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1.
Proteins secreted by the type V secretion system (T5SS), known as autotransporters, are large extracellular virulence proteins localized to the bacterial poles. In this study, we characterized two novel autotransporter proteins of ‘
Candidatus
Liberibacter asiaticus’ (Las), and redesignated them as LasAI and LasAII in lieu of the previous names HyvI and HyvII. As a phloem-limited, intracellular bacterial pathogen, Las has a significantly reduced genome and causes huanglongbing (HLB), a devastating disease of citrus worldwide. Bioinformatic analyses revealed that LasAI and LasAII share the structural features of an autotransporter family containing large repeats of a passenger domain and a unique C-terminal translocator domain. When fused to the GFP gene and expressed in E. coli, the LasAI C-terminus and the full length LasAII were localized to the bacterial poles, similar to other members of autotransporter family. Despite the absence of a typical signal peptide, LasAI was found to localize at the cell surface by immuno-dot blot using a monoclonal antibody against the partial LasAI protein. Its surface localization was also confirmed by the removal of the LasAI antigen using a proteinase K treatment of the intact bacterial cells. When co-inoculated with a P19 gene silencing suppressor and transiently expressed in tobacco leaves, the GFP-LasAI translocator targeted to the mitochondria. This is the first report that Las encodes novel autotransporters that target to mitochondria when expressed in the plants. These findings may lead to a better understanding of the pathogenesis of this intracellular bacterium. 相似文献
2.
Generation of photoelectric potential in chromatophores of Rhodopseudomonas sphaeroides has been measured (i) spectrophotometrically, using electrochromic shift of carotenoid absorption band or (ii) electrometrically, by means of two electrodes separated by a collodion film covered on one side with chromatophores. A 15 ns laser flash was used to induce a single turnover of photosynthetic reaction centers. It was found that results obtained by both methods are similar in (i) direction of electric vector (the chromatophore interior positive) and (ii) redox titration curves (Em = 10mV). The magnitudes of the photopotential were about 60 and 25 mV, when monitored with spectral and electrometric techniques, respectively. In both cases, the rise times of the photopotentials were faster than time resolution of the techniques used. Decay of the response of carotenoids was found to be slower than that in the collodion film system. The addition of ubiquinone Q10 into the decane solution of asolectin used to impregnate the collodion film led to slowing down of the decay. The carotenoid response decay could be accelerated by FCCP or o-phenanthroline. In the latter case, the shape of the decay curve coincides with decay of the photopotential measured in the collodion film system. It is suggested that decane extracts secondary ubiquinone from chromatophores attached to the collodion film. Such an unfavorable effect can be strongly decreased by added ubiquinone 相似文献
3.
Entrance of lactic acid bacteria into the interior of brined cucumbers was found to be greatly influenced by gas composition of the cucumbers before brining. Exchange of the internal gas of fresh cucumbers with O2 resulted in absorption of bacteria into the subsequently brined fruit within a few hours. Bacteria were absorbed into nonexchanged cucumbers to a lesser extent. Little bacterial absorption occurred in N2-exchanged cucumbers. Stomata of the cucumber skin appeared to be a likely port for bacterial entry. When Pediococcus cerevisiae or Lactobacillus plantarum cells were added to the brine of O2-exchanged cucumbers, the respective cell types colonized in large numbers within intercellular spaces and vascular elements of mesocarp tissue during fermentation of the cucumbers. Implications of these observations, particularly with regard to bloater formation in brined cucumbers, are discussed. 相似文献
4.
A non-chemical means of preventing premature pole failure in soil-contact was investigated by applying open-ended cylindrical sleeves of heat-shrink polyethylene to the soil-contact surfaces of Eucalyptus grandis poles as physical barriers to fungal colonisation from soil in sub-tropical South Africa. The test site was managed under flood-irrigation to represent vineyard conditions. After exposure for 26 weeks all untreated unsleeved poles had failed, whereas sleeved poles were colonised by fungi but remained relatively sound. Unsleeved poles treated with 16 kg CCA m−3 were colonised by fungi at their soil-contact surfaces, whereas their sleeved counterparts were uncolonised. Unsleeved poles treated with 100 kg creosote m−3 were extensively covered by biofilm and showed incipient decay at their soil-contact surfaces, whereas their sleeved counterparts were uncolonised. 相似文献
5.
