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1.
Many algae are auxotrophs for vitamin B12 (cobalamin), which they need as a cofactor for B12‐dependent methionine synthase (METH). Because only prokaryotes can synthesize the cobalamin, they must be the ultimate source of the vitamin. In the laboratory, a direct interaction between algae and heterotrophic bacteria has been shown, with bacteria supplying cobalamin in exchange for fixed carbon. Here we establish a system to study this interaction at the molecular level. In a culture of a B12‐dependent green alga Chlamydomonas nivalis, we found a contaminating bacterium, identified by 16S rRNA analysis as Mesorhizobium sp. Using the sequenced strain of M. loti (MAFF303099), we found that it was able to support the growth of B12‐dependent Lobomonas rostrata, another green alga, in return for fixed carbon. The two organisms form a stable equilibrium in terms of population numbers, which is maintained over many generations in semi‐continuous culture, indicating a degree of regulation. However, addition of either vitamin B12 or a carbon source for the bacteria perturbs the equilibrium, demonstrating that the symbiosis is mutualistic and facultative. Chlamydomonas reinhardtii does not require B12 for growth because it encodes a B12‐independent methionine synthase, METE, the gene for which is suppressed by addition of exogenous B12. Co‐culturing C. reinhardtii with M. loti also results in reduction of METE expression, demonstrating that the bacterium can deliver the vitamin to this B12‐independent alga. We discuss the implications of this for the widespread distribution of cobalamin auxotrophy in the algal kingdom.  相似文献   

2.
Some ecologically important phytoplankters released vitamins into culture medium during growth. Skeletonema costatum and Stephanopyxis turris (vitamin B12-requirers) produced both thiamine (vitamin B1) and biotin when growing with either 12 or 2 ng vitamin B12/liter. Gonyaulax polyedra (vitamin B12-requirer) produced thiamine with 12 ng vitamin B12/liter, and Coccolithus huxleyi (thiamine-requirer) produced vitamin B12 and biotin with 120 ng thiamine/liter, but only biotin with 10 ng thiamine/liter. The amount of vitamin produced by an alga and rate at which it was produced varied with the phytoplankter, the concentration of the required vitamin, and incubation time. Vitamins produced during early and exponential growth were due to excretions, and those produced at stationary growth resulted from excretion and release due to cell lysis. Uptake of the required vitamin by all phytoplankters was greatest during the first few days of incubation. On continued incubation the rate of uptake/cell decreased. In the sea phytoplankters may contribute a major portion of the amount of dissolved vitamins.  相似文献   

3.
Two of the mechanisms for vitamin B12 deficiency, leading to megaloblastic anemia, are the result of surgically produced abnormalities of the gastrointestinal tract. The basic mechanism is different for each lesion.Total gastrectomy results in complete lack of intrinsic factor which is necessary for vitamin B12 absorption. It is believed that if patients survive long enough and are not given prophylactic vitamin B12 therapy, all would develop megaloblastic anemia.Intestinal anastomosis leading to stasis of intestinal contents, with overgrowth of bacteria may cause vitamin B12 deficiency through bacterial interference with the utilization of vitamin B12.Use of radioactive vitamin B12 (cobalt60-labeled B12) has led to a better understanding of the pathogenesis of both types of megaloblastic anemia. The radioactive vitamin provides a useful tool for study of its absorption from the gastrointestinal tract.  相似文献   

4.
A widespread and complex distribution of vitamin requirements exists over the entire tree of life, with many species having evolved vitamin dependence, both within and between different lineages. Vitamin availability has been proposed to drive selection for vitamin dependence, in a process that links an organism''s metabolism to the environment, but this has never been demonstrated directly. Moreover, understanding the physiological processes and evolutionary dynamics that influence metabolic demand for these important micronutrients has significant implications in terms of nutrient acquisition and, in microbial organisms, can affect community composition and metabolic exchange between coexisting species. Here we investigate the origins of vitamin dependence, using an experimental evolution approach with the vitamin B12-independent model green alga Chlamydomonas reinhardtii. In fewer than 500 generations of growth in the presence of vitamin B12, we observe the evolution of a B12-dependent clone that rapidly displaces its ancestor. Genetic characterization of this line reveals a type-II Gulliver-related transposable element integrated into the B12-independent methionine synthase gene (METE), knocking out gene function and fundamentally altering the physiology of the alga.  相似文献   

