Pyrroloquinoline quinone production defines the ability of Devosia species to degrade deoxynivalenol.

Deoxynivalenol (DON) is a prevalent mycotoxin that primarily contaminates cereal crops and animal feed, posing a significant risk to human and animal health. In recent years, an increasing number of Devosia strains have been identified as DON degradation bacteria, and significant efforts have been made to explore their potential applications in the food and animal feed industries. However, the characteristics and mechanisms of DON degradation in Devosia strains are still unclear. In this study, we identified a novel DON degrading bacterium, Devosia sp. D-G15 (D-G15), from soil samples. The major degradation products of DON in D-G15 were 3-keto-DON, 3-epi-DON and an unidentified product, compound C. The cell viability assay showed that the DON degradation product of D-G15 revealed significantly reduced toxicity to HEK293T cells compared to DON. Three enzymes for DON degradation were further identified, with G15-DDH converting DON to 3-keto-DON and G15-AKR1/G15-AKR6 reducing 3-keto-DON to 3-epi-DON. Interestingly, genome comparison of Devosia strains showed that the pyrroloquinoline quinone (PQQ) synthesis gene cluster is a unique feature of DON degradation strains. Subsequently, adding PQQ to the cultural media of Devosia strains without PQQ synthesis genes endowed them with DON degradation activity. Furthermore, a novel DON-degrading enzyme G13-DDH (<30% homology with known DON dehydrogenase) was identified from a Devosia strain that lacks PQQ synthesis ability. In summary, a novel DON degrading Devosia strain and its key enzymes were identified, and PQQ production was found as a distinct feature among Devosia strains with DON degradation activity, which is important for developing Devosia strain-based technology in DON detoxification.

Photosynthesis in the near infrared: the γ subunit of Blastochloris viridis LH1 red-shifts absorption beyond 1000†nm.

The reaction centre (RC) in purple phototrophic bacteria is encircled by the primary light-harvesting complex 1 (LH1) antenna, forming the RC-LH1 'core' complex. The Qy absorption maximum of LH1 complexes ranges from ∼875-960 nm in bacteriochlorophyll (BChl) a-utilising organisms, to 1018 nm in the BChl b-containing complex from Blastochloris (Blc.) viridis. The red-shifted absorption of the Blc. viridis LH1 was predicted to be due in part to the presence of the γ subunit unique to Blastochloris spp., which binds to the exterior of the complex and is proposed to increase packing and excitonic coupling of the BChl pigments. The study by Namoon et al. provides experimental evidence for the red-shifting role of the γ subunit and an evolutionary rationale for its incorporation into LH1. The authors show that cells producing RC-LH1 lacking the γ subunit absorb maximally at 972 nm, 46 nm to the blue of the wild-type organism. Wavelengths in the 900-1000 nm region of the solar spectrum transmit poorly through water, thus γ shifts absorption of LH1 to a region where photons have lower energy but are more abundant. Complementation of the mutant with a divergent copy of LH1γ resulted in an intermediate red shift, revealing the possibility of tuning LH1 absorption using engineered variants of this subunit. These findings provide new insights into photosynthesis in the lowest energy phototrophs and how the absorption properties of light-harvesting complexes are modified by the recruitment of additional subunits.

Electronic Structure Effects Related to the Origin of the Remarkable Near-Infrared Absorption of Blastochloris viridis' Light Harvesting 1-Reaction Center Complex.

Various photosynthetic organisms have evolved to absorb light in different regions of the visible light spectrum, thus adapting to the various lighting conditions available on Earth. While most of these autotrophic organisms absorb wavelengths around the 700-800 nm region, some are capable of red-shifted absorptions above this range, but none as remarkably as Blastochloris viridis whose main absorption is observed at 1015 nm, approximately 220 nm (0.34 eV) lower in energy than their main constituent pigments, BChl-b, whose main absorption is observed at 795 nm. The structure of its light harvesting 1-reaction center was recently elucidated by cryo-EM; however, the electronic structure details behind this red-shifted absorption remain unattended. We used hybrid quantum mechanics/molecular mechanics (QM/MM) calculations to optimize one of the active centers and performed classical molecular dynamics (MD) simulations to sample conformations beyond the optimized structure. We did excited state calculations with the time-dependent density functional theory method at the CAM-B3LYP/cc-pVDZ level of theory. We reproduced the near IR absorption by sequentially modifying the number of components involved in our systems using representative structures from the calculated MD ensemble. Natural transition orbital analysis reveals the participation of the BChl-b fragments to the main transition in the native structure and the structures obtained from the QM/MM and MD simulations. H-bonding pigment-protein interactions play a role on the conformation stabilization and orientation; however, the bacteriochlorin ring conformations and the exciton delocalization are the most relevant factors to explain the red-shifting phenomenon.

