Devosia aquimaris sp. nov., isolated from seawater of the Changjiang River estuary of China.

A gram-stain-negative, aerobic, rod-shaped bacterium strain CJK-A8-3T was isolated from a polyamine-enriched seawater sample collected from the Changjiang River estuary of China. The colonies were white and circular. Strain CJK-A8-3T grew optimally at 35 °C, pH 7.0 and 1.5% NaCl. Its polar lipids contained phosphatidylglycerol, phosphatidic acid, unidentified glycolipids, and a combination of phospholipids and glycolipids. The respiratory quinone was ubiquinone-10, and its main fatty acids were C16:0, 11-methyl C18:1ω7c and Summed Feature 8 (including C18:1ω7c/C18:1ω6c). The phylogenetic tree based on 16S rRNA genes placed strain CJK-A8-3T in a new linage within the genus Devosia. 16S rRNA gene sequence of strain CJK-A8-3T showed identities of 98.50% with Devosia beringensis S02T, 98.15% with D. oryziradicis, and 98.01% with D. submarina JCM 18935T. The genome size of strain CJK-A8-3T was 3.81 Mb with the DNA G + C content 63.9%, higher than those of the reference strains (60.4-63.8%). The genome contained genes functional in the metabolism of terrigenous aromatic compounds, alkylphosphonate and organic nitrogen, potentially beneficial for nutrient acquirement and environmental remediation. It also harbored genes functional in antibiotics resistance and balance of osmotic pressure, enhancing their adaptation to estuarine environments. Both genomic investigation and experimental verification showed that strain CJK-A8-3T could be versatile and efficient to use diverse organic nitrogen compounds as carbon and nitrogen sources. Based on phenotypic, chemotaxonomic, phylogenetic and genomic characteristics, strain CJK-A8-3T was identified as a novel Devosia species, named as Devosia aquimaris sp. nov. The type strain is CJK-A8-3T (= MCCC 1K06953T = KCTC 92162T).

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.

Characterization of regioisomeric diterpenoid tails in bacteriochlorophylls produced by geranylgeranyl reductase from Halorhodospira halochloris and Blastochloris viridis.

Geranylgeranyl reductase (GGR) encoded by the bchP gene catalyzes the reductions of three unsaturated C = C double bonds (C6 = C7, C10 = C11, and C14 = C15) in a geranylgeranyl (GG) group of the esterifying moiety in 17-propionate residue of bacteriochlorophyll (BChl) molecules. It was recently reported that GGR in Halorhodospira halochloris potentially catalyzes two hydrogenations, yielding BChl with a tetrahydrogeranylgeranyl (THGG) tail. Furthermore, its engineered GGR, in which N-terminal insertion peptides characteristic for H. halochloris were deleted, performed single hydrogenation, producing BChl with a dihydrogeranylgeranyl (DHGG) tail. In some of these enzymatic reactions, it remained unclear in which order the C = C double bond in a GG group was first reduced. In this study, we demonstrated that the (variant) GGR from H. halochloris catalyzed an initial reduction of the C6 = C7 double bond to yield a 6,7-DHGG tail. The intact GGR of H. halochloris catalyzed the further hydrogenation of the C14 = C15 double bonds to give a 6,7,14,15-THGG group, whereas deleting the characteristic peptide region from the GGR suppressed the C14 = C15 reduction. We also verified that in a model bacterium, Blastochloris viridis producing standard BChl-b, the reduction of a GG to phytyl group occurred via 10,11-DHGG and 6,7,10,11-THGG. The high-performance liquid chromatographic elution profiles of BChls-a/b employed in this study are essential for identifying the regioisomeric diterpenoid tails in the BChls of phototrophic bacteria distributed in nature and elucidating GGR enzymatic reactions.

Complete genome sequence of Devosia beringensis S02T, a type strain with genes involved in deoxynivalenol degradation.

