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991.
The 2,4-dichlorophenoxyacetic acid (2,4-D) degrading pseudomonad, Pseudomonas cepacia DBO1(pRO101), was inoculated at approximately 107 CFU/g into sterile and non-sterile soil amended with 0, 5 or 500 ppm 2,4-D and the survival of the strain was studied for a period of 44 days. In general, the strain survived best in sterile soil. When the sterile soil was amended with 2,4-D, the strain survived at a significantly higher level than in non-amended sterile soil. In non-sterile soil either non-amended or amended with 5 ppm 2,4-D the strain died out, whereas with 500 ppm 2,4-D the strain only declined one order of magnitude through the 44 days.The influence of 0,0.06, 12 and 600 ppm 2,4-D on short-term (48 h) survival of P. cepacia DBO1(pRO101) inoculated to a level of 6×104, 6×106 or 1×108 CFU/g soil was studied in non-sterile soil. Both inoculum level and 2,4-D concentration were found to have a positive influence on numbers of P. cepacia DBO1(pRO101). At 600 ppm 2,4-D growth was significant irrespective of the inoculation level, and at 12 ppm growth was stimulated at the two lowest inocula levels.
P. cepacia DBO1(pRO101) was able to survive for 15 months in sterile buffers kept at room temperature. During this starvation, cells shrunk to about one third the volume of exponentially growing cells.Abbreviations AODC
acridine orange direct count
- CFU
colony forming units
- PTYG-Agar
peptone, tryptone, yeast & glucose agar
- TET
tetracycline
- LB
Luria Bertani medium 相似文献
992.
The luminous responses to electrical stimulation of isolated polyps of 4 deep-water anthozoans are described. All show facilitatory responses and summation at stimulus frequencies > 2 s–1. The responses of the gorgonian Acanella arbuscula comprise a slow summation of weak individual flashes. It is suggested that there is no fundamental difference between deep and shallow species, nor between the responses of scyphozoans, such as Pelagia and Atolla, and anthozoans, such as those described here. Both facilitated and decremental responses can be obtained from each of the 2 groups and the complexity of in vivo responses may be as much a reflection of selective pressures on the neural pathways as on the bioluminescent systems themselves. 相似文献
993.
Blood-brain barrier alterations in bacterial meningitis: Development of an in vitro model and observations on the effects of lipopolysaccharide 总被引:3,自引:0,他引:3
Allan R. Tunkel Susan W. Rosser Eric J. Hansen W. Michael Scheld 《In vitro cellular & developmental biology. Animal》1991,27(2):113-120
Summary To further examine the effects of purifiedHaemophilus influenzae type b lipopolysaccharide (LPS) on blood-brain barrier permeability, we have developed an in vitro model of the BBB. Microvascular
endothelial cells were isolated from rat cerebral cortices by enzymatic digestion, dextran centrifugation, and separation
on percoll gradients. The cells were determined to be endothelial in origin by positive fluorescent staining for Factor VIII-related
antigen and the ability to take up acetylated low density lipoproteins, and their cerebral origin by the formation of junctional
complexes in vitro. Cells were seeded onto semipermeable polycarbonate filters and permeability assessed by measuring traversal
of radioactive albumin across the monolayer. Treatment of the cells with LPS at concentrations of 1.0μg/ml and 0.1μg/ml for 4 h led to statistically significant increases in albumin permeability of 4.6% (P=0.001) and 5.6% (P<0.001), respectively, without evidence of cell death as assessed by release of lactate dehydrogenase into the media. These
results indicate that LPS significantly increases albumin permeability across a monolayer of cerebral microvascular endothelial
cells in the absence of host inflammatory cells. Future studies on the effects of LPS on intracellular regulation will determine
the mechanisms responsible for these alterations.
Supported by a research grant (RO1-AI17904) and a training grant (T32-AI07046) from the National Institute of Allergy and
Infectious Diseases, Bethesda, MD. W. Michael Scheld is an established investigator of the American Heart Association. 相似文献
994.