Devosia rhizoryzae sp. nov., and Devosia oryziradicis sp. nov., novel plant growth promoting members of the genus Devosia, isolated from the rhizosphere of rice plants.

Two novel Gram-negative, aerobic, asporogenous, motile, rod-shaped, orange and white pigmented, designated as LEGU1T and G19T, were isolated from the roots of rice plants, collected from Goyang, South Korea. Phylogenetic analysis based on their 16S rRNA gene sequences revealed that they belonged to the genus Devosia and formed a different lineage and clusters with different members of the genus Devosia. These strains shared common chemotaxonomic features. In particular, they had Q-10 as the sole quinone, phosphatidylglycerol, diphosphatidylglycerol as the principal polar lipids and C16:0, C18:1ω7c 11-methyl and summed feature 8 (comprising C18:1ω7c/C18:1ω6c) as the main fatty acids. The draft genome sequences of strains LEGU1T and G19T were 3,524,978 and 3,495,520 bp in size, respectively. Their average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values were 72.8-81.9% and 18.7-25.1%, respectively, with each other and type strains of related species belonging to the genus Devosia, suggesting that these two strains represent novel species. The G + C content of strains LEGU1T and G19T were 62.1 and 63.8%, respectively. Of the two strains, only LEGU1T produced carotenoid and flexirubin-type pigment. Both strains produced siderophore and indole acetic acid (IAA) in the presence of L-tryptophan. Siderophore biosynthesis genes, auxin responsive genes and tryptophan biosynthesis genes were present in their genomes. The present study aimed to determine the detailed taxonomic positions of the strains using the modern polyphasic approach. Based on the results of polyphasic analysis, these strains are suggested to be two novel bacterial species within the genus Devosia. The proposed names are D. rhizoryzae sp. nov., and Devosia oryziradicis sp. nov., respectively. The plant growth promoting effects of these strains suggest that they can be exploited to improve rice crop productivity. The type strain of D. rhizoryzae is LEGU1T (KCTC 82712T = NBRC 114485T) and D. oryziradicis is G19T (KCTC 82688T = NBRC 114842T).

The Mechanisms of Electrogenic Reactions in Bacterial Photosynthetic Reaction Centers: Studies in Collaboration with Alexander Konstantinov.

In this review, we discuss our studies conducted in 1985-1988 in collaboration with A. A. Konstantinov, one of the top scientists in the field of membrane bioenergetics. Studying fast kinetics of membrane potential generation in photosynthetic reaction centers (RCs) of purple bacteria in response to a laser flash has made it possible to examine in detail the mechanisms of electrogenic reactions at the donor and acceptor sides of RCs. Electrogenesis associated with the intraprotein electron transfer from the exogenous secondary donors, redox dyes, and soluble cytochrome (cyt) c to the photooxidized dimer of bacteriochlorophyll P870 was studied using proteoliposomes containing RCs from the non-sulfur purple bacterium Rhodospirillum rubrum. It was found that reduction of the secondary quinone electron acceptor QB accompanied by its protonation in the chromatophores from R. rubrum in response to every second light flash was electrogenic. Spectral characteristics and redox potentials of the four hemes in the tightly bound cyt c in the RC of Blastochloris viridis and electrogenic reactions associated with the electron transfer within the RC complex were identified. For the first time, relative amplitudes of the membrane potential generated in the course of individual electrogenic reactions were compared with the distances between the redox cofactors determined based on the three-dimensional structure of the Bl. viridis RC.