Members of the genus Devosia are known for their abilities to degrade deoxynivalenol (DON). The type strain Devosia beringensis S02T (= JCM 33772 = CCTCC AB 2019343) was isolated from sediment of the Bering Sea and identified in 2021. However, the genome sequence of D. beringensis S02T remains unclear, which complicates the exploration into the function and ecological role of this strain in marine sediment. The genome of D. beringensis S02T contained a 4,048,765 bp chromosome with a G + C content of 63.84 mol%. Potential genes involved in DON degradation were found in the genome. In addition, multiple genes involved in polysaccharide degradation, including agarose, chitin, carrageen, pectate, starch, and xylan, were also annotated in the genome. These findings indicated the potential of strain S02T to be used for DON degradation and its ecological function in the carbon cycle in marine sediment.

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 salina sp. nov., isolated from South China Sea sediment.

An aerobic, Gram-stain-negative, rod-shaped and motile strain, designated SCS-3T, was isolated from deep-sea sediment of the South China Sea. Phylogenetic analysis based on the 16S rRNA gene sequence similarities revealed that strain SCS-3T represented a novel species of the genus Devosia, with closely related strains 'Devosia sediminis' MSA67T (98.61 %), Devosia riboflavina IFO13584T (98.22 %) and Devosia indica IO390501T (97.72 %). The G+C content of the genomic DNA is 63.44 mol%. The digital DNA-DNA hybridization values with 'D. sediminis' MSA67T, D. riboflavina IFO13584T and D. indica IO390501T were 24.50, 21.8 and 24.80 %, respectively. The major polar lipids of strain SCS-3T were diphosphatidylglycerol, phosphatidylglycerol and three unidentified glycolipids. Ubiquinone-10 was the sole isoprenoid quinone, and C16 : 0, C18 : 1 ω7c 11-methyl and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) were the major fatty acids. Based on polyphasic taxonomic data, strain SCS-3T represents a novel species of the genus Devosia, for which the name Devosia salina sp. nov. is proposed. The type strain is SCS-3T (=JCM 34403T=GDMCC 1.2221T).

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).

Structure of the Cell-Wall-Associated Polysaccharides from the Deep-Sea Marine Bacterium Devosia submarina KMM 9415T.

Two cell-wall-associated polysaccharides were isolated and purified from the deep-sea marine bacterium Devosia submarina KMM 9415T, purified by ultracentrifugation and enzymatic treatment, separated by chromatographic techniques, and studied by sugar analyses and NMR spectroscopy. The first polysaccharide with a molecular weight of about 20.7 kDa was found to contain d-arabinose, and the following structure of its disaccharide repeating unit was established: →2)-α-d-Araf-(1→5)-α-d-Araf-(1→. The second polysaccharide was shown to consist of d-galactose and a rare component of bacterial glycans-d-xylulose: →3)-α-d-Galp-(1→3)-ß-d-Xluf-(1→.

Devosia equisanguinis sp. nov., isolated from horse blood.

A Gram-stain-negative, aerobic, non-endospore-forming organism isolated from horse blood was studied for its taxonomic allocation. On the basis of 16S rRNA gene sequence similarity comparisons, strain M6-77T grouped within the genus Devosia and was most closely related to Devosia elaeis (97.6 %) and Devosia indica (97.55 %). The 16S rRNA gene sequence similarity to type strains of other Devosia species was below 97.5 %. The average nucleotide identity and digital DNA-DNA hybridization values between the M6-77T genome assembly and those of the closest relative Devosia type strains were <85 and <25 %, respectively. Strain M6-77T grew optimally at 25-37 °C (range: 10-36 °C), at a pH range of pH 6.5-10.5 and in the presence of up to 3 % (w/v) NaCl. The fatty acid profile from whole-cell hydrolysates supported the allocation of the strain to the genus Devosia. Major fatty acids were C18 : 1 ω7c, 11-methyl C18 : 1 ω7c and C16 : 0. The quinone system consisted exclusively of ubiquinone Q-10. The polar lipid profile was composed of the major lipids diphosphatidylglycerol, phosphatidylglycerol and three unidentified glycolipids. In the polyamine pattern, putrescine was predominant and spermidine was detected in moderate amounts. The diamino acid of the peptidoglycan was meso-diaminopimelic acid. In addition, the results of physiological and biochemical tests also allowed phenotypic differentiation of strain M6-77T from the closely related species. Hence, M6-77T represents a new species of the genus Devosia, for which we propose the name Devosia equisanguinis sp. nov., with M6-77T (=CIP 111628T=LMG 30659T=CCM 8868T) as the type strain.

