Influence of Legionella pneumophila and other water bacteria on the survival and growth of Acanthamoeba polyphaga

We investigated in solid medium, in water microcosm co-cultures and by light and transmission electron microscopy the influence of Legionella pneumophila Lp-1, Pseudomonas aeruginosa ATCC 27853, Burkholderia cepacia ATCC 25416 and Pseudomonas fluorescens SSD35 on the growth and survival of Acanthamoeba polyphaga. The infection with L. pneumophila was microscopically characterized by the presence of few bacteria inside protozoa at 4th h, and by the beginning of disruptive effects in late phase of trial. In water microcosm studies, performed at different temperature, the more significant interactions were observed at 30°C. In these conditions, L. pneumophila caused a marked reduction in trophozoite and cyst counts from the 4th day until the end of incubation (11 days). B. cepacia showed, by microscopic observation, few and generally single rods within protozoan phagosomes and caused a light reduction of trophozoite viability and cyst formation in co-cultures. A more invasive type of endocytosis, characterized by an early invasion with the presence of a high bacteria number inside amoebae, was observed for Pseudomonas strains. P. fluorescens produced a violent lysis of the host, whereas P. aeruginosa did not cause lysis or suffering. These results underline that water bacteria other than legionella are capable of intracellular survival in Acanthamoeba, influencing the protozoa viable cycle.     

1株鞘细菌的分离筛选及对铅离子吸附条件的研究

通过单因素试验设计,探讨了不同鞘细菌添加量、初始浓度的铅离子溶液、吸附时溶液的温度和p H对鞘细菌吸附铅离子的影响。在此基础上,采用4因素3水平正交试验设计,进一步探讨鞘细菌对铅离子吸附影响的主要因素及最佳吸附组合。试验结果表明,最佳吸附组合为鞘细菌制备液添加量0.3 g/L、吸附溶液中铅离子初始浓度10 mg/L、摇床振荡吸附温度30℃以及吸附液p H 8。在此条件下,鞘细菌吸附铅离子的吸附量为3.09 mg/g,吸附率达92.74%。     

Identification of two carbonic anhydrases in the mantle of the European Abalone Haliotis tuberculata (Gastropoda, Haliotidae): phylogenetic implications

Carbonic anhydrases (CAs) represent a diversified family of metalloenzymes that reversibly catalyze the hydration of carbon dioxide. They are involved in a wide range of functions, among which is the formation of CaCO(3) skeletons in metazoans. In the shell-forming mantle tissues of mollusks, the location of the CA catalytic activity is elusive and gives birth to contradicting views. In the present paper, using the European abalone Haliotis tuberculata, a key model gastropod in biomineralization studies, we identified and characterized two CAs (htCA1 and htCA2) that are specific of the shell-forming mantle tissue. We analyzed them in a phylogenetic context. Combining various approaches, including proteomics, activity tests, and in silico analyses, we showed that htCA1 is secreted but is not incorporated in the organic matrix of the abalone shell and that htCA2 is transmembrane. Together with previous studies dealing with molluskan CAs, our findings suggest two possible modes of action for shell mineralization: the first mode applies to, for example, the bivalves Unio pictorum and Pinctada fucata, and involves a true CA activity in their shell matrix; the second mode corresponds to, for example, the European abalone, and does not include CA activity in the shell matrix. Our work provides new insight on the diversity of the extracellular macromolecular tools used for shell biomineralization study in mollusks.     

Isolation and characterization of polymorphic microsatellite markers from the velvet tree, Miconia calvescens DC. (Melastomataceae)

Nine polymorphic microsatellite loci were isolated and characterized from the invasive velvet tree (Miconia calvescens DC.), a serious forest invader in tropical Pacific oceanic islands. These loci provided markers with polymorphism of three to 10 alleles per locus within 95 individuals. The expected and observed heterozygosities ranged from 0.0367 to 0.5053 and from 0.0370 to 0.2473, respectively. These markers should be useful to study dispersal and the invasion genetics of the velvet tree.     

Phylogeny of the Afro-Madagascan Aristea (Iridaceae) revisited in the light of new data on pollen morphology

Scanning and electron microscopic studies of the pollen grains of several species of the sub-Saharan African and Madagascan genus Aristea of c . 50 species, supplement data from an earlier study and enable us to include these species in a phylogenetic analysis. TEM examination of a range of pollen grains of representative pollen types in Aristea makes it possible to reinterpret past SEM results so that apertures covered with exine masses and previously called sulculate, are now seen to be either zonasulculate or dizonasulculate. Revised and expanded data are combined in a matrix together with new data for seed morphology in the genus, which like the capsules is remarkably diverse, including angular seeds with reticulate sculpturing, lamellate or triangular-columnar seeds with smooth or reticulate surfaces and with smooth or papillate or areolate margins. This new phylogenetic analysis suggests that Aristea should remain treated as comprising three subgenera. In subgenus Eucapsulares we add a new section Latifolieae for A. latifolia , which seems an isolated relic restricted to the mountains of the Cape Region of South Africa, an area of winter rainfall. Species with similar unspecialized capsule and seed morphology occur only in eastern south and tropical Africa and Madagascar, but they have derived pollen morphology whereas the pollen of A. latifolia is plesiomorphic. This species appears to be the closest living ancestor of the genus. In subgenus Aristea we continue to recognize three sections, sect. Racemosae , sect. Singulares and sect. Aristea. Nesting of subgenus Pseudaristea within section Racemosae of subgenus Aristea is probably an artefact of the analysis and does not receive bootstrap support, and hence we continue to recognize this group of species at subgeneric rank.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 41–68.     