5.
【目的】红杆菌科(Rhodobacteraceae)细菌为凡纳滨对虾肠道微生物的优势类群,在健康对虾肠道中具有较高的相对丰度,是指示对虾健康的关键类群,探究对虾肠道红杆菌科细菌定向富集和分离方法,可为对虾养殖益生菌菌剂的研发提供基础。【方法】利用16S rRNA基因高通量测序技术研究不同碳源添加对凡纳滨对虾肠道中红杆菌科细菌的富集作用,筛选对红杆菌科细菌有显著富集作用的碳源;利用纯培养技术从红杆菌科细菌富集的样品中定向分离红杆菌科细菌,并对其进行鉴定和遗传多样性分析。【结果】添加短链脂肪酸(乙酸、丙酸、丁酸、戊酸)和碳酸氢钠对红杆菌科细菌有显著富集作用,主要富集到Cribrihabitans、Tritonibacter、Rhodovulum、Ruegeria、Sagittula和Thalassobius属相关菌株;对红杆菌科细菌相对丰度最高的样品进行稀释涂布培养,共分离纯化出303株细菌,分属于2门12科,其中红杆菌科细菌为主导类群共119株,主要包括Tritonibacter (90株)、Phaeobacter (25株)、Sulfitobacter (1株)、Ruegeria (1...  相似文献   

6.
Antibiotic-resistant Escherichia coli strains including extended-spectrum β-lactamase (ESBL) isolates are globally widespread in medical, food, and environmental sources. Some of these strains are considered the most pathogenic bacteria in humans. The present work examined the predominance of antibiotic resistance in E. coli strains in wound infections comparing with E. coli strains isolated from a raw milk as a potential source of those strains. The wound infections included abdomen, anus, arm, back, buttock, chest, foot, hand, head, leg, lung, mouth, neck, penis, thigh, toe, and vagina infections. In total, 161 and 153 isolates identified as E. coli were obtained from wound infections and raw milk, respectively. A Vitek 2 system innovated by bioMérieux, France was applied to perform the identification and susceptibility tests. The E. coli isolates that have ability to produce ESBL were detected by an ESBL panel and NO45 card (bioMérieux). Over half of the E. coli were from abdomen, back, and buttock wound infections. More than 50%of the E. coli isolates obtained from wound infections were resistant to cefazolin, ampicillin, cefuroxime, ciprofloxacin, mezlocillin, moxifloxacin, piperacillin, and tetracycline; 70% of the isolates from wound infections and 0% of the isolates from raw milk were E. coli isolates produced ESBL. The data showed that the strains resistance to multi-antibiotic and produced ESBL are more widespread among wound infections than in raw milk.  相似文献   

7.
A method of adaptation to cobalt nitrate at high concentrations allowed us to isolate 46 strains of propionic acid bacteria Propionibacterium acidipropionici, resistant to excessive amounts of Co2+ in the medium. Studies of these strains revealed cultures that were most potent in synthesizing vitamin B12. The yield of vitamin B12 was increased 3 times, compared to parent strains.  相似文献   