Hyphomicrobium album sp. nov., isolated from mountain soil and emended description of genus Hyphomicrobium.

A soil bacterium, designated XQ2T, was isolated from Lang Mountain in Hunan province, P. R. China. The strain is Gram stain negative, facultative anaerobic, and the cells are motile and rod-shaped. The 16S rRNA gene sequence of strain XQ2T shared the highest similarities with Hyphomicrobium sulfonivorans S1T (97.1%), Pedomicrobium manganicum ACM 3038T (95.9%) and Hyphomicrobium aestuarii DSM 1564T (95.4%) and grouped with H. sulfonivorans S1T. The average nucleotide identity (ANI) values and the DNA-DNA hybridization (dDDH) values between strain XQ2T and H. sulfonivorans S1T were 86.6% and 55.4% respectively. Strain XQ2T had a genome size of 3.91 Mb and the average G+C content was 65.1%. The major fatty acids (> 5%) were C18:1ω6c, C18:1ω7c, C19:0 cyclo ω8c, C16:0 and C18:0. The major respiratory quinone was Q-9 (82.8%) and the minor one was Q-8 (17.2%). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, unidentified phospholipid and two unidentified lipids. On the basis of phenotypic, chemotaxonomic and phylogenetic characteristics, strain XQ2T represents a novel species of the genus Hyphomicrobium, for which the name Hyphomicrobium album sp. nov. is proposed. The type strain is XQ2T (= KCTC 82378T = CCTCC AB 2020178T). The genus description is also emended.

Structural and catalytic characterization of Blastochloris viridis and Pseudomonas aeruginosa homospermidine synthases supports the essential role of cation-π interaction.

Polyamines influence medically relevant processes in the opportunistic pathogen Pseudomonas aeruginosa, including virulence, biofilm formation and susceptibility to antibiotics. Although homospermidine synthase (HSS) is part of the polyamine metabolism in various strains of P. aeruginosa, neither its role nor its structure has been examined so far. The reaction mechanism of the nicotinamide adenine dinucleotide (NAD+)-dependent bacterial HSS has previously been characterized based on crystal structures of Blastochloris viridis HSS (BvHSS). This study presents the crystal structure of P. aeruginosa HSS (PaHSS) in complex with its substrate putrescine. A high structural similarity between PaHSS and BvHSS with conservation of the catalytically relevant residues is demonstrated, qualifying BvHSS as a model for mechanistic studies of PaHSS. Following this strategy, crystal structures of single-residue variants of BvHSS are presented together with activity assays of PaHSS, BvHSS and BvHSS variants. For efficient homospermidine production, acidic residues are required at the entrance to the binding pocket (`ionic slide') and near the active site (`inner amino site') to attract and bind the substrate putrescine via salt bridges. The tryptophan residue at the active site stabilizes cationic reaction components by cation-π interaction, as inferred from the interaction geometry between putrescine and the indole ring plane. Exchange of this tryptophan for other amino acids suggests a distinct catalytic requirement for an aromatic interaction partner with a highly negative electrostatic potential. These findings substantiate the structural and mechanistic knowledge on bacterial HSS, a potential target for antibiotic design.

Devosia beringensis sp. nov., isolated from surface sediment of the Bering Sea.

