marine Gammaproteobacteria belonging to the genera Shewanella, Alteromonas, Pseudoalteromonas, Marinobacterium, Microbulbifer, and Marinobacter was carried out. The bacteria exhibited genus-specific profiles of ubiquinones, phospholipids, and fatty acids, which can serve as reliable chemotaxonomic markers for tentative identification of new isolates. The studied species of the genus Shewanella were distinguished by the presence of two types of isoprenoid quinones, namely, ubiquinones Q-7 and Q-8 and menaquinones MK-7 and MMK-7; five phospholipids typical of this genus, namely, phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), lyso-PE, and acyl-PG; and the fatty acids [15:0, 16:0, 16:1 (n-7), 17:1 (n-8), i-13:0, and i-15:0]. The high level of branched fatty acids (38–45%) and the presence of eicosapentaenoic acid (4%) may serve as criteria for the identification of this genus. Unlike Shewanella spp., bacteria of the other genera contained a single type of isoprenoid quinone: Q-8 (Alteromonas, Pseudoalteromonas, Marinobacterium, and Microbulbifer) or Q-9 (Marinobacter). The phospholipid compositions of these bacteria were restricted to three components: two major phospholipids (PE and PG) and a minor phospholipid, bisphosphatidic acid (Alteromonas and Pseudoalteromonas) or DPG (Marinobacterium, Microbulbifer, and Marinobacter). The bacteria exhibited genus-specific profiles of fatty acids.     

Biotransformation of Unsaturated Long-Chain Fatty Acids by Eubacterium lentum

Eubacterium lentum (33 strains) isomerized the 12-cis double bond of C₁₈ fatty acids with cis double bonds at C-9 and C-12 into an 11-trans double bond before reduction of the 9-cis double bond. The 14-cis double bond of homo-γ-linolenic acid was isomerized by 29 strains into a 13-trans double bond. The same strains isomerized the 14-cis double bond of arachidonic acid into a 13-trans double bond and then isomerized the 8-cis double bond into a 7-trans double bond; the 13-cis double bond of 10-cis, 13-cis-nonadecadienoic acid was isomerized into a 12-trans double bond. None of these isomerization products was further reduced. Studies with resting cells showed optimal isomerization velocity at a linoleic acid concentration of 37.5 μM; higher concentrations were inhibitory. The pH optimum for isomerization was 7.5 to 8.5. The isomerase was inhibited by the sulfhydryl reagents iodoacetamide, bromoacetate, and N-ethylmaleimide and by the chelators EDTA and 1,10-phenanthroline.     

Cis-unsaturated fatty acids modulate the function of the cell-surface cAMP receptor of Dictyostelium discoideum

The binding of cAMP to the chemotactic cAMP receptor in intact Dictyostelium discoideum cells and isolated membranes is strongly inhibited by unsaturated fatty acids. In isolated membranes, cis-unsaturated fatty acids decreased the number of accessible cAMP binding sites, without significantly altering their affinity. Most potent were C₁₈ and C₂₀ cis-poly unsaturated fatty acids, like arachidonic acid, linoleic acid and linolenic acid. Trans-unsaturated fatty acid was less potent than its cis isomer, while saturated fatty acids did not affect the binding of cAMP to receptors at all. Oxidation reactions were not important for the effect of unsaturated fatty acids. When membranes were preincubated with millimolar concentrations of Ca²⁺, the effect of unsaturated fatty acids was strongly diminished. Mg²⁺ was ineffective. Ca²⁺, if presented after the incubation of membranes with unsaturated fatty acids, did not reverse the inhibitory effect. The specificity of the fatty acid effect, and the interference with Ca²⁺, but not Mg²⁺, suggest that the properties of the cAMP receptor are changed as a result of alterations in the lipid bilayer structure of the membrane.     

