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1.
The diverse morphology of the filamentous organism Streptomyces hygroscopicus var. geldanus was characterised by image analysis under various environmental conditions. In the presence of surfactant compounds, a significant decrease in the mean pellet diameter was observed. Cell aggregation was also influenced by spore inoculum level, with high concentrations reducing pellet size. In addition, the dispersion of pellets was found to increase with the inclusion of glass beads to submerged shake-flask cultures. In all cases, production of the secondary metabolite geldanamycin was determined to be dependent on the morphological profile of the organism, with a concomitant increase of 88% in geldanamycin yield observed as the mean pellet diameter was reduced by 70%. Thus, to maximise the yield of geldanamycin, it is necessary to limit pellet formation in Streptomyces hygroscopicus var. geldanus to an appropriate size. 相似文献
2.
von Rad U Klein I Dobrev PI Kottova J Zazimalova E Fekete A Hartmann A Schmitt-Kopplin P Durner J 《Planta》2008,229(1):73-85
3.
Gametophores of mosses Mnium undulatum and Polytrichum commune were submerged in distilled water or in calcium chloride solution (0.9 mM Ca2+) to induce hypoxia. The net photosynthetic (PN) and dark respiration rate (RD) were measured in the air containing 300–400 μmol(CO2)·mol−1(air) and 0.21 mol(O2)·mol−1(air). PN of M. undulatum gametophores decreased to 58 % of the control after 1-h submersion in water, whereas to 80 % of the control in P. commune gametophores. A smaller decrease in PN was observed when the gametophores were immersed in CaCl2 solution. In hypoxia, RD in the tested mosses species was a little higher than in the control. 相似文献
4.
It was investigated whether quorum sensing (QS) mediated by N-acylhomoserine lactones (AHLs) was important for heterotrophic bacteria from the littoral zone of the oligotrophic Lake Constance
for growth with organic particles. More than 900 colonies from lake water microcosms with artificial organic aggregates consisting
of autoclaved unicellular algae embedded in agarose beads were screened for AHL-production. AHL-producing bacteria of the
genus Aeromonas enriched in the microcosms but AHLs could not be detected in any microcosm. To test for a potential function of AHL-mediated
QS, growth experiments with the wild type and an AHL-deficient mutant of Aeromonas hydrophila in lake water microcosms were performed. Growth of both strains did not differ in single cultures and showed no mutual influence
in co-cultures. In co-cultures with a competitor bacterium belonging to the Cytophaga–Flavobacterium group, growth of both A. hydrophila strains was reduced while growth of the competitor bacterium was not affected. Exogenous AHL-addition did not influence growth
of the Aeromonas strains in any microcosm experiment. These results showed that AHL-mediated QS was not required for A. hydrophila during colonization and degradation of organic particles in lake water microcosms, suggesting that cell–cell signalling of
heterotrophic bacteria in oligotrophic waters relies on novel signal molecules. 相似文献
5.
6.
Background
Differentiating Dictyostelium discoideum amoebae respond upon cAMP-stimulation with an increase in the cytosolic free Ca2+ concentration ([Ca2+]i) that is composed of liberation of stored Ca2+ and extracellular Ca2+-influx. In this study we investigated whether intracellular cAMP is involved in the control of [Ca2+]i. 相似文献7.
Schaloske RH Lusche DF Bezares-Roder K Happle K Malchow D Schlatterer C 《BMC cell biology》2005,6(1):13
Background
Stimulation of Dictyostelium discoideum with cAMP evokes an elevation of the cytosolic free Ca2+ concentration ([Ca2+]i). The [Ca2+]i-change is composed of liberation of stored Ca2+ and extracellular Ca2+-entry. The significance of the [Ca2+]i-transient for chemotaxis is under debate. Abolition of chemotactic orientation and migration by Ca2+-buffers in the cytosol indicates that a [Ca2+]i-increase is required for chemotaxis. Yet, the iplA - mutant disrupted in a gene bearing similarity to IP3-receptors of higher eukaryotes aggregates despite the absence of a cAMP-induced [Ca2+]i-transient which favours the view that [Ca2+]i-changes are insignificant for chemotaxis. 相似文献8.
