Biosynthesis of 3-thia-α-amino acids on a carrier peptide.

A subset of natural products, such as polyketides and nonribosomal peptides, is biosynthesized while tethered to a carrier peptide via a thioester linkage. Recently, we reported that the biosyntheses of 3-thiaglutamate and ammosamide, single amino acid-derived natural products, employ a very different type of carrier peptide to which the biosynthetic intermediates are bound via an amide linkage. During their biosyntheses, a peptide aminoacyl-transfer ribonucleic acid (tRNA) ligase (PEARL) first loads an amino acid to the C terminus of the carrier peptide for subsequent modification by other enzymes. Proteolytic removal of the modified C-terminal amino acid yields the mature product. We termed natural products that are biosynthesized using such pathways pearlins. To investigate the diversity of pearlins, in this study we experimentally characterized another PEARL-encoding biosynthetic gene cluster (BGC) from Tistrella mobilis (tmo). The enzymes encoded in the tmo BGC transformed cysteine into 3-thiahomoleucine both in vitro and in Escherichia coli. During this process, a cobalamin-dependent radical S-adenosylmethionine (SAM) enzyme catalyzes C-isopropylation. This work illustrates that the biosynthesis of amino acid-derived natural products on a carrier peptide is a widespread strategy in nature and expands the spectrum of thiahemiaminal analogs of amino acids that may serve a broader, currently unknown function.

Formulation of biogenic fluorescent pigmented PHB nanoparticles from Rhodanobacter sp. for drug delivery.

Biogenic nanoparticles (NPs) have emerged as promising therapeutic formulations in effective drug delivery. Despite of various positive attributes, these NPs are often conjugated with various cytotoxic organic fluorophores for bioimaging, thereby reducing its effectiveness as a potential carrier. Herein, we aim to formulate biogenic fluorescent pigmented polyhydroxybutyrate (PHB) NPs from Rhodanobacter sp. strain KT31 (OK001852) for drug delivery. The bacterial strain produced 0.5 g L-1 of polyhydroxyalkanoates (PHAs) from 2.04 g L-1 of dry cell weight (DCW) under optimised conditions via submerged fermentation. Further, structural, thermal, and morphological charactersiation of the extracted PHAs was conducted using advance analytical technologies. IR spectra at 1719.25 cm-1 confirmed presence of C = O functional group PHB. NMR and XRD analysis validated the chemical structure and crystallinity of PHB. TG-DTA revealed Tm (168 °C), Td (292 °C), and Xc (35%) of the PHB. FE-SEM imaging indicated rough surface of the PHB film and the biodegradability was confirmed from open windro composting. WST1 assay showed no significant cell death (> 50%) from 100 to 500 µg/mL, endorsing non-cytotoxic nature of PHB. PHB NPs were uniform, smooth and spherical with size distribution and mean zeta potential 44.73 nm and 0.5 mV. IR and XRD peaks obtained at 1721.75 cm-1 and 48.42 Å denoted C = O and crystalline nature of PHB. Cell proliferation rate of PHB NPs was quite significant at 50 µg/mL, establishing the non-cytotoxic nature of NPs. Further, in vitro efficacy of the PHB NPs needs to be evaluated prior to the biomedical applications.

Recent progress in the use of purple non-sulfur bacteria as probiotics in aquaculture.

The use of probiotics in aquaculture is widely recognized as an ecological and cost-effective approach to raising healthy, pathogen-tolerant aquatic animals, including fish and shrimp. In particular for shrimp, probiotics are viewed as a promising countermeasure to the recent severe damage to the shrimp industry by bacterial and viral pathogens. Purple non-sulfur bacteria (PNSB) are Gram-negative, non-pathogenic bacteria with wide application potential in agriculture, wastewater treatment, and bioenergy/biomaterials production. In aquaculture, lactic bacteria and Bacillus are the major probiotic bacteria used, but PNSB, like Rhodopseudomonas and Rhodobacter, are also used. In this review, we summarize the previous work on the use of PNSB in aquaculture, overview the previous studies on the stimulation of innate immunity of shrimp by various probiotic microorganisms, and also share our results in the probiotic performance of Rhodovulum sulfidophilum KKMI01, a marine PNSB, which showed a superior effect in promotion of growth and stimulation of immunity in shrimp at a quite low concentration of 1 × 103 cfu (colony forming unit)/ml in rearing water.