Rebai Ben Ammar Soumaya Kilani Ines Bouhlel Ines Skandrani Aicha Naffeti Jihed Boubaker Mohamed Ben Sghaier Wissem Bhouri Amor Mahmoud Leila Chekir-Ghedira Kamel Ghedira 《Annals of microbiology》2007,57(3):453-460
The petroleum ether, chloroformic, ethyl acetate, methanolic, Total Oligomers Flavonoids (TOF) enriched extracts, water extract as well as its fractions A1, A2, A3 obtained from aerial parts ofRhamnus alaternus, a Tunisian-Mediterranean medicinal species, were investigated for the contents of phenolic compounds, cytotoxic activity against the K562 human chronic myelogenous leukaemia cell line and L1210 leukaemia murine cells and for antibacterial activity against Gram positive and Gram negative bacterial reference strains. A pronounced cytotoxic effect on both the cell lines was shown in the TOF, ethyl acetate, methanolic, aqueous extracts and A2 fraction, with respectively IC50 values 75, 232, 298, 606 and 571 μg/ml on K562 cells and 198, 176, 767, 560 and 614 μg/ml on L1210 cell line. Significant activity against bacterial reference strains:Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Salmonella enteritidis andSalmonella typhimurium was shown with ethyl acetate, TOF extracts and A2 fraction. The antimicrobial and cytotoxic activities showed byR. alatemus depended on the chemical composition of the tested extracts. 相似文献
6.
Spatial Distribution of Potential in a Flat Cell: Application to the Catfish Horizontal Cell Layers 总被引:3,自引:0,他引:3
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An analytical solution is obtained for the three-dimensional spatial distribution of potential inside a flat cell, such as the layer of horizontal cells, as a function of its geometry and resistivity characteristics. It was found that, within a very large range of parameter values, the potential is given by [Formula: see text] where r = ρ/ρ0, = z/ρ0, ρ = (Ri/Rm)·ρ0, δ = h/ρ0; K is a constant; J is the assumed synaptic current; ρ, z are cylindrical coordinates; ρ0 is the radius of the synaptic area of excitation; h is the cell thickness; and Ri, Rm are the intracellular and membrane resistivities, respectively. Formula A closely fits data for the spatial decay of potential which were obtained from the catfish internal and external horizontal cells. It predicts a decay which is exponential down to about 40% of the maximum potential but is much slower than exponential below that level, a characteristic also exhibited by the data. Such a feature in the decay mode allows signal integration over the large retinal areas which have been observed experimentally both at the horizontal and ganglion cell stages. The behavior of the potential distribution as a function of the flat cell parameters is investigated, and it is found that for the range of the horizontal cell thicknesses (10-50 μ) the decay rate depends solely on the ratio Rm/Ri. Data obtained from both types of horizontal cells by varying the diameter of the stimulating spot and for three widely different intensity levels were closely fitted by equation A. In the case of the external horizontal cell, the fit for different intensities was obtained by varying the ratio Rm/Ri; in the case of the internal horizontal cell it was found necessary, in order to fit the data for different intensities, to vary the assumed synaptic current J. 相似文献
7.
