Genetic structure of expanding wolf (Canis lupus) populations in Italy and Croatia,and the early steps of the recolonization of the Eastern Alps

After centuries of range contraction and demographic declines wolves are now expanding in Europe, colonizing regions from where they have been absent for centuries. Wolf colonizing the western Alps originate by the expansion of the Italian population. Vagrant wolves of Italian and Dinaric-Balkan origins have been recently observed in the Eastern Alps. In this study we compared the genetic structure of wolf populations in Italy and Croatia, aiming to identify the sources of the ongoing recolonization of the Eastern Alps. DNA samples, extracted from 282 Italian and 152 Croatian wolves, were genotyped at 12 autosomal microsatellites (STR), four Y-linked STR and at the hypervariable part of the mitochondrial DNA control-region (mtDNA CR1). Wolves in Croatia and Italy underwent recent demographic bottlenecks, but they differ in genetic diversity and population structure. Wolves in Croatia were more variable at STR loci (N_A = 7.4, H_O = 0.66, H_E = 0.72; n = 152) than wolves in Italy (N_A = 5.3, H_O = 0.57, H_E = 0.58; n = 282). We found four mitochondrial DNA (mtDNA CR1) and 11 Y-STR haplotypes in Croatian wolves, but only one mtDNA CR1 and three Y-STR haplotypes in Italy. Wolves in Croatia were subdivided into three genetically distinct subpopulations (in Dalmatia, Gorski kotar and Lika regions), while Italian wolves were not sub-structured. Assignment testing shows that the eastern and central Alps are recolonized by wolves dispersing from both the Italian and Dinaric populations. The recolonization of the Alps will predictably continue in the future and the new population will be genetically admixed and very variable with greater opportunities for local adaptations and survival.     

A probability distribution model of small -scale species richness in plant communities

We devised a probability distribution model that best expressed species richness per quadrat in grassland communities, and clarified the mechanism by which the mean richness per quadrat was always larger than the variance among quadrats. Our model will aid in the understanding of community structures, and allow comparisons among different communities. The model was constructed based on relatively simple theoretical assumptions about the mechanisms in play in target communities. We assumed in the model that the number of species occurring in an actual quadrat, j, is the sum of “the fundamental number of species”, k (constant), and “a fluctuating number of species”, i (a Poisson variate with the mean of μ); that is, j = k + i, where i, j and k are non-negative integers. The probability that j species occur in a quadrat is given by a Poisson-like distribution (extended Poisson), with two parameters k and μ. The mean species richness in the probability distribution is expressed by λ (= k + μ), and the variance is λ − k. The proposed model afforded a good fit for the observed frequency distribution of species richness per quadrat. If even one species is common among many quadrats, the mean number of species per quadrat is greater than the variance. The greater the number of common species among quadrats is, the larger is the value of k, and then the more pronounced is the difference between the mean and the variance (although the variance does not change). We fitted the model to 55 datasets collected by ourselves from grasslands in various locations (Tibet, Inner Mongolia, Slovakia, or Japan), with varying quadrat size (0.25, 0.0625, or 0.01 m²), and under differing management status (various stocking densities).     

Prevalence of the microsporidian Nosema ceranae in honeybee (Apis mellifera) apiaries in Central Italy