Haematospirillum jordaniae Cellulitis and Bacteremia.

We isolated Haematospirillum jordaniae from a positive blood culture from a 57-year-old man in Slovenia who had bacteremia and bullous cellulitis of lower extremities. The infection was successfully treated with ciprofloxacin. Our findings signal the need for increased awareness about the clinical course of H. jordaniae and its potential effects as a human pathogen.

Intracellular replication of Inquilinus limosus in bronchial epithelial cells.

Inquilinus limosus is an emerging multi-resistant opportunistic pathogen documented mainly in cystic fibrosis patients. Infection with I. limosus is accompanied by either an acute respiratory exacerbation or a progressive loss of pulmonary function. This study examined the interaction of Inquilinus limosus with the bronquial human epithelial cell line 16HBE14o-. Almost 100% of the bacteria that attached to the bronquial cells were found internalized and located in acidic LAMP2 positive compartments. According to confocal studies combined with antibiotic protection assays, I. limosus is able to survive and eventually replicate in these compartments. I. limosus was found nontoxic to cells and did not induce neither IL-6 nor IL-8 cytokine production, a characteristic that may help the bacteria to evade host immune response. Overall, this study indicates that I. limosus displays pathogenic properties based on its ability to survive intracellularly in epithelial cells eventually leading to antibiotic failure and chronic infection.

Chemosynthetic symbiont with a drastically reduced genome serves as primary energy storage in the marine flatworm Paracatenula.

Hosts of chemoautotrophic bacteria typically have much higher biomass than their symbionts and consume symbiont cells for nutrition. In contrast to this, chemoautotrophic Candidatus Riegeria symbionts in mouthless Paracatenula flatworms comprise up to half of the biomass of the consortium. Each species of Paracatenula harbors a specific Ca Riegeria, and the endosymbionts have been vertically transmitted for at least 500 million years. Such prolonged strict vertical transmission leads to streamlining of symbiont genomes, and the retained physiological capacities reveal the functions the symbionts provide to their hosts. Here, we studied a species of Paracatenula from Sant'Andrea, Elba, Italy, using genomics, gene expression, imaging analyses, as well as targeted and untargeted MS. We show that its symbiont, Ca R. santandreae has a drastically smaller genome (1.34 Mb) than the symbiont´s free-living relatives (4.29-4.97 Mb) but retains a versatile and energy-efficient metabolism. It encodes and expresses a complete intermediary carbon metabolism and enhanced carbon fixation through anaplerosis and accumulates massive intracellular inclusions such as sulfur, polyhydroxyalkanoates, and carbohydrates. Compared with symbiotic and free-living chemoautotrophs, Ca R. santandreae's versatility in energy storage is unparalleled in chemoautotrophs with such compact genomes. Transmission EM as well as host and symbiont expression data suggest that Ca R. santandreae largely provisions its host via outer-membrane vesicle secretion. With its high share of biomass in the symbiosis and large standing stocks of carbon and energy reserves, it has a unique role for bacterial symbionts-serving as the primary energy storage for its animal host.

Interaction between Microalgae P. tricornutum and Bacteria Thalassospira sp. for Removal of Bisphenols from Conditioned Media.

