scholarly journals Lipid Biomarkers and Carbon Isotope Signatures of a Microbial (Beggiatoa) Mat Associated with Gas Hydrates in the Gulf of Mexico

2005 ◽  
Vol 71 (4) ◽  
pp. 2106-2112 ◽  
Author(s):  
Chuanlun L. Zhang ◽  
Zhiyong Huang ◽  
James Cantu ◽  
Richard D. Pancost ◽  
Robin L. Brigmon ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Confocal Microscopy ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Gulf Of Mexico ◽  
Gas Hydrates ◽  
Lipid Biomarkers ◽  
Rrna Gene ◽  
Sulfur Oxidizing ◽  
Sulfur Oxidizing Bacteria

ABSTRACT White and orange mats are ubiquitous on surface sediments associated with gas hydrates and cold seeps in the Gulf of Mexico. The goal of this study was to determine the predominant pathways for carbon cycling within an orange mat in Green Canyon (GC) block GC 234 in the Gulf of Mexico. Our approach incorporated laser-scanning confocal microscopy, lipid biomarkers, stable carbon isotopes, and 16S rRNA gene sequencing. Confocal microscopy showed the predominance of filamentous microorganisms (4 to 5 μm in diameter) in the mat sample, which are characteristic of Beggiatoa. The phospholipid fatty acids extracted from the mat sample were dominated by 16:1ω7c/t (67%), 18:1ω7c (17%), and 16:0 (8%), which are consistent with lipid profiles of known sulfur-oxidizing bacteria, including Beggiatoa. These results are supported by the 16S rRNA gene analysis of the mat material, which yielded sequences that are all related to the vacuolated sulfur-oxidizing bacteria, including Beggiatoa, Thioploca, and Thiomargarita. The δ13C value of total biomass was −28.6‰; those of individual fatty acids were −29.4 to −33.7‰. These values suggested heterotrophic growth of Beggiatoa on organic substrates that may have δ13C values characteristic of crude oil or on their by-products from microbial degradation. This study demonstrated that integrating lipid biomarkers, stable isotopes, and molecular DNA could enhance our understanding of the metabolic functions of Beggiatoa mats in sulfide-rich marine sediments associated with gas hydrates in the Gulf of Mexico and other locations.

scholarly journals Ribulose-1,5-bisphosphate carboxylase/oxygenase genes as a functional marker for chemolithoautotrophic halophilic sulfur-oxidizing bacteria in hypersaline habitats

Microbiology ◽  
2010 ◽  
Vol 156 (7) ◽  
pp. 2016-2025 ◽  
Author(s):  
Tatjana P. Tourova ◽  
Olga L. Kovaleva ◽  
Dimitry Yu. Sorokin ◽  
Gerard Muyzer
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Gene Tree ◽  
Hypersaline Lake ◽  
Rrna Gene ◽  
Gene Encoding ◽  
Bisphosphate Carboxylase ◽  
Pure Cultures ◽  
Sulfur Oxidizing ◽  
Sulfur Oxidizing Bacteria

The presence and diversity of the cbb genes encoding the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) (a key enzyme of the Calvin–Benson cycle of autotrophic CO2 assimilation) were investigated in pure cultures of seven genera of halophilic chemolithoautotrophic sulfur-oxidizing bacteria (SOB) and in sediments from a hypersaline lake in which such bacteria have been recently discovered. All of the halophilic SOB strains (with the exception of Thiohalomonas nitratireducens) possessed the cbbL gene encoding RuBisCO form I, while the cbbM gene encoding RuBisCO form II was detected only in some of the pure cultures. The general topologies of the CbbL/CbbM trees and the 16S rRNA gene tree were different, but both markers showed that the halophilic SOB genera formed independent lineages in the Gammaproteobacteria. In some cases, such as with several strains of the genus Thiohalospira and with Thioalkalibacter halophilus, the cbbL clustering was incongruent with the positions of these strains on the ribosomal tree. In the cbbM tree, the clustering of Thiohalospira and Thiohalorhabdus strains was incongruent with their branching in both cbbL and 16S rRNA gene trees. cbbL and cbbM genes related to those found in the analysed halophilic SOB were also detected in a sediment from a hypersaline lake in Kulunda Steppe (Russia). Most of the cbbL and cbbM genes belonged to members of the genus Thiohalorhabdus. In the cbbL clone library, sequences related to those of Halothiobacillus and Thiohalospira were detected as minor components. Some of the environmental cbbM sequences belonged to as yet unknown phylotypes, representing deep lineages of halophilic autotrophs.