Nosema ceranae and Nosema apis are microsporidia which play an important role in the epidemiology of honeybee microsporidiosis worldwide. Nosemiasis reduces honeybee population size and causes significant losses in honey production. To the best of our knowledge, limited information is available about the prevalence of nosemiasis in Italy. In this research, we determined the occurrence of Nosema infection in Central Italy. Thirty-eight seemingly healthy apiaries (2 to 4 hives each) were randomly selected and screened from April to September 2014 (n = 11) or from May to September 2015 (n = 27). The apiaries were located in six areas of Central Italy, including Lucca (n = 11), Massa Carrara (n = 9), Pisa (n = 9), Leghorn (n = 7), Florence (n = 1), and Prato (n = 1) provinces. Light microscopy was carried out according to current OIE recommendations to screen the presence of microsporidiosis in adult worker honeybees. Since the morphological characteristics of N. ceranae and N. apis spores are similar and can hardly be distinguished by optical microscopy, all samples were also screened by multiplex polymerase chain reaction (M-PCR) assay based on 16S rRNA-gene-targeted species-specific primers to differentiate N. ceranae from N. apis. Furthermore, PCR-positive samples were also sequenced to confirm the species of amplified Nosema DNA. Notably, Nosema spores were detected in samples from 24 out of 38 (63.2%, 95% CI: 47.8–78.5%) apiaries. Positivity rates in single provinces were 10/11, 8/9, 3/9, 1/7, or 1/1 (n = 2). A full agreement (Cohen's Kappa = 1) was assessed between microscopy and M-PCR. Based on M-PCR and DNA sequencing results, only N. ceranae was found. Overall, our results highlighted that N. ceranae infection occurs frequently in the cohort of honeybee populations that was examined despite the lack of clinical signs. These findings suggest that colony disease outbreaks might result from environmental factors that lead to higher susceptibility of honeybees to this microsporidian.     

A multiple free-radical scavenging (MULTIS) study on the antioxidant capacity of a neuroprotective drug,edaravone as compared with uric acid,glutathione, and trolox

Edaravone (3-methyl-1-phenyl-2-pyrazoline-5-one) is a neuroprotective drug that has been used for brain ischemia injury treatment. Because its activity is speculated to be due to free radical scavenging activity, we carried out a quantitative determination of edaravone’s free radical scavenging activity against multiple free radical species. Electron spin resonance (ESR) spin trapping-based multiple free-radical scavenging (MULTIS) method was employed, where target free radicals were hydroxyl radical, superoxide anion, alkoxyl radical, alkylperoxyl radical, methyl radical, and singlet oxygen. Edaravone showed relatively high scavenging abilities against hydroxyl radical (scavenging rate constant k = 2.98 × 10¹¹ M⁻¹ s⁻¹), singlet oxygen (k = 2.75 × 10⁷ M⁻¹ s⁻¹), and methyl radical (k = 3.00 × 10⁷ M⁻¹ s⁻¹). Overall, edaravone’s scavenging activity against multiple free radical species is as robust as other known potent antioxidant such as uric acid, glutathione, and trolox. A radar chart illustration of the MULTIS activity relative to uric acid, glutathione, and trolox indicates that edaravone has a high and balanced antioxidant activity with low specificity.     

An investigation into the butyrylcholinesterase-catalyzed hydrolysis of formylthiocholine using heavy atom kinetic isotope effects

Heavy atom kinetic isotope effects (KIEs) were determined for the butyrylcholinesterase-catalyzed hydrolysis of formylthiocholine (FTC). The leaving-S, carbonyl-C, and carbonyl-O KIEs are ³⁴k = 0.994 ± 0.004, ¹³k = 1.0148 ± 0.0007, and ¹⁸k = 0.999 ± 0.002, respectively. The observed KIEs support a mechanism for both acylation and deacylation where the steps up to and including the formation of the tetrahedral intermediate are at least partially rate determining. These results, in contrast to previous studies with acetylthiocholine, suggest that the decomposition of a tetrahedral intermediate is not rate-determining for FTC hydrolysis. Structural differences between the two substrates are likely responsible for the observed mechanism change with FTC.     

Purification,kinetic and thermodynamic characterization of soluble acid invertase from sugarcane (Saccharum officinarum L.)