Incorporation of cis-parinaric acid,a fluorescent fatty acid,into synaptosomal phospholipids by an acyl-CoA acyltransferase

The cis-isomer of parinaric acid, a naturally occurring C-18 polyene fatty acid, was incubated with brain subcellular fractions and the polarization of fluorescence increased in a time dependent manner. Greatest increases occurred in synaptosomal and microsomal membranes. This increase in polarization of fluorescence was found with the cis, but not the trans, isomer of parinaric acid and required Mg²⁺ or Ca²⁺ and was stimulated by coenzyme A and ATP. Synaptosomes were incubated with cis-parinaric acid and lipids were extracted and examined by high performance liquid chromatography. The highest incorporations of cis-parinaric acid were found in phosphatidylcholine (71%) and phosphatidylethanolamine (20%) while only traces were found in phosphatidylserine and phosphatidylinositol. [³H]Oleic acid was also incorporated into membrane phospholipids and unlabeled oleic acid blocked incorporation of cis-parinaric acid. It is proposed that cis-parinaric acid, like fatty acids normally found in brain, is incorporated into membrane phospholipids by an acyl-CoA acyltransferase. The presence of this enzyme in nervous tissue may make it possible to easily introduce fluorescent fatty acid probes into membrane phospholipids and to thereby facilitate study of membrane-mediated processes.     

Omega-cyclohexyl fatty acids in acidophilic thermophilic bacteria. Studies on their presence, structure, and biosynthesis using precursors labeled with stable isotopes and radioisotopes.

Omega-Cyclohexyl undecanoic acid and omega-cyclohexyl tridecanoic acid were found in 10 strains of acido-thermophilic bacteria isolated from different Japanese hot springs. These unusual fatty acids were found in the esterified form in glyceride type complex lipids and constituted 74 to 93% of the total fatty acids in the bacteria. The fatty acids other than omega-cyclohexyl fatty acids found were 14-methyl hexadecanoic acid (3 to 15%) and 15-methyl hexadecanoic acid (1 to 6%), and trace amounts of straight chain and methyl-branched tetra- and penta-decanoic acids. Biosynthesis of omega-cyclohexyl fatty acids increased with increase in the concentration of glucose in the culture medium. The metabolism of omega-cyclohexyl fatty acids was studied using deuterium-labeled precursors by mass fragmentation analysis. The deuterium of [2-D]glucose was specifically incorporated into position 2 of the cyclohexyl ring of the fatty acids, indicating that the ring was synthesized from the glucose molecule. Radioactivity was efficiently incorporated into the omega-cyclohexyl fatty acids from labeled glucose, shikimate, and cyclohexyl carboxylate. These findings indicate that omega-cyclohexyl fatty acids are synthesized with glucose through shikimic acid and probably cyclohexyl carboxylyl-CoA derivative as the intermediates.     

A rapid method for isolating glandular trichomes

A physical method is described for the rapid isolation of plant trichomes, with emphasis on stalked glandular types. The technique involved breaking frozen trichomes with powdered dry ice and collection of glandular heads by sieving from larger tissue fragments. This method was applied to several plants that bear similar stalked trichomes: geranium (Pelargonium), potato (Solanum tuberosum), tomato (Lycopersicon esculentum), squash (Cucurbita pepo), and velvetleaf (Abutilon theophrasti). The tissue preparation was of sufficient quality without further purification for biochemical and molecular studies. The preparation maintained the biochemical integrity of the trichomes for active enzymes and usable nucleic acids. A large quantity of tissue can be harvested; for example, 351 milligrams dry weight of glandular trichomes were harvested from geranium pedicels in 12 hours. The utility of the technique was demonstrated by examining the fatty acid composition of tall glandular trichomes of geraniums, Pelargonium ×hortorum L.H. Bailey. These purified cells contained high concentrations of unusual ω5-unsaturated fatty acids, proportionally 23.4% of total fatty acids in the trichomes. When the trichomes were removed, the supporting tissue contained no ω5-fatty acids, thereby unequivocally localizing ω5-fatty acids to the trichomes. Because ω5-fatty acids are unique precursors for the biosynthesis of ω5-anacardic acids, we conclude that anacardic acid synthesis must occur in the glandular trichomes.     