scholarly journals Salegentibacter catena sp. nov., isolated from sediment of the South China Sea, and emended description of the genus Salegentibacter

2007 ◽  
Vol 57 (2) ◽  
pp. 219-222 ◽  
Author(s):  
Jiao-Yan Ying ◽  
Zhi-Pei Liu ◽  
Bao-Jun Wang ◽  
Xin Dai ◽  
Su-Sheng Yang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
South China Sea ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
South China ◽  
The South China Sea ◽  
Rrna Gene ◽  
The South ◽  
China Sea ◽  
Emended Description

A novel marine bacterial strain, HY1T, was isolated from sediment of the South China Sea. The strain was aerobic and heterotrophic and formed saffron yellow-pigmented colonies on marine agar 2216. Cells were non-motile, Gram-negative rods, frequently occurring in chains. blastn searches revealed that the 16S rRNA gene sequence of strain HY1T showed high similarity with those of members of the genera Gillisia (91.7–93.8 %) and Salegentibacter (92.6–93.5 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain clustered with members of both Salegentibacter and Gillisia and phylogenetic trees constructed using three different methods (neighbour-joining, maximum-parsimony and minimum-evolution) indicated that strain HY1T clustered more frequently with members of the genus Salegentibacter. The DNA G+C content of strain HY1T was 44.4 mol% and its major cellular fatty acids (⩾5 % of the total fatty acids) were iso-15 : 1 (5.0 %), iso-15 : 0 (6.8 %), anteiso-15 : 0 (6.4 %), 15 : 0 (10.4 %), iso-16 : 0 (13.5 %), summed feature 3 (comprising iso-15 : 0 2-OH and/or 16 : 1ω7c; 6.3 %), iso-17 : 0 3-OH (5.2 %) and 17 : 0 2-OH (5.0 %). Cells contained menaquinone 6. Based on the phylogenetic and phenotypic analyses, strain HY1T should be classified as representing a novel species within the genus Salegentibacter, for which the name Salegentibacter catena sp. nov. is proposed. The type strain is HY1T (=CGMCC 1.6101T=JCM 14015T). Based on this study and on previously described Salegentibacter species, an emended description of the genus Salegentibacter is given.

scholarly journals Kaistia terrae sp. nov., isolated from a wetland in Korea

2010 ◽  
Vol 60 (4) ◽  
pp. 949-952 ◽  
Author(s):  
Soo-Jin Kim ◽  
Hang-Yeon Weon ◽  
Yi-Seul Kim ◽  
Rangasamy Anandham ◽  
Seung-Hee Yoo ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Sequence Analysis ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Dna Hybridization ◽  
Gene Sequence ◽  
16S Rrna Gene Sequence ◽  
Rrna Gene ◽  
Rrna Gene Sequence ◽  
Gene Sequence Analysis

An ivory-coloured bacterium, designated strain 5YN7-3T, was isolated from a wetland, Yongneup, Korea. Cells of the strain were aerobic, Gram-stain-negative, non-motile and short rods. 16S rRNA gene sequence analysis demonstrated that strain 5YN7-3T belongs to the order Rhizobiales of the class Alphaproteobacteria and is closely related to Kaistia soli 5YN9-8T (97.8 %), Kaistia granuli Ko04T (97.6 %) and Kaistia adipata Chj404T (97.4 %). Strain 5YN7-3T showed DNA–DNA hybridization values of 28, 22 and 35 % with K. granuli Ko04T, K. soli 5YN9-8T and K. adipata Chj404T, respectively. The major fatty acids were C18 : 1 ω7c (51.2 %), C19 : 0 cyclo ω8c (25.0 %), C18 : 0 (12.9 %) and C16 : 0 (10.8 %) (>10 % of total fatty acids). Ubiquinone-10 was the major isoprenoid quinone and the DNA G+C content was 66.5 mol%. The phenotypic characteristics in combination with 16S rRNA gene sequence analysis and DNA–DNA hybridization data clearly define strain 5YN7-3T as a novel species of the genus Kaistia, for which the name Kaistia terrae sp. nov. is proposed. The type strain is 5YN7-3T (=KACC 12910T =DSM 21341T).