We report for the first time kinetic and thermodynamic properties of soluble acid invertase (SAI) of sugarcane (Saccharum officinarum L.) salt sensitive local cultivar CP 77-400 (CP-77). The SAI was purified to apparent homogeneity on FPLC system. The crude enzyme was about 13 fold purified and recovery of SAI was 35%. The invertase was monomeric in nature and its native molecular mass on gel filtration and subunit mass on SDS-PAGE was 28 kDa. SAI was highly acidic having an optimum pH lower than 2. The acidic limb was missing. Proton transfer (donation and receiving) during catalysis was controlled by the basic limb having a pKa of 2.4. Carboxyl groups were involved in proton transfer during catalysis. The kinetic constants for sucrose hydrolysis by SAI were determined to be: k_m = 55 mg ml^?1, k_cat = 21 s^?1, k_cat/k_m = 0.38, while the thermodynamic parameters were: ΔH* = 52.6 kJ mol^?1, ΔG* = 71.2 kJ mol^?1, ΔS* = ?57 J mol^?1 K^?1, ΔG*_E–S = 10.8 kJ mol^?1 and ΔG*_E–T = 2.6 kJ mol^?1. The kinetics and thermodynamics of irreversible thermal denaturation at various temperatures 53–63 °C were also determined. The half -life of SAI at 53 and 63 °C was 112 and 10 min, respectively. At 55 °C, surprisingly the half -life increased to twice that at 53 °C. ΔG*, ΔH* and ΔS* of irreversible thermal stability of SAI at 55 °C were 107.7 kJ mol^?1, 276.04 kJ mol^?1 and 513 J mol^?1K^?1, respectively.     

Comparison of oxygen mass transfer coefficient in simple and extractive fermentation systems

Aeration and agitation are important variables to ensure effective oxygen transfer rate during aerobic bioprocesses; therefore, the knowledge of the volumetric mass transfer coefficient (k_La) is required. In view of selecting the optimum oxygen requirements for extractive fermentation in aqueous two-phase system (ATPS), the k_La values in a typical ATPS medium were compared in this work with those in distilled water and in a simple fermentation medium, in the absence of biomass. Aeration and agitation were selected as the independent variables using a 2² full factorial design. Both variables showed statistically significant effects on k_La, and the highest values of this parameter in both media for simple fermentation (241 s⁻¹) and extractive fermentation with ATPS (70.3 s⁻¹) were observed at the highest levels of aeration (5 vvm) and agitation (1200 rpm). The k_La values were then used to establish mathematical correlations of this response as a function of the process variables. The exponents of the power number (N³D²) and superficial gas velocity (V_s) determined in distilled water (α = 0.39 and β = 0.47, respectively) were in reasonable agreement with the ones reported in the literature for several aqueous systems and close to those determined for a simple fermentation medium (α = 0.38 and β = 0.41). On the other hand, as expected by the increased viscosity in the presence of polyethylene glycol, their values were remarkably higher in a typical medium for extractive fermentation (α = 0.50 and β = 1.0). A reasonable agreement was found between the experimental data of k_La for the three selected systems and the values predicted by the theoretical models, under a wide range of operational conditions.     

Synthesis of novel 4-nitropyrrole-based semicarbazide and thiosemicarbazide hybrids with antimicrobial and anti-tubercular activity

We report the synthesis and screening of forty novel 4-nitropyrrole-semicarbazide conjugates inspired from the reported bio-potential of bromopyrrole alkaloids and semicarbazide derivatives for antimicrobial activity. Herein, hybrids 5k–5o, 5r, 5s and 5t displayed four-fold increased activity (MIC = 0.39 μg/mL) against Escherichia coli compared to standard ciprofloxacin. Eight hybrids, 5k–5o and 5r–5t displayed equal antibacterial activity (MIC = 1.56 μg/mL) against Klebsiella pneumonia compared to standard ciprofloxacin. Hybrid, 5k–5o (MIC = 0.195 μg/mL) displayed highly potent antibacterial activity against MSSA as compared to standard ciprofloxacin. Eight-fold superior activity was observed for four hybrids 5k–5m and 5o (MIC = 0.39 μg/mL) against MRSA. Further, nine hybrids displayed four-fold superior antifungal activity (MIC = 0.78 μg/mL) compared to standard Amphotericin B. Encouraging MICs of these hybrids recognize them as promising leads for development of potential antimicrobial drugs.     