We studied the efficiency of three culture series of the microalgae Phaeodactylum tricornutum (P. tricornutum) and bacteria Thalassospira sp. (axenic microalgae, bacterial culture and co-culture of the two) in removing bisphenols (BPs) from their growth medium. Bacteria were identified by 16S ribosomal RNA polymerase chain reaction (16S rRNA PCR). The microorganism growth rate was determined by flow cytometry. Cultures and isolates of their small cellular particles (SCPs) were imaged by scanning electron microscopy (SEM) and cryogenic transmission electron microscopy (Cryo-TEM). BPs were analyzed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). Our results indicate that some organisms may have the ability to remove a specific pollutant with high efficiency. P. tricornutum in axenic culture and in mixed culture removed almost all (more than 99%) of BPC2. Notable differences in the removal of 8 out of 18 BPs between the axenic, mixed and bacterial cultures were found. The overall removals of BPs in axenic P. tricornutum, mixed and bacterial cultures were 11%, 18% and 10%, respectively. Finding the respective organisms and creating microbe societies seems to be key for the improvement of wastewater treatment. As a possible mediating factor, numerous small cellular particles from all three cultures were detected by electron microscopy. Further research on the mechanisms of interspecies communication is needed to advance the understanding of microbial communities at the nano-level.

Arenibaculum pallidiluteum gen. nov., sp. nov., a novel bacterium in the family Azospirillaceae, isolated from desert soil, and reclassification of Skermanella xinjiangensis to a new genus Deserticella as Deserticella xinjiangensis comb. nov., and transfer of the genera Indioceanicola and Oleisolibacter from the family Rhodospirillaceae to the family Azospirillaceae.

A novel pale orange-coloured bacterium, designated strain SYSU D00532T, was isolated from sandy soil collected from the Gurbantunggut desert in Xinjiang, PR China. Cells of strain SYSU D00532T were found to be aerobic, Gram-stain-negative, oxidase-positive, catalase-positive, motile and rod-shaped with a single polar or subpolar flagellum. Growth occurred at 15-45 °C (optimum, 28-37 °C, pH 5.0-8.0 (optimum, pH 6.0-7.0) and with 0-1.5% NaCl (w/v; optimum, 0.5 %). The major polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and phosphatidylglycerol. Unidentified aminolipids, unidentified polar lipids, an unidentified aminophospholipid and an unidentified phospholipid were also detected. The major respiratory quinone was ubiquinone-10 and the major fatty acids were summed feature 8 (C18:1 ω7c and/or C18:1 ω6c), C16:0 and C19:0 cyclo ω8c. The genomic DNA G+C content was 69.8 mol%. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SYSU D00532T belonged to the family Azospirillaceae and showed 93.4% (Desertibacter roseus 2622T), 93.2% (Skermanella xinjiangensis 10-1-101T), 93.2% ('Skermanella rubra' YIM 93097T) and 92.4% (Desertibacter xinjiangensis M71T) similarities. Based on the phylogenetic, phenotypic and chemotaxonomic data, strain SYSU D00532T is proposed to represent a new species of a new genus, named Arenibaculum pallidiluteum gen. nov., sp. nov., within the family Azospirillaceae. The type strain is SYSU D00532T (=KCTC 82269T=CGMCC 1.18631T=MCCC 1K04984T). We also propose the reclassification of Skermanella xinjiangensis to a new genus Deserticella as Deserticella xinjiangensis comb. nov., and the transfer of the genera Indioceanicola and Oleisolibacter from the family Rhodospirillaceae to the family Azospirillaceaewe based on the phylogenetic results.

Biodiversity of magnetotactic bacteria in the tropical marine environment of Singapore revealed by metagenomic analysis.

