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1.
Tuberculosis (TB) remains broadly present in the Americas despite intense global efforts for its control and elimination. Starting from a large dataset comprising spoligotyping (n = 21183 isolates) and 12-loci MIRU-VNTRs data (n = 4022 isolates) from a total of 31 countries of the Americas (data extracted from the SITVIT2 database), this study aimed to get an overview of lineages circulating in the Americas. A total of 17119 (80.8%) strains belonged to the Euro-American lineage 4, among which the most predominant genotypic family belonged to the Latin American and Mediterranean (LAM) lineage (n = 6386, 30.1% of strains). By combining classical phylogenetic analyses and Bayesian approaches, this study revealed for the first time a clear genetic structuration of LAM9 sublineage into two subpopulations named LAM9C1 and LAM9C2, with distinct genetic characteristics. LAM9C1 was predominant in Chile, Colombia and USA, while LAM9C2 was predominant in Brazil, Dominican Republic, Guadeloupe and French Guiana. Globally, LAM9C2 was characterized by higher allelic richness as compared to LAM9C1 isolates. Moreover, LAM9C2 sublineage appeared to expand close to twenty times more than LAM9C1 and showed older traces of expansion. Interestingly, a significant proportion of LAM9C2 isolates presented typical signature of ancestral LAM-RDRio MIRU-VNTR type (224226153321). Further studies based on Whole Genome Sequencing of LAM strains will provide the needed resolution to decipher the biogeographical structure and evolutionary history of this successful family. 相似文献
2.
Omar Cáceres Nalin Rastogi Carlos Bartra David Couvin Marco Galarza Luis Asencios Alberto Mendoza-Ticona 《PloS one》2014,9(12)
Background
Peru holds the fourth highest burden of tuberculosis in the Americas. Despite an apparently well-functioning DOTS control program, the prevalence of multidrug resistant tuberculosis (MDR-TB) continues to increase. To worsen this situation, cases of extensively drug resistance tuberculosis (XDR-TB) have been detected. Little information exists about the genetic diversity of drug-susceptible vs. MDR-TB and XDR-TB.Methods
Cryopreserved samples of XDR strains from 2007 to 2009 (second semester), were identified and collected. Starting from 227 frozen samples, a total of 142 XDR-TB strains of Mycobacterium tuberculosis complex (MTBC; 1 isolate per patient) were retained for this study. Each strain DNA was analyzed by spoligotyping and the 15-loci Mycobacterial Interspersed Repetitive Unit (MIRU-15).Results
Among the 142 isolates analyzed, only 2 samples (1.41%) could not be matched to any lineage. The most prevalent sublineage was Haarlem (43.66%), followed by T (27.46%), LAM (16.2%), Beijing (9.15%), and X clade (1.41%). Spoligotype analysis identified clustering for 128/142 (90.1%) isolates vs. 49/142 (34.5%) with MIRUs. Of the samples, 90.85% belonged to retreated patients. The drug resistant profile demonstrated that 62.67% showed resistance to injectable drugs capreomycin (CAP) and kanamycin (KAN) vs. 15.5% to CAP alone and 21.8% to KAN alone. The SIT219/T1 and SIT50/H3 were the most prevalent patterns in our study. The spoligoforest analysis showed that SIT53/T1 was at the origin of many of the T lineage strains as well as a big proportion of Haarlem lineage strains (SIT50/H3, followed by SIT47/H1, SIT49/H3, and SIT2375/H1), as opposed to the SIT1/Beijing strains that did not appear to evolve into minor Beijing sublineages among the XDR-TB strains.Conclusion
In contrast with other Latin-American countries where LAM sublineage is the most predominant, we found the Haarlem to be the most common followed by T sublineage among the XDR-TB strains. 相似文献3.