Bacterial resistance and detoxification of heavy metals 总被引:4,自引:0,他引:4
Jeffrey W. Williams 《Enzyme and microbial technology》1984,6(12):530-537
Microbial cells have resistances to essentially all of the toxic heavy metals of the Periodic Table. In bacterial cells, the genetic determinants of these resistances are frequently found on small extrachromosomal plasmids and transposons. Sometimes the resistances are associated with detoxifying enzymes. This is true for the Hg2+ → Hg0 reductase, the As3+ → As5+ oxidase and the Cr6+ → Cr3+ reductase. In other cases, such as As5+, Ag+ and Cd2+, no change in redox state occurs but, rather, uptake and transport differences accompany resistance determinants. This article summarizes what is known of bacterial metal resistances for which enzymatic detoxification is known to be the mechanism of resistance. The characteristics and functions of the enzymes are described, as well as a summary of the newer DNA sequence analysis (basic science) and bench-scale efforts (applied science) for the mercuric resistance system. 相似文献
995.
A cultured soybean cell line, SB-1 was used to evaluate the initial interaction between the soybean cells andRhizobium japonicum. Co-culturing ofR. japonicum with SB-1 cells in suspension resulted in strain-specific polar attachment. This attachment can be inhibited by galactose and antibodies raised against seed soybean agglutinin (SBA). A lectin was purified from SB-1 cells which shares properties with SBA in terms of immunological reactivity, sugar binding activity, polypeptide molecular weight and peptide maps. When the SB-1 cells were co-cultured withR. japonicum for three weeks in solid agar medium, histological staining revealed bacterial penetration into certain SB-1 cells. Furthermore, there were focal regions of cells with prominent nuclei representing actively proliferating regions. These observations are analogous to that ofin vivo nodule initiation in soybean roots. 相似文献
996.
ATP-dependent protein kinase activities were detected in both membrane and cytoplasmic fractions from the oral pathogen Streptococcus mutans. Different polypeptides were phosphorylated by endogenous kinase(s) in the two fractions. In membranes, five phosphoproteins were detected with apparent masses of 82, 37, 22, 12, and 10 kilodaltons (KD). In cytoplasm, two major acid-stable phosphoproteins were found. One was identified as HPr of the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS), while the other had an apparent mass of 61 KD. Both of these proteins were phosphorylated on a seryl residue. Fructose 1,6-bisphosphate stimulated phosphorylation of HPr by the kinase and inhibited phosphorylation of the 61-KD protein. In contrast, fructose 1-phosphate, 2-phosphoglycerate, 3-phosphoglycerate, and dihydroxyacetone phosphate inhibited phosphorylation of HPr and stimulated phosphorylation of the 61-KD protein. Several other glycolytic intermediates as well as inorganic phosphate inhibited phosphorylation of either or both proteins. Preincubation of cytoplasm with PEP prior to incubation with ATP reduced the amount of phospho-(seryl)-HPr formed, but not that of the 61-KD phosphoprotein. The latter protein has not yet been identified but has properties that suggest that it may be the protein kinase itself. These results provide evidence for one or more soluble ATP-dependent protein kinases in S mutans that are regulated by glycolytic intermediates and that may play a role in the modulation of carbohydrate uptake and metabolism in this organism. A model for feedback regulation of sugar transport in S mutans, mediated by an allosterically regulated kinase, is presented. 相似文献
997.
Two-wk-old broiler chicks were inoculated via crop intubation withEimeria acervulina at two doses: 105 or 106 sporulated oocysts/bird or withEimeria tenella at a dose of 105 sporulated oocysts/bird. Serum and liver samples were collected on days 3 and 6 post-inoculation (PI). There were no significant
changes in serum or liver zinc, copper, and iron concentrations in any of the infected groups by 3 d PI. However, on d 6,
PI serum protein was significantly reduced in all of the infected groups compared to their pair-fed controls. The chicks infected
withE. tennella had significantly reduced serum zinc (1.20 vs 1.77 μg/mL) and iron (0.44 vs 1.28 μg/mL) concentrations and significantly
elevated serum copper (0.28 vs 0.17 μg/mL) and ceruloplasmin levels (20.33 vs 11.11 μg/mL) compared to their pair-fed counterparts.
Those chicks infected withE. acervulina (106 oocysts/bird) exhibited significantly reduced serum iron concentration by 6 days PI (0.90 vs 1.14 μg/mL). Liver zinc was
significantly increased in the chicks infected withE. tenella (349 vs 113 μg/g dry liver wt), as was copper (24 vs 19 μg/g), whereas liver iron concentration was significantly reduced
(172 vs 243 μg/g) compared to pair-fed controls. At both dose levels, the chicks infected withE. acervulina exhibited a significant reduction in liver iron by 6 d PI. Hepatic cytosol metals generally reflected whole tissue levels.