We examined the effects of increasing salt concentrations on the decay of the common aquatic angiosperm, Triglochin procerum R. Br. (Juncaginaceae) from a freshwater wetland close to Gippsland Lakes, eastern Vic., Australia. Rate of decay, measured as leaf mass loss, and microbial enzymatic activity, used as a surrogate for microbial activity, were measured on leaves placed in mesocosms ranging in electrical conductivity from 100 to 45,000 EC. The rate of leaf mass loss was up to three times slower in salt concentrations of 45,000 EC (∼69% ash-free dry leaf weight remaining after 21 days), compared to salt concentrations of 100 EC (∼23%). Enzymatic activity on the leaves at 45,000 EC (0.56, A490) was about one-half that on leaves in 100 EC (1.00, A490). A second experiment measured the same variables for leaves placed in solutions of NaCl, marine salt, or an organic osmoticum, polyethylene glycol (200 Da molecular weight). Results indicated that the inhibition of leaf mass loss was ∼1.5 times greater in NaCl (∼39% remaining after 21 days) than an organic osmoticum, polyethylene glycol (∼24% remaining after 21 days), indicating a role for ionic toxicity in the salt effects. Enzymatic activity on leaves was significantly inhibited in NaCl (0.50, A490) compared with marine salt (0.74, A490) or polyethylene glycol (0.72, A490). Our findings suggest several implications for the effects of acute secondary salinisation on organic matter decomposition. Inhibition of decay rates due to acute increase in salt concentration is related to decreased enzymatic activity on decaying leaves. This relationship has ramifications for microzoan food webs based on a microbial loop of bacterial production and consumption and availability of degraded organic matter entering metazoan food webs. 相似文献
8.
Petra Weißhaupt Annette Naumann Wolfgang Pritzkow Matthias Noll 《Mycological Progress》2013,12(2):283-290
The white-rot fungus Hypholoma fasciculare coexists with a bacterial community that uses low-molecular weight carbon sources provided by fungal, extracellular enzyme activities. Since fungal development on wood is limited by the availability of nitrogen (N), bacteria could contribute to the N supply. To prove or disapprove an interaction in terms of N transfer, N sources of the fungus and the coexisting bacterial isolates were investigated, and the bacterial N2 fixation was quantified. Fungal, fungal—bacterial and bacterial wood decomposition was analysed by Fourier transform infrared spectroscopy (FTIR), mass loss and surface pH. Microbial N preferences were investigated by elemental analysis isotope ratio mass spectrometry (IRMS). In addition, diazotrophic activity was explored after cultivation under a 15?N2/O2 atmosphere. Decomposition was similar with and without bacteria and both H. fasciculare and coexisting bacteria preferred reduced N species, such as urea, ammonium and organic N. In most of the bacteria, the 15?N abundance in the biomass increased significantly but to a low extent if they were cultivated under a 15?N2/O2 atmosphere. This effect is considered an artefact and attributed to adsorption rather than to bacterial N2 fixation activity. Hence, the bacteria coexisting with H. fasciculare rather competed for the same N sources than supported fungal N supply by diazotrophic activity. 相似文献
9.
(1) The relationship between activation of the membrane-bound ATPase and the stimulation of dissipation of the flash-induced membrane potential by preillumination was studied in intact spinach leaves by measuring the ATPase activity of rapidly isolated chloroplasts and the decay of the flash-induced 515-nm absorbance change (ΔA515) in intact leaves. (2) The decay of ΔA515 was accelerated by preillumination. The ΔA515 decay in leaves treated with N,N′-dicyclohexylcarbodiimide (DCCD) became slower and was not accelerated by preillumination. However, treatment with DCCD did not lower the intensity of delayed fluorescence. (3) Membrane-bound ATPase of chloroplasts which were rapidly isolated from the preilluminated leaves (90 s preparation time) showed a higher activity (over 200 μmol Pi/mg chlorophyll per h in the case of 2-min preillumination) than that of chloroplasts isolated from dark-adapted leaves. (4) The acceleration of ΔA515 decay and the activation of ATPase showed similar dependences on illumination time in intact leaves. 3-(3′,4′-Dichlorophenyl)-1,1-dimethylurea, carbonyl cyanide p-chlorophenylhydrazone and DCCD inhibited the activation of ATPase and the acceleration of the ΔA515 decay by preillumination. (5) The ATPase activity of chloroplasts isolated from illuminated leaves showed a single exponential decay (‘dark inactivation in vitro’). The ATPase activity induced by illuminating the leaves became lower as the dark interval between illumination and the isolation of chloroplasts was increased (‘dark inactivation in vivo’). The time course of the decay of activity had a lag and showed a sigmoidal curve when plotted semilogarithmically. The decay had an apparent half-time of 25 min. (6) The recovery of the accelerated ΔA515 decay in preilluminated leaves to the original slow rate showed a sigmoidal decay similar to that of the activity of ATPase in intact leaves with a half-time of about 23 min in the dark. (7) It was concluded that the decay rate of ΔA515 reflected the chloroplast ATPase activity in intact leaves and that the ion conductance of thylakoid membrane was mainly determined by the H+ flux through the ATPase, the activity of which was increased after the formation of the high-energy state. 相似文献
10.