Strain S02T was isolated from a surface sediment sample collected from the Bering Sea (64.3361° N, 170.9541° W). The cells were Gram-stain-negative, motile and rod-shaped. The temperature range for growth was 4-25 °C and the pH for growth was 5.5-9.0, with optimum growth occurring at 20-25 °C and pH 7.0-8.0. Growth occurred in the presence of 0-7 % (w/v) NaCl (optimum, 2-5 %). Strain S02T had menaquinone-8 as the major respiratory quinone and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C16:0, C17 : 0 cyclo, summed feature 3 (C16 : 1 ω7c /C16 : 1 ω7c), C17 : 0 and C18 : 0 as major fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and two glycolipids. The genomic DNA G+C content was approximately 63.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S02T belonged to the genus Devosia. Strain S02T showed the highest sequence similarities to Devosia psychrophila Cr7-05T (97.5 %), Devosia naphthalenivorans CM5-1T (97.7 %), Devosia submarina KMM 9415T (97.4 %), Devosia epidermidihirudinis E84T (97.44 %), Devosia euplotis LIV5T (97.1 %) and Devosia limi DSM 17137T (96.7 %). On the basis of phylogenetic analyses and phenotypic characteristics, a novel species of the genus Devosia, Devosia beringensis sp. nov., is proposed, with the type strain S02T (=JCM 33772=CCTCC AB 2019343).

Genomic diversity, life strategies and ecology of marine HTVC010P-type pelagiphages.

SAR11 bacteria dominate ocean surface bacterioplankton communities, and play an important role in marine carbon and nutrient cycling. The biology and ecology of SAR11 are impacted by SAR11 phages (pelagiphages) that are highly diverse and abundant in the ocean. Among the currently known pelagiphages, HTVC010P represents an extremely abundant but under-studied phage group in the ocean. In this study, we have isolated seven new HTVC010P-type pelagiphages, and recovered 77 nearly full-length HTVC010P-type metagenomic viral genomes from marine metagenomes. Comparative genomic and phylogenomic analyses showed that HTVC010P-type pelagiphages display genome synteny and can be clustered into two major subgroups, with subgroup I consisting of strictly lytic phages and subgroup II mostly consisting of phages with potential lysogenic life cycles. All but one member of the subgroup II contain an integrase gene. Site-specific integration of subgroup II HTVC010P-type pelagiphage was either verified experimentally or identified by in silico genomic sequence analyses, which revealed that various SAR11 tRNA genes can serve as the integration sites of HTVC010P-type pelagiphages. Moreover, HTVC010P-type pelagiphage integration was confirmed by the detection of several Global Ocean Survey (GOS) fragments that contain hybrid phage-host integration sites. Metagenomic recruitment analysis revealed that these HTVC010P-type phages were globally distributed and most lytic subgroup I members exhibited higher relative abundance. Altogether, this study significantly expands our knowledge about the genetic diversity, life strategies and ecology of HTVC010P-type pelagiphages.

Description of Devosia faecipullorum sp. nov., harboring antibiotic- and toxic compound-resistace genes, isolated from poultry manure.

A polyphasic taxonomic approach was used to characterize a Gram-stain-negative bacterium, designated strain CC-YST696T, harbouring antibiotic- and toxic compound-resistace genes, isolated from poultry manure in Taiwan. Cells of CC-YST696T were short rods, motile with polar flagella, catalase- and oxidase-positive. Optimal growth occurred at 30 °Ð¡, pH 9 and with 1 % NaCl. The results of phylogenetic analyses based on 16S rRNA genes revealed a distinct taxonomic position attained by CC-YST696T associated with Devosia chinhatensis (97.9 % sequence identity), Devosia riboflavina (97.3 %) and Devosia indica (97.2 %), and with lower sequence similarity values to other species. Average nucleotide identity (ANI) values were 72.8-80.0 % (n=17) compared within the type strains of species of of the genus Devosia. CC-YST696T contained C16:0, C18:0, C18:1ω7c 11-methyl and C18:1ω6c/ C18:1ω7c as the predominant fatty acids. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids, three unidentified glycolipids, two unidentified phospholipids and three unidentified lipids. The DNA G+C content was 62.2 mol% and the predominant quinone was ubiquinone Q-10. On the basis of its distinct phylogenetic, phenotypic and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence and ANI analyses, strain CC-YST696T is proposed to represent a novel species of the genus Devosia, for which the name Devosia faecipullorum sp. nov. (type strain CC-YST696T=BCRC 81284T=JCM 34167T) is proposed.