An avifaunal survey of mesic manmade ecosystems “Oases” in algerian hot-hyperarid lands

Man made ecosystems of dry lands are key habitats due to their ecological characteristics to survey biodiversity. This study investigated bird diversity in three oases of the Northern Algerian Sahara (i.e., Biskra in 2006, Oued Souf in 2008 and Ouargla in 2009), by using the spot-mapping method. Bird density “D” (pairs/10 ha), species richness “S” (number species), diversity (Shannon index) “H′” (in bits), and evenness “E” varied from one oasis to another (Biskra: D = 98.5, S = 47, H′ = 4.49, E = 0.81; Oued Souf: D = 96, S = 33, H′ = 3.9, E = 0.77; Ouargla: D = 91.5, S = 44, H′ = 4.39, E = 0.80). Differences in bird diversity between the monitored palm groves are due to the ecological characteristics of each environment. Documented literature outlined close taxonomic similarities between bird assemblages of the study area with many Northern Saharan oases. The Hybrid Sparrow Passer domesticus x Passer. hispaniolensis and some Columbidae species including Columba livia, Streptopelia turtur, Streptopelia senegalensis, and Streptopelia decaocto were the abundant species throughout surveyed oases in which they represented more than half (55.6%) of the sum of species densities (D = 286 pairs/10 ha). These synthropic species have known a huge expansion of their distribution range throughout Algerian oases. The correspondence analysis allowed the aggregation of both families and species into oasis they belong to. One-way ANOVA was tested to analyse variations of both family and species densities between studied oases. The ANOVA revealed there was no significant variation either in family densities (p = 0.937) or in bird densities (p = 0.622) between the surveyed oases because of the small size of bird populations.     

Macrophyte decomposition in a surface-flow ammonia-dominated constructed wetland: Rates associated with environmental and biotic variables

Decomposition of senesced culm material of two bulrush species was studied in a surface-flow ammonia-dominated treatment wetland in southern California. Decomposition of the submerged culm material during summer months was relatively rapid (k = 0.037 day⁻¹), but slowed under extended submergence (up to 245 days) and during fall and spring sampling periods (k = 0.009–0.014 day⁻¹). Stepwise regression of seasonal data indicated that final water temperature and abundance of the culm-mining midge, Glyptotendipes, were significantly associated with culm decomposition. Glyptotendipes abundance, in turn, was correlated with water quality parameters such as conductivity and dissolved oxygen and ammonia concentrations. No differences were detected in decomposition rates between the bulrush species, Schoenoplectus californicus and Schoenoplectus acutus.     

Molecular cloning and functional analysis of the ortho-hydroxylases of p-coumaroyl coenzyme A/feruloyl coenzyme A involved in formation of umbelliferone and scopoletin in sweet potato,Ipomoea batatas (L.) Lam.

Ortho-hydroxylation of cinnamates is a key step in coumarin biosynthesis in plants. Ortho-hydroxylated cinnamates undergo trans/cis isomerization of the side-chain and then lactonization to form coumarins. Sweet potato [Ipomoea batatas (L.) Lam.] accumulates umbelliferone and scopoletin after biotic and abiotic stresses. To elucidate molecular aspects of ortho-hydroxylation involved in umbelliferone formation in sweet potato, isolation and characterization of cDNAs encoding 2-oxoglutarate-dependent dioxygenases (2OGD) was performed from sweet potato tubers treated with a chitosan elicitor. Five cDNAs (designated as Ib) encoding a protein of 358 amino acid residues were cloned, and these were categorized into two groups, Ib1 and Ib2, based on their amino acid sequences. Whether the recombinant Ib proteins had any enzymatic activity toward cinnamates was examined. Ib1 proteins exhibited ortho-hydroxylation activity toward feruloyl coenzyme A (CoA) to form scopoletin (K_m = ∼10 μM, k_cat = ∼2.7 s⁻¹). By contrast, Ib2 proteins catalyzed ortho-hydroxylation of feruloyl-CoA (K_m = 7.3–14.0 μM, k_cat = 0.28–0.55 s⁻¹) and also of p-coumaroyl-CoA (K_m = 6.1–15.2 μM, k_cat = 0.28–0.64 s⁻¹) to form scopoletin and umbelliferone, respectively. Fungal and chitosan treatments increased levels of umbelliferone and its glucoside (skimmin) in the tubers, and expression of the Ib2 gene was induced concomitantly.     