scholarly journals Paucibacter toxinivorans gen. nov., sp. nov., a bacterium that degrades cyclic cyanobacterial hepatotoxins microcystins and nodularin

2005 ◽  
Vol 55 (4) ◽  
pp. 1563-1568 ◽  
Author(s):  
Jarkko Rapala ◽  
Katri A. Berg ◽  
Christina Lyra ◽  
R. Maarit Niemi ◽  
Werner Manz ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Gene Sequence ◽  
Sequence Similarity ◽  
Carbon Sources ◽  
16S Rrna Gene Sequence ◽  
Rrna Gene ◽  
Rrna Gene Sequence

Thirteen bacterial isolates from lake sediment, capable of degrading cyanobacterial hepatotoxins microcystins and nodularin, were characterized by phenotypic, genetic and genomic approaches. Cells of these isolates were Gram-negative, motile by means of a single polar flagellum, oxidase-positive, weakly catalase-positive and rod-shaped. According to phenotypic characteristics (carbon utilization, fatty acid and enzyme activity profiles), the G+C content of the genomic DNA (66·1–68·0 mol%) and 16S rRNA gene sequence analysis (98·9–100 % similarity) the strains formed a single microdiverse genospecies that was most closely related to Roseateles depolymerans (95·7–96·3 % 16S rRNA gene sequence similarity). The isolates assimilated only a few carbon sources. Of the 96 carbon sources tested, Tween 40 was the only one used by all strains. The strains were able to mineralize phosphorus from organic compounds, and they had strong leucine arylamidase and chymotrypsin activities. The cellular fatty acids identified from all strains were C16 : 0 (9·8–19 %) and C17 : 1 ω7c (<1–5·8 %). The other predominant fatty acids comprised three groups: summed feature 3 (<1–2·2 %), which included C14 : 0 3-OH and C16 : 1 iso I, summed feature 4 (54–62 %), which included C16 : 1 ω7c and C15 : 0 iso OH, and summed feature 7 (8·5–28 %), which included ω7c, ω9c and ω12t forms of C18 : 1. A more detailed analysis of two strains indicated that C16 : 1 ω7c was the main fatty acid. The phylogenetic and phenotypic features separating our strains from recognized bacteria support the creation of a novel genus and species, for which the name Paucibacter toxinivorans gen. nov., sp. nov. is proposed. The type strain is 2C20T (=DSM 16998T=HAMBI 2767T=VYH 193597T).

scholarly journals Sulfurimonas xiamenensis sp. nov. and Sulfurimonas lithotrophica sp. nov., hydrogen- and sulfur-oxidizing chemolithoautotrophs within the Epsilonproteobacteria isolated from coastal sediments, and an emended description of the genus Sulfurimonas

2020 ◽  
Vol 70 (4) ◽  
pp. 2657-2663 ◽  
Author(s):  
Shasha Wang ◽  
Lijing Jiang ◽  
Xuewen Liu ◽  
Suping Yang ◽  
Zongze Shao
Keyword(s):  
Fatty Acids ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Type Species ◽  
Elemental Sulfur ◽  
Rrna Gene ◽  
16S Rrna Gene Sequences ◽  
Content Type ◽  
Link Type ◽  
Emended Description