Most studies on the diversity of magnetotactic bacteria (MTB) have been conducted on samples obtained from the Northern or the Southern hemispheres. The diversity of MTB in tropical Asia near the geo-equator, with a close-to-zero geomagnetic inclination, weak magnetic field and constantly high seawater temperature has never been explored. This study aims to decipher the diversity of MTB in the marine environment of Singapore through shotgun metagenomics. Although MTB has been acknowledged to be ubiquitous in aquatic environments, we did not observe magnetotactic behaviour in the samples. However, we detected the presence and determined the diversity of MTB through bioinformatic analyses. Metagenomic analysis suggested majority of the MTB in the seafloor sediments represents novel MTB taxa that cannot be classified at the species level. The relative abundance of MTB (~0.2-1.69%) in the samples collected from the marine environment of Singapore was found to be substantially lower than studies for other regions. In contrast to other studies, the genera Magnetovibrio and Desulfamplus, but not Magnetococcus, were the dominant MTB. Additionally, we recovered 3 MTB genomic bins that are unclassified at the species level, with Magnetovibrio blakemorei being the closest-associated genome. All the recovered genomic bins contain homologs of at least 5 of the 7 mam genes but lack homologs for mamI, a membrane protein suggested to take part in the magenetosome invagination. This study fills in the knowledge gap of MTB biodiversity in the tropical marine environment near the geo-equator. Our findings will facilitate future research efforts aiming to unravel the ecological roles of MTB in the tropical marine environments as well as to bioprospecting novel MTB that have been adapted to tropical marine environments for biotechnological applications.

Pacificispira spongiicola gen. nov., sp. nov., a nitrate-reducing bacterium isolated from tropical western Pacific.

The Gram-stain-negative, strictly aerobic, curved-to-spiral rod-shaped bacterial strain, designated KN72T, was isolated from the Caroline Seamounts in the Pacific Ocean. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain KN72T was a member of the family Rhodospirillaceae and formed a distinct lineage. Strain KN72T contained ubiquinone-10 as the major respiratory quinone. The polar lipid profiles contained phosphatidylethanolamine, phosphatidylglycerol, one aminolipid and three phospholipids. The predominant cellular fatty acids were C16:0 and summed feature 8 (comprising C18:1ω7c/C18:1ω6c). The strain KN72T displayed highest 16S rRNA gene sequence similarities with Hwanghaeella grinnelliae Gri0909T (92.3%), Marivibrio halodurans ZB80T (91.0%) and Aestuariispira insulae AH-MY2T (90.1%). The DNA G+C content of strain KN72T was 61.1%. Collectively, based on phenotypic, chemotaxonomic, phylogenetic and genomic evidence presented, strain KN72T represents a novel species of a novel genus of the family Rhodospirillaceae, for which the name Pacificispira spongiicola gen. nov., sp. nov. is proposed. The type strain is KN72T (= CGMCC 1.17142T = KCTC 72429T).

Nisaea sediminum sp. nov., a heavy metal resistant bacterium isolated from marine sediment in the East China Sea.

A Gram-negative, rod-shaped, motile and strictly aerobic bacterium, designated NBU1469T, was isolated from marine sediment sampled on Meishan Island located in the East China Sea. Strain NBU1469T grew optimally at temperature of 40 °C, NaCl concentration of 2.0% (w/v) and pH 7.5. Catalase and oxidase activities, H2S production, nitrate reduction and hydrolysis of Tween 20 were positive. Indole, methyl red reaction, urease, hydrolysis of gelatin, starch, casein, Tweens 40, 60 and 80 were negative. The major cellular fatty acids were C16:0, C19:0 cyclo ω8c and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). The only respiratory quinone was ubiquinone-10 (Q-10). The major polar lipids were phosphatidylglycerol, two unidentified amino-phospholipids and two unidentified phospholipids. Comparative analysis of the 16S rRNA gene sequence showed highest similarities to the species with validated name Nisaea nitritireducens DR41_18T (98.1%) and Nisaea denitrificans DR41_21T (97.6%). Phylogenetic analyses indicated that strain NBU1469T formed a distinct lineage with strains Nisaea nitritireducens DR41_18T and Nisaea denitrificans DR41_21T within the genus Nisaea. The average nucleotide identity and digital DNA-DNA hybridization values between strain NBU1469T and related species of genus Nisaea were well below the threshold limit for prokaryotic species delineation. The DNA G + C content was 63.6%. Based on its phenotypic, chemotaxonomic and genotypic data, strain NBU1469T is considered to be a representative of a novel species in the genus Nisaea, for which the name Nisaea sediminum sp. nov. is proposed. The type strain is NBU1469T (=KCTC 82224 T =MCCC 1K04763T).