The foodborne pathogen Bacillus cereus can form biofilms on various food contact surfaces, leading to contamination of food products. To study the mechanisms of
biofilm formation by B. cereus, a Tn5401 library was generated from strain UW101C. Eight thousand mutants were screened in EPS, a low nutrient medium. One mutant
(M124), with a disruption in codY, developed fourfold less biofilm than the wild-type, and its defective biofilm phenotype was rescued by complementation.
Addition of 0.1% casamino acids to EPS prolonged the duration of biofilms in the wild-type but not codY mutant. When decoyinine, a GTP synthesis inhibitor, was added to EPS, biofilm formation was decreased in the wild-type but
not the mutant. The codY mutant produced three times higher protease activity than the wild-type. Zymogram and SDS-PAGE data showed that production
of the protease (∼130 kDa) was repressed by CodY. Addition of proteinase K to EPS decreased biofilm formation by the wild-type.
Using a dpp-lacZ fusion reporter system, it was shown that that the B. cereus CodY can sense amino acids and GTP levels. These data suggest that by responding to amino acids and intracellular GTP levels
CodY represses production of an unknown protease and is involved in biofilm formation. 相似文献
9.
Young Chul Kwon Sinil Kim Yong Seok Lee Je Chul Lee Myung-Je Cho Woo-Kon Lee Hyung-Lyun Kang Jae-Young Song Seung Chul Baik Hyeon Su Ro 《Journal of microbiology (Seoul, Korea)》2016,54(5):387-395
HP0059, an uncharacterized gene of Helicobacter pylori, encodes a 284-aa-long protein containing a nuclear localization sequence (NLS) and multiple leucine-rich heptad repeats. Effects of HP0059 proteins in human stomach cells were assessed by incubation of recombinant HP0059 proteins with the AGS human gastric carcinoma cell line. Wild-type HP0059 proteins showed cytotoxicity in AGS cells in a concentration-dependent manner, whereas NLS mutant protein showed no effect, suggesting that the cytotoxicity is attributed to host nuclear localization. AGS cells transfected with pEGFP-HP0059 plasmid showed strong GFP signal merged to the chromosomal DNA region. The chromosome was fragmented into multiple distinct dots merged with the GFP signal after 12 h of incubation. The chromosome fragmentation was further explored by incubation of AGS chromosomal DNA with recombinant HP0059 proteins, which leaded to complete degradation of the chromosomal DNA. HP0059 protein also degraded circular plasmid DNA without consensus, being an indication of DNase I activity. The DNase was activated by MgCl2, but not by CaCl2. The activity was completely blocked by EDTA. The optimal pH and temperature for DNase activity were 7.0–8.0 and 55°C, respectively. These results indicate that HP0059 possesses a novel DNase I activity along with a role in the genomic instability of human gastric cells, which may result in the transformation of gastric cells. 相似文献
10.
Toshiyuki Kaneko Naoya Takahashi Munehiro Kikuyama 《The Journal of membrane biology》2009,228(1):33-42
In order to confirm that mechanosensitive Ca2+ channels are activated by membrane stretching, we stretched or compressed the plasma membrane of Chara by applying osmotic shrinkage or swelling of the cell by varying the osmotic potential of the bathing medium. Aequorin studies
revealed that treatments causing membrane stretching induced a transient but large increase in cytoplasmic concentration of
Ca2+ (Δ[Ca2+]c). However, the observed Δ[Ca2+]c decreased during the treatments, resulting in membrane compression. A second experiment was carried out to study the relationship
between changes in membrane potential (ΔE
m) and stretching or compression of the plasma membrane. Significant ΔE
m values, often accompanied by an action potential, were observed during the initial exchange of the bathing medium from a
hypotonic medium to a hypertonic one (plasmolysis). ΔE
m appears to be triggered by a partial stretching of the membrane as it was peeled from the cell wall. After plasmolysis, other
exchanges from hypertonic to hypotonic media, with their accompanying membrane stretching, always induced large ΔE
m values and were often accompanied by an action potential. By contrast, action potentials were scarcely observed during other
exchanges from hypotonic to hypertonic solutions (=membrane compression). Thus, we concluded that activation of the mechanosensitive
channels is triggered by membrane stretching in Chara. 相似文献
11.