Strains 1-1NT and GYSZ_1T were isolated from marine sediments collected from the coast of Xiamen, PR China. Cells of the two strains were Gram-stain-negative, rod-shaped or slightly curved. Strain 1-1NT was non-motile, whereas strain GYSZ_1T was motile by means of one polar flagellum. The temperature, pH and salinity concentration ranges for growth of 1-1NT were 10–45 °C (optimum 30 °C), pH 5.5–8.0 (optimum 7.0) and 0–90 g l−1 NaCl (optimum 50 g l−1), while the growth of GYSZ_1T occurred at 4–45 °C (optimum 33 °C), pH 5.0–8.5 (optimum 6.5) and 5–90 g l−1 NaCl (optimum 20 g l−1). The two novel isolates were obligate chemolithoautotrophs capable of growth using hydrogen, thiosulfate, sulfide or elemental sulfur as the sole energy source, and nitrate, elemental sulfur or molecular oxygen as an electron acceptor. The major fatty acids of 1-1NT were C16 : 1ω7c, C16 : 0, C18 : 1ω7c and C18 : 0, while the predominant fatty acids of strain GYSZ_1T were C16 : 1ω7c, C16 : 0, C18 : 1ω7c and C14 : 0 3-OH. The DNA G+C contents of 1-1NT and GYSZ_1T were 34.5 mol% and 33.2 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that 1-1NT and GYSZ_1T represented members of the genus Sulfurimonas , with the highest sequence similarities to Sulfurimonas crateris SN118T (97.4 %) and Sulfurimonas denitrificans DSM 1251T (94.7 %), respectively. However, 1-1NT and GYSZ_1T shared 95.5 % similarity of 16S rRNA gene sequences, representing different species of the genus Sulfurimonas . On the basis of the physiological properties and the results of phylogenetic analyses, including average nucleotide identity and in silico DNA–DNA hybridization values, strains 1-1NT and GYSZ_1T represent two novel species within the genus Sulfurimonas , for which the names Sulfurimonas xiamenensis sp. nov. and Sulfurimonas lithotrophica sp. nov. are proposed, with the type strains 1-1NT (=MCCC 1A14514T=KCTC 15851T) and GYSZ_1T (=MCCC 1A14739T=KCTC 15853T), respectively. Our results also justify an emended description of the genus Sulfurimonas .

scholarly journals Fecal Short-Chain Fatty Acids Are Not Predictive of Colonic Tumor Status and Cannot Be Predicted Based on Bacterial Community Structure

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Marc A. Sze ◽  
Begüm D. Topçuoğlu ◽  
Nicholas A. Lesniak ◽  
Mack T. Ruffin ◽  
Patrick D. Schloss
Keyword(s):  
Colorectal Cancer ◽  
Fatty Acids ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Sequence Data ◽  
Short Chain Fatty Acids ◽  
Tumor Burden ◽  
Short Chain ◽  
Rrna Gene ◽  
Chain Fatty Acids

ABSTRACT Colonic bacterial populations are thought to have a role in the development of colorectal cancer with some protecting against inflammation and others exacerbating inflammation. Short-chain fatty acids (SCFAs) have been shown to have anti-inflammatory properties and are produced in large quantities by colonic bacteria that produce SCFAs by fermenting fiber. We assessed whether there was an association between fecal SCFA concentrations and the presence of colonic adenomas or carcinomas in a cohort of individuals using 16S rRNA gene and metagenomic shotgun sequence data. We measured the fecal concentrations of acetate, propionate, and butyrate within the cohort and found that there were no significant associations between SCFA concentration and tumor status. When we incorporated these concentrations into random forest classification models trained to differentiate between people with healthy colons and those with adenomas or carcinomas, we found that they did not significantly improve the ability of 16S rRNA gene or metagenomic gene sequence-based models to classify individuals. Finally, we generated random forest regression models trained to predict the concentration of each SCFA based on 16S rRNA gene or metagenomic gene sequence data from the same samples. These models performed poorly and were able to explain at most 14% of the observed variation in the SCFA concentrations. These results support the broader epidemiological data that questions the value of fiber consumption for reducing the risks of colorectal cancer. Although other bacterial metabolites may serve as biomarkers to detect adenomas or carcinomas, fecal SCFA concentrations have limited predictive power. IMPORTANCE Considering that colorectal cancer is the third leading cancer-related cause of death within the United States, it is important to detect colorectal tumors early and to prevent the formation of tumors. Short-chain fatty acids (SCFAs) are often used as a surrogate for measuring gut health and for being anticarcinogenic because of their anti-inflammatory properties. We evaluated the fecal SCFA concentrations of a cohort of individuals with different colonic tumor burdens who were previously analyzed to identify microbiome-based biomarkers of tumors. We were unable to find an association between SCFA concentration and tumor burden or use SCFAs to improve our microbiome-based models of classifying people based on their tumor status. Furthermore, we were unable to find an association between the fecal community structure and SCFA concentrations. Our results indicate that the association between fecal SCFAs, the gut microbiome, and tumor burden is weak.