8.
An intervening sequence (IVS) can be present or absent in the 23S rRNA of Campylobacter jejuni and Campylobacter coli. As part of a survey, we used a polymerase chain reaction (PCR) assay to detect the presence of the IVS in 43 isolates of C. coli and 82 isolates of C. jejuni. An IVS was present in 40 (93.0%) of the C. coli and only 34 (41.5%) of the C. jejuni isolates. Twelve (27.9%) of the C. coli isolates and seven (8.5%) of the C. jejuni isolates resulted in two polymerase chain reaction products, indicating heterogeneity in the presence of the 23S rRNA IVS. Fourteen of the isolates with two products were evaluated by pulse-field gel electrophoresis; 13 different patterns were observed. The total band size of one isolate was substantially greater than the expected 1.7 Mb, possibly indicating a mixed culture. Southern blot analyses demonstrated the expected three rRNA operons in all tested isolates. Nested PCR reactions with operon-specific primers followed by primers for the IVS confirmed that the strains of interest contained either one or two operons carrying the IVS and the remaining operon(s) did not. Sequence analysis of the IVS and flanking regions of the 23S rRNA genes did not discriminate C. jejuni and C. coli as distinct populations. These results indicate horizontal transfer of 23S rRNA genes or portions of the genes between C. jejuni and C. coli. Also, data showing sequence polymorphisms between the three 23S rRNA loci outside of the IVS region suggest that the isolates with intra-genomic heterogeneity appear to be members of clones that have an ancient defect in gene conversion mechanisms needed for concerted evolution of the ribosomal operons.  相似文献   

9.
Lactobacillus fermentum isolated from sourdough was able to produce riboflavin. Spontaneous roseoflavin-resistant mutants were obtained by exposing the wild strain (named L. fermentum PBCC11) to increasing concentrations of roseoflavin. Fifteen spontaneous roseoflavin-resistant mutants were isolated, and the level of vitamin B2 was quantified by HPLC. Seven mutant strains produced concentrations of vitamin B2 higher than 1 mg L?1. Interestingly, three mutants were unable to overproduce riboflavin even though they were able to withstand the selective pressure of roseoflavin. Alignment of the rib leader region of PBCC11 and its derivatives showed only point mutations at two neighboring locations of the RFN element. In particular, the highest riboflavin-producing isolates possess an A to G mutation at position 240, while the lowest riboflavin producer carries a T to A substitution at position 236. No mutations were detected in the derivative strains that did not have an overproducing phenotype. The best riboflavin overproducing strain, named L. fermentum PBCC11.5, and its parental strain were used to fortify bread. The effect of two different periods of fermentation on the riboflavin level was compared. Bread produced using the coinoculum yeast and L. fermentum PBCC11.5 led to an approximately twofold increase of final vitamin B2 content.  相似文献   

10.
Vitamin B12 is an essential micronutrient synthesized by microorganisms. Mammals including humans have evolved ways for transport and absorption of this vitamin. Deficiency of vitamin B12 (either due to low intake or polymorphism in genes involved in absorption and intracellular transport of this vitamin) has been associated with various complex diseases. Genome-wide association studies have recently identified several common single nucleotide polymorphisms (SNPs) in fucosyl transferase 2 gene (FUT2) to be associated with levels of vitamin B12—the strongest association was with a non-synonymous SNP rs602662 in this gene. In the present study, we attempted to replicate the association of this SNP (rs602662) in an Indian population since a significant proportion has been reported to have low levels of vitamin B12 in this population. A total of 1146 individuals were genotyped for this SNP using a single base extension method and association with levels of vitamin B12 was assessed in these individuals. Regression analysis was performed to analyze the association considering various confounding factors like for age, sex, diet, hypertension, diabetes mellitus and coronary artery disease status. We found that the SNP rs602662 was significantly associated with the levels of vitamin B12 (p value < 0.0001). We also found that individuals adhering to a vegetarian diet with GG (homozygous major genotype) have significantly lower levels of vitamin B12 in these individuals. Thus, our study reveals that vegetarian diet along with polymorphism in the FUT2 gene may contribute significantly to the high prevalence of vitamin B12 deficiency in India.  相似文献   