Purple non-sulfur bacteria technology: a promising and potential approach for wastewater treatment and bioresources recovery.

Shortage of water, energy, and bioresources in the world has led to the exploration of new technologies that achieve resource recovery from wastewater, which has become a new sustainable trend. Photosynthetic non-sulfur bacteria (PNSB), the most ancient photo microorganism, not only treats different wastewater types, but also generates PNSB cells, which are non-toxic bioresources and containing many value-added products. These bioresources can be used as raw materials in the agricultural, food, and medical industries. Therefore, PNSB or PNSB-based wastewater resource recovery technology can be simultaneously used to treat wastewater and produce useful bioresources. Compared with traditional wastewater treatment, this technology can reduce CO2 emissions, promote the N recovery ratio and prevent residual sludge disposal or generation. After being developed for over half a century, PNSB wastewater resource recovery technology is currently extended towards industrial applications. Here, this technology is comprehensively introduced in terms of (1) PNSB characteristics and metabolism; (2) PNSB wastewater treatment and bioresource recovery efficiency; (3) the relative factors influencing the performance of this technology, including light, oxygen, strains, wastewater types, hydraulic retention time, on wastewater treatment, and resource production; (4) PNSB value-added bioresources and their generation from wastewater; (5) the scale-up history of PNSB technology; (6) Finally, the future perspectives and challenges of this technology were also analysed and summarised.

Hypericibacter terrae gen. nov., sp. nov. and Hypericibacter adhaerens sp. nov., two new members of the family Rhodospirillaceae isolated from the rhizosphere of Hypericum perforatum.

Two strains of the family Rhodospirillaceae were isolated from the rhizosphere of the medicinal plant Hypericum perforatum. Cells of both strains were Gram-stain-negative, motile by means of a single polar flagellum, non-spore-forming, non-capsulated, short rods that divided by binary fission. Colonies were small and white. Strains R5913T and R5959T were oxidase-positive, mesophilic, neutrophilic and grew optimally without NaCl. Both grew under aerobic and microaerophilic conditions and on a limited range of substrates with best results on yeast extract. Major fatty acids were C19 : 0 cyclo ω8c and C16 : 0; in addition, C18 : 1ω7c was also found as a predominant fatty acid in strain R5913T. The major respiratory quinone was ubiquinone 10 (Q-10). The DNA G+C contents of strains R5913T and R5959T were 66.0 and 67.4 mol%, respectively. 16S rRNA gene sequence comparison revealed that the closest relatives (<92 % similarity) of the strains are Oceanibaculum pacificum MCCC 1A02656T, Dongia mobilis CGMCC 1.7660T, Dongia soli D78T and Dongia rigui 04SU4-PT. The two novel strains shared 98.6 % sequence similarity and represent different species on the basis of low average nucleotide identity of their genomes (83.8 %). Based on the combined phenotypic, genomic and phylogenetic investigations, the two strains represent two novel species of a new genus in the family Rhodospirillaceae, for which the name Hypericibacter gen. nov. is proposed, comprising the type species Hypericibacter terrae sp. nov. (type strain R5913T=DSM 109816T=CECT 9472T) and Hypericibacter adhaerens sp. nov. (type strain R5959T=DSM 109817T=CECT 9620T).

Skermanella pratensis sp. nov., isolated from meadow soil, and emended description of the genus Skermanella.