María Elvira Balcells Patricia García Paulina Meza Carlos Pe?a Marcela Cifuentes David Couvin Nalin Rastogi 《PloS one》2015,10(2)
Tuberculosis (TB) remains a significant public health problem worldwide, but the ecology of the prevalent mycobacterial strains, and their transmission, can vary depending on country and region. Chile is a country with low incidence of TB, that has a geographically isolated location in relation to the rest of South American countries due to the Andes Mountains, but recent migration from neighboring countries has changed this situation. We aimed to assess the genotypic diversity of Mycobacterium tuberculosis complex (MTBC) strains in Santiago, Chile, and compare with reports from other Latin-American countries. We analyzed MTBC isolates from pulmonary tuberculosis cases collected between years 2008 and 2013 in Central Santiago, using two genotyping methods: spoligotyping and 12-loci mycobacterial interspersed repetitive unit-variable number of tandem repeats (MIRU-VNTRs). Data obtained were analyzed and compared to the SITVIT2 database. Mean age of the patients was 47.5 years and 61% were male; 11.6% were migrants. Of 103 strains (1 isolate/patient) included, there were 56 distinct spoligotype patterns. Of these, 16 strains (15.5%) corresponded to orphan strains in the SITVIT2 database, not previously reported. Latin American and Mediterranean (LAM) (34%) and T (33%) lineages were the most prevalent strains, followed by Haarlem lineage (16.5%). Beijing family was scarcely represented with only two cases (1.9%), one of them isolated from a Peruvian migrant. The most frequent clustered spoligotypes were SIT33/LAM3 (10.7%), SIT53/T1 (8.7%), SIT50/H3 (7.8%), and SIT37/T3 (6.8%). We conclude that LAM and T genotypes are the most prevalent genotypes of MTBC in Santiago, Chile, and together correspond to almost two thirds of analyzed strains, which is similar to strain distribution reported from other countries of Latin America. Nevertheless, the high proportion of SIT37/T3, which was rarely found in other Latin American countries, may underline a specific history or demographics of Chile related to probable human migrations and evolutions. 相似文献
4.
Reliability of laboratory models in the analysis of TBP2 and other meningococcal antigens 总被引:1,自引:0,他引:1
L. Ferrón C.M. Ferreirós M.T. Criado M. Pintor 《FEMS immunology and medical microbiology》1994,9(4):299-305
Abstract Lipoarabinomannan derived from the virulent Erdman strain and a rapidly growing, laboratory-attenuated strain of Mycobacterium tuberculosis were evaluated for their ability to modulate the production of nitric oxide (NO) by macrophages activated with IFN-γ or IFN-γ and LPS. It was observed that in macrophages pretreated with 100 μg ml−1 LAM, the NO induced by IFN-γ alone was augmented while the NO induced by IFN-γ and LPS was reduced. LAM was also shown to synergize with IFN-γ in the induction of NO, with AraLAM from the attenuated strain exhibiting greater potency than ManLAM from the Erdman strain. Despite the modulation of NO production, LAM did not affect the IFN-γ-induced macrophage growth inhibition of Francisella tularensis LVS, an organism whose growth inhibition in activated macrophages is dependent upon NO. 相似文献
5.
Timothée Ouassa Emanuele Borroni Guillaume Yao Loukou Hortense Faye-Kette Jacquemin Kouakou Hervé Menan Daniela Maria Cirillo 《PloS one》2012,7(9)
Background
Genotyping methods are useful tools to provide information on tuberculosis epidemic. They can allow a better response from health authorities and the implementation of measures for tuberculosis control. This study aimed to identify the main lineages and clades of Mycobacterium tuberculosis complex strains circulating in Côte d’Ivoire.Methods/Main Findings
Strains isolated from sputum samples of patients ongoing retreatment from all the country were characterized by spoligotyping and by MIRU-VNTR. Profiles obtained by spoligotyping were first compared to the SITVIT/SpolDB4 database for family assignment. Of 194 strains analysed, 146 (75.3%) belonged to the T lineage. The most predominant spoligotype was the shared international type 53 with 135 strains (69.6%). In contrast with neighbouring countries, LAM (11 strains, 5.7%) and H (9 strains 4.6%) lineages were slightly represented. Only 3 Beijing strains (1.5%) and 4 strains of Mycobacterium africanum (2%) were found. Analysis of the results obtained with MIRU-VNTR revealed also a high level of clustering.Conclusion/Significance
The population of Mycobacterium tuberculosis complex strains among retreatment cases in Côte d’Ivoire exhibits a low diversity, allowing to assume recent transmission and locally based infection. 相似文献6.