Novel Technique for Measuring Tissue Firmness within Tomato (Lycopersicon esculentum Mill.) Fruit
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Developmental changes of tomato (Lycopersicon esculentum) fruit tissues during maturation were analyzed by a physically defined method (stress-relaxation analysis). The tip of a conical probe connected to a load sensor was positioned on the cut surface of a sliced tomato fruit, and the decay of the imposed stress was monitored. Stress-relaxation data thus obtained were used for the calculation of three stress-relaxation parameters. Different zones within tomato fruit harvested at six different ripening stages were analyzed. One of the stress-relaxation parameters, minimum stress-relaxation time (T0), decreased as the fruits matured. The decrease in T0 was first found in the core of the carpel junction within the endopericarp at the blossom end during the breaker stage. The decrease in T0 progressed from the blossom end, through the equatorial region and finally throughout the shoulder, as the fruit matured. In mature green fruit, T0 values within the placenta and the proximal carpel junction were lower than those by other parts of the fruit. For all measurements the maximum stress-relaxation time was not substantially changed during maturation, nor were their changes observed in different regions of the fruit. The observed relaxation rate was therefore correlated with softening. The results indicate that fruit softening may be physically associated with the stress-relaxation parameter, T0, and the extent of softening is a function of position within the fruit. Decreases in T0 value appear to be correlated with the reported regional variation in the appearance of polygalacturonase. 相似文献
11.
The properties of slowly inactivating delayed-rectifier K+ current (IKdr) were investigated in NG108-15 neuronal cells differentiated with long-term exposure to dibutyryl cyclic AMP. Slowly inactivating IKdr could be elicited by prolonged depolarizations from −50 to +50 mV. These outward K+ currents were found to decay at potentials above −20 mV, and the decay became faster with greater depolarization. Cell exposure to aconitine resulted in the reduction of IKdr amplitude along with an accelerated decay of current inactivation. Under current-clamp recordings, a delay in the initiation of action potentials (APs) in response to prolonged current stimuli was observed in these cells. Application of aconitine shortened the AP initiation in combination with an increase in both width of spike discharge and firing frequency. The computer model, in which state-dependent inactivation of IKdr was incorporated, was also implemented to predict the firing behavior present in NG108-15 cells. As the inactivation rate constant of IKdr was elevated, the firing frequency was progressively increased along with a shortening of the latency for AP appearance. Our theoretical work and the experimental results led us to propose a pivotal role of slowly inactivating IKdr in delayed firing of APs in NG108-15 cells. The results also suggest that aconitine modulation of IKdr gating is an important molecular mechanism through which it can contribute to neuronal firing. 相似文献
12.
Physiological Aspects of Biosynthesis of Lignin Peroxidases by Phanerochaete chrysosporium 总被引:2,自引:0,他引:2
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Methods based on UV-visible diffuse reflectance spectroscopy were used to study the physiological aspects of lignin-peroxidase biosynthesis by Phanerochaete chrysosporium. Here we introduce the use of cytochrome aa3 as an indicator of active fungal biomass and of its redox state to calculate the oxygen mass transport coefficient between the growth medium and the fungal cell interior. When lignin peroxidase biosynthesis was enhanced by the addition of Tween 80 or Tween 20 to the growth medium, a higher proportion of reduced cytochrome aa3 and a higher oxygen diffusion barrier were observed compared with control cultures. In cultures supplemented with Tween 80 or Tween 20, a higher oxygen mass transport coefficient between the growth medium and the interior of the fungal cell was also found. The beginning of the lignin peroxidase activity in these cultures was found to coincide with a temporary cessation in the dry biomass increase and a reduction in the relative active-biomass concentration. During the lignin peroxidase activity, a decrease in the intracellular pH and an increase in the growth medium pH were determined in cultures supplemented with Tween 80. 相似文献
13.