A novel Gram-stain-negative, light pink-coloured, short rod-shaped, designated strain W17T, was isolated from a meadow soil sample collected from Xinjiang, PR China. The 16S rRNA gene sequence analysis indicated that strain W17T was related most closely to Skermanella rosea M1T (98.72 %) and Skermanella mucosa 8-14-6T (98.44 %). However, strain W17T showed a low level of DNA-DNA relatedness to S. rosea M1T (32.4±2.6 %) and S. mucosa 8-14-6T (33.5±0.1 %). The genome size of the novel strain was 5.87 Mb and the genomic DNA G+C content was 67.27 mol%. The only respiratory quinone of strain W17T was Q-10. Diphosphatidylglycerol, phosphatidylglycerol. phosphatidylethanolamine and phosphatidylcholine were the major polar lipids. The predominant cellular fatty acids were C18 : 1ω6c and/or C18 : 1ω7c (48.53 %), C16 : 0 (20.88 %) and C18 : 0 (14.92 %). The phylogenetic, phenotypic and chemotaxonomic data showed that strain W17T represents a novel species of the genus Skermanella, for which the name Skermanella pratensis sp. nov. is proposed. The type strain is W17T (=GDMCC 1.1392T=KCTC 62434T).

Ferrovibrio terrae sp. nov., isolated from soil.

Designated strain K5T was isolated from soil on Jeju Island. The bacterium was aerobic, Gram-stain-negative, oxidase-positive, catalase-low activity, motile, short-rod shaped, opaque and formed white colonies that were circular, raised and had entire margins. Strain K5T was able to grow at 15-40 °C, pH 4-9 and at 0-2 % (w/v) NaCl concentration. Phylogenetic analysis based on its 16S rRNA gene sequences indicated that strain K5T is closely related to Ferrovibrio soli A15T (98.9 % sequence similarity), Ferrovibrio denitrificans Sp-1T (98.7 %) and Ferrovibrio xuzhouensis LM-6T (97.4 %). The sole respiratory quinone was determined to be ubiquinone-10. The dominant fatty acids of strain K5T were summed feature 8 (C18 : 1 ω7c / C18 : 1ω6c, 29.8 %), C19 : 0 cyclo ω8c (20.2 %) and C16 : 0 (24.4 %). DNA G+C content was 63.6 % and DNA-DNA relatedness between strain K5T and other three members of the genus Ferrovibrio ranged from 24 to 28 %. The major polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine and aminolipids. Moreover, polyphasic characterization revealed that strain K5T represents a novel species in the genus Ferrovibrio, for which the name Ferrovibrio terrae sp. nov. is proposed. The type strain is K5T (=KCCM 43295T=LMG 30611T).

Denitrobaculum tricleocarpae gen. nov., sp. nov., a marine bacterium from coralline algae Tricleocarpa sp.

A Gram-stain-negative, non-spore-forming, aerobic, motile, curved rod-shaped bacterium, designed strain R148T was isolated from a coralline algae Tricleocarpa sp. collected from Weizhou island, PR China. The optimal growth of R148T occurred at 25 °C, pH 8-9 in the presence of 0.5 % (w/v) NaCl on the basis of amended marine broth 2216. The genomic DNA G+C content was 59.5 mol%. The only detected respiratory quinone was Q-10. The major polar lipids were phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, and three unidentified ninhydrin-positive lipids. The major cellular fatty acids were C18 : 1ω7c, C16 : 1ω7c, C19 : 0cyclo 9, 10 DMA and C18 : 0. The results of 16S rRNA gene-based global alignment indicated that the closest neighbour of strain R148T was Pelagibius litoralis DSM 21314T (93.1 % similarity), the second is Limibacillus halophilus KCTC 42420T (92.2 %). The results of phylogenetic analysis indicated that R148T forms a distinct branch in the robust clade of R148T and P. litoralis DSM 21314T, while the taxonomic position of this clade in the family Rhodospirillaceae is ambiguous among phylogenetic approaches. The low 16S rRNA gene similarity and distinct polar lipid and cellular fatty acid profile could readily distinguish R148T from closely related type strains. So R148T is suggested to represent a novel species in a novel genus, for which the name Denitrobaculum tricleocarpae gen. nov., sp. nov. is proposed. The type strain is R148T (=MCCC 1K03781T=KCTC 72137T).