Ultrafast structural changes within a photosynthetic reaction centre.

Photosynthetic reaction centres harvest the energy content of sunlight by transporting electrons across an energy-transducing biological membrane. Here we use time-resolved serial femtosecond crystallography1 using an X-ray free-electron laser2 to observe light-induced structural changes in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds. Structural perturbations first occur at the special pair of chlorophyll molecules of the photosynthetic reaction centre that are photo-oxidized by light. Electron transfer to the menaquinone acceptor on the opposite side of the membrane induces a movement of this cofactor together with lower amplitude protein rearrangements. These observations reveal how proteins use conformational dynamics to stabilize the charge-separation steps of electron-transfer reactions.

An uncharacterized clade in the DMSO reductase family of molybdenum oxidoreductases is a new type of chlorate reductase.

The dimethylsulfoxide (DMSO) reductase family of enzymes has many subfamilies catalysing unique biogeochemical reactions. It also has many uncharacterized subfamilies. Comparative genomics predicted one such subfamily to participate in a key step of the chlorine cycle because of a conserved genetic association with chlorite dismutase, implying they produce chlorite through chlorate or perchlorate reduction. We determined the activity of the uncharacterized enzyme by comparing strains in the phototrophic genus Rhodoplanes that encode either a typical perchlorate reductase or the uncharacterized enzyme. Rpl. piscinae and Rpl. elegans, which encode perchlorate reductase, grew by using perchlorate as an electron acceptor. In contrast, Rpl. roseus, which encodes the uncharacterized enzyme, grew by chlorate reduction but not by perchlorate reduction. This is the first report of perchlorate and chlorate being used as respiratory electron acceptors by phototrophs. When both chlorate and perchlorate were present, Rpl. roseus consumed only chlorate. Highly concentrated Rpl. roseus cells showed some perchlorate consumption, but chlorate consumption occurred at a 10-fold higher rate. Together, these genomic and physiological data define a new group of chlorate reductases. Some organisms encode both this chlorate reductase and a perchlorate reductase, raising new questions about the physiology and evolution of chlorine oxyanion respiration.

Enzymatic degradation of deoxynivalenol by a novel bacterium, Pelagibacterium halotolerans ANSP101.

Deoxynivalenol (DON), a toxic secondary metabolite produced by Fusarium species that mainly infests cereals such as wheat and corn, threatens human and livestock health. The present study describes the characterization of a novel bacterial strain, Pelagibacterium halotolerans ANSP101 which is capable of transforming DON to less-toxic product 3-keto-deoxynivalenol by the oxidation of the C3 hydroxyl group. Strain ANSP101 was isolated from a seawater sample from a depth of 55 m in Chinese Bohai sea. The strain was identified as Pelagibacterium halotolerans by morphology characterization and 16S rDNA gene sequencing. The DON degrading activity of strain ANSP101 was predominantly attributed to the bacterial cell lysate. Besides, the cell lysate was sensitive to sodium dodecyl sulfate, heat, and proteinase K treatment, indicating that the intracellular proteins or enzymes are responsible for the DON degradation. The optimal temperature and pH for the maximal degradation of DON were 40 °C and pH 8.0 by the cell lysate. These results provide the potential use of P. halotolerans ANSP101 as a detoxification agent for DON decontamination in cereals and feed.

Defining the Environmental Adaptations of Genus Devosia: Insights into its Expansive Short Peptide Transport System and Positively Selected Genes.