Devosia sediminis sp. nov., isolated from subterranean sediment.

A novel Gram-negative, cream-colored, rod-shaped, aerobic, non-motile bacterium, designated MSA67T, was isolated from a subterranean sediment sample of the Mohe Basin in Northeast China. Strain MSA67T was detected to grow at 4-40 °C (optimum 28-30 °C), pH 5.0-10.0 (optimum, pH 7.0) and in 0.0-8.0% (w/v) NaCl (optimum 2.0-3.0%). Phylogenetic analysis based on 16S rRNA gene sequence revealed that strain MSA67T was a member of the genus Devosia, with the highest similarity with D. riboflavina IFO13584T (98.0%) and D. chinhatensis IPL18T (97.0%). The major cellular fatty acids are C16:0, C18:1ω7c 11-methyl and C18:1ω6c and/or C18:1ω7c. The major polar lipids are diphosphatidylglycerol, phosphatidylglycerol, glycolipids and three unidentified phospholipids. The major respiratory quinone is ubiquinone 10 (Q-10). The genomic size of strain MSA67T is 4.1 MB and DNA G + C content is 63.6%. Based on genotypic, phenotypic and phylogenetic results, strain MSA67T is concluded to represent a novel species of the genus Devosia, for which the name Devosia sediminis sp. nov. is proposed. The type strain is MSA67T (= CGMCC 1.18467T = KCTC 82192T).

Devosia aurantiaca sp. nov., Isolated from Mountain Soil and Proposal of Albitalea gen. nov. to Replace the Illegitimate Prokaryotic Genus Name Geomonas Khan et al. 2020.

Strain H239T, a gram-negative, strictly aerobic, and oxidase-positive, and catalase-negative bacterium, was isolated from mountain soil in Gangwon-do of South Korea. Colonies were orange colored, and cells were motile rods with a single polar flagellum. Growth was observed between 25 and 30 °C (optimum, 30 °C), between pH 7.0 and pH 9.0 (optimum, pH 7.5), and in the presence of 0-1.5% (w/v) NaCl (optimum 0.5-1%). Ubiquinone-10 was detected as the sole respiratory quinone. The major fatty acids (>10%) of strain H239T were C18:1 ω7c, C18:0, and C16:0. The polar lipids detected from strain H239T consisted of two unidentified glycolipids, two unidentified phospholipids, and three unidentified polar lipids. The G+C content of strain H239T based on its genome sequence was 62.0 mol%. Comparative 16S rRNA gene sequence analysis indicated that strain H239T was most closely related to Devosia chinhatensis IPL18T (97.7%), Devosia submarina KMM 9415T (97.7%), and Devosia yakushimensis Yak96BT (97.3%). Phylogenetic analyses based on the 16S rRNA gene and whole-genome sequences revealed that strain H239T formed a distinct phyletic lineage as a new species within the genus Devosia. Based on its physiological, chemotaxonomic, and molecular properties, strain H239T represents a novel species of the genus Devosia, for which the name Devosia aurantiaca sp. nov. is proposed. The type strain is H239T (=KACC 21662T=JCM 33930T). In addition, because the prokaryotic genus name Geomonas Khan et al. 2020 is a later homonym of Geomonas Xu et al. 2020, the name is illegitimate (Principle 6 in the International Code of Nomenclature of Prokaryotes). Therefore, we propose to replace the problematic prokaryotic names Geomonas and Geomonas soli with Albitalea with Albitalea terrae, respectively.

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.

Different co-occurring bacteria enhance or decrease the growth of the microalga Nannochloropsis sp. CCAP211/78.

