The Reconfiguring Self

This essay presents a theory about cultural systems of self. It counters disclaimers as to the possibility of building cross-culturally valid theory, often taken to be the intellectual outcome of postmodernism. Nonetheless, such theory is a logical descendant of the postmodern project, predicating multiple selves and multiple constructions of social reality. It offers an explanatory framework for conceptions of personhood that are loosely interconnected and only partially and problematically shared between culture members.     

The Body Nearer the Self

Colonizing the Body: State Medicine and Epidemic Disease in Nineteenth-Century India . David Arnold.
Reading the Social Body . Catherine T. Burroughs and Jeffrey David Ehrenreich, eds.
Little Big Men: Bodybuilding Subculture and Gender Construction . Alan M. Klein.     

福州沿海海藻共附生真菌的抗氧化活性研究

目的:从福州沿海海藻中分离海藻共附生真菌,并通过抗氧化活性筛选获得活性菌株,为今后从该菌株中发现活性显著、结构新颖的天然抗氧化剂奠定基础.方法:首先通过多种方法从海藻样品中分离尽可能多的真菌;然后进行小量发酵、萃取和浓缩,得到这些真菌的发酵浸膏,并以DPPH自由基为活性筛选模型筛选得到抗氧化活性菌株;最后通过ITS序列鉴定菌种并采用高效液相色谱法对其化学成分进行初步分析.结果:从5个海藻样品中共分离纯化得到26株真菌并从中筛选出1株抗氧化活性明显的菌株,经鉴定为青霉菌属的桔青霉菌Penicillium citrinum.结论:海藻共附生真菌是寻找生物活性物质的重要资源,它为抗氧化活性先导化合物的发现提供了思路.随着我国科研水平的日益提高和海藻真菌受关注程度的不断提升,有望从中发现许多结构新颖、活性显著的抗氧化剂.     

Symbiotic association in Chlorella culture

Chlorella sorokiniana IAM C-212 has long been maintained in slant culture as a mixed strain, representing an associated natural microbial consortium. In this study, the consortium was separated and five nonalgal constituents, a fungal strain (CSSF-1), and four bacterial strains (CSSB-1, CSSB-2, CSSB-3, and CSSB-4) were isolated and identified. 16S rDNA sequence analysis revealed that strains CSSB-1, CSSB-2, CSSB-3, and CSSB-4 were close to Ralstonia pickettii (99.8% identity), Sphingomonas sp. DD38 (99.4% identity), Microbacterium trichotecenolyticum (98.6% identity), and Micrococcus luteus (98.6% identity) respectively. 18S rDNA sequence analysis revealed that strain CSSF-1 resembled Acremonium-like hyphomycete KR21-2 (98.8%). The fungal strain CSSF-1 and one of the bacterial strains, CSSB-3, were found to promote the growth of Chlorella while the presence of bacterial strains CSSB-1 and CSSB-2 had no effect. Strain CSSB-4 could not be subcultured so its role was not elucidated. These results show that the interaction between Chlorella and its symbionts under photoautotrophic conditions involved both mutualism and commensalisms. The chlorophyll content of mixed strain was stable in long-term cultivation (7 months) while the chlorophyll content of a pure culture showed a marked decline. Electron microscopic analysis showed the two bacterial strains CSSB-2 and CSSB-3 were harbored on the sheath excreted by Chlorella, while the fungal strain CSSF-1 and the bacterial strain CSSB-1 directly adhered to the Chlorella cell surface. This report is the first observation of a symbiotic relationship among fungus, bacteria, and Chlorella, and the first observation of direct adhesion of fungus and bacteria to Chlorella in a consortium.     

昆虫病原线虫的共生细菌

昆虫病原线虫与其共生细菌二者互惠共生 :共生细菌需要昆虫病原线虫作为载体以寄生寄主昆虫并做为自己的营养来源 ,而昆虫病原线则需要依靠共生细菌来杀死昆虫。综述了共生细菌的病原作用、抗菌作用与杀虫作用 ,评述了共生细菌的基因工程进展 ,讨论了昆虫共生细菌在昆虫病原线虫致病性的作用。     

Symbiotic DNA in eukaryotic genomes

The recent explosive growth of molecular genetic databases has yielded increasingly detailed insights into the evolutionary dynamics of eukaryotic genomes. DNA sequences with the self-encoded ability to transpose and replicate are unexpectedly abundant and widespread in eukaryotic genomes. They seem to be sexual parasites. By dispersing themselves among the chromosomes, they increase their transmission rates and can invade outcrossing populations despite reducing host fitness. Once established, molecular parasites may themselves be parasitized by other elements, and through selection for reduced virulence may become beneficial genes. Elements have been isolated at various stages in this progression, from transposons that regulate their own transposition rates, to fundamental components of eukaryotic cytology, such as telomeres.     