Devosia are well known for their dominance in soil habitats contaminated with various toxins and are best characterized for their bioremediation potential. In this study, we compared the genomes of 27 strains of Devosia with aim to understand their metabolic abilities. The analysis revealed their adaptive gene repertoire which was bared from 52% unique pan-gene content. A striking feature of all genomes was the abundance of oligo- and di-peptide permeases (oppABCDF and dppABCDF) with each genome harboring an average of 60.7 ± 19.1 and 36.5 ± 10.6 operon associated genes respectively. Apart from their primary role in nutrition, these permeases may help Devosia to sense environmental signals and in chemotaxis at stressed habitats. Through sequence similarity network analyses, we identified 29 Opp and 19 Dpp sequences that shared very little homology with any other sequence suggesting an expansive short peptidic transport system within Devosia. The substrate determining components of these permeases viz. OppA and DppA further displayed a large diversity that separated into 12 and 9 homologous clusters respectively in addition to large number of isolated nodes. We also dissected the genome scale positive evolution and found genes associated with growth (exopolyphosphatase, HesB_IscA_SufA family protein), detoxification (moeB, nifU-like domain protein, alpha/beta hydrolase), chemotaxis (cheB, luxR) and stress response (phoQ, uspA, luxR, sufE) were positively selected. The study highlights the genomic plasticity of the Devosia spp. for conferring adaptation, bioremediation and the potential to utilize a wide range of substrates. The widespread toxin-antitoxin loci and 'open' state of the pangenome provided evidence of plastic genomes and a much larger genetic repertoire of the genus which is yet uncovered.

Protective Effects of Bacillus subtilis ANSB060, Bacillus subtilis ANSB01G, and Devosia sp. ANSB714-Based Mycotoxin Biodegradation Agent on Mice Fed with Naturally moldy Diets.

Mycotoxins are toxic secondary metabolites produced by toxigenic fungi that commonly contaminate agricultural crops. The purpose of the current study was to evaluate whether Bacillus subtilis ANSB060, Bacillus subtilis ANSB01G, and Devosia sp. ANSB714-based mycotoxin biodegradation agent (MBA) could alleviate the negative effects of naturally moldy diet containing aflatoxin (AF), zearalenone (ZEN), and deoxynivalenol (DON) on growth performance, serum immune function, and antioxidant capacity as well as tissue residues in mice. A total of 54 mice were randomly divided into three dietary treatments: basal diet (CON), multi-mycotoxins contaminated diet (MCD) containing AF, ZEN and DON and multi-mycotoxins contaminated diet plus MBA at a dose of 1.0 g kg-1 feed (MCD + MBA). Mice fed with moldy diet showed a significant decrease in body weight gain (p < 0.05), whereas the relative weight of the liver, spleen and uterus were remarkably increased (p < 0.05). Serum IgA and IgM contents were significantly decreased in MCD treatment compared with that in CON treatment (p < 0.05). In contrast, serum interleukin-1ß (IL-1ß), interleukin-2 (IL-2), and interleukin-6 (IL-6) concentrations were significantly promoted in mice fed with moldy diet (p < 0.05). Besides, the exposure to mycotoxins caused marked down-regulation of serum superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in mice (p < 0.05). The addition of MBA effectively counteracted these toxic effects of moldy diet on mice. And DON residues in kidneys of mice consuming moldy diet were eliminated by the supplementation with MBA. Taken together, Bacillus subtilis ANSB060, Bacillus subtilis ANSB01G, and Devosia sp. ANSB714-based mycotoxin biodegradation agent has great potential use as a microbial additive to counteract mycotoxins contamination in food and feed.

Phospholipid distributions in purple phototrophic bacteria and LH1-RC core complexes.

In contrast to plants, algae and cyanobacteria that contain glycolipids as the major lipid components in their photosynthetic membranes, phospholipids are the dominant lipids in the membranes of anoxygenic purple phototrophic bacteria. Although the phospholipid compositions in whole cells or membranes are known for a limited number of the purple bacteria, little is known about the phospholipids associated with individual photosynthetic complexes. In this study, we investigated the phospholipid distributions in both membranes and the light-harvesting 1-reaction center (LH1-RC) complexes purified from several purple sulfur and nonsulfur bacteria. 31P NMR was used for determining the phospholipid compositions and inductively coupled plasma atomic emission spectroscopy was used for measuring the total phosphorous contents. Combining these two techniques, we could determine the numbers of specific phospholipids in the purified LH1-RC complexes. A total of approximate 20-30 phospholipids per LH1-RC were detected as the tightly bound lipids in all species. The results revealed that while cardiolipin (CL) exists as a minor component in the membranes, it became the most abundant phospholipid in the purified core complexes and the sum of CL and phosphatidylglycerol accounted for more than two thirds of the total phospholipids for most species. Preferential association of these anionic phospholipids with the LH1-RC is discussed in the context of the recent high-resolution structure of this complex from Thermochromatium (Tch.) tepidum. The detergent lauryldimethylamine N-oxide was demonstrated to selectively remove phosphatidylethanolamine from the membrane of Tch. tepidum.