一种新的延胡索酸水合酶抗体的制备及功能研究

延胡索酸水合酶(fumarate hydratase,FH)是三羧酸循环(tricarboxylic acid cycle,TCA)中的一个关键性酶。FH的基因突变将导致延胡索酸合酶缺乏症、遗传性平滑肌瘤和肾细胞癌(hereditary leiomyomatosis and renal cell carcinoma,HLRCC)等疾病。FH缺失导致HLRCC分子的确切生物学机制尚不明确。作者将FH基因片段克隆到原核表达载体上,在大肠杆菌中表达GST-FH(400-510)融合蛋白。该融合蛋白为抗原免疫小鼠获得抗体,通过免疫印迹实验证明了该抗体的特异性并发现FH在心脏和肝脏中的含量较高。通过免疫共沉淀实验发现,在大鼠肝脏组织中FH可能与多个蛋白形成蛋白复合物。     

Natural hybridization of two species of tetraploid barbels: Barbus meridionalis and Barbus barbus (Osteichtyes, Cyprinidae) in southern France

Natural hybridization of Barbus barbus and B. meridionalis has been demonstrated in southern France. A genetical study (isozyme electrophoresis) of these species and their hybrids revealed the characteristics of hybridization. Ten enzyme markers and five morphological parameters were used to distinguish between the two parent species. Enzymatic divergence between the parent species included fixed allelic differences at certain loci and reduction in enzymatic activity, including the silencing of certain genes. A morphological study revealed a good correlation between the isozyme markers and morphological characters. Backcrosses were observed and this raises the question of the integrity of the parent species.     

温度、pH对非光合微生物菌群固碳效率的影响及其成因分析

CO2是主要的温室气体,也是地球上最丰富的碳源和可再生资源,本实验通过研究温度和pH对非光合固碳微生物固碳效率的影响,以期获得非光合固碳微生物适宜的固碳条件,并通过16SrDNA序列分析,研究了不同条件对固碳微生物群落结构的影响及其与固碳效率的相关性。结果表明,好氧／厌氧固碳微生物菌群生长的最适pH均在7左右。好氧固碳微生物菌群可在较大的温度范围（10℃-40℃）内良好生长,但其固碳速率在10℃左右时最高,之后微生物固碳速率随温度上升而下降,在40℃时,微生物固碳速率开始回升。厌氧时微生物的固碳效率随温度的变化情况与好氧时相似,但总体效果要比其在好氧时低20％～25％。由DGGE图谱及戴斯系数分析可得培养温度和pH对群落结构有显著影响,不同pH和温度条件下优势菌差异显著,这可能是固碳效率变化的重要原因之一。     

Parental and genetic factors rather than nesting forest patch size affect physiological traits of offspring in an area‐sensitive passerine: an experimental study

Our understanding of the effects of habitat loss on individual performance is limited due to a lack of experimental studies that take the potential genetic and parental effects producing phenotypic variation into consideration. To assess the relative role of habitat loss on offspring phenotype while controlling for the confounding effects of genetic and parental variation we performed a partial cross‐fostering experiment using the Eurasian Treecreeper Certhia familiaris. The experiment was carried out by swapping half the nestlings in a brood between small and large nesting forest patches to determine the effect of nesting forest patch size on five nestling traits reflecting morphological size, body condition, physiological stress and inflammation status. There was no effect of nesting forest patch size on the offspring traits examined. Instead, we found evidence of genetic and early parental effects on all traits except inflammation status, as well as parental effects after cross‐fostering for all of the measured offspring traits. Our results suggest that genetic and parental effects should be taken into account when making inferences about species’ responses to habitat loss.     

Interactions between Thaumarchaea,Nitrospira and methanotrophs modulate autotrophic nitrification in volcanic grassland soil

Ammonium/ammonia is the sole energy substrate of ammonia oxidizers, and is also an essential nitrogen source for other microorganisms. Ammonia oxidizers therefore must compete with other soil microorganisms such as methane-oxidizing bacteria (MOB) in terrestrial ecosystems when ammonium concentrations are limiting. Here we report on the interactions between nitrifying communities dominated by ammonia-oxidizing archaea (AOA) and Nitrospira-like nitrite-oxidizing bacteria (NOB), and communities of MOB in controlled microcosm experiments with two levels of ammonium and methane availability. We observed strong stimulatory effects of elevated ammonium concentration on the processes of nitrification and methane oxidation as well as on the abundances of autotrophically growing nitrifiers. However, the key players in nitrification and methane oxidation, identified by stable-isotope labeling using ¹³CO₂ and ¹³CH₄, were the same under both ammonium levels, namely type 1.1a AOA, sublineage I and II Nitrospira-like NOB and Methylomicrobium-/Methylosarcina-like MOB, respectively. Ammonia-oxidizing bacteria were nearly absent, and ammonia oxidation could almost exclusively be attributed to AOA. Interestingly, although AOA functional gene abundance increased 10-fold during incubation, there was very limited evidence of autotrophic growth, suggesting a partly mixotrophic lifestyle. Furthermore, autotrophic growth of AOA and NOB was inhibited by active MOB at both ammonium levels. Our results suggest the existence of a previously overlooked competition for nitrogen between nitrifiers and methane oxidizers in soil, thus linking two of the most important biogeochemical cycles in nature.