11.
Five strains (JA325, JA389, JA473, JA563 and JA582) of Gram stain-negative, vibrioid to spiral shaped, phototrophic purple bacteria were isolated from solar salterns of India. All strains contained bacteriochlorophyll-a and carotenoids of the spirilloxanthin series as photosynthetic pigments. C18:1ω7c, C18:1ω7c 11-methyl and C16:0 were the major fatty acids of all strains. Diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), ornithine lipid (OL), an unidentified phospholipid (PL), and an unidentified aminolipid (AL) were the major polar lipids of all the strains. According to 16S rRNA gene sequences, all strains clustered phylogenetically with the only species of the genus Rhodothalassium (99.8–99.3% sequence similarity) but only strains JA325 and JA563 were distinctly related (60 + 1.5% DNA–DNA hybridization [DDH]) to the type strain Rhodothalassium salexigens DSM 2132T. However, the genotypic data of strains JA325 and JA563 was not supported because of a large number of phenotypic differences compared to the type strain, therefore, it is proposed that all five newly isolated strains were R. salexigens-like strains. In addition, phylogenetically, the Rhodothalassium clade represented a distinct lineage and formed a deep branch with less than 90% 16S rRNA gene sequence similarity to other orders of the Alphaproteobacteria, and characteristic phenotypic properties also distinguished these bacteria from other purple non-sulfur bacteria. Therefore, the novel family Rhodothalassiaceae fam. nov. and the novel order Rhodothalassiales ord. nov. are proposed for the distinct phyletic line represented by the genus Rhodothalassium.  相似文献   

12.
13.
The edible blue-green alga (cyanobacterium), Suizenji-nori, contained 143.8±22.4 μg of vitamin B12 per 100 g dry weight of the alga (mean±SE, n=4). A corrinoid compound was purified from the dried Suizenji-nori, and partially characterized. The silica gel 60 TLC and reversed-phase HPLC patterns of the purified corrinoid compound were not identical to those of true vitamin B12, but to those of pseudovitamin B12 which is inactive for humans.  相似文献   

14.
Austrian isolates ofFusarium subglutinans andFusarium proliferatum were studied for their ability to produce beauvericin, moniliformin and fumonisin B1 and B2 under laboratory conditions. Analytical methodology for beauvericin was specially adapted for this task. Our analyses showed that the strains produced beauvericin up to 687 mg /kg maize and moniliformin up to 70 mg/kg. The culture ofF. proliferatum in addition produced fumonisin B1 and B2 at levels of 106 and 61 mg/kg,respectively. The preliminary toxicity experiments performed in this study clearly indicated a toxic effect of beauvericin on the contractility of mammalian smooth muscle and thus on mammalian cells.  相似文献   

15.
Vitamin B12 is a complex biomolecule that acts as a cofactor for a variety of enzymes in microbial metabolism. Pseudomonas denitrificans is exclusively used as an industrial strain for the production of vitamin B12 under aerobic conditions. However, only a few strains of Pseudomonas have been reported to possess the capability of producing this vitamin and they are strongly patent-protected. To improve the applicability of the vitamin B12-producing microorganisms, a new isolate was obtained from municipal waste samples and characterized for its biological properties. The new isolate, designated as SP2, was identified to be a Pseudomonas species based on the sequence homology of its 16S rDNA. Pseudomonas species SP2 had essential genes for vitamin B12 synthesis such as cobB and cobQ and produced a similar amount of vitamin B12 (10.6 ± 0.05 μg/mL) as P. denitrificans ATCC 13867 in 24 h flask culture. SP2 grew well under aerobic condition with the maximum specific growth rate (µ max ) of 0.91 ± 0.03/h, but showed a poor growth under micro-aerobic conditions. SP2 was resistant to antibiotics like streptomycin, carbenicillin, ampicillin, cefpodoxime, colistin, nalidixic acid and sparfloxacin. The ability of SP2 to grow faster and produce vitamin B12 under aerobic conditions makes it a promising host for the production of some biochemicals requiring a coenzyme B12-dependent enzyme, such as glycerol dehydratase.  相似文献   