Biodegradation of deoxynivalenol and its derivatives by Devosia insulae A16.

Deoxynivalenol (DON), a notorious mycotoxin mainly found in Fusarium-contaminated crops, causes great loss in livestock farming and severe safety risks to human health. Here we report the isolation of a Gram-negative bacterial strain with effective biodegrading abilities on DON and its derivatives including 3-acetyl-DON and 15-acetyl-DON. The strain was identified as Devosia insulae A16 on the basis of morphological and physiological characteristics and 16S rRNA-based phylogenetic analysis. D. insulae A16 was able to degrade 88% of 20 mg/l DON within 48 h under aerobic conditions at 35 °C and neutral pH. The major degradation product of DON and its derivatives was 3-keto-DON by the oxidation of the hydroxyl group at C-3. Both 3-acetyl-DON and 15-acetyl-DON underwent a deacetylation reaction to generate DON prior to the degradation to 3-keto-DON. The results provide the potential use of D. insulae A16 as a biodegradation agent to control DON contamination in cereals.

Massive over-representation of solute-binding proteins (SBPs) from the tripartite tricarboxylate transporter (TTT) family in the genome of the α-proteobacterium Rhodoplanes sp. Z2-YC6860.

Lineage-specific expansion (LSE) of protein families is a widespread phenomenon in many eukaryotic genomes, but is generally more limited in bacterial genomes. Here, we report the presence of 434 genes encoding solute-binding proteins (SBPs) from the tripartite tricarboxylate transporter (TTT) family, within the 8.2 Mb genome of the α-proteobacterium Rhodoplanes sp. Z2-YC6860, a gene family over-representation of unprecedented abundance in prokaryotes. Representing over 6 % of the total number of coding sequences, the SBP genes are distributed across the whole genome but are found rarely in low-GC islands, where the gene density for this family is much lower. This observation, and the much higher sequence identity between the 434 Rhodoplanes TTT SBPs compared with the average identity between homologues from different species, is indicative of a key role for LSE in the expansion. The TTT SBP genes were found in the vicinity of genes encoding membrane components of transport systems from different families, as well as regulatory proteins such as histidine-kinases and transcription factors, indicating a broad range of functions around the sensing, response and transport of organic compounds. A smaller expansion of TTT SBPs is known in some species of the ß-proteobacteria Bordetella and we observed similar expansions in other ß-proteobacterial lineages, including members of the genus Comamonas and the industrial biotechnology organism Cupriavidus necator, indicating that strong environmental selection can drive SBP duplication and specialisation from multiple evolutionary starting points.

An Efficient Gas Chromatography-Mass Spectrometry Approach for the Simultaneous Analysis of Deoxynivalenol and Its Bacterial Metabolites 3-keto-DON and 3- epi-DON.

Deoxynivalenol (DON) is one of the major toxic secondary metabolites produced by Fusarium fungi in cereal grains. Among the many promising strategies of DON detoxification are the microbial and enzymatic ones, which transform DON to nontoxic DON metabolites. Thus, proper analytical methods are needed for those DON metabolites. In this study, a robust gas chromatography-mass spectrometry (GC-MS) procedure was developed and validated for the simultaneous analysis of DON and two of its bacterial metabolites, 3-keto-DON and 3- epi-DON. The procedure involves a straightforward vacuum drying and derivatization step before the subsequent GC-MS analysis. Following the optimized protocol, DON and these two metabolites were separated on a capillary column within 15 min. The linear ranges for the these compounds were 10 to 2,000 ng mL-1 with correlation coefficients >0.99. For DON, 3- epi-DON, and 3-keto-DON, the limits of detection were 0.8, 3.0, and 0.05 ng mL-1, and the limits of quantification were 2.6, 10.0, and 1.0 ng mL-1, respectively. For all three compounds, the obtained relative standard deviation was 1.2 to 5.5%, and the recovery rates were 89.5 to 103.6%. The developed method was further validated by analyzing DON metabolites resulting from the biotransformation of DON initiated by cell-free lysates of the bacterium Devosia mutans 17-2-E-8. The developed protocol was sensitive, precise, accurate, and robust for the determination of DON, 3- epi-DON, and 3-keto-DON in liquid media and potentially other complex matrices without interference from other compounds.