The Symbiotic Anthozoan: A Physiological Chimera between Alga and Animal

The symbiotic life style involves mutual ecological, physiological,structural, and molecular adaptations between the partners.In the symbiotic association between anthozoans and photosyntheticdinoflagellates (Symbiodinium spp., also called zooxanthellae),the presence of the endosymbiont in the animal cells has constrainedthe host in several ways. It adopts behaviors that optimizephotosynthesis of the zooxanthellae. The animal partner hashad to evolve the ability to absorb and concentrate dissolvedinorganic carbon from seawater in order to supply the symbiont'sphotosynthesis. Exposing itself to sunlight to illuminate itssymbionts sufficiently also subjects the host to damaging solarultraviolet radiation. Protection against this is provided bybiochemical sunscreens, including mycosporine-like amino acids,themselves produced by the symbiont and translocated to thehost. Moreover, to protect itself against oxygen produced duringalgal photosynthesis, the cnidarian host has developed certainantioxidant defenses that are unique among animals. Finally,living in nutrient-poor waters, the animal partner has developedseveral mechanisms for nitrogen assimilation and conservationsuch as the ability to absorb inorganic nitrogen, highly unusualfor a metazoan. These facts suggest a parallel evolution ofsymbiotic cnidarians and plants, in which the animal host hasadopted characteristics usually associated with phototrophicorganisms.     

Resource Optimization and Symbiotic Nitrogen Fixation

In temperate forests, symbiotic nitrogen (N) fixation is restricted to the early phases of succession despite the persistence of N limitation on production late in succession. This paradox has yet to be explained adequately. We hypothesized that the restriction of N fixation to early stages of succession results from the optimization of resource allocation in the vegetation. Because of this optimization, N fixation should be restricted to periods when fixation is less costly than N uptake. Our analysis differs from others in the way we calculate the cost of N uptake; we assess the cost of N uptake as the amount of carbon (C) that could be assimilated if the resources necessary to acquire one gram of N from the soil were allocated instead to photosynthesis. We then simulate N fixation as an asymptotic function of the difference in cost between N uptake and N fixation and proportional to the abundance of host tissues for the N-fixing symbionts. The factors that contribute to conditions that favor N fixation are (a) elevated-carbon dioxide (CO₂) concentrations, (b) an open canopy, (c) low available N in the soil, and (d) a soil volume already well exploited by roots. Our results indicate that changes in the relative cost of uptake vs fixation can explain most of the pattern in fixation through both primary and secondary succession, but that competitive interactions with nonfixing species play a role in the final exclusion of fixation in later stages of succession. Received 26 September 2000; accepted 31 January 2001.     

Symbiotic relations of human and microorganisms

Symbiosis has been considered as a biological basis of infectious process. Particular attention was paid to the change of paradigm in symbiology and the appearance of a novel term--associative symbiosis. Principal structural-and-functional elements of associative symbiosis were estimated, and 3 vectors of infectious process such as i) host--normaflora, ii) host--associants, iii) associants--indigious microflora (microsymbiocenosis) were isolated. Functions of microsymbionts that determine colonization resistance of the host, and the formation of dysbioses and pathobiocenoses were reviewed. Phenomenon of microbial recognition for "self-nonself" has been revealed on the basis of opportunistic (increase/decrease) interactions on growth persistent (including biofilm formation) peculiarities of a pair "dominant-associant" under conditions of microsymbiocenosis in human. Material was presented to characterize the role of intercellular interactions of symbionts at the level of prokaryotes, pro-eukaryotes under conditions of infectious pathology.     

Reinventing Identities: The Gendered Self in Discourse

Reinventing Identities: The Gendered Self in Discourse. Mary Bucholtz. A. C. Liang. and Laurel Sutton. eds. New York: Oxford University Press, 1999. 431 pp.     

Symbiotic nitrogen fixation under stress conditions

Summary An outline is given of the possibility selecting Rhizobium strains capable of performing a relatively good symbiosis with leguminous plants, growing under stress conditions. A Rhizobium strain capable of nodulating pea plants in acid soils is described. A pea cultivar, resistant to the majority of Rhizobium strains when growing at 20°C, is found to require a short period of a higher temperature for successful nodulation. The effect of non-photosynthetic light and its possible significance under natural conditions is discussed.