《Biochimica et Biophysica Acta - Proteins and Proteomics》2002,1598(1-2):46-54
The water-binding properties of bovine lens α-crystallin, collagen from calf skin and bovine serum albumin (BSA), were investigated with various techniques. The water absorptive capacity was obtained in high vacuum desorption experiments volumetrically, and also gravimetrically in controlled atmosphere experiments. NMR spin–echo technique was used to study the hydration of protein samples and to determine the spin–spin relaxation times (T2) from the protons of water, absorbed on the proteins. Isolated bovine lenses were sectioned into 11–12 morphological layers (from anterior cortex through nucleus to posterior cortex). Crystallin profiles were obtained for each lens layer using thin-layer isoelectric focusing in polyacrylamide gel (IEF). The water content in relation to dry weight of proteins was measured in individual morphological lens layers. During the water vapor uptake P/P0=0.75, α-crystallin did not absorb water, suggesting that hydrophobic regions of the protein are exposed to the aqueous solvent. At P/P0=1.0, the absorption of water by α-crystallin was 17% with a single component decay character of spin–echo (T2=3 ms). Addition of water to α-crystallin to about 50% of its w/w in the protein sample showed T2=8 ms with only one single component decay of the spin–echo signal. The single component decay character of the spin–echo indicates at the tightly bound water by α-crystallin. Under a relative humidity P/P0=1.0, collagen and BSA absorbed correspondingly 19.3% and 28% of water and showed a two-component decay curve with T2 of about 5 and 40 ms. The findings demonstrate the presence of two water fractions in collagen and BSA which are separated in space. The IEF data suggest a tight binding of water with α-crystallin with similar distribution patterns in the lens layers. The IEF data demonstrate a possible chaperone-like function for α-crystallin in the nucleus and inner cortex of the lens, but not in the outer cortex. To conclude, it was found that α-crystallin can immobilize and bind water to a greater extent than other proteins such as collagen and BSA. These results shed new light on structural properties of α-crystallin and have important implications for understanding the mechanism of the chaperone-like action of this protein in the lens and non-ocular tissues. 相似文献
14.
The Temporal Scaling of Bacterioplankton Composition: High Turnover and Predictability during Shrimp Cultivation 总被引:4,自引:0,他引:4
Jinbo Xiong Jianlin Zhu Kai Wang Xin Wang Xiansen Ye Lian Liu Qunfen Zhao Manhua Hou Linglin Qiuqian Demin Zhang 《Microbial ecology》2014,67(2):256-264
The spatial distribution of microbial communities has recently been reliably documented in the form of a distance–similarity decay relationship. In contrast, temporal scaling, the pattern defined by the microbial similarity–time relationships (STRs), has received far less attention. As a result, it is unclear whether the spatial and temporal variations of microbial communities share a similar power law. In this study, we applied the 454 pyrosequencing technique to investigate temporal scaling in patterns of bacterioplankton community dynamics during the process of shrimp culture. Our results showed that the similarities decreased significantly (P?=?0.002) with time during the period over which the bacterioplankton community was monitored, with a scaling exponent of w?=?0.400. However, the diversities did not change dramatically. The community dynamics followed a gradual process of succession relative to the parent communities, with greater similarities between samples from consecutive sampling points. In particular, the variations of the bacterial communities from different ponds shared similar successional trajectories, suggesting that bacterial temporal dynamics are predictable to a certain extent. Changes in bacterial community structure were significantly correlated with the combination of Chl a, TN, PO4 3-, and the C/N ratio. In this study, we identified predictable patterns in the temporal dynamics of bacterioplankton community structure, demonstrating that the STR of the bacterial community mirrors the spatial distance–similarity decay model. 相似文献
15.