Sandarakinotalea sediminis gen. nov., sp. nov., a novel member of the family Flavobacteriaceae

2006 ◽  
Vol 56 (5) ◽  
pp. 959-963 ◽  
Author(s):  
Shams Tabrez Khan ◽  
Yasuyoshi Nakagawa ◽  
Shigeaki Harayama
Keyword(s):  
Fatty Acids ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Gene Sequence ◽  
Heterotrophic Bacteria ◽  
Sequence Similarity ◽  
16S Rrna Gene Sequence ◽  
Rrna Gene ◽  
Rrna Gene Sequence ◽  
The Family

Four Gram-negative, orange-coloured, aerobic, heterotrophic bacteria were isolated from sediment samples collected on the Pacific coast of Japan near the cities of Toyohashi and Katsuura. 16S rRNA gene sequence analysis indicated that these strains form a distinct lineage within the family Flavobacteriaceae. The four isolates shared 99.9–100 % 16S rRNA gene sequence similarity with each other and showed 88–90.9 % similarity with their neighbours in the family Flavobacteriaceae. The four strains also shared high DNA–DNA reassociation values of 67–99 % with each other. All the strains grew at 37 °C but not at 4 °C, and degraded gelatin, starch and DNA. The major fatty acids were i-C15 : 0, a-C15 : 0, i-C16 : 0 and i-C17 : 0 3-OH. However, two common fatty acids of members of the Flavobacteriaceae, i-C15 : 1 and a-C15 : 1, were absent in these strains. The DNA G+C contents of the four strains were in the range 35–37 mol%. On the basis of the polyphasic evidence, it was concluded that these strains should be classified as a novel genus and a novel species in the family Flavobacteriaceae, for which the name Sandarakinotalea sediminis gen. nov., sp. nov. is proposed. The type strain of Sandarakinotalea sediminis is CKA-5T (=NBRC 100970T=LMG 23247T).

scholarly journals Oceanibulbus indolifex gen. nov., sp. nov., a North Sea alphaproteobacterium that produces bioactive metabolites

2004 ◽  
Vol 54 (4) ◽  
pp. 1177-1184 ◽  
Author(s):  
Irene Wagner-Döbler ◽  
Holger Rheims ◽  
Andreas Felske ◽  
Aymen El-Ghezal ◽  
Dirk Flade-Schröder ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Phylogenetic Analysis ◽  
Fatty Acid ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
North Sea ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
Gene Sequences ◽  
16S Rrna Gene Sequences

A water sample from the North Sea was used to isolate the abundant heterotrophic bacteria that are able to grow on complex marine media. Isolation was by serial dilution and spread plating. Phylogenetic analysis of nearly complete 16S rRNA gene sequences revealed that one of the strains, HEL-45T, had 97·4 % sequence similarity to Sulfitobacter mediterraneus and 96·5 % sequence similarity to Staleya guttiformis. Strain HEL-45T is a Gram-negative, non-motile rod and obligate aerobe and requires sodium and 1–7 % sea salts for growth. It contains storage granules and does not produce bacteriochlorophyll. Optimal growth temperatures are 25–30 °C. The DNA base composition (G+C content) is 60·1 mol%. Strain HEL-45T has Q10 as the dominant respiratory quinone. The major polar lipids are phosphatidyl glycerol, diphosphatidyl glycerol, phosphatidyl choline, phosphatidyl ethanolamine and an aminolipid. The fatty acids comprise 18 : 1ω7c, 18 : 0, 16 : 1ω7c, 16 : 0, 3-OH 10 : 0, 3-OH 12 : 1 (or 3-oxo 12 : 0) and traces of an 18 : 2 fatty acid. Among the hydroxylated fatty acids only 3-OH 12 : 1 (or 3-oxo 12 : 0) appears to be amide linked, whereas 3-OH 10 : 0 appears to be ester linked. The minor fatty acid components (between 1 and 7 %) allow three subgroups to be distinguished in the Sulfitobacter/Staleya clade, placing HEL-45T into a separate lineage characterized by the presence of 3-OH 12 : 1 (or 3-oxo 12 : 0) and both ester- and amide-linked 16 : 1ω7c phospholipids. HEL-45T produces indole and derivatives thereof, several cyclic dipeptides and thryptanthrin. Phylogenetic analysis of 16S rRNA gene sequences and chemotaxonomic data support the description of a new genus and species, to include Oceanibulbus indolifex gen. nov., sp. nov., with the type strain HEL-45T (=DSM 14862T=NCIMB 13983T).