H. SUGITA, J. KAWASAKI, J. KUMAZAWA AND Y. DEGUCHI. 1996. The amylase-producing ability of intestinal bacteria in one marine crab and seven fish species was determined. Mean total viable counts ranged from 1.3 × 105 to 1.5 × 108 cfu g−1 , and Vibrionaceae were predominant in all specimens. Of 1585 strains examined, 341 (21.5%) produced ≥0.01 U amylase ml−1 . Percentage of producers (≥0.01 U ml−1 ) differed among genera/families. High abilities (≥0.05 U ml−1 ) were found in 1.4-3.6% of Enterobacteriaceae, Pseudomonas and Vibrionaceae strains. On the other hand, percentage of producers varied with animal species. These results reveal that the amylase producers were widely distributed in the digestive tracts of coastal animals including crabs and fish, irrespective of their food habitats. 相似文献
7.
Observations on the growth and production of chub Leuciscus cephalus and dace Leuciscus leuciscus in a small lowland river in southeast England 总被引:1,自引:0,他引:1
SUMMARY. The River Eden (Kent, England) holds a mixed coarse fish population in which minnows ( Phoxinus phoxinus ), gudgeon ( Gobio gobio ), chub ( Leuciscus cephalus ) and dace ( Leuciscus leuciscus ) are numerically predominant. Chub and dace provide the major interest to anglers and their growth and production were studied. Observed growth rates of both species were marginally below recorded averages from other British habitats. Back-calculations showed that year-class strength and relative growth rates varied between years. Instantaneous mortality rate Z was 0.147 for chub aged 1–10, 0.438 for chub aged 10 and over, and 0.172 for dace. Exclusive of the 0-group, fish numbers, biomass (wet wt) and production were found to be 0.1305 m-2 , 19.12 gm-2 and 5.38 gm-2 year-1 , respectively, for chub and 0.0968 m-2 , 4.33 gm-2 and 1.69 gm-2 year-1 for dace. Smoothing of data produced theoretical production figures of 6.69 gm-2 year-1 for chub and 1.15 gm-2 year-1 for dace. 相似文献
8.
Background
Multi Drug Resistant Tuberculosis (MDR TB) is a threat to global tuberculosis control. A significant fitness cost has been associated with DR strains from specific lineages. Evaluation of the influence of the competing drug susceptible strains on fitness of drug resistant strains may have an important bearing on understanding the spread of MDR TB. The aim of this study was to evaluate the fitness of MDR TB strains, from a TB endemic region of western India: Mumbai, belonging to 3 predominant lineages namely CAS, Beijing and MANU in the presence of drug susceptible strains from the same lineages.Methodology
Drug susceptible strains from a single lineage were mixed with drug resistant strain, bearing particular non synonymous mutation (rpoB D516V; inhA, A16G; katG, S315T1/T2) from the same or different lineages. Fitness of M.tuberculosis (M.tb) strains was evaluated using the difference in growth rates obtained by using the CFU assay system.Conclusion/Significance
While MANU were most fit amongst the drug susceptible strains of the 3 lineages, only Beijing MDR strains were found to grow in the presence of any of the competing drug susceptible strains. A disproportionate increase in Beijing MDR could be an alarm for an impending epidemic in this locale. In addition to particular non synonymous substitutions, the competing strains in an environment may impact the fitness of circulating drug resistant strains. 相似文献9.
The amylase-producing ability of the intestinal microflora in cultured specimens of ayu, carp, channel catfish, Japanese eel and tilapia was determined. Mean viable counts of aerobes and anaerobes ranged from 1·1×106 to 3·7×108 cfu g−1 and from 1·3×103 to 1·6×108 cfu g−1 , respectively. Aeromonas spp. and Bacteroidaceae were predominant in four to five fish species. Of 206 strains examined, 65 (31·6%) produced ≥0·01 U amylase ml−1 . The percentage of producers differed among families and genera of bacteria and fish species. While 56% of the anaerobes produced amylase, only 20% of the aerobes did. More than 50% of Aeromonas , Bacteroidaceae and Clostridium strains produced amylase efficiently while Acinetobacter , coryneforms, Enterobacteriaceae, Moraxella , Plesiomonas and Streptococcus strains did not. High amylase production (≥0·05 U ml−1 ) was found in 12 strains, 11 from Aeromonas and one Pseudomonas . The percentage of high amylase producers in Japanese eel was lower than the other four fish (2–30%). These results strongly suggest that the amylase produced by the intestinal microflora play an important role in the digestion of starch in freshwater fish to some extent. 相似文献
10.
1. Although large cladocerans are usually uncommon in large rivers, Daphnia lumholtzi (an exotic species in North America) is widespread and occasionally abundant. We collected zooplankton on the Illinois River (Illinois, U.S.A.) in 1995 and 1996 and found that the peak density of D. lumholtzi (25 L−1 ) typically exceeded that of all native species combined. Maximum density occurred during warm periods (up to 27 °C) when concentrations of inorganic suspended sediments were high (>50 mg L−1 ).