Oleiliquidispirillum nitrogeniifigens gen. nov., sp. nov., a new member of the family Rhodospirillaceae isolated from oil reservoir water.

A novel Gram-staining-negative, spiral-shaped bacterium, designated strain 64-1T, was isolated from oil reservoir water collected from Liaohe oilfield, north-eastern China. Growth occurred at 15-55 °C and pH 6.0-10.0. The sole respiratory quinone was Q-10. The predominant cellular fatty acids were summed feature 8 (C18 : 1 ω7c /C18 : 1 ω6c), C16 : 0 and C19 : 0 cyclo ω8c. The polar lipids consisted of phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylcholine (PC), an unidentified aminophospholipid (UAPL), an unidentified aminolipid (UAL) and two unidentified polar lipids (UPL). The genomic DNA G+C content of strain 64-1T was 64.5 mol%. Strain 64-1T shared the highest 16S rRNA gene sequence similarities with Phaeospirillum chandramohanii JA145T (92.0 %) and Telmatospirillum siberiense 26-4b1T (91.8 %). In the phylogenetic trees, the strain constituted a sub-cluster within the family Rhodospirillaceae. Based on the results of morphological, physiological, biochemical and phylogenetic analysis, strain 64-1T represents a new species of a novel genus within the family Rhodospirillaceae, for which the name Oleiliquidispirillum nitrogeniifigens gen. nov., sp. nov. is proposed. The type strain is 64-1T (=CGMCC 1.16798T=LMG 31399T).

Benchmark and performance of long-range corrected time-dependent density functional tight binding (LC-TD-DFTB) on rhodopsins and light-harvesting complexes.

The chromophores of rhodopsins (Rh) and light-harvesting (LH) complexes still represent a major challenge for a quantum chemical description due to their size and complex electronic structure. Since gradient corrected and hybrid density functional approaches have been shown to fail for these systems, only range-separated functionals seem to be a promising alternative to the more time consuming post-Hartree-Fock approaches. For extended sampling of optical properties, however, even more approximate approaches are required. Recently, a long-range corrected (LC) functional has been implemented into the efficient density functional tight binding (DFTB) method, allowing to sample the excited states properties of chromophores embedded into proteins using quantum mechanical/molecular mechanical (QM/MM) with the time-dependent (TD) DFTB approach. In the present study, we assess the accuracy of LC-TD-DFT and LC-TD-DFTB for rhodopsins (bacteriorhodopsin (bR) and pharaonis phoborhodopsin (ppR)) and LH complexes (light-harvesting complex II (LH2) and Fenna-Matthews-Olson (FMO) complex). This benchmark study shows the improved description of the color tuning parameters compared to standard DFT functionals. In general, LC-TD-DFTB can exhibit a similar performance as the corresponding LC functionals, allowing a reliable description of excited states properties at significantly reduced cost. The two chromophores investigated here pose complementary challenges: while huge sensitivity to external field perturbation (color tuning) and charge transfer excitations are characteristic for the retinal chromophore, the multi-chromophoric character of the LH complexes emphasizes a correct description of inter-chromophore couplings, giving less importance to color tuning. None of the investigated functionals masters both systems simultaneously with satisfactory accuracy. LC-TD-DFTB, at the current stage, although showing a systematic improvement compared to TD-DFTB cannot be recommended for studying color tuning in retinal proteins, similar to some of the LC-DFT functionals, because the response to external fields is still too weak. For sampling of LH-spectra, however, LC-TD-DFTB is a viable tool, allowing to efficiently sample absorption energies, as shown for three different LH complexes. As the calculations indicate, geometry optimization may overestimate the importance of local minima, which may be averaged over when using trajectories. Fast quantum chemical approaches therefore may allow for a direct sampling of spectra in the near future.