Effects of plant diversity on microbial biomass and community metabolic profiles in a full-scale constructed wetland

There has been less understanding of relations of microbial community patterns with plant diversity in constructed wetlands. We conducted a single full-scale subsurface vertical flow constructed wetland (SVFCW, 1000 m²) study focusing on domestic wastewater processing. This study measured the size and structure of microbial community using fumigation extraction and BIOLOG Ecoplate? techniques, to examine the effects of macrophyte diversity on microbial communities that are critical in treatment efficiency of constructed wetlands. We also determined the relationship of plant diversity (species richness) with its biomass production under disturbance of the same wastewater supply. Linear regression analysis showed that plant biomass production strongly correlated with plant species richness (R = 0.407, P < 0.001). Increase in plant species richness increased microbial biomass carbon and nitrogen (R = 0.494, P < 0.001; R = 0.465, P < 0.001) and utilization of amino acids on Ecoplates (R = 0.235, P = 0.03), but limited the utilization of amine/amides (R = ?0.338, P = 0.013). Principal components analysis (PCA) showed that the diversity and community-level physiological profiles (CLPP) of microbial community at 168 h of incubation strongly depended on the presence or absence of plant species in the SVFCW system, but not on the species richness. This is the first step toward understanding relations of plant diversity with soil microbial community patterns in constructed wetlands, but the effect of species diversity on microbial community should be further studied.     

Synthesis,in vitro evaluation and molecular docking studies of novel amide linked triazolyl glycoconjugates as new inhibitors of α-glucosidase

A series of N-substituted amide linked triazolyl β-d-glucopyranoside derivatives (4a-l) were synthesized and their in vitro inhibitory activity against yeast α-glucosidase enzyme [EC.3.2.1.20] was assessed. Compounds 4e (IC₅₀ = 156.06 μM), 4f (IC₅₀ = 147.94 μM), 4k (IC₅₀ = 127.71 μM) and 4l (IC₅₀ = 121.33 μM) were identified as the most potent inhibitors for α-glucosidase as compared to acarbose (IC₅₀ = 130.98 μM) under the same in vitro experimental conditions. Kinetic study showed that both 4e and 4f inhibit the enzyme in a competitive manner with p-nitrophenyl α-d-glucopyranoside as substrate. Molecular docking studies of 4e, 4f, 4k and 4l were also carried out using homology model of α-glucosidase to find out the binding modes responsible for the inhibitory activity. This study revealed that the binding affinity of compounds 4e, 4f, 4k and 4l for α-glucosidase were −8.2, −8.6, −8.3 and −8.5 kcal/mol respectively, compared to that of acarbose (−8.9 kcal/mol). The results suggest that the N-substituted amide linked triazole glycoconjugates can reasonably mimic the substrates for the yeast α-glucosidase.     