2. Using a life table experiment, we examined the effects of variation in suspended sediment (0 and 80 mg L−1 ) and food (104 and 105 Ankistrodesmus cells mL−1 ) on fitness of D. lumholtzi and the native Daphnia parvula. Daphnia lumholtzi had greater survivorship than D. parvula in most treatments and higher life-time fertility than D. parvula in all treatments. Both species achieved their fastest intrinsic rates of growth in treatments with high food, but their responses to suspended solids differed. The growth rate of D. lumholtzi in high food was slightly increased by higher turbidity, whereas that of D. parvula was depressed.
3. Results suggest that the ability of D. lumholtzi to tolerate suspended solids is an important factor contributing to its success in invading North American rivers. 相似文献
2. Using a life table experiment, we examined the effects of variation in suspended sediment (0 and 80 mg L
3. Results suggest that the ability of D. lumholtzi to tolerate suspended solids is an important factor contributing to its success in invading North American rivers. 相似文献
11.
Abstract The Het+ Nif+ and Het− Nif− strains of Nostoc muscorum sensitive to growth inhibition by methylamine (MA), overcame the MA inhibition as a result of their mutation to l -methionine- dl -sulfoximide (MSX)-resistant phenotype, which enabled them to assimilate MA like an ammonium nitrogen source. The MSX-resistant Het+ Nif+ strain synthesized the inhibitor-resistant transferase-defective glutamine synthetase (GS), which unlike parental GS underwent MA-dependent in vivo activation. These results suggest the involvement of GS enzyme in control of MA assimilation in cyanobacteria. 相似文献
12.
Sune Pettersson 《Physiologia plantarum》1986,66(1):122-128
Plants of barley ( Hordeum vulgare L. cv. Salve) were grown with 6.5–35% relative increase of K+ supply per day (RKR) using a special computer-controlled culture unit. After a few days on the culture solution the plants adapted their relative growth rate (RGR) to the rate of nutrient supply. The roots of the plants remained in a low salt status irrespective of the rate of nutrient supply, whereas the concentration of K+ in shoots increased with RKR. Both Vmax and Km for K+ (86 Rb) influx increased with RKR. It is concluded that with a continuous and stable K+ stress, the K+ uptake system is adjusted to provide an effective K+ uptake at each given RKR. Allosteric regulation of K+ influx does not occur and efflux of K+ is very small. 相似文献
13.
Annemieke F. Pronk Charles Affourtit Cyril Mashingaidze Adriaan H. Stouthamer Henk W. van Verseveld Fred C. Boogerd 《FEMS microbiology letters》1995,129(2-3):149-155
Abstract The in situ method for determination of reduction levels of cytochromes b and c pools during steady-state growth (Pronk et al., Anal. Biochem. 214, 149–155, 1993) was applied to chemostat cultures of the wild-type, a cytochrome aa3 single mutant and a cytochrome aa3 /d double mutant of Azorhizobium caulinodans . For growth with NH4 + as the N source, the results indicate that (i) the aa3 mutant strains growing at a dissolved O2 tension of 0.5% possess an active alternative cytochrome c oxidase, which is hardly present during fully aerobic growth, and assuming that (i) also pertains to the wild-type, (ii) the wild-type uses cytochrome aa3 under fully aerobic conditions. For growth with N2 as the N source, it was found that the aa3 mutant strains growing at dissolved O2 tensions ranging from 0.5 to 3.0% also contain an active alternative cytochrome c oxidase. 相似文献
14.
Dimethylsulfoxide reduction by marine sulfate-reducing bacteria 总被引:2,自引:0,他引:2
Henk M. Jonkers Marc J.E.C. van der Maarel Hans van Gemerden Theo A. Hansen 《FEMS microbiology letters》1996,136(3):283-287
Abstract Dimethylsulfoxide (DMSO) reduction occurred in five out of nine strains of sulfate-reducing bacteria from marine or saline environments, but not in three freshwater isolates. DMSO reduction supported growth in all positive strains. In Desulfovibrio desulfuricans strain PA2805, DMSO reduction occurred simultaneously with sulfate reduction and was not effectively inhibited by molybdate, a specific inhibitor of sulfate reduction. The growth yield per mol lactate was 26% higher with DMSO than with sulfate as electron acceptor. In extracts of cells of strain PA2805 grown on sulfate, a low level of DMSO-reducing activity was present (0.013 μmol (mg protein)− min− ); higher levels were found in cells grown on DMSO (0.56 μmol (mg protein)− min− ). In anoxic marine environments DMSO reduction by sulfate-reducing bacteria may lead to enhanced dimethylsulfide emission rates. 相似文献
15.