scholarly journals Sphingomonas rubra sp. nov., isolated from bioreactor wastewater

2011 ◽  
Vol 61 (5) ◽  
pp. 1028-1032 ◽  
Author(s):  
Ying-Yi Huo ◽  
Xue-Wei Xu ◽  
Sheng-Pan Liu ◽  
Heng-Lin Cui ◽  
Xue Li ◽  
...  
Keyword(s):  
Fatty Acids ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Gene Sequence ◽  
Batch Reactor ◽  
Sensu Stricto ◽  
16S Rrna Gene Sequence ◽  
Rrna Gene ◽  
Rrna Gene Sequence ◽  
Sequence Similarities

A Gram-reaction-negative, rod-shaped, motile, neutrophilic bacterium, designated strain BH3T, was isolated from wastewater of a sequential batch reactor treating wastewater taken from a leather plant. The isolate grew in 0–8 % (w/v) NaCl, at pH 6–9 and at 4–45 °C. Chemotaxonomic analysis showed that strain BH3T had characteristics typical of members of the genus Sphingomonas, such as the presence of sphingolipids, Q-10 and 2-hydroxymyristic acid and the absence of 3-hydroxy fatty acids. The presence of C18 : 1ω7c (39.2 %) and C16 : 0 (11.2 %) as major fatty acids, C14 : 0 2-OH (20.6 %) as the major 2-hydroxy fatty acid and homospermidine as the major polyamine indicated that strain BH3T belonged to the genus Sphingomonas sensu stricto. The genomic DNA G+C content of strain BH3T was 65.6 mol%. 16S rRNA gene sequence similarities between the isolate and closely related members of the genus Sphingomonas sensu stricto ranged from 92.6 to 97.3 %, the highest sequence similarities being to Sphingomonas melonis DSM 14444T (97.3 %) and Sphingomonas aquatilis DSM 15581T (97.3 %). Based on its phenotypic characteristics and the results of DNA–DNA hybridization studies and 16S rRNA gene sequence comparisons, strain BH3T represents a novel species of the genus Sphingomonas sensu stricto, for which the name Sphingomonas rubra sp. nov. is proposed. The type strain is BH3T ( = CGMCC 1.9113T  = JCM 16230T).

scholarly journals An Oleaginous Bacterium That Intrinsically Accumulates Long-Chain Free Fatty Acids in its Cytoplasm

2013 ◽  
Vol 80 (3) ◽  
pp. 1126-1131 ◽  
Author(s):  
Taiki Katayama ◽  
Manabu Kanno ◽  
Naoki Morita ◽  
Tomoyuki Hori ◽  
Takashi Narihiro ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Lactic Acid ◽  
16S Rrna ◽  
Cell Membrane ◽  
16S Rrna Gene ◽  
Free Fatty Acids ◽  
Biodiesel Production ◽  
Rrna Gene ◽  
Content Type ◽  
Long Chain

ABSTRACTMedium- and long-chain fatty acids are present in organisms in esterified forms that serve as cell membrane constituents and storage compounds. A large number of organisms are known to accumulate lipophilic materials as a source of energy and carbon. We found a bacterium, designated GK12, that intrinsically accumulates free fatty acids (FFAs) as intracellular droplets without exhibiting cytotoxicity. GK12 is an obligatory anaerobic, mesophilic lactic acid bacterium that was isolated from a methanogenic reactor. Phylogenetic analysis based on 16S rRNA gene sequences showed that GK12 is affiliated with the familyErysipelotrichaceaein the phylumFirmicutesbut is distantly related to type species in this family (less than 92% similarity in 16S rRNA gene sequence). Saturated fatty acids with carbon chain lengths of 14, 16, 18, and 20 were produced from glucose under stress conditions, including higher-than-optimum temperatures and the presence of organic solvents that affect cell membrane integrity. FFAs were produced at levels corresponding to up to 25% (wt/wt) of the dry cell mass. Our data suggest that FFA accumulation is a result of an imbalance between excess membrane fatty acid biosynthesis due to homeoviscous adaptation and limited β-oxidation activity due to anaerobic growth involving lactic acid fermentation. FFA droplets were not further utilized as an energy and carbon source, even under conditions of starvation. A naturally occurring bacterium that accumulates significant amounts of long-chain FFAs with noncytotoxicity would provide useful strategies for microbial biodiesel production.

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