Structural and functional analyses of Mycobacterium tuberculosis Rv3315c-encoded metal-dependent homotetrameric cytidine deaminase

The emergence of drug-resistant strains of Mycobacterium tuberculosis, the causative agent of tuberculosis, has exacerbated the treatment and control of this disease. Cytidine deaminase (CDA) is a pyrimidine salvage pathway enzyme that recycles cytidine and 2′-deoxycytidine for uridine and 2′-deoxyuridine synthesis, respectively. A probable M. tuberculosis CDA-coding sequence (cdd, Rv3315c) was cloned, sequenced, expressed in Escherichia coli BL21(DE3), and purified to homogeneity. Mass spectrometry, N-terminal amino acid sequencing, gel filtration chromatography, and metal analysis of M. tuberculosis CDA (MtCDA) were carried out. These results and multiple sequence alignment demonstrate that MtCDA is a homotetrameric Zn²⁺-dependent metalloenzyme. Steady-state kinetic measurements yielded the following parameters: K_m = 1004 μM and k_cat = 4.8 s^?1 for cytidine, and K_m = 1059 μM and k_cat = 3.5 s^?1 for 2′-deoxycytidine. The pH dependence of k_cat and k_cat/K_M for cytidine indicate that protonation of a single ionizable group with apparent pK_a value of 4.3 abolishes activity, and protonation of a group with pK_a value of 4.7 reduces binding. MtCDA was crystallized and crystal diffracted at 2.0 Å resolution. Analysis of the crystallographic structure indicated the presence of a Zn²⁺ coordinated by three conserved cysteines and the structure exhibits the canonical cytidine deaminase fold.     

Symmetric adamantyl-diureas as soluble epoxide hydrolase inhibitors

A series of inhibitors of the soluble epoxide hydrolase (sEH) containing two urea groups has been developed. Inhibition potency of the described compounds ranges from 2.0 μM to 0.4 nM. 1,6-(Hexamethylene)bis[(adamant-1-yl)urea] (3b) was found to be a potent slow tight binding inhibitor (IC₅₀ = 0.5 nM) with a strong binding to sEH (K_i = 3.1 nM) and a moderately long residence time on the enzyme (k_off = 1.05 × 10⁻³ s⁻¹; t_1/2 = 11 min).     

Synthesis and anti-acetylcholinesterase properties of novel β- and γ-substituted alkoxy organophosphonates

Activated organophosphate (OP) insecticides and chemical agents inhibit acetylcholinesterase (AChE) to form OP-AChE adducts. Whereas the structure of the OP correlates with the rate of inhibition, the structure of the OP-AChE adduct influences the rate at which post-inhibitory reactivation or aging phenomena occurs. In this report, we prepared a panel of β-substituted ethoxy and γ-substituted propoxy phosphonoesters of the type p-NO₂PhO-P(X)(R)[(O(CH₂)_nZ] (R = Me, Et; X = O, S; n = 2, 3; Z = halogen, OTs) and examined the inhibition of three AChEs by select structures in the panel. The β-fluoroethoxy methylphosphonate analog (R = Me, Z = F, n = 2) was the most potent anti-AChE compound comparable (k_i ～6 × 10⁶ M^?1 min^?1) to paraoxon against EEAChE. Analogs with Z = Br, I, or OTs were weak inhibitors of the AChEs, and methyl phosphonates (R = Me) were more potent than the corresponding ethyl phosphonates (R = Et). As expected, analogs with a thionate linkage (PS) were poor inhibitors of the AChEs.     

Vibrio aestivus sp. nov. and Vibrio quintilis sp. nov., related to Marisflavi and Gazogenes clades,respectively