Marine photosynthetic microalgae are ubiquitously associated with bacteria in nature. However, the influence of these bacteria on algal cultures in bioreactors is still largely unknown. In this study, eighteen different bacterial strains were isolated from cultures of Nannochloropsis sp. CCAP211/78 in two outdoor pilot-scale tubular photobioreactors. The majority of isolates was affiliated with the classes Alphaproteobacteria and Flavobacteriia. To assess the impact of the eighteen strains on the growth of Nannochloropsis sp. CCAP211/78, 24-well plates coupled with custom-made LED boxes were used to simultaneously compare replicate axenic microalgal cultures with addition of individual bacterial isolates. Co-culturing of Nannochloropsis sp. CCAP211/78 with these strains demonstrated distinct responses, which shows that the technique we developed is an efficient method for screening the influence of harmful/beneficial bacteria. Two of the tested strains, namely a strain of Maritalea porphyrae (DMSP31) and a Labrenzia aggregata strain (YP26), significantly enhanced microalgal growth with a 14% and 12% increase of the chlorophyll concentration, respectively, whereas flavobacterial strain YP206 greatly inhibited the growth of the microalga with 28% reduction of the chlorophyll concentration. Our study suggests that algal production systems represent a 'natural' source to isolate and study microorganisms that can either benefit or harm algal cultures.

Pelagibacterium limicola sp. nov., isolated from a soda alkali-saline soil.

A Gram-staining negative, motile, non-spore-forming, rod-shaped bacterium, designated NAJP-14T, was isolated from the alkali-saline soil in Heilongjiang, Northeast China. Phylogenetic analysis based on 16S rRNA gene sequencing illustrated that strain NAJP-14T was a member of the genus Pelagibacterium, and shared 94.6-96.6% sequence identities to species from the genus Pelagibacterium. Strain NAJP-14T grew at 20-45 °C (optimum, 30 °C), pH 7.0-10.0 (optimum, pH 8.0) and in the presence of up to 5% w/v NaCl. The menaquinone was determined to be Q (10). The major fatty acids were identified as C18:1w6c (38.7%), C16:0 (16.2%) and C19:0 cyclo w8c (13.9%). The G + C content of the genomic DNA was 61.2%. Out of the 3442 predicted genes, 3391 were protein-coding genes and 51 were ncRNA. Digital DNA-DNA hybridization (dDDH) estimation and average nucleotide identity (ANI) of the strain NAJP-14T and the type strains of related species in the same family ranged between 17.9 and 21.8% and between 61.4 and 78.7%, respectively. Based on these data, it is concluded that strain NAJP-14T possesses sufficient characteristics to differentiate it from all recognized Pelagibacterium species, and should be considered as a novel species for which the name Pelagibacterium limicola sp. nov. is proposed. The type strain is NAJP-14T (= CGMCC 1.16631T, = JCM 33746T).

Hongsoonwoonella zoysiae gen. nov., sp. nov., a new member of the family Stappiaceae isolated from a tidal mudflat.

A Gram stain-negative bacterial strain, designated SY4-7T, was isolated from rhizosphere mudflat of a halophyte (Zoysia sinica) collected around Seonyu Island, Republic of Korea. Cells of the organism were strictly aerobic, non-sporulating, non-motile rods and grew at 20-42 °C, pH 6-8 and 1-6% (w/v) NaCl. The 16S rRNA gene-based phylogenetic analyses revealed that strain SY4-7T formed an independent cluster separated from the recognized genera of the family Stappiaceae, which was also supported by phylogenomic analysis-based 92-core gene sequences. The type stains of the phylogenetically closest relatives were Stappia indica (95.6% sequence similarity), Stappia stellulata (95.1%) and Roseibium hamelinense (95.1%). The isoprenoid quinone was Q-10. The polar lipids consisted of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, three unidentified aminophospholipids, an unidentified phosphoglycolipid, an unidentified aminolipid, two unidentified phospholipids and an unidentified lipid. The major cellular fatty acids are C18:1ω7c and C19:1 cyclo ω8c. The G + C content of the genomic DNA is 60.7%. Discrimination of the organism from all the recognized genera of the family Stappiaceae was apparent by the chemotaxonomic and phylogenetic features. Based on the results presented here, strain SY4-7T (= KCTC 72226T = NBRC 113902T) represents a novel species of a new genus in the family Stappiaceae, for which the name Hongsoonwoonella zoysiae sp. nov. is proposed.