Fatty acid composition of <Emphasis Type="Italic">Wautersia eutropha</Emphasis> lipids under conditions of active polyhydroxyalkanoates synthesis

The fatty acid composition of the lipids of a Wautersia eutropha polyhydroxyalkanoate-producing strain was studied by chromato-mass spectrometry. A total of 27 fatty acids were identified; their distribution in the cell fractions was determined. In the cytoplasmic membrane, palmitic, palmitoleic, and cis-vaccenic acids were the major components. Long-chain β-hydroxy acids and myristic acids (components of the lipopolysaccharides of the cell envelope) predominated in the fraction of strongly bound lipids. When the polymer was actively synthesized, the content of cyclopropane acids in the easily extracted lipids increased and the content of the corresponding monoenoic acids decreased. The strongly bound lipids had a high content of long-chain β-hydroxy acids (more than 50% of the total fatty acids). These results made it possible to determine the source of polyhydroxyalkanoate (PHA) contamination and to choose the strategy for their purification.     

Ethanol-Mediated Variations in Cellular Fatty Acid Composition and Protein Profiles of Two Genotypically Different Strains of Escherichia coli O157:H7

Two strains of Escherichia coli O157:H7 were grown in tryptic soy broth (TSB, pH 7.1) supplemented with 0, 2.5, 5.0, 7.5, and 10% ethanol at 30°C for up to 54 h. Growth rates in TSB supplemented with 0, 2.5, and 5.0% ethanol decreased with an increase in ethanol concentration. Growth was not observed in TSB supplemented with 7.5 or 10% ethanol. The pH of TSB containing 5.0% ethanol decreased to 5.8 within 12 h and then increased to 7.0 at 54 h. The ethanol content in TSB supplemented with 2.5 or 5.0% ethanol did not change substantially during the first 36 h of incubation but decreased slightly thereafter, indicating utilization or degradation of ethanol by both strains. Glucose was depleted in TSB supplemented with 0, 2.5, or 5.0% ethanol within 12 h. Cells grown under ethanol stress contained a higher amount of fatty acids. With the exceptions of cis-oleic acid and nonadecanoic acid, larger amounts of fatty acid were present in stationary-phase cells of the two strains grown in TSB supplemented with 5.0% ethanol for 30 h than in cells grown in TSB without ethanol for 22 h. The trans-oleic acid content was 10-fold higher in the cells grown in TSB with 5.0% ethanol than those grown in TSB without ethanol. In contrast, cis-oleic acid was not detected in ethanol-stressed cells but was present at concentrations of 0.32 and 0.36 mg/g of cells of the two strains grown in TSB without ethanol. Protein content was higher in ethanol-stressed cells than in nonstressed cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein profiles varied qualitatively as affected by the strain and the presence of ethanol in TSB. An ethanol-mediated protein (28 kDa) was observed in the ethanol-stressed cells but not in control cells. It is concluded that the two test strains of E. coli O157:H7 underwent phenotypic modifications in cellular fatty acid composition and protein profiles in response to ethanol stress. The potential for cross protection against subsequent stresses applied in food preservation technologies as a result of these changes is under investigation.     

Stability of Lactic Acid Bacteria to Freezing as Related to Their Fatty Acid Composition