The Influence of Food Intake Specificity in Children with Autism on Gut Microbiota.

Autism spectrum disorder (ASD) is a complex of neurodevelopmental conditions with increasing incidence. The microbiota of children with ASD is distinct from neurotypical children, their food habits are also different, and it is known that nutrient intake influences microbiota in a specific way. Thus, this study investigates the food habits of children with ASD and their association with the gut microbiota. Children with ASD had their dietary energy intakes similar to controls, but they more often demonstrated food selectivity, which seemed to result in deficiency of micronutrients such as vitamins K, B6, C, iron, cooper, docosahexaenoic and docosapentanoic acid. Using high-throughput sequencing, a DNA library of intestinal microbiota was performed. Core microbiota was similar in children with and without ASD, but Dichelobacter, Nitriliruptor and Constrictibacter were found to be putative markers of ASD. The changes in gut microbiota that we observed in connection to food selectivity, intake of fats and omega-3 in particular, fermented milk products and animal/plant protein consumption had similar character, independent of diagnosis. However, high fibre intake was connected with a decreased α-diversity only in children with ASD. High carbohydrate and fibre intake influenced ß-diversity, changing the abundance of Bacteroides and other genera, many of them members of the Clostidiaceae. Modulating food habits of ASD children can influence their gut microbiota composition.

Genomic evidence of the illumination response mechanism and evolutionary history of magnetotactic bacteria within the Rhodospirillaceae family.

BACKGROUND: Magnetotactic bacteria (MTB) are ubiquitous in natural aquatic environments. MTB can produce intracellular magnetic particles, navigate along geomagnetic field, and respond to light. However, the potential mechanism by which MTB respond to illumination and their evolutionary relationship with photosynthetic bacteria remain elusive. RESULTS: We utilized genomes of the well-sequenced genus Magnetospirillum, including the newly sequenced MTB strain Magnetospirillum sp. XM-1 to perform a comprehensive genomic comparison with phototrophic bacteria within the family Rhodospirillaceae regarding the illumination response mechanism. First, photoreceptor genes were identified in the genomes of both MTB and phototrophic bacteria in the Rhodospirillaceae family, but no photosynthesis genes were found in the MTB genomes. Most of the photoreceptor genes in the MTB genomes from this family encode phytochrome-domain photoreceptors that likely induce red/far-red light phototaxis. Second, illumination also causes damage within the cell, and in Rhodospirillaceae, both MTB and phototrophic bacteria possess complex but similar sets of response and repair genes, such as oxidative stress response, iron homeostasis and DNA repair system genes. Lastly, phylogenomic analysis showed that MTB cluster closely with phototrophic bacteria in this family. One photoheterotrophic genus, Phaeospirillum, clustered within and displays high genomic similarity with Magnetospirillum. Moreover, the phylogenetic tree topologies of magnetosome synthesis genes in MTB and photosynthesis genes in phototrophic bacteria from the Rhodospirillaceae family were reasonably congruent with the phylogenomic tree, suggesting that these two traits were most likely vertically transferred during the evolution of their lineages. CONCLUSION: Our new genomic data indicate that MTB and phototrophic bacteria within the family Rhodospirillaceae possess diversified photoreceptors that may be responsible for phototaxis. Their genomes also contain comprehensive stress response genes to mediate the negative effects caused by illumination. Based on phylogenetic studies, most of MTB and phototrophic bacteria in the Rhodospirillaceae family evolved vertically with magnetosome synthesis and photosynthesis genes. The ancestor of Rhodospirillaceae was likely a magnetotactic phototrophic bacteria, however, gain or loss of magnetotaxis and phototrophic abilities might have occurred during the evolution of ancestral Rhodospirillaceae lineages.