Metallothionein (MT)-bound zinc was significantly elevated in the chicks infected withE. tenella. Iron bound to a high molecular weight, heat-stable protein fraction (presumably cytoplasmic ferritin) was significantly
reduced in chicks infected withE. acervulina, as well as those infected withE. tenella. Collectively, the changes in serum zinc, copper, and iron concentrations, as well as the changes in hepatic zinc and MT-zinc
concentrations in the chicks infected withE. tenella were similar to changes evoked during an acute phase response to infection. It is possible that a secondary bacterial infection
or inflammation stemming from erosion of the lining of the cecum may play a role in the response of trace element metabolism
to theE. tenella infection.
Mentions of a trademarkr, proprietary product or specific equipment does not consitute a guarantee or warranty by the US Department
of Agriculture and does not imply its approval to the exclusion of other products. 相似文献
998.
In anoxic salt marsh sediments of Sapelo Island, GA, USA, the vertical distribution of CH4 production was measured in the upper 20 cm of surface sediments in ten locations. In one section of high marsh sediments,
the concentration and oxidation of acetate in sediment porewaters and the rate and amount of14C acetate and14CO2 incorporation into cellular lipids of the microbial population were investigated. CH4 production rates ranged from <1 to 493 nM CH4 gram sediment−1 day−1 from intact subcores incubated under nitrogen. Replacement with H2 stimulated the rate of methane release up to nine fold relative to N2 incubations. Rates of lipid synthesis from CO2 averaged 39.2 ×10−2nanomoles lipid carbon cm3 sediment−1 hr−1, suggesting that CO2 may be an important carbon precursor for microbial membrane synthesis in marsh sediments under anoxic conditions. Qualitative
measurements of lipid synthesis rates from acetate were found to average 8.7 × 10−2 nanomoles. Phospholipids were the dominant lipids synthesized by both substrates in sediment cores, accounting for an average
of 76.6% of all lipid radioactivity. Small amounts of ether lipids indicative of methanogenic bacteria were observed in cores
incubated for 7 days, with similar rates of synthesis for both CO2 and acetate. The low rate of ether lipid synthesis suggests that either methanogen lipid biosynthesis is very slow or that
methanogens represent a small component of total microbial lipid synthesis in anoxic sediments.
present address: The University of Maryland,, Chesapeake Biological Laboratory, Box 38, Solomons, MD 20688, USA 相似文献
999.
Antoon W.J. van Pelt Henny C. van der Mei Hendrik J. Busscher Joop Arends Anton H. Weerkamp 《FEMS microbiology letters》1984,25(2-3):279-282
Abstract The surface free energies ( γ b ) of a variety of oral streptococci were determined from contact angle measurements on bacterial deposits, using the concept of dispersion and polar components. At least four strains of each species were tested. Strains of Streptococcus mutans, S. sanguis and S. salivarius possessed relatively high surface free energies (103 ± 12 mJ · m−2 ) and at the species level no significant difference was found. In contrast, the strains of S. mitis had remarkably low surface free energies (45 ± 14 mJ · m−2 ). S. milleri appeared to be a heterogeneous species, showing surface free energies over a range of 32–119 mJ · m−2 . No significant differences were observed between laboratory strains and strains freshly isolated from the oral cavity. 相似文献
1000.
为探究造纸废水活性污泥中微生物群落结构多样性以及对造纸废水处理效果的影响,利用Illumina MiSeq 高通量测序方法,分析在处理造纸废水过程中,同一运行阶段两个并联氧化沟内活性污泥的微生物群落与多样性组成。结果表明,系统中处理造纸废水的活性污泥在同一废水条件下微生物群落结构总体稳定,优势细菌为绿弯菌门(Chloroflexi)、拟杆菌门(Bacteroidota)、变形菌门(Proteobacteria)、Myxococcota、放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)等。最重要的优势细菌类群为Chloroflexi,相对丰度占比为47.67%~48.22%,远远高于其他废水中Chloroflexi的占比,其中厌氧绳菌纲(Anaerolineae)是其主要成员,占比84.39%~88.34%,可针对性地去除造纸废水中的污染物。造纸废水活性污泥样品中存在大量特殊功能菌群,其在废水中污染物尤其是木质素的去除中发挥着重要作用。 相似文献