The viability of Streptococcus lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h was better preserved when the cells were grown in medium supplemented with oleic acid or Tween 80 (polyoxyethylene sorbitan monooleate). A pronounced change in the cellular fatty acid composition was noted when the bacteria were grown in the presence of Tween 80. In S. lactis the ratio of unsaturated to saturated fatty acids increased from 1.18 to 2.55 and in Lactobacillus sp. A-12 it increased from 0.85 to 1.67 when Tween 80 was added to the growth medium. The antibiotic cerulenin markedly inhibited the growth of lactic acid bacteria in tomato juice (TJ) medium but had almost no effect on the growth of the bacteria in TJ medium containing Tween 80 (or oleic acid). The antibiotic inhibited markedly the incorporation of [1-¹⁴C]acetate but had no inhibitory effect on the incorporation of exogenous [1-¹⁴C]oleate (or [1-¹⁴C]palmitate) into the lipid fractions of lactic acid bacteria. Thus, the fatty acid composition of lactic acid bacteria, inhibited by the antibiotic cerulenin, can be modulated by exogenously added oleic acid (or Tween 80) without the concurrent endogenous fatty acid synthesis from acetate. The data obtained suggest that cerulenin inhibits neither cyclopropane fatty acid synthesis nor elongation of fatty acid acyl intermediates. The radioactivity of cells grown in the presence of [1-¹⁴C]oleate and cerulenin was associated mainly with cyclopropane Δ19:0, 20:0 + 20:1, and 21:0 acids. As a consequence, cerulenin caused a decrease in the ratio of unsaturated to saturated fatty acids in lactic acid bacteria as compared with cells grown in TJ medium plus Tween 80 but without cerulenin. Cerulenin caused a decrease in the viability of S. lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h only when Tween 80 was present in the growth medium. We conclude that the sensitivity of lactic acid bacteria to damage from freezing can be correlated with specific alterations in the cellular fatty acids.     

Intraspecies variability of cellular fatty acids among soil and intestinal strains of Desulfovibrio desulfuricans.

A comparison of cellular fatty acid profiles of Desulfovibrio desulfuricans DSM 642 and 14 wild strains of this species, isolated from two completely different environments, soil and the human intestine, was carried out. All the D. desulfuricans strains grown on lactate and sulfate indicated the presence of considerable amounts of i-C15:0, i-C17:1 and C16:0. Although differences in the quantities of individual fatty acids present in each strain were clear in the group of soil strains (similarity, 67.6%), in contrast to almost identical fatty acid patterns (similarity, near 100%) in the intestinal strains, the results were variable within the limits acceptable for species demonstration. The higher similarity of the fatty acid profiles of intestinal strains may be a result of the similarity of biocenoses in the human digestive tract. The coefficients of variability of i-C17:1 and i-C15:0 (the major branched-chain fatty acids), as well as clustering of the investigated strains compared with strains described in the literature after plotting percentages of i-C17:1 fatty acid against i-C15:0 fatty acid, confirmed a certain heterogeneity of cellular fatty acid profiles within the group of soil strains, in contrast to almost ideal homogeneity within the group of intestinal isolates. Intestinal strains contained a higher ratio of saturated to unsaturated fatty acids (2.2 +/- 0.14) than did soil strains (1.6 +/- 0.2; in one case, 2.7). We propose that intestinal D. desulfovibrio bacteria should be assumed to be a highly homogeneous group and should be represented by the strain D. desulfuricans subsp. intestinus in collections of microbial cultures.     

Effect of Growth Temperature on Fatty Acid Composition of Ten Thermus Strains

The fatty acid composition of Thermus spp., including T. aquaticus ATCC 25104, T. thermophilus DSM 579, T. flavus DSM 674, and seven wild strains was examined. Organisms were tested at a minimum of either 35, 40, or 45°C and at an optimum of 60 or 70°C. Total fatty acid content per dry weight of cells varied between 1.2 and 3.7%, and the quantity of fatty acids was higher at the high temperature range in the majority of strains. At the optimum temperature, strains could be assigned to three chemotaxonomic groups with reference to the ratio of iso C_15:0/iso C_17:0. In six of the strains the ratio of iso C_15:0/iso C_17:0 remained unchanged at the minimum temperature, whereas in four strains the ratio was reversed. The proportion of the C_15:0 and C_17:0 isobranched acids was decreased and the proportion of anteisobranched fatty acids, namely anteiso C_15:0, anteiso C_17:0, and anteiso C_17:1, was increased at the lower temperature range. Some changes were seen in the levels of the n-C_16:0 and iso C_16:0 acids, but these were strain specific.