The enzymatic detoxification of the mycotoxin deoxynivalenol: identification of DepA from the DON epimerization pathway.

The biological detoxification of mycotoxins, including deoxynivalenol (DON), represents a very promising approach to address the challenging problem of cereal grain contamination. The recent discovery of Devosia mutans 17-2-E-8 (Devosia spp. 17-2-E-8), a bacterial isolate capable of transforming DON to the non-toxic stereoisomer 3-epi-deoxynivalenol, along with earlier reports of bacterial species capable of oxidizing DON to 3-keto-DON, has generated interest in the possible mechanism and enzyme(s) involved. An understanding of these details could pave the way for novel strategies to manage this widely present toxin. It was previously shown that DON epimerization proceeds through a two-step biocatalysis. Significantly, this report describes the identification of the first enzymatic step in this pathway. The enzyme, a dehydrogenase responsible for the selective oxidation of DON at the C3 position, was shown to readily convert DON to 3-keto-DON, a less toxic intermediate in the DON epimerization pathway. Furthermore, this study provides insights into the PQQ dependence of the enzyme. This enzyme may be part of a feasible strategy for DON mitigation within the near future.

From Macrocrystals to Microcrystals: A Strategy for Membrane Protein Serial Crystallography.

Serial protein crystallography was developed at X-ray free-electron lasers (XFELs) and is now also being applied at storage ring facilities. Robust strategies for the growth and optimization of microcrystals are needed to advance the field. Here we illustrate a generic strategy for recovering high-density homogeneous samples of microcrystals starting from conditions known to yield large (macro) crystals of the photosynthetic reaction center of Blastochloris viridis (RCvir). We first crushed these crystals prior to multiple rounds of microseeding. Each cycle of microseeding facilitated improvements in the RCvir serial femtosecond crystallography (SFX) structure from 3.3-Å to 2.4-Å resolution. This approach may allow known crystallization conditions for other proteins to be adapted to exploit novel scientific opportunities created by serial crystallography.

Pelagibacterium lentulum sp. nov., a marine bacterium from the culture broth of Picochlorum sp. 122.

A Gram-stain-negative, motile, non-spore-forming, rod-shaped bacterium, designated strain B2T, was isolated from the culture broth of a marine microalga, Picochlorum sp. 122. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain B2T forms a robust cluster with members of the genus Pelagibacterium, and shares the highest sequence similarity of 96.80 % with Pelagibacterium halotolerans CGMCC 1.7692T. Optimal growth of strain B2T was observed at 33 °C, at pH 8 and in the presence of 1 % (w/v) NaCl. The predominant ubiquinone of strain B2T was Q-10, and the G+C content of the genomic DNA was 58.6 mol%. The major fatty acid profile comprised C18 : 1ω7c/ω6c, C19 : 0 cyclo ω8c and C16 : 0. The major polar lipids of strain B2T were diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and seven unidentified lipids. Comprehensive analyses based on a polyphasic characterization of strain B2T indicated that it represents a novel species of the genus Pelagibacterium, for which the name Pelagibacterium lentulum sp. nov. is proposed. The type strain is B2T (=MCCC 1K03218T=CGMCC 1.15896T=KCTC 52551T).

The enzymatic epimerization of deoxynivalenol by Devosia mutans proceeds through the formation of 3-keto-DON intermediate.