Elicitation can lead to overproduction of secondary metabolites in plants and microbes. Potential changes in cytosolic Ca2+ levels in bacteria were studied in response to elicitation. We report, for the first time, the effect of oligosaccharide
elicitors on intracellular Ca2+ levels. The apoaequorin gene was cloned into Escherichia coli DH5α and Bacillus subtilis 1604 cultures. Addition of elicitors, oligoguluronate and mannan oligosaccharides, to the cultures caused up to 11-fold increase
in cytosolic Ca2+ in E. coli and tenfold increase in B. subtilis. These increases in Ca2+ levels could therefore contribute to the enhancement of secondary metabolite levels. 相似文献
12.
Björn D. Heijstra Franz B. Pichler Quanfeng Liang Razel G. Blaza Susan J. Turner 《Antonie van Leeuwenhoek》2009,95(4):343-349
Extracellular DNA can play a structural role in the microbial environment. Here evidence is presented that an environmental
isolate of Acidovorax
temperans utilises extracellular DNA for intercellular and cell-surface attachment and that Type IV pili and electrostatic interactions
play a role in this interaction. Preliminary attempts to isolate and purify extracellular polysaccharides from A. temperans strain CB2 yielded significant amounts of DNA raising the question of whether this molecule was present as a structural component
in the extracellular matrix. The role of DNA in attachment was indicated by experiments in which the addition of DNase to
liquid medium inhibited the attachment of Acidovorax to glass wool. A Tn5 insertional mutant, lacking Type IV pili, was unable to initiate attachment. Addition of DNase caused rapid detachment of
bound cells, but no detachment occurred when proteinase, RNase or inactivated DNase were used. Addition of MgCl2 also caused significant detachment, supporting the possible mechanistic role of electrostatic interactions in the attachment
process. Although attachment was apparent in early to mid-log phase growth, surprisingly DNA was not detected in the culture
supernatant until late stationary phase and coincided with an appreciable loss of cell viability. This suggests that during
log-phase growth attachment is mediated by eDNA that is released in low quantities and/or is highly localised within the extracellular
matrix and also that stationary phase DNA release through widespread cell lysis may be a separate and unrelated event. 相似文献
13.
Supplementation with CaCl2·2H2O (50 mg l−1) or CuSO4·5H2O (10 mg l−1) improved mannitol production by Candida magnoliae by 14.5 and 18.6% (25 and 32 g/L), respectively. When used in combination, they acted synergistically: Ca2+ decreased the intracellular concentration of mannitol 30%, whereas Cu2+ increased the intracellular activity of mannitol dehydrogenase 1.6-times more than control. Ca2+ probably works by altering the permeability of cells to mannitol, whereas, Cu2+ increases the activity of an enzyme responsible for mannitol biosynthesis. 相似文献
14.
The previously selected strain Streptomyces griseus var. streptomycini is able to hydrolyze colloid as well as crystal forms of chitin. During the submerged cultivation in the medium with crystal
chitin, the chitinase activity achieved the maximal value after 46–50 h of culturing. Use of colloid chitin as an inductor
allowed increasing the chitinolytic activity by 33%. Adding of mannose to the medium increased the chitinase activity of the
producer by two times. It has been shown that the chitinase biosynthesis bears an inducible nature. 相似文献
15.
Field observations and inoculation experiments revealed that Uromyces appendiculatus var. azukicola has an autoecious and macrocyclic life cycle and produces spermogonia, aecia, uredinia, and telia on Vigna angularis var. angularis and V. angularis var. nipponensis. From inoculation experiments, it was suggested that this rust fungus has different host relationships from other varieties. Morphological examinations revealed that the characteristics of urediniospores and teliospores are different among varieties, although aeciospores are morphologically similar to each other.Contribution no. 182, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan 相似文献
16.
Uroz S Oger P Chhabra SR Cámara M Williams P Dessaux Y 《Archives of microbiology》2007,187(3):249-256
Abtsract
Comamonas strain D1 enzymatically inactivates quorum-sensing (QS) signal molecules of the N-acyl homoserine lactone (N-AHSL) family, and exhibits the broadest inactivation range of known bacteria. It degrades N-AHSL with acyl-side chains ranging from 4 to 16 carbons, with or without 3-oxo or 3-hydroxy substitutions. N-AHSL degradation yields HSL but not N-acyl homoserine: strain D1 therefore harbors an amidohydrolase activity. Strain D1
is the fifth bacterium species in which an N-AHSL amidohydrolase is described. Consistent with its N-AHSL degradation ability, strain D1 efficiently quenches various QS-dependent functions in other bacteria, such as violacein
production by Chromobacterium violaceum and pathogenicity and antibiotic production in Pectobacterium. 相似文献
17.