16.
Antibiotic-resistant Staphylococci are a global issue affecting humans, animals, and numerous natural environments. Antibiotic-resistant Staphylococcus epidermidis is an opportunistic pathogen frequently isolated from patients and healthy individuals. This study aimed to examine the antibiotic resistance of S. epidermidis isolated from patients, healthy students and compare the results with antibiotic-resistant bacteria isolated from pasteurized milk. Clinical strain isolation was performed in several hospitals in the Riyadh. Skin swabs from 100 healthy undergraduate candidate students were obtained at King Saud University. The pasteurized milk samples were obtained from local market (company, X). After isolation, identification and susceptibility tests were performed using an automated system. A multiplex tuf gene-based PCR assay was used to confirm identification. Biofilm production and biofilm-related gene expression were studied. S. epidermidis represented 17% of clinical bacterial isolates, and 1.7% of isolates obtained from healthy students were multiantibiotic-resistant. All patient strains were teicoplanin- and vancomycin-susceptible, while all student strains were gentamicin-, levofloxacin-, moxifloxacin-, and trimethoprim/sulfamethoxazole-susceptible. All the bacteria isolated from pasteurized milk were benzylpenicillin and oxacillin-resistant strains. Of the S. epidermidis strains, 91% could produce biofilms, and mecA, icaADBR, ica-ADB, ica-AD, ica-A only, and ica-C only were expressed in 83, 17.1, 25.7, 37.1, 20, and 0% of the strains, respectively. This work demonstrates that S. epidermidis can be accurately identified using a multiplex tuf-based assay, and that multiantibiotic-resistant S. epidermidis strains are widespread amongst patients and healthy students.  相似文献   

17.
Corrinoids are essential cofactors of reductive dehalogenases in anaerobic bacteria. Microorganisms mediating reductive dechlorination as part of their energy metabolism are either capable of de novo corrinoid biosynthesis (e.g., Desulfitobacterium spp.) or dependent on exogenous vitamin B12 (e.g., Dehalococcoides spp.). In this study, the impact of exogenous vitamin B12 (cyanocobalamin) and of tetrachloroethene (PCE) on the synthesis and the subcellular localization of the reductive PCE dehalogenase was investigated in the Gram-positive Desulfitobacterium hafniense strain Y51, a bacterium able to synthesize corrinoids de novo. PCE-depleted cells grown for several subcultivation steps on fumarate as an alternative electron acceptor lost the tetrachloroethene-reductive dehalogenase (PceA) activity by the transposition of the pce gene cluster. In the absence of vitamin B12, a gradual decrease of the PceA activity and protein amount was observed; after 5 subcultivation steps with 10% inoculum, more than 90% of the enzyme activity and of the PceA protein was lost. In the presence of vitamin B12, a significant delay in the decrease of the PceA activity with an ∼90% loss after 20 subcultivation steps was observed. This corresponded to the decrease in the pceA gene level, indicating that exogenous vitamin B12 hampered the transposition of the pce gene cluster. In the absence or presence of exogenous vitamin B12, the intracellular corrinoid level decreased in fumarate-grown cells and the PceA precursor formed catalytically inactive, corrinoid-free multiprotein aggregates. The data indicate that exogenous vitamin B12 is not incorporated into the PceA precursor, even though it affects the transposition of the pce gene cluster.  相似文献   

18.
Vitamin B12 is an essential nutrient required for crucial metabolic processes in humans. Vitamin B12-producing lactic acid bacteria (LAB) have been attracting increased attentions currently because of the generally recognized as safe (GRAS) status. Most of recent studies focused on Lactobacillus, and little is known about B12-producing Enterococcus. In the present study, five Enterococcus strains isolated from infant feces were identified as vitamin B12 producers. Among them, Enterococcus faecium LZ86 had the highest B12 production (499.8 ± 83.7 μg/L), and the B12 compound from LZ86 was identified as the biological active adenosylcobalamin, using reversed phase high-performance liquid (RP-HPLC) chromatogram. We examined basic probiotic and safety properties of E. faecium LZ86 and found that it was able to survive harsh environmental conditions (hot temperature, cold temperature, ethanol and osmotic stresses), tolerate gastric acid (pH 2.0, 3 h) and bile salts (0.3%), and adhere to Caco-2 cells. We also showed that E. faecium LZ86 is devoid of transferable antibiotic resistance and potential virulence factors. Together, here we report a B12-producing E. faecium strain LZ86 firstly, which has desirable probiotic properties and may serve as a good candidate for vitamin B12 fortification in food industry.  相似文献   