The enzymatic detoxification of deoxynivalenol (DON) is a promising mitigation strategy for addressing this mycotoxin contamination of cereal grains. A recently described bacterium, Devosia mutans 17-2-E-8, capable of transforming DON into its non-toxic stereoisomer 3-epi-DON, holds promise for the development of such applications. Earlier observations suggested that DON epimerization proceeds via a two-step catalysis with 3-keto-DON as an intermediate. The results of this study indicate that NADPH is required for DON epimerization by cell-free protein extracts of D. mutans, while high concentrations of glucose and sucrose have a suppressive effect. Chemically synthesized 3-keto-DON incubated with D. mutans protein fractions enriched by ammonium sulfate precipitation at 35-55% saturation selectively reduced 3-keto-DON to 3-epi-DON, but fell short of supporting the complete epimerization of DON. In addition, seven Devosia species investigated for DON epimerization were all able to reduce 3-keto-DON to 3-epi-DON, but only a few were capable of epimerizing DON. The above observations collectively confirm that the enzymes responsible for the oxidation of DON to 3-keto-DON are physically separate from those involved in 3-keto-DON reduction to 3-epi-DON. The enzymatic nature of DON epimerization suggests that the process could be used to develop genetically engineered crops or microorganisms, ultimately reducing foodborne exposure of consumers and farm animals to DON.

Carotenoid-to-Bacteriochlorophyll Energy Transfer in the LH1-RC Core Complex of a Bacteriochlorophyll b Containing Purple Photosynthetic Bacterium Blastochloris viridis.

Carotenoid-to-bacteriochlorophyll energy transfer has been widely investigated in bacteriochlorophyll (BChl) a-containing light harvesting complexes. Blastochloris viridis utilizes BChl b, whose absorption spectrum is more red-shifted than that of BChl a. This has implications on the efficiency and pathways of carotenoid-to-BChl energy transfer in this organism. The carotenoids that comprise the light-harvesting reaction center core complex (LH1-RC) of B. viridis are 1,2-dihydroneurosporene and 1,2-dihydrolycopene, which are derivatives of carotenoids found in the light harvesting complexes of several BChl a-containing purple photosynthetic bacteria. Steady-state and ultrafast time-resolved optical spectroscopic measurements were performed on the LH1-RC complex of B. viridis at room and cryogenic temperatures. The overall efficiency of carotenoid-to-bacteriochlorophyll energy transfer obtained from steady-state absorption and fluorescence measurements were determined to be ∼27% and ∼36% for 1,2-dihydroneurosporene and 1,2-dihydrolycopene, respectively. These results were combined with global fitting and target analyses of the transient absorption data to elucidate the energetic pathways by which the carotenoids decay and transfer excitation energy to BChl b. 1,2-Dihydrolycopene transfers energy to BChl b via the S2 → Qx channel with kET2 = (500 fs)(-1) while 1,2-dihydroneurosporene transfers energy via S1→ Qy (kET1 = (84 ps)(-1)) and S2 → Qx (kET2 = (2.2 ps)(-1)) channels.

Pelagibacterium lixinzhangensis sp. nov., a Novel Member of the Genus Pelagibacterium.

A Gram-negative, rod shaped and non-spore-forming bacterium, strain H642(T), was isolated from a desert sample collected from Xinjiang province of China, and subjected to a polyphasic taxonomic investigation. Strain H642(T) grew between 20 and 40 °C (optimal 28-37 °C), pH 6.0-10.0 (optimal 7.0-9.0) and at NaCl concentrations between 1.0 and 20.0 % (optimal 2.0-8.0 %). It was positive for catalase, but negative for oxidase. Ubiquinone-10 was present as the major respiratory ubiquinone. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, four unknown glycolipids and one unknown lipid. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain H642(T) belongs to the genus Pelagibacterium. Strain H642(T) was most closely related to Pelagibacterium halotolerans (with 98.4 % similarity), Pelagibacterium nitratireducens (97.3 %) and Pelagibacterium luteolum (96.2 %). DNA-DNA reassociation values between strain H642(T), P. halotolerans B2(T) and P. nitratireducens JLT2005(T) were 38.0 and 25.3 %, respectively. The genomic DNA G + C content of strain H642(T) was determined to be 44.4 mol%. Based on genotypic, chemotaxonomic and phenotypic data, strain H642(T) represents a novel species of the genus Pelagibacterium, for which the name Pelagibacterium lixinzhangensis sp. nov is proposed. The type strain is H642(T) (=CGMCC 1.10230(T)=JCM 16597(T)).