The growth of a strain of Rhizobium trifolii and of R. meliloti was studied in broth and peat cultures to determine the relative toxicity of Na+ and Cl- . The following salts were added in a range of concentrations: Na2 HPO4 as a source of Na+ , CaCl2 .2H2 O as a source of Cl- , and NaCl. Disodium hydrogen orthophosphate affected the growth rate of both strains in broth culture but not in peat culture. Unexpectedly, calcium chloride was more toxic than NaCl in broth and peat culture. The toxicity of NaCl can be ascribed to the Cl- . Rhizobium meliloti strains grew on 3·5% NaCl after adaptation during a long period. Rhizobia for soya bean and cowpea grew at 0·5% NaCl and those for clover and pea, at 1·0% NaCl. 相似文献
16.
Sidra E. G. Vasconcellos Chyntia Carolina Acosta Lia Lima Gomes Emilyn Costa Concei??o Karla Valéria Lima Marcelo Ivens de Araujo Maria de Lourdes Leite Flávio Tannure Paulo Cesar de Souza Caldas Harrison M. Gomes Adalberto Rezende Santos Michel K. Gomgnimbou Christophe Sola David Couvin Nalin Rastogi Neio Boechat Philip Noel Suffys 《PloS one》2014,9(10)
Rio de Janeiro is endemic for tuberculosis (TB) and presents the second largest prevalence of the disease in Brazil. Here, we present the bacterial population structure of 218 isolates of Mycobacterium tuberculosis, derived from 186 patients that were diagnosed between January 2008 and December 2009. Genotypes were generated by means of spoligotyping, 24 MIRU-VNTR typing and presence of fbpC103, RDRio and RD174. The results confirmed earlier data that predominant genotypes in Rio de Janeiro are those of the Euro American Lineages (99%). However, we observed differences between the classification by spoligotyping when comparing to that of 24 MIRU-VNTR typing, being respectively 43.6% vs. 62.4% of LAM, 34.9% vs. 9.6% of T and 18.3% vs. 21.5% of Haarlem. Among isolates classified as LAM by MIRU typing, 28.0% did not present the characteristic spoligotype profile with absence of spacers 21 to 24 and 32 to 36 and we designated these conveniently as “LAM-like”, 79.3% of these presenting the LAM-specific SNP fbpC103. The frequency of RDRio and RD174 in the LAM strains, as defined both by spoligotyping and 24 MIRU-VNTR loci, were respectively 11% and 15.4%, demonstrating that RD174 is not always a marker for LAM/RDRio strains. We conclude that, although spoligotyping alone is a tool for classification of strains of the Euro-American lineage, when combined with MIRU-VNTRs, SNPs and RD typing, it leads to a much better understanding of the bacterial population structure and phylogenetic relationships among strains of M. tuberculosis in regions with high incidence of TB. 相似文献
17.
I Mokrousov A Vyazovaya T Otten V Zhuravlev E Pavlova L Tarashkevich V Krishevich B Vishnevsky O Narvskaya 《PloS one》2012,7(7):e41318
This study aimed to characterize the population structure of Mycobacterium tuberculosis in Pskov oblast in northwestern Russia, to view it in the geographical context, to compare drug resistance properties across major genetic families. Ninety M. tuberculosis strains from tuberculosis (TB) patients, permanent residents in Pskov oblast were subjected to LAM-specific IS6110-PCR and spoligotyping, followed by comparison with SITVITWEB and MIRU-VNTRplus databases. The Beijing genotype (n = 40) was found the most prevalent followed by LAM (n = 18), T (n = 13), Haarlem (n = 10), Ural (n = 5), and Manu2 (n = 1); the family status remained unknown for 3 isolates. The high rate of Beijing genotype and prevalence of LAM family are similar to those in the other Russian settings. A feature specific for M. tuberculosis population in Pskov is a relatively higher rate of Haarlem and T types. Beijing strains were further typed with 12-MIRU (followed by comparison with proprietary global database) and 3 hypervariable loci QUB-3232, VNTR-3820, VNTR-4120. The 12-MIRU typing differentiated 40 Beijing strains into 14 types (HGI = 0.82) while two largest types were M2 (223325153533) prevalent throughout former USSR and M11 (223325173533) prevalent in Russia and East Asia. The use of 3 hypervariable loci increased a discrimination of the Beijing strains (18 profiles, HGI = 0.89). Both major families Beijing and LAM had similar rate of MDR strains (62.5 and 55.6%, respectively) that was significantly higher than in other strains (21.9%; P = 0.001 and 0.03, respectively). The rpoB531 mutations were more frequently found in Beijing strains while LAM drug resistant strains mainly harbored rpoB516 and inhA −15 mutations. Taken together with a high rate of multidrug resistance among Beijing strains from new TB cases (79.3% versus 44.4% in LAM), these findings suggest the critical impact of the Beijing genotype on the current situation with MDR-TB in the Pskov region in northwestern Russia. 相似文献
18.