Two new Vibrio species, Vibrio aestivus and Vibrio quintilis, are described after a polyphasic characterization of strains M22^T, M61 and M62^T, isolated from seawater collected off a beach on the East coast of Spain (Valencia). All three strains are Gram negative, mesophilic, slightly halophilic, fermentative rods. V. aestivus (M22^T = CECT 7558^T = CAIM 1861^T = KCTC 23860^T and M61 = CECT 7559 = CAIM 1862 = KCTC 23861) is oxidase positive, reduces nitrates to nitrites, is negative for Voges Proskauer, arginine dihydrolase and indole and non hydrolytic on most substrates tested. The 16S rRNA gene sequences of M22^T and M61 are most similar to Vibrio marisflavi (97.1–97.2%) but phylogenetic analysis using NJ, MP and ML methods display Vibrio stylophorae (96.2% similarity) as sibling species. The three species form a deep clade in the genus Vibrio. Average Nucleotide Identity (ANI) values, determined as a measure of overall genomic resemblance, confirmed that strains M22^T and M61 are members of the same species, different to V. marisflavi CECT 7928^T.V. quintilis (M62^T = CECT 7734^T = CAIM 1863^T = KCTC 23833^T) is aerogenic, arginine dihydrolase and Voges Proskauer positive, oxidase negative and unable to reduce nitrate, traits shared by most species in the Gazogenes clade. It is unpigmented and does not grow on TCBS Agar. 16S rRNA gene similarities to its nearest species, Vibrio aerogenes and Vibrio mangrovi, are 97.6% and 96.0% respectively. Strain M62^T and V. aerogenes CECT 7868^T display ANI values well below the 95% boundary for genomic species.     

Population structure and genetic diversity of Dysosma versipellis (Berberidaceae), a rare endemic from China

Dysosma versipellis (Berberidaceae) is an endangered and endemic species in China. To provide scientific foundation for formulating conservation strategies, we sampled six extant populations of this species and assessed the levels and patterns of genetic diversity using ISSR markers (11 primers). Of 144 bands detected 57.64% were polymorphic, but on average only 20.72% were polymorphic within populations. Our results revealed a low level of intraspecific genetic diversity (at population level: H_pop = 0.082, H_B = 0.177, SI = 0.1194; at species level: H_pop = 0.207, H_B = 0.378, SI = 0.3069). A high level of genetic differentiations among populations was detected based on Nei's genetic diversity analysis (60%), AMOVA analysis (65%), and Bayesian analysis (53%). The low levels of heterozygosity and high genetic differentiation observed in D. versipellis may be the consequence of low rate of natural recruitment, clonal growth, gene drift, and habitat fragmentation. Based on this, we suggest that in situ conservation be an important and practical measure for maintaining the genetic diversity of this species. Ex situ conservation should sample from different populations across the distribution range of the species to conserve high genetic diversity.     

The carbon flux of global rivers: A re-evaluation of amount and spatial patterns

Global rivers connect three large carbon reservoirs in the world: soil, atmosphere, and ocean. The amount and spatial pattern of riverine carbon flux are essential for the global carbon budget but are still not well understood. Therefore, three linear regression models for riverine DOC (dissolved organic carbon), POC (particulate organic carbon), and DIC (dissolved inorganic carbon) fluxes were established with related generating and transfer factors based on an updated global database. The three models then were applied to simulate the spatial distribution of riverine DOC, POC, and DIC fluxes and to estimate the total global riverine carbon flux. The major conclusions of this study are as follows: the correlation analysis showed that riverine DOC flux is significantly related to discharge (r² = 0.93, n = 109) and soil organic carbon amount (r² = 0.60), POC flux increases with discharge (r² = 0.55, n = 98) and amount of soil erosion (r² = 0.48), and DIC flux is strongly linked to CO₂ consumption by rock weathering (r² = 0.66, n = 111) and discharge (r² = 0.63). In addition, Asia exports more DOC and POC than other continents and North America exports more DIC. The Atlantic Ocean accepts the major portion of riverine DOC, POC, and DIC fluxes of all the oceans. The highest riverine DOC flux occurs in the 0–30°S zone, and the highest riverine POC and DIC fluxes appear in the 30–60°N zone. Furthermore, re-estimation revealed that global rivers export approximately 1.06 Pg C to oceans every year, including 0.24 Pg DOC, 0.24 Pg POC, 0.41 Pg DIC, and 0.17 Pg PIC.