《Saudi Journal of Biological Sciences》2017,24(6):1288-1293
The antimicrobial activity of plant extract of Peganum harmala, a medicinal plant has been studied already. However, knowledge about bacterial diversity associated with different parts of host plant antagonistic to different human pathogenic bacteria is limited. In this study, bacteria were isolated from root, leaf and fruit of plant. Among 188 bacterial isolates isolated from different parts of the plant only 24 were found to be active against different pathogenic bacteria i.e. Escherichia coli, Methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecium, Enterococcus faecalis and Pseudomonas aeruginosa. These active bacterial isolates were identified on the basis of 16S rRNA gene analysis. Total population of bacteria isolated from plant was high in root, following leaf and fruit. Antagonistic bacteria were also more abundant in root as compared to leaf and fruit. Two isolates (EA5 and EA18) exhibited antagonistic activity against most of the targeted pathogenic bacteria mentioned above. Some isolates showed strong inhibition for one targeted pathogenic bacterium while weak or no inhibition for others. Most of the antagonistic isolates were active against MRSA, following E. faecium, P. aeruginosa, E. coli and E. faecalis. Taken together, our results show that medicinal plants are good source of antagonistic bacteria having inhibitory effect against clinical bacterial pathogens. 相似文献
16.
The activity and decay characteristics of nitrate reductase from wheat (Triticum aestivum) were studied in crude, partially-purified and highly-purified preparations. The decay of nitrate reductase activity in crude extracts was due to spontaneous dissociation of the enzyme and to the effects of two decay factors, one present in the 0–30% and the other in the 50–70% saturated (NH4)2SO4 fraction of a crude extract. Low rates of factor-mediated NR decay in vitro were associated with high levels of NR activity in vivo. 相似文献
17.
Elisa Haug-Schifferdecker Deniz Arican Reinhard Brückner Lutz Heide 《The Journal of biological chemistry》2010,285(22):16487-16494
Five fungal genomes from the Ascomycota (sac fungi) were found to contain a gene with sequence similarity to a recently discovered small group of bacterial prenyltransferases that catalyze the C-prenylation of aromatic substrates in secondary metabolism. The genes from Aspergillus terreus NIH2624, Botryotinia fuckeliana B05.10 and Sclerotinia sclerotiorum 1980 were expressed in Escherichia coli, and the resulting His8-tagged proteins were purified and investigated biochemically. Their substrate specificity was found to be different from that of any other prenyltransferase investigated previously. Using 2,7-dihydroxynaphthalene (2,7-DHN) and dimethylallyl diphosphate as substrates, they catalyzed a regiospecific Friedel-Crafts alkylation of 2,7-DHN at position 3. Using the enzyme of A. terreus, the Km values for 2,7-DHN and dimethylallyl diphosphate were determined as 324 ± 25 μm and 325 ± 35 μm, respectively, and kcat as 0.026 ± 0.001 s−1. A significantly lower level of prenylation activity was found using dihydrophenazine-1-carboxylic acid as aromatic substrate, and only traces of products were detected with aspulvinone E, flaviolin, or 4-hydroxybenzoic acid. No product was formed with l-tryptophan, l-tyrosine, or 4-hydroxyphenylpyruvate. The genes for these fungal prenyltransferases are not located within recognizable secondary metabolic gene clusters. Their physiological function is yet unknown. 相似文献
18.