Spermatozoa of the sea urchin, Hemicentrotus pulcherrimus (108 cells/ml), preincubated with unfertilized eggs deprived of jelly coats (more than l05 cells/ml) at 20°C for 20min in Mg2+ free artificial sea water containing 1 mM Ca2+ (MFASW), exhibited very low respiration, which was enhanced by 2, 4 dinitrophenol (DNP). The fertilization rate in MFASW was usually less than 5% and was about 25% at most. Preincubation with fertilized eggs (with and without a fertilization membrane) in MFASW did not reduced the respiratory rate of spermatozoa. The rate of sperm respiration was lower in MFASW than in artificial sea water (ASW), but was higher than the respiratory rate of spermatozoa preincubated in MFASW with unfertilized eggs. Sperm respiration in MFASW or in ASW was not stimulated by 2, 4 dinitrophenol. Almost complete inhibition of sperm respiration was obtained with unfertilized eggs fixed with glutaraldehyde at concentrations of above 105 cells/ml in MFASW and of about l04 cells/ml in ASW. The respiratory rate of spermatozoa treated with fixed eggs was enhanced by DNP. It is concluded that the respiratory rate of the spermatozoa is reduced by their interaction with unfertilized eggs before their penetration into the eggs. 相似文献
19.
Thirty-nine samples of freshly drawn ewes' milk collected at 13 farms, and 120 samples of raw ewes' milk collected on arrival at a dairy were examined. Farm samples had geometric mean counts of 4.4 × 102 Enterobacteriaceae/ml, 3.9 × 102 coliforms/ml and 2.0 × 102 faecal coliforms/ml, whereas the respective mean counts were 6.2 × 103 /ml, 5.4 × 103 /ml and 1.3 × 103 /ml for dairy samples. Salmonellas were not detected by enrichment procedures in any of the 159 samples examined. Escherichia coli (47.5% strains), Enterobacter cloacae (17.7%), Ent. agglomerans (11.3%), Hafnia alvei (6.5%) and Klebsiella oxytoca (6.0%) were the predominant species in 434 Enterobacteriaceae strains isolated from farm samples. Levels and species of Enterobacteriaceae found in the present work in raw ewes' milk imply a considerable risk of early blowing in cheese-making from unpasteurized milk. 相似文献
20.
Two cultivars of wheat (Triticum aestivum L. cvs Kadett and WW 20299) were grown for 9 days with 20% relative increase in nutrient supply per day at pH 4.1. Aluminium at 50 μ M retarded the growth of roots more than that of shoots in both cultivars, thus decreasing the root/shoot ratio. The inhibition was largest in WW 20299. With long term Al treatment (9 days), Km for K+ (86 Rb) influx increased five times in both cultivars and Vmax decreased in WW 20299. Efflux of K+ (86 Rb) was little affected. When the roots were treated with aluminium for two days, only relative growth rate of roots was retarded, while growth of shoots was unaffected and influx of K+ (86 Rb) adjusted to the actual K+ demand of the plants. It is concluded that the effects of aluminium on K+ uptake in these wheat cultivars are not primary factors contributing to aluminium sensitivity. However, in soil with Al the demand for a comparatively high concentration of K+ to maintain an adequate K+ uptake rate, in combination with a slow growth rate of the roots, may secondarily lead to K+ deficiency in the plants. 相似文献