19.
As vitamin B12 is only synthesized by bacteria, ruminant products, especially dairy products, are excellent sources of this vitamin. This study aims to identify if diet and cow characteristics could affect vitamin B12 concentration in milk of dairy cows. Information on 1484 first, 1093 second and 1763 third and greater parity Holstein cows in 100 herds was collected during three consecutive milkings. During the first morning milking, all dietary ingredients given to cows were sampled and quantities offered were recorded throughout the day. Nutrient composition of ingredients was obtained by wet chemistry to reconstitute nutrient composition of the ration. Milk samples were taken with in-line milk meters during the evening milking of the 1st day and the morning milking of the 2nd day and were analyzed for vitamin B12 concentration. Milk yields were recorded and milk components were separately analyzed for each milking. Daily vitamin B12 concentration in milk was obtained using morning and evening vitamin B12 concentrations weighted with respective milk yield, then divided by daily yield. To decrease the number of interdependent variables to include in the multivariable model, a principal component analysis was carried out. Daily milk concentration of vitamin B12 averaged 3809±80 pg/ml, 4178±79 pg/ml and 4399±77 pg/ml for first, second and third, and greater lactation cows. Out of 11 principal components, six were significantly related to daily milk concentration of vitamin B12 when entered in the multivariable model. Results suggested that vitamin B12 concentration in milk was positively related to percentage of fiber and negatively related to starch as well as energy of the diet. Negative relationships were noted between vitamin B12 concentration in milk and milk yield as well as milk lactose concentration and positive relationships were observed between vitamin B12 concentration in milk and milk fat as well as protein concentrations. The percentages of chopped mixed silage and commercial energy supplement in the diet as well as cow BW were positively related to vitamin B12 in milk and percentages of baled mixed silage, corn and commercial protein supplement in the ration were negatively related to vitamin B12 concentration in milk. The pseudo-R2 of the model was low (52%) suggesting that diet and cow characteristics have moderate impact on vitamin B12 concentration in milk. Moreover, when entering solely the principal component related to milk production in the model, the pseudo-R2 was 46%. In conclusion, it suggests that studied diet characteristics have a marginal impact on vitamin B12 concentration in milk variation.  相似文献   

20.
Marine sponge–associated actinomycetes are considered as promising sources for the discovery of novel biologically active compounds. In the present study, a total of 64 actinomycetes were isolated from 12 different marine sponge species that had been collected offshore the islands of Milos and Crete, Greece, eastern Mediterranean. The isolates were affiliated to 23 genera representing 8 different suborders based on nearly full length 16S rRNA gene sequencing. Four putatively novel species belonging to genera Geodermatophilus, Microlunatus, Rhodococcus and Actinomycetospora were identified based on a 16S rRNA gene sequence similarity of < 98.5% to currently described strains. Eight actinomycete isolates showed bioactivities against Trypanosma brucei brucei TC221 with half maximal inhibitory concentration (IC50) values <20 μg/mL. Thirty four isolates from the Milos collection and 12 isolates from the Crete collection were subjected to metabolomic analysis using high resolution LC-MS and NMR for dereplication purposes. Two isolates belonging to the genera Streptomyces (SBT348) and Micromonospora (SBT687) were prioritized based on their distinct chemistry profiles as well as their anti-trypanosomal activities. These findings demonstrated the feasibility and efficacy of utilizing metabolomics tools to prioritize chemically unique strains from microorganism collections and further highlight sponges as rich source for novel and bioactive actinomycetes.  相似文献   

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