Hans-Uwe Dahms Tilmann Harder 《Journal of experimental marine biology and ecology》2007,341(2):228-238
The relationship between monobacterial films and the preference of harpacticoid copepods for such films was investigated using still water multiple-choice assays with natural biofilm and sterile conditions as controls. Adult Schizopera sp. were most attracted by a heterogeneous natural biofilm, followed by monospecies-biofilms of Rhodovulum sp., Vibrio proteolyticus, and Flexibacter sp. The preferred bacterial films stemmed from different phylogenetic and physiological groups. The results indicated that the harpacticoid Schizopera sp. was effectively and differentially attracted by bacterial films. Since bacteria constitute a substantial portion of the organic carbon available at the sea bottom as nutritive sources for harpacticoid copepods, we subsequently examined the influence of 9 bacterial strains and a natural biofilm as a nutrient source on the growth and reproductive performance of ontogenetic stages (nauplii and copepodids) of Schizopera sp. The food value of bacterial strains was assayed in terms of life table data that provided growth parameters. All variables were affected by the type of food offered. A diet on Rhodovulum sp. resulted in optimal growth performance of nauplii and copepodids demonstrating that bacteria can be used as a sole diet to support postembryonic development. The present study is the first to link behavioral preferences to bacterial biofilms with life history parameters when cultivating harpacticoid copepods on the same bacterial strains as the only diet. This study revealed a discrepancy between the biofilm favored (natural biofilm) and the one leading to maximal reproductive performance (monobacterial film of Rhodovulum sp. MB253) as indicated by major life table data as net reproductive rate (Ro), mean generation time (Tm), and capacity for increase (rc). 相似文献
19.
《Fungal Ecology》2016
Ectomycorrhizal fungi produce low molecular weight organic compounds, supporting diverse microbial communities. To link mycorrhizal root exudation directly to bacterial responses, we used Scots pine exudates with (Suillus variegatus and Piloderma fallax) and without mycorrhiza as substrata for forest soil bacteria. Bacterial growth and vitality was monitored, and community composition determined using T-RFLP, cloning and sequencing. We investigated if the amount of organic acids in exudates explained bacterial growth, and whether bacterial communities were influenced by pre-exposure to elevated atmospheric CO2. We demonstrated functional differences in bacterial growth rates related to CO2. There was a shift in the bacterial community (e.g. Burkholderia sp. and gamma-proteobacteria) toward organisms better able to rapidly utilize exudates when pine microcosms were pre-exposed to elevated CO2. Soil bacteria from all treatments tended to grow more abundantly and rapidly in exudates from Piloderma-colonized seedlings, suggesting that the organic acids and/or unidentified compounds present supported greater growth. 相似文献
20.
Je Chul Lee Dong Sun Kim Dong Chan Moon Jung-Hwa Lee Mi Jin Kim Su Man Lee Yong Seok Lee Se-Won Kang Eun Jung Lee Sang Sun Kang Eunpyo Lee Sung Hee Hyun 《Journal of microbiology (Seoul, Korea)》2009,47(5):641-645
Nuclear targeting of bacterial proteins is an emerging pathogenic mechanism whereby bacterial proteins can interact with nuclear molecules and alter the physiology of host cells. The fully sequenced bacterial genome can predict proteins that target the nuclei of host cells based on the presence of nuclear localization signal (NLS). In the present study, we predicted bacterial proteins with the NLS sequences from Klebsiella pneumoniae by bioinformatic analysis, and 13 proteins were identified as carrying putative NLS sequences. Among them, HsdM, a subunit of KpnAl that is a type I restriction-modification system found in K. pneumoniae, was selected for the experimental proof of nuclear targeting in host cells. HsdM carried the NLS sequences, 7KKAKAKK13, in the N-terminus. A transient expression of HsdM-EGFP in COS-1 cells exhibited exclusively a nuclear localization of the fusion proteins, whereas the fusion proteins of HsdM with substitutions in residues lysine to alanine in the NLS sequences, 7AAAKAAA13, were localized in the cytoplasm. HsdM was co-localized with importin o in the nuclei of host cells. Recombinant HsdM alone methylated the eukaryotic DNA in vitro assay. Although HsdM tested in this study has not been considered to be a virulence factor, the prediction of NLS motifs from the full sequenced genome of bacteria extends our knowledge of functional genomics to understand subcellular targeting of bacterial proteins. 相似文献