18.
Tae-Sung?Kim Jung-Ro?Lee Sebastin?Raveendar Gi-An?Lee Young-Ah?Jeon Ho-Sun?Lee Kyung-Ho?Ma Sok-Young?Lee Jong-Wook?Chung
Molecular markers derived from the complete chloroplast genome can provide effective tools for species identification and phylogenetic resolution. Complete chloroplast (cp) genome sequences of Capsicum species have been reported. We herein report the complete chloroplast genome sequence of Capsicum baccatum var. baccatum, a wild Capsicum species. The total length of the chloroplast genome is 157,145 bp with 37.7 % overall GC content. One pair of inverted repeats, 25,910 bp in length, was separated by a small single-copy region (17,974 bp) and large single-copy region (87,351 bp). This region contains 86 protein-coding genes, 30 tRNA genes, 4 rRNA genes, and 11 genes contain one or two introns. Pair-wise alignments of chloroplast genome were performed for genome-wide comparison. Analysis revealed a total of 134 simple sequence repeat (SSR) motifs and 282 insertions or deletions variants in the C. baccatum var. baccatum cp genome. The types and abundances of repeat units in Capsicum species were relatively conserved, and these loci could be used in future studies to investigate and conserve the genetic diversity of the Capsicum species. 相似文献
19.
Effects of intracellular Mg2+ on a native Ca2+-and voltage-sensitive large-conductance K+ channel in cultured human renal proximal tubule cells were examined with the patch-clamp technique in the inside-out mode.
At an intracellular concentration of Ca2+ ([Ca2+]i) of 10−5–10−4 M, addition of 1–10 mM Mg2+ increased the open probability (Po) of the channel, which shifted the Po –membrane potential (Vm) relationship to the negative voltage direction without causing an appreciable change in the gating charge (Boltzmann constant).
However, the Mg2+-induced increase in Po was suppressed at a relatively low [Ca2+]i (10−5.5–10−6 M). Dwell-time histograms have revealed that addition of Mg2+ mainly increased Po by extending open times at 10−5 M Ca2+ and extending both open and closed times simultaneously at 10−5.5 M Ca2+. Since our data showed that raising the [Ca2+]i from 10−5 to 10−4 M increased Po mainly by shortening the closed time, extension of the closed time at 10−5.5 M Ca2+ would result from the Mg2+-inhibited Ca2+-dependent activation. At a constant Vm, adding Mg2+ enhanced the sigmoidicity of the Po–[Ca2+]i relationship with an increase in the Hill coefficient. These results suggest that the major action of Mg2+ on this channel is to elevate Po by lengthening the open time, while extension of the closed time at a relatively low [Ca2+]i results from a lowering of the sensitivity to Ca2+ of the channel by Mg2+, which causes the increase in the Hill coefficient.
M. Kubokawa and Y. Sohma contributed equally to this work. 相似文献
20.
Minhong Huang Min Li Zhixiang Feng Yang Liu Yiwen Chu Yongqiang Tian 《World journal of microbiology & biotechnology》2011,27(9):2103-2109
Rapamycin produced by Streptomyces hygroscopicus displays immunosuppressive, antifungal, anti-tumor, anti-inflammatory and neuro-regenerative properties. To enhance production
of rapamycin, aveR, a stimulator in Streptomyces avermitilis, was integrated into the chromosome of S. hygroscopicus TYQ0915. This resulted in a 274.9% increase of rapamycin production in an exconjugant S. hygroscopicus AVH1124. Introduction of aveR acts pleiotropically by affecting growth and sporulation of S. hygroscopicus AVH1124, although aveR is verified to be a pathway-specific regulator in S. avermitilis. This study proved that introduction of a homologous regulatory gene from the same protein family enhanced rapamycin production. 相似文献