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C S Buer K T Gahagan GA Swartzlander Jr P J Weathers 《Journal of industrial microbiology & biotechnology》1998,21(4-5):233-236
Comparison of the optical trapping efficiency of Agrobacterium rhizogenes and A. tumefaciens strains indicates the A. rhizogenes strain, ATCC 11325, is significantly less efficiently trapped than A. rhizogenes A4, ATCC 15834, and the A. tumefaciens strain LBA4404. Differences were also found in capsule generation, growth media viscosity, and transmission electron microscopy
negative staining. These observations imply a difference in surface structure exists. Calcofluor fluorescence suggests the
difference involves an exopolysaccharide.
Received 1 July 1998/ Accepted in revised form 5 October 1998 相似文献
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SUNG MIN BOO HAN SOON KIM WOONGGHI SHIN GA HUN BOO SUNG MI CHO BOK YEON JO JEE‐HWAN KIM JIN HEE KIM EUN CHAN YANG PETER A. SIVER ALEXANDER P. WOLFE DEBASHISH BHATTACHARYA ROBERT A. ANDERSEN HWAN SU YOON 《Molecular ecology》2010,19(19):4328-4338
The global distribution, abundance, and diversity of microscopic freshwater algae demonstrate an ability to overcome significant barriers such as dry land and oceans by exploiting a range of biotic and abiotic colonization vectors. If these vectors are considered unlimited and colonization occurs in proportion to population size, then globally ubiquitous distributions are predicted to arise. This model contrasts with observations that many freshwater microalgal taxa possess true biogeographies. Here, using a concatenated multigene data set, we study the phylogeography of the freshwater heterokont alga Synura petersenii sensu lato. Our results suggest that this Synura morphotaxon contains both cosmopolitan and regionally endemic cryptic species, co‐occurring in some cases, and masked by a common ultrastructural morphology. Phylogenies based on both proteins (seven protein‐coding plastid and mitochondrial genes) and DNA (nine genes including ITS and 18S rDNA) reveal pronounced biogeographic delineations within phylotypes of this cryptic species complex while retaining one clade that is globally distributed. Relaxed molecular clock calculations, constrained by fossil records, suggest that the genus Synura is considerably older than currently proposed. The availability of tectonically relevant geological time (107–108 years) has enabled the development of the observed, complex biogeographic patterns. Our comprehensive analysis of freshwater algal biogeography suggests that neither ubiquity nor endemism wholly explains global patterns of microbial eukaryote distribution and that processes of dispersal remain poorly understood. 相似文献
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植被状况对乔木幼苗物种多样性的影响 总被引:3,自引:0,他引:3
运用灰色关联度分析亚热带常绿阔叶林植被状况对乔木幼苗物种多样性的影响。结果表明,所选取的植被状况参数对乔木幼苗物种多样性有不同的影响,对乔木幼苗物种多样性影响较大的是草本层的Simpson指数、灌木层Simpson指数和灌木层盖度,影响较小的为草本层盖度和灌木层Shannon-Wiener指数。乔木幼苗4个物种多样性指数受植被状况影响的顺序为:Pielou均匀性指数>Shannon-Wiener指数>物种丰富度指数>Simpson指数。草本层、灌木层和乔木层对乔木幼苗的物种多样性有不同的影响,其影响方式也不一样。 相似文献
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Production of laccase activity by nine strains of Chalara paradoxa isolated from olive mill wastewater disposal ponds were studied. Enzyme extracts obtained from cultured broths by adsorption on hydroxyapatite showed a single band of laccase activity on ABTS after polyacrylamide gel electrophoresis (PAGE). They showed small mobility differences, with molecular masses of 67 to 68 kDa. Enzymes from the different strains oxidized a variety of phenolic and non-phenolic substances, and they could be divided into two groups according to their relative activities on substrates. All laccases showed a dual pH dependence of activity, with a maximum in the range of pH 3.0 to 4.5 for ABTS, o-dianisidine and 2,6-dimethoxyphenol, and pH 6.0 (Group 1) or pH 6.5 (Group 2) for syringaldazine and other substrates. Optimal temperatures were in the range of 10 to 28 degrees C for two strains (maximum at 10 degrees C) and 10 to 37 degrees C for the rest. The different enzymes were partially inactivated by heating at 60 degrees C and totally inactivated at 70 degrees C. Laccases were stable in a pH range of 3.0 to 9.0 (except for strain 36A, which was partially inactivated at pH 3.0), but became inactivated at pH 2.0. Altogether these data suggest that Ch. paradoxa strains produce different laccase isoenzymes. 相似文献
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FRÉDÉRIC SÈBE THIERRY AUBIN RAYMOND NOWAK OLIVIER SÈBE GAËLLE PERRIN PASCAL POINDRON 《Bioacoustics.》2013,22(3):341-355
ABSTRACT In domestic sheep Ovis aries, the mother and the young display a preferential bond for each other that relies on multimodal inter-individual recognition. Lambs show a preference for their own dam shortly after birth, and this is important for their survival. The role of acoustic cues in this early preference for the mother is not clear. The aim of the present work was to analyze the timing of acoustic recognition of the mother and to identify the physical parameters used in the recognition of maternal bleats by the lamb. In a first study, we investigated the ability of lambs to discriminate between the bleats of their own mother and an alien equivalent mother in a two-choice test. Both ewes were hidden behind a canvas sheet and lambs were not allowed to approach the dams closer than 1 m, thus preventing visual as well as olfactory perception. Tests were conducted 12 hr, 24 hr or 48 hr after birth (n=19 or 20/group). An indication of vocal discrimination was already present at 24 hr and at 48 hr lambs spent significantly more time near their mother than near the alien dam. In a second step, we investigated which physical parameters of the bleats were important for recognition. For this, we conducted playback experiments with modified bleats at two weeks postpartum. Ours results show that lambs pay attention to a combination of various time, energy and frequency parameters: timbre (distribution of energy within the spectrum), amplitude and frequency modulations appear to be the most important parameters encoding the individual signature. We conclude that vocal recognition between the ewe and her lamb plays an important role in the display of preferential mother-young bond from very early on. Our studies also demonstrate that the encoding of the individual signature is not limited to the frequency domain but rather involves a multiparametric encoding process. 相似文献
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目的:观察长期家庭氧疗配合呼吸操治疗慢性阻塞性肺疾病(COPD)的临床效果。、方法:选择本院收治的COPD患者80例,随机分为研究组和对照组,各40例,两组均给予常规治疗,研究组同时由医务人员指导给予家庭氧疗和呼吸操训练,随访1年.观察两组治疗前、治疗后6个月和1年肺功能,应用StGeorge’S呼吸问卷(SGRQ)评价生存质量、结果:研究组1年内急性发作1次5人,2次2人,3次及以上1人,对照组1年内急性发作1次9人,2次7人,3次及以上4人(P〈0.05);研究组治疗后6个月、1年用力肺活量(FVC)、第1秒用力呼气容积(FEVl)和FEVl/FVC均明显升高(P〈0.05),对照组治疗后6个月、1年FVC、FEVI/FVC与治疗前比较无统计学差异(P〉0.05);研究组治疗后6个月、1年SGRQ明显降低(P〈0.05),对照组治疗后6个月、1年SGRQ与治疗前比较无统计学差异(P〉0.05).结论:家庭氧疗配合呼吸操能明显改善COPD患者肺功能,延缓患者肺功能恶化,提高